You searched for subject:(Microchannel). Showing records 1 – 30 of 217 total matches.
1. VanderPutten, Michael. Evaluation of the Predictive Capability of Two-Phase Flow Maps for Microchannel Condensation of R-134a at Low Mass Flux Conditions.
▼ Predicting condensation flow regimes and the associated heat transfer and pressure drop in microchannels is critical for designing terrestrial and space systems for heating, cooling, power generation, and advanced manufacturing. It is well established that in flows approaching the microscale (Dh < 1 mm) gravity-dominated flow regimes become less relevant, with stratified and wavy flows being replaced by the intermittent and annular regimes. While a large body of work has been developed to investigate fluid behavior in microscale channels, past research has focused primarily on adiabatic air-water studies at relatively high superficial velocities or condensing refrigerants at large mass fluxes (G > 100 kg-m-2-s-1). Fluid visualization results from these studies have been used to develop many of the flow regime maps currently available for estimating heat transfer and pressure drop. Review of these flow maps shows that at microscale channel diameters and low mass fluxes, common flow regime predictions begin to break down. In the current research, two-phase flow regime data is obtained via high-speed visualization of condensing flows of R-134a at mass fluxes from 80 to 150 kg-m-2-s-1 in square microchannels (Dh = 840 μm) at quality ranging from 0.01 to 0.60. A relatively small experimental uncertainty in thermodynamic quality (Uavg ≈ 3%) was maintained by enforcing a large temperature difference across the water-side (ΔT > 10°C). To mitigate maldistribution in the channels, vapor enters the test section superheated and is condensed to the desired quality before entering the viewing section. All data points were found to be either wavy or wavy-annular flow, and did not compare well to predictions made by commonly used flow regime maps for both micro and macro channel flow. Additional research is required to better understand the characteristics of low mass-flux two phase flows in microchannel geometries. Advisors/Committee Members: Fronk, Brian (advisor), Pence, Deborah (committee member).
VanderPutten, Michael. "Evaluation of the Predictive Capability of Two-Phase Flow Maps for Microchannel Condensation of R-134a at Low Mass Flux Conditions." 2017. Masters Thesis, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/61677.
VanderPutten, Michael. "Evaluation of the Predictive Capability of Two-Phase Flow Maps for Microchannel Condensation of R-134a at Low Mass Flux Conditions." 2017. Web. 18 Apr 2019.
VanderPutten M. Evaluation of the Predictive Capability of Two-Phase Flow Maps for Microchannel Condensation of R-134a at Low Mass Flux Conditions. [Internet] [Masters thesis]. Oregon State University; 2017. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/61677.
2. Fisher, Luke W. Single- and multi-functional arrayed microchannel fluidic devices.
▼ Novel fluidic devices that utilize an array of microchannels to achieve their designed purpose are discussed. Examples of devices include: fuel reforming using Microreactors, chip cooling using microchannel heat sinks, and microchannel devices used for biological applications. The devices that have directly contributed to this research include: a microchannel water pasteurizer and a microchannel device for waste heat energy conversion. The water pasteurizer discussion focuses on the design, fabrication, and testing of the device. The design and fabrication of a microchannel boiler (waste heat energy conversion) is also discussed, but the device has not yet been tested. These devices were designed using well-established heat exchanger calculation methods (log mean temperature difference) and fabrication methods (chemical etching and diffusion bonding). The pasteurizer testing returned positive results; the thermal profile matched the predictions and the device was capable of pasteurizing water per the design inputs. Advisors/Committee Members: Peterson, Richard (advisor), Haapala, Karl (committee member).
Fisher, Luke W. "Single- and multi-functional arrayed microchannel fluidic devices." 2010. Masters Thesis, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/16516.
Fisher, Luke W. "Single- and multi-functional arrayed microchannel fluidic devices." 2010. Web. 18 Apr 2019.
Fisher LW. Single- and multi-functional arrayed microchannel fluidic devices. [Internet] [Masters thesis]. Oregon State University; 2010. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/16516.
3. Brannon, Samuel T. Half Array Architecture for Advancing Microchannel Heat Recuperation to Market.
▼ High temperature microchannel heat recuperators (HTμRs) offer an efficient means of improving reactor process thermal efficiency by offering smaller form factors due to increased heat transfer surface area density and volumetric heat transfer rate over traditional heat exchanger designs. To date, HTμRs face cost and reliability challenges. In this work, a HTμR design was developed capable of utilizing high volume manufacturing methods to improve raw material utilization and cost. The design utilizes a microchannel flow insert (MFI) to resist differential pressures within low pressure channels eliminating the need for photochemical machining. The MFIs are placed within a laser-welded microchannel half array which is inserted within a metal housing to establish the counter flow path. Analytical and computational models were developed to guide the structural, thermal and fluidic design of the sub-millimeter MFI for waste heat applications. A forming process was developed for producing the MFIs and experimental investigations were used to validate structural, thermal and fluidic performance. A robust microforming fabrication process was developed capable of providing average MFI heights of 529 μm with 0.5% standard deviation. MFIs were analyzed for out-of-plane compressive stiffness and compressive strength over multiple loading cycles to validate both analytical and finite element models. A finite element model provided a model error of 6.8% for compressive stiffness. The unbonded μPTN design presented yields an 88% decrease in structural panel size compared to macro-pyramidal truss networks for a given loading condition while maintaining similar panel area. Single layer fluid flow experiments were conducted to determine the average Nusselt number and pressure drop in microchannels both with and without an MFI installed. The MFI increased the average Nusselt number by 2.9x due to increased fluid mixing. The pressure drop through the MFI was found to be on average five times higher than the empty channel due to reduced flow cross-section area. The network pressure drop model yielded a percent error at low Reynolds numbers of 5.2%. Subsequently, a 3.5 kW HTμR made of Inconel 625 was designed for waste heat recovery with an inlet temperature of 850°C. A subscale HTμR was fabricated and tested to validate the 3.5 kW design. The sub-scale five layer HTμR was tested with a hot side inlet temperature of 300°C. The sub-scale device performed as expected in terms of effectiveness (4.3% error), duty (4.3% error), and MFI channel pressure drop (-2.6% error). These results were used to scale a 3.5 kW Inconel 625 HTμR with a heat transfer surface area density of 1,633 m²/m³, a volumetric heat transfer coefficient of 2.3 MW/(m³K), and a volumetric heat transfer rate of 32 MW/m³ providing improved results versus high temperature recuperator designs in literature. Advisors/Committee Members: Paul, Brian K. (advisor), Malhotra, Rajiv (committee member).
Brannon, Samuel T. "Half Array Architecture for Advancing Microchannel Heat Recuperation to Market." 2017. Doctoral Dissertation, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/60584.
Brannon, Samuel T. "Half Array Architecture for Advancing Microchannel Heat Recuperation to Market." 2017. Web. 18 Apr 2019.
Brannon ST. Half Array Architecture for Advancing Microchannel Heat Recuperation to Market. [Internet] [Doctoral dissertation]. Oregon State University; 2017. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/60584.
4. Asumpinpong, Kasidid. Development of a microchannel device for adsorption cooling application.
▼ Single-layer and three-layer microchannel adsorption devices were fabricated by procedure that was newly developed. Aluminum was chosen for metal housing while the adsorption pair was silica gel and water. Each adsorption layer contained two layers of 250 μm-thick silica gel. Both silica gel layers opened to the same layer of adsorption channels. The layers of air flow channels were placed between two adsorption layers, including over the top and below the bottom adsorption layers. Each layer of adsorption channels and air flow channels contained array of six microchannels. Each microchannel was 400 μm tall, 5.8 mm wide and 4.4 cm long. The device was bonded by B-staged epoxy thin film at moderate temperature of 120°C. The overall dimensions of the fabricated device were 5 cm x 5 cm x 10.2 mm for the three-layer device. A maximum coefficient of performance (COP) of 0.506 was achieved at the evaporator temperature of 22°C, adsorption temperature of 23°C and desorption temperature of 50°C. The highest specific cooling power (SCP) obtained was 601 W/kg silica gel when desorption temperature was increased to 70°C The overall performance of the device improved slightly when the air flow rate was increased. The COP increased by a factor of 2.4 when the number of adsorption layers increased from 1 to 3. The results from simulation model agreed with the experimental results and also showed that both COP and SCP decreased drastically when evaporator temperature was far below the adsorption temperature. Advisors/Committee Members: Rorrer, Gregory L. (advisor), Chang, Chih-hung (committee member).
Asumpinpong, Kasidid. "Development of a microchannel device for adsorption cooling application." 2009. Masters Thesis, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/10672.
Asumpinpong, Kasidid. "Development of a microchannel device for adsorption cooling application." 2009. Web. 18 Apr 2019.
Asumpinpong K. Development of a microchannel device for adsorption cooling application. [Internet] [Masters thesis]. Oregon State University; 2009. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/10672.
5. Aquino, Paul. Piezoelectric flexing and output voltage of a microchannel heat engine.
Aquino, Paul. "Piezoelectric flexing and output voltage of a microchannel heat engine." 2010. Thesis, University of Ontario Institute of Technology. Accessed April 18, 2019. http://hdl.handle.net/10155/117.
Aquino, Paul. "Piezoelectric flexing and output voltage of a microchannel heat engine." 2010. Web. 18 Apr 2019.
Aquino P. Piezoelectric flexing and output voltage of a microchannel heat engine. [Internet] [Thesis]. University of Ontario Institute of Technology; 2010. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/10155/117.
6. Burdette, Aaron J. Fabrication and Utilization of Microfluidic Devices to Study Mechanical Properties of BT-20 and Hs 578T Human Breast Cancer Cells.
▼ This study aimed to look for differences in observable measures that were related to the mechanical properties of two primary breast cancer cell lines: BT-20 and Hs 578T. Microfluidic channels were designed that mimicked the microvasculature, and cell entry time, morphology and transit velocity were measured. Understanding the differences in mechanical properties may give insight into the mechanisms that allow different types of cancer cells to leave the primary tumor and travel to secondary sites (metastasis). It was found that the two cell lines have different entry times, a measure that has been found to be related to membrane cortical stiffness, with Hs 578T cells having cortical stiffness that is smaller than that for BT-20 cells. When the size of the microchannels was decreased slightly, however, so that the Hs 578T cell nuclei were deformed but not the nuclei of BT-20 cells, the Hs 578T cells were found to have much longer entry times than BT-20 cells. These results demonstrated that there were differences in observed mechanical behaviors between the cell lines that could be diagnostic. It was also found that cell size affects the transit velocities of the cells, with larger cells having decreased velocities.To determine if there were difference in mechanical behaviors for sub-populations within the cell lines with different expression patterns of CD24/44, the cells were sorted based on their expression of those markers. After 12-18 passages, the cells drifted from4 their original sorted expression profiles, but differences in expression pattern were stillmeasurable with flow cytometry. No significant differences were seen for entry time or elongation index (EI), however a statistically significant difference was seen for transit velocities, demonstrating a possible connection between CD24/44 expression and velocity through the channels. Advisors/Committee Members: Tees, David (Committee Chair).
Burdette, Aaron J. "Fabrication and Utilization of Microfluidic Devices to Study Mechanical Properties of BT-20 and Hs 578T Human Breast Cancer Cells." 2014. Masters Thesis, Ohio University. Accessed April 18, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1408624952.
Burdette, Aaron J. "Fabrication and Utilization of Microfluidic Devices to Study Mechanical Properties of BT-20 and Hs 578T Human Breast Cancer Cells." 2014. Web. 18 Apr 2019.
Burdette AJ. Fabrication and Utilization of Microfluidic Devices to Study Mechanical Properties of BT-20 and Hs 578T Human Breast Cancer Cells. [Internet] [Masters thesis]. Ohio University; 2014. [cited 2019 Apr 18]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1408624952.
7. Lin, Chih-Yi. Flow Visualization and Velocity Measurements in a Liquid Microchannel.
▼ A microparticle image velocimetry (MPIV) system has been used to measure streamwise and spanwise velocity fields along a 100 Ã200 Ã20 mm microchannel with a hydraulic diameter of 133.3 at 10â¦Reâ¦421.4. The measuring technique uses 1 diameter orange fluorescent polystyrene flow tracing particles, a pulsed Nd: YAG double resonant tube laser with a micro electroscope, and a high resolution CCD camera to record particle-image fields. Local velocity profiles as flow proceeds downstream were measured at particular positions to examine the entrance effect and hydrodynamically fully developed length as well as velocity slip at wall for liquid flow in a microchannel. Velocity slip exists with a considerable value over the entire range of Re under study. Moreover, the friction factors were calculated and compared with those of previous study. Good agreement was found which also assesses the accuracy of the present results. Advisors/Committee Members: S.S.Hsieh (committee member), C.C.Su (chair), C.J.Ho (chair).
Lin, Chih-Yi. "Flow Visualization and Velocity Measurements in a Liquid Microchannel." 2004. Thesis, NSYSU. Accessed April 18, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0712104-105102.
Lin, Chih-Yi. "Flow Visualization and Velocity Measurements in a Liquid Microchannel." 2004. Web. 18 Apr 2019.
Lin C. Flow Visualization and Velocity Measurements in a Liquid Microchannel. [Internet] [Thesis]. NSYSU; 2004. [cited 2019 Apr 18]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0712104-105102.
8. Patton, Chris. Clearing bubble blockages in micro channels using a model predictive controller.
▼ Micro scale systems are being utilized in a wide variety of chemical, biological and heat exchanger applications, but suffer from the development of vapor bubbles inside the microchannels due to convective boiling, leading to decreases in system performance. In this work, a simulation-based control strategy is employed to eliminate flow maldistribution in parallel microchannels. System identification techniques are utilized to produce a reduced-order, input-output model that captures the essential dynamics of the full nonlinear flow, in terms of a relationship between the valve angles and the exit flow rate for each channel. The resulting linear model is subsequently incorporated into a model predictive control scheme to identify flow maldistribution from exit flow velocities and prescribe actuation of the channel valves to clear blockages and effectively redistribute the flow. Computational fluid dynamics simulations of a microchannel geometry consisting of three channels with controllable valves was used to investigate both the predictive performance of the reduced order model as well as the ability of the controller to clear bubble disturbances. Flow simulations illustrated the effectiveness of the control design, which quickly and efficiently varied channel valves to clear a single bubble from the channel and equalize flow rates. While the controller was successful in regulating flow and dealing with single bubble disturbances, future work is required in effectively handling blockages in multiple channels simultaneously. Advisors/Committee Members: Schmitt, John (advisor), Tumer, Kagan (committee member).
Patton, Chris. "Clearing bubble blockages in micro channels using a model predictive controller." 2009. Masters Thesis, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/12929.
Patton, Chris. "Clearing bubble blockages in micro channels using a model predictive controller." 2009. Web. 18 Apr 2019.
Patton C. Clearing bubble blockages in micro channels using a model predictive controller. [Internet] [Masters thesis]. Oregon State University; 2009. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/12929.
9. Eluri, Ravindranadh T. Nanoparticle-assisted diffusion brazing of metal microchannel arrays : nanoparticle synthesis, deposition, and characterization.
▼ Microchannel process technology (MPT) offers several advantages to the field of nanomanufacturing: 1) improved process control over very short time intervals owing to shorter diffusional distances; and 2) reduced reactor size due to high surface area to volume ratios and enhanced heat and mass transfer. The objective of this thesis was to consider how nanomaterials, produced in part using MPT, could be used to solve problems associated with the fabrication of MPT devices. Specifically, many MPT devices are produced using transient liquid-phase brazing involving an electroplated interlayer consisting of a brazing alloy designed for melting temperature suppression. Unfortunately, these alloys can form brittle secondary phases which significantly reduce bond strength. In contrast, prior efforts have shown that it is possible to leverage the size-dependent properties of nanomaterials to suppress brazing temperatures. In this prior work, thin films of off-the-shelf elemental nanoparticles were used as interlayers yielding joints with improved mechanical properties. In the present investigation, efforts have been made to characterize the synthesis and deposition of various elemental nanoparticle suspensions for use in the transient liquid-phase brazing of aluminum and stainless steel. Advances were used to demonstrate the nanoparticle-assisted diffusion brazing of a microchannel array. In the first section, a silver nanoparticle (AgNP) interlayer was produced for the diffusion brazing of heat exchanger aluminum. Efforts are made to examine the effect of braze filler particle size (~5 nm and ~50 nm) and processing parameters (heating rate: 5ºC/min and 25ºC/min; brazing temperature: 550ºC and 570ºC) on thin coupons of diffusion-brazed 3003 Al. A tensile strength of 69.7 MPa was achieved for a sample brazed at 570°C for 30 min under 1 MPa with an interlayer thickness of approximately 7 μm. Further suppression of the brazing temperature to 500ºC was achieved by sputtering a 1 µm thick layer of Cu before depositing a 5 nm thick film of AgNPs resulting in a lap shear strength of 45.3±0.2 MPa. In the middle section of this thesis, several techniques are investigated for the synthesis of sub 10 nm diameter nickel nanoparticles (NiNPs) to be used in the diffusion brazing of 316L stainless steel. The average NiNP size was varied from 9.2 nm to 3.9 nm based on the synthesis technique, solvent and reducing agent used. Conventional wet-chemical synthesis using NiCl₂.6H₂O in ethylene glycol (solvent) and N₂H₄.H₂O (reducing agent) resulted in the formation of 5.4 ± 0.9 nm NiNPs. Continuous flow synthesis using a microchannel T-mixer (barrel diameter of 521µm) and a 10 second residence time of reactants in a bath temperature of 130ºC resulted in a particle size of with 5.3 ± 1 nm. To make the synthesis safer and less energy intense, microwave heating was used along with less toxic Ni(CH₃CO₂)₂·4H₂O (nickel salt), propylene glycol (solvent) and NaPH₂O₂ (reducing agent) yielding 3.9 ± 0.8 nm diameter NiNPs. For the final… Advisors/Committee Members: Paul, Brian K. (advisor), Haapala, Karl R. (committee member).
Eluri, Ravindranadh T. "Nanoparticle-assisted diffusion brazing of metal microchannel arrays : nanoparticle synthesis, deposition, and characterization." 2012. Doctoral Dissertation, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/28651.
Eluri, Ravindranadh T. "Nanoparticle-assisted diffusion brazing of metal microchannel arrays : nanoparticle synthesis, deposition, and characterization." 2012. Web. 18 Apr 2019.
Eluri RT. Nanoparticle-assisted diffusion brazing of metal microchannel arrays : nanoparticle synthesis, deposition, and characterization. [Internet] [Doctoral dissertation]. Oregon State University; 2012. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/28651.
10. Kwak, Younghoon. Experimental study of two-phase gas-liquid flow in a microscale fractal-like branching flow network.
▼ Two-phase gas-liquid flows in microscale fractal-like branching channel flow networks were experimentally studied to assess the validity of existing void fraction correlations and flow regimes based on superficial gas and liquid velocities. Void fractions were assessed using two different methods. First, void fraction data were acquired using a High-Speed-High-Resolution (HSHR) camera and computed by area-based two-dimensional image analysis. Void fraction data were also computed using a slip ratio, defined as gas velocity over liquid velocity. Liquid velocity represents the bulk-averaged liquid velocity as determined by microscale particle image velocimetry (micro-PIV). Gas velocity was determined by averaging gas-liquid interface velocities made at the channel centerline. The fractal-like branching channel flow network has five bifurcation levels of different channel widths varying from 400 µm to 100 µm with a fixed channel depth of 250 µm. Each downstream width decreases by 30% whereas the downstream lengths increase by 40%. The total flow length through a single path is approximately 18 mm. Filtered air and deionized water were used as the gas and liquid working fluids, respectively. Mass flow rates of air and water into each k=0 branch were varied from 0.3 g/min to 2.5 g/min and from 5.2x10⁻⁵ g/min to 1.3x10⁻² g/min, respectively. These flow rates yielded superficial air and water velocities through the same branch level between 0.007 m/s and 1.8 m/s and between 0.05 m/s and 0.42 m/s, respectively. For each branching level, due to an increase in flow area, the superficial liquid and gas flow rates change. A two-phase flow regime map was generated for each level of the fractal-like branching flow network and compared to maps developed using the Taitel and Dukler (1976) model and to maps presented in Chung and Kawaji (2004). Flow regime transitions are well predicted with the Taitel and Dukler (1976) model for each branching level. Void fraction assessed using the slip ratio shows very good agreement with the homogeneous void fraction model for all branching levels. On the other hand, void fraction determined by area-based two-dimensional image analysis shows better agreement with the void fraction correlation of Zivi (1964). Advisors/Committee Members: Pence, Deborah V. (advisor), Narayanan, Vinod (committee member).
Kwak, Younghoon. "Experimental study of two-phase gas-liquid flow in a microscale fractal-like branching flow network." 2008. Doctoral Dissertation, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/9049.
Kwak, Younghoon. "Experimental study of two-phase gas-liquid flow in a microscale fractal-like branching flow network." 2008. Web. 18 Apr 2019.
Kwak Y. Experimental study of two-phase gas-liquid flow in a microscale fractal-like branching flow network. [Internet] [Doctoral dissertation]. Oregon State University; 2008. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/9049.
11. Simon, Saumya Susan. Simulation of the Flow of a Single Stranded Dna in a Channel Using Dissipative Particle Dynamics.
▼ Separation of DNA has significant importance in understanding the genome of an organism for genetic engineering and DNA profiling for forensics. The purpose of the study was to simulate a system containing solvent and DNA particles through a pressure-driven two-dimensional microchannel using Dissipative Particle Dynamics. This computational fluid method is simulated in Matlab using the modified velocity-Verlet algorithm. The computational method DPD was modified and the simulated channel flow was compared to the theoretical flow between two-dimensional parallel plates. The boundary conditions include both solid `frozen' particle walls and periodic boundary conditions. The DNA particles are then inserted into the channel to understand their physical properties as they migrate through a pressure-driven channel. Their extension due to stretching and folding is studied to understand the relaxation time of the DNA strand in the channel for a set of varied conditions. no-slip boundary region was altered to enforce the wall boundary conditions and to prevent the wall penetration by DPD fluid particles. The modified DPD weighting functions resolve the low Schmidt number and low viscosity typical of DPD and increase particle interaction between DPD fluid particles. However, this modification cannot be performed when simulating DNA particles as worm-like chain models as they do not generate accurate physical properties of DNA particles. The extensions of the DNA strands are simulated under the influence of different external forces and the relaxation time was reported.
Simon, Saumya Susan. "Simulation of the Flow of a Single Stranded Dna in a Channel Using Dissipative Particle Dynamics." 2011. Thesis, Oklahoma State University. Accessed April 18, 2019. http://hdl.handle.net/11244/10064.
Simon, Saumya Susan. "Simulation of the Flow of a Single Stranded Dna in a Channel Using Dissipative Particle Dynamics." 2011. Web. 18 Apr 2019.
Simon SS. Simulation of the Flow of a Single Stranded Dna in a Channel Using Dissipative Particle Dynamics. [Internet] [Thesis]. Oklahoma State University; 2011. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/11244/10064.
12. Sinclair, Alexander. Steady and oscillatory flow in the entrance region of microchannels.
▼ The entrance region of a fluid channel is where the velocity distribution changes substantially from its initial condition at the entrance to that of fully developed flow. This region is particularly influential in microchannels as it may be a substantial portion of the total channel length, meaning that pressure drop and heat transfer are significantly different than for fully developed flow. Despite the fact that much work has been done on the development of steady flow, no reliable correlations exist for low Reynolds (Re) number flows in rectangular channels, and there is even less data available for oscillatory flows. It follows that a greater understanding of flow development would aid in the design of devices using microchannels in particular, since they involve low Reynolds numbers and are often oscillatory.In this study a microfluidic device was developed to generate controllable oscillatory flow together with a modular interface system to allow a reliable connection to a syringe pump so as to generate steady and pulsatile flows. The flow of de-ionised water from a large planar plenum into a square channel, nominally 50 by 50 micrometres, was studied under steady, oscillatory and pulsatile flow conditions. Time and phase averaged velocity fields were measured using micro-Particle Image Velocimetry.Steady flow was studied in the entrance region of the microchannel for Reynolds numbers, 1<Re<60. Entrance lengths were calculated from the measured centerline velocities. The expected non-linear relationship between entrance length with Re, for low Reynolds numbers was found, and the flow was shown to develop much faster than predicted by existing correlations due to the planar entry. An entrance length correlation is proposed for steady flow under these conditions.Oscillatory flow (zero net flow) was examined with Stokes number, S, <2.45. Time varying entrance lengths were calculated and these varied significantly over an oscillation cycle. Pulsatile flow (a mean flow superimposed on the oscillatory flow) for S=2.45 was examined for a range of oscillatory to steady flow ratios, 0.9<A<3.73. The entrance length was found to vary in time about the steady flow value. For both oscillatory and pulsatile conditions, the maximum entrance length was accurately described by the proposed steady flow correlation for entrance length, based on Re at peak flow. These results represent the first systematic experimental study into oscillatory entrance flows. Advisors/Committee Members: Rosengarten, Gary, RMIT, Timchenko, Victoria, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW.
Sinclair, Alexander. "Steady and oscillatory flow in the entrance region of microchannels." 2012. Doctoral Dissertation, University of New South Wales. Accessed April 18, 2019. http://handle.unsw.edu.au/1959.4/51801 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:10468/SOURCE02?view=true.
Sinclair, Alexander. "Steady and oscillatory flow in the entrance region of microchannels." 2012. Web. 18 Apr 2019.
Sinclair A. Steady and oscillatory flow in the entrance region of microchannels. [Internet] [Doctoral dissertation]. University of New South Wales; 2012. [cited 2019 Apr 18]. Available from: http://handle.unsw.edu.au/1959.4/51801 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:10468/SOURCE02?view=true.
13. Li, Huize. Periodic reverse flow in microchannel evaporators.
▼ Periodic flow reversal which is associated with boiling instabilities is a very commonly seen phenomenon in small scale heat removal applications, for instance, microchannel heat sinks for cooling of electronics. Due to the industry's strict requirement for thermal stability, previous research on flow instabilities in microchannels has been largely focused on heat sinks for electronic cooling. There is a lack of understanding of the effect of flow reversal in microchannel heat exchangers, which are used in air conditioning and refrigeration applications. This thesis first presents the visualization of flow reversal in a microchannel as part of a realistic automotive evaporator. The flow regimes inside of the microchannel are recorded under both two phase feeding and liquid only feeding modes. In the two-phase feeding mode, churn, bubbly/slug, and annular flows occur alternatively, but the period of each flow regime is not constant. Flow reversal is only witnessed occasionally in the bubbly/slug flow regime. In the liquid feeding mode, only liquid and bubbly/slug flows are observed. Reverse flow occurs periodically. The duration of flow reversal is much shorter in the two-phase feeding mode than in the liquid feeding mode. Most likely it is due to higher upstream resistance caused by two-phase refrigerant feeding. After confirming the existence of flow reversal in microchannel heat exchangers which are used in air conditioning applications, this thesis presents a newly developed mechanistic model of bubble dynamics in a single microchannel, which demonstrates how flow reversal is generated. The comparison between high-speed visualization of in-channel flow regimes and simulation results shows that this model is capable of capturing the transient flow regime and slug velocity inside of a single microchannel and predicting flow reversal. The model quantitatively demonstrates the mechanism of flow reversal. Within one periodic cycle, the evolution of flow regime, pressure distribution along channel length and mass flux at tube inlet are well correlated with each other. The local pressure peak caused by the build-up of downstream flow resistance can cause a positive pressure gradient, which induces flow reversal. In the third part of the thesis, the effects of channel geometries on flow reversal are presented. Multiple evaporators with different geometries are tested using R134a as the refrigerant. In each evaporator, the reversed vapor flow is vented out of the inlet header and the flow rate is measured. It has been found experimentally that under the same heat flux, superheat and channel length, the microchannel evaporator with smaller diameter generates more reversed vapor flow (per unit mass flow rate of supplied liquid refrigerant) at a higher frequency. A simulation generated by the aforementioned mechanistic model under the same condition demonstrates that smaller diameter creates more rapid growth of vapor slugs and allocates more flow resistance to the downstream section. As a result, the incoming flow… Advisors/Committee Members: Hrnjak, Predrag S (advisor), Hrnjak, Predrag S (Committee Chair), Jacobi, Anthony M (committee member), Elbel, Stefan (committee member), Dutton, J Craig (committee member), Col, Davide Del (committee member).
Li, Huize. "Periodic reverse flow in microchannel evaporators." 2017. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed April 18, 2019. http://hdl.handle.net/2142/97406.
Li, Huize. "Periodic reverse flow in microchannel evaporators." 2017. Web. 18 Apr 2019.
Li H. Periodic reverse flow in microchannel evaporators. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2017. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/2142/97406.
14. Kalani, Ankit. Experimental investigation of pool boiling performance with ethanol and fc-87 on open microchannel surfaces.
▼ The growing trend in miniaturization of electronics has generated a need for efficient thermal management of these devices. Boiling has the ability to dissipate large quantity of heat while maintaining a small temperature difference. Vapor chamber with pool boiling offers an effective way to provide cooling and maintaining temperature uniformity. The objective of the current work is to investigate pool boiling performance of ethanol and FC - 87 on microchannel surfaces. Ethanol is an attractive working fluid due to its better heat transfer performance and higher heat of vaporization compared to refrigerants, and lower boiling point compared to water. The saturation temperature of ethanol can be further reduced to temperatures suitable for electronics cooling by lowering the system pressure. Fluorocarbons are considered to be ideal fluids for electronics cooling due to their low normal boiling point, dielectric and inert nature. FC - 87 is selected for the current work. Ethanol is tested at four different absolute pressures, 101.3 kPa, 66.7 kPa, 33.3 kPa and 16.7 kPa using different microchannel surface configurations. Heat dissipation in excess of 900 kW/m2 was obtained while maintaining the wall surface below 85 °C at 33 kPa. Flammability, toxicity and temperature overshoot issues need to be addressed before practical implementation of ethanol-based cooling systems in electronics cooling application. FC - 87 with microchannel yields average performance when compared to literature. Effect of surface area is identified as the key reason for performance enhancement. A new finned structure is developed, which gave a heat flux value 1.25 MW/m2 at 40 °C wall superheat for FC - 87 at atmospheric conditions. Advisors/Committee Members: Kandlikar, Satish.
Kalani, Ankit. "Experimental investigation of pool boiling performance with ethanol and fc-87 on open microchannel surfaces." 2012. Thesis, Rochester Institute of Technology. Accessed April 18, 2019. https://scholarworks.rit.edu/theses/5898.
Kalani, Ankit. "Experimental investigation of pool boiling performance with ethanol and fc-87 on open microchannel surfaces." 2012. Web. 18 Apr 2019.
Kalani A. Experimental investigation of pool boiling performance with ethanol and fc-87 on open microchannel surfaces. [Internet] [Thesis]. Rochester Institute of Technology; 2012. [cited 2019 Apr 18]. Available from: https://scholarworks.rit.edu/theses/5898.
15. Bazargan, Vahid. Micro flow control using thermally responsive polymer solutions .
▼ Microfluidics refers to devices and methods for controlling and manipulating fluid flows at length scales less than a millimeter. Miniaturization of a laboratory to a small device, usually termed as lab-on-a-chip, is an advanced technology that integrates a microfluidic system including channels, mixers, reservoirs, pumps and valves on a micro scale chip and can manipulate very small sample volumes of fluids. While several flow control concepts for microfluidic devices have been developed to date, here flow control concepts based on thermally responsive polymer solutions are presented. In particular, flow control concepts base on the thermally triggered reversible phase change of aqueous solutions of the polymer Pluronic will be discussed. Selective heating of small regions of microfluidic channels, which leads to localized gel formation in these channels and reversible channel blockage, will be used to control a membrane valve that controls flow in a separate channel. This new technology will allow generating inexpensive portable bioanalysis tools where microvalve actuation occurs simply through heaters at a constant pressure source without a need for large external pressure control systems as is currently the case. Furthermore, a concept for controlled cross-channel transport of particles and potentially cells is presented that relies on the continuous regeneration of a gel wall at the diffusive interface of two co-streaming fluids in a microfluidic channel.
Bazargan, Vahid. "Micro flow control using thermally responsive polymer solutions ." 2008. Thesis, University of British Columbia. Accessed April 18, 2019. http://hdl.handle.net/2429/2638.
Bazargan, Vahid. "Micro flow control using thermally responsive polymer solutions ." 2008. Web. 18 Apr 2019.
Bazargan V. Micro flow control using thermally responsive polymer solutions . [Internet] [Thesis]. University of British Columbia; 2008. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/2429/2638.
16. Odukoya, Adedoyin. Fluid transport and entropy production in electrochemical and microchannel droplet flows.
▼ The growth of energy demand in the world requires addressing the increasing power requirements of industrial and residential consumers. Optimizing the design of new and existing large power producing systems can efficiently increase energy supply to meet the growing demand. Hydrogen as an energy carrier is a promising sustainable way to meet the growing energy demand, while protecting the environment. This thesis investigates the efficient production of hydrogen from the electrolysis of copper chloride, by predicting entropy production as a result of diffusive mass transfer. Also, this thesis investigates the possibility of producing electrical energy from waste heat produced by industrial or other sources. The thermocapillary motion of fluid droplet in a closed rectangular microchannel is used to generate electrical energy from waste heat in a piezoelectric membrane by inducing mechanical deformation as a result of the droplet motion. Modeling, fabrication, and experimental measurement of a micro heat engine (MHE) are investigated in this study. Analytical and experimental results are reported for both circular and rectangular microchannels. A novel fabrication technique using lead zirconate titanate (PZT) as substrate in microfluidic application is presented in this study. This thesis develops a predictive model of the entropy production due to thermal and fluid irreversibilities in the microchannel. Thermocapillary pressure and friction forces are modelled within the droplet, as well as surface tension hysteresis during start-up of the droplet motion. A new analytical model is presented to predict the effect of transient velocity on the voltage production in the MHE. In order to predict the effect of the applied stress on voltage, the different layers of deposition are considered for thin film laminates. The highest efficiency of the system from simulated taking into iv account the electromechanical coupling factor is about 1.6% with a maximum voltage of 1.25mV for the range of displacement considered in this study. In addition, new experimental and analytical results are presented for evaporation and de-pinning of deionised water and toluene droplets in rectangular microchannels fabricated from Su-8 2025 and 2075. Advisors/Committee Members: Naterer, Greg F..
Odukoya, Adedoyin. "Fluid transport and entropy production in electrochemical and microchannel droplet flows." 2012. Thesis, University of Ontario Institute of Technology. Accessed April 18, 2019. http://hdl.handle.net/10155/236.
Odukoya, Adedoyin. "Fluid transport and entropy production in electrochemical and microchannel droplet flows." 2012. Web. 18 Apr 2019.
Odukoya A. Fluid transport and entropy production in electrochemical and microchannel droplet flows. [Internet] [Thesis]. University of Ontario Institute of Technology; 2012. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/10155/236.
17. Higgins, Peter Webb. Micro channel cooler performance improvement by insonation.
▼ The motivation for this work is the need to remove waste heat from laser diodes and high speed transistors in processes which are exponentially increasing past 1 kW/cm2 as anticipated by Moore's Law. The hypothesis guiding the work is that ultrasonic insonation of micro coolers employed to dissipate these heat loads can improve heat removal. It is thought that the mechanism promoting the benefit is enhancement of the ability of the coolant to remove latent heat in two-phase operation by managing entrained bubble size near the cooler's exit so as to forestall flow reduction or blockage caused by large bubbles, wedges and slugs accumulating there. Insonation experiments to prove the hypothesis have been done on several micro channel coolers in the range 4-80 kHz to quantify improvement in heat flux removal. In order to understand how insonation would produce benefit in heat removal, a research effort was undertaken to study the affect of 5-30 Pa acoustic fields on air bubbles rising in small aquariums. This involved developing a Faraday cage shielded acoustic probe, along with a force-beam calibration tool, for measuring field levels near a strongly electromagnetic-radiating ultrasonic source. Experiments were conducted on columns of pseudo monodisperse, sub-millimeter diameter air bubbles in water, and other fluids using bubble generators optimized for this purpose. A numerical analysis model based on energy balance of the acoustic work done on a bubble resulted in predicting mass transfer flux, and in quantifying bubble shrinkage and growth when irradiated on either side of its resonance. The model, and experiments show that bubble populations can be predictably altered by ultrasound. The research was concluded by identifying and quantifying micro channel cooler performance change when insonated in the range 4-80 kHz. It was discovered that 28 and 58 kHz radiation of exchangers having hydraulic diameters spanning 0.02 to 0.6 mm could produce heat flux removal improvements of 5 W/cm2 in devices normally removing less than 30 W/cm2, a factor of 17%. Peak thermal resistance improvement approaching 60 % has been observed. Advisors/Committee Members: Corinne S. Lengsfeld, Phillip Danielson.
Higgins, Peter Webb. "Micro channel cooler performance improvement by insonation." 2012. Doctoral Dissertation, U of Denver. Accessed April 18, 2019. https://digitalcommons.du.edu/etd/825.
Higgins, Peter Webb. "Micro channel cooler performance improvement by insonation." 2012. Web. 18 Apr 2019.
Higgins PW. Micro channel cooler performance improvement by insonation. [Internet] [Doctoral dissertation]. U of Denver; 2012. [cited 2019 Apr 18]. Available from: https://digitalcommons.du.edu/etd/825.
18. Torgerson, Daniel Eric. Microscale loss coefficients through expansion and contraction xurographic microchannels.
▼ Xurography is a novel manufacturing process for microfluidic systems, providing rapid prototyping capability at low cost compared to traditional microfabrication technologies. An experimental study of flow characteristics in rectangular xurographic microchannels is reported. Mean microchannel depth, defined by the thickness of the double-sided adhesive kapton tape that forms the channel pattern, is ~110 ?m. The microchannels are capped with glass and mechanically reinforced to withstand the high operating pressures that accompany high Reynolds number Re flow (250 – 3500). Channel aspect ratios range from 0.45 to 0.074. Width and length measurements are performed using optical microscopy. Microchannel height is measured using a unique nondestructive laser interferometry technique, capable of accurate measurement of the enclosed, compressed microchannels. Data are reported for friction factor, critical Reynolds number, and minor losses in expansions and contractions. Expansion and contraction area ratios are 2, 3, and 5. The experimental Poissuille number in laminar flow for all aspect ratios is in good agreement with theoretical values.
Torgerson, Daniel Eric. "Microscale loss coefficients through expansion and contraction xurographic microchannels." 2010. Masters Thesis, University of Utah. Accessed April 18, 2019. http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/914/rec/770.
Torgerson, Daniel Eric. "Microscale loss coefficients through expansion and contraction xurographic microchannels." 2010. Web. 18 Apr 2019.
Torgerson DE. Microscale loss coefficients through expansion and contraction xurographic microchannels. [Internet] [Masters thesis]. University of Utah; 2010. [cited 2019 Apr 18]. Available from: http://content.lib.utah.edu/cdm/singleitem/collection/etd2/id/914/rec/770.
19. Yu, Jiwon 1982-. Experimental Investigation of Forced Convection Heat Transfer of Nanofluids in a Microchannel using Temperature Nanosensors.
▼ Experiments were performed to study forced convective heat transfer of de-ionized water (DI water) and aqueous nanofluids flowing in a microchannel. An array of temperature nanosensors, called ?Thin Film Thermocouples (TFT)?, was utilized for performing the experimental measurements. TFT arrays were designed (which included design of photomask layout), microfabricated, packaged and assembled for testing with the experimental apparatus. Heat removal rates from the heated surface to the different testing fluids were measured by varying the coolant flow rates, wall temperatures, nanoparticle material, nanoparticle morphology (shape and nanoparticle size) as well as mass concentrations of nanoparticles in the coolants. Anomalous thermal behavior was observed in the forced convective heat transfer experiments. Precipitation of the nanoparticles on the heat exchanging surface was monitored using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray spectroscopy (EDX). Isolated precipitation of nanoparticles is expected to cause formation of ?nanofins? leading to enhancement of surface area and thus resulting in enhanced convective heat transfer to the nanofluid coolants. However, excessive precipitation (caused due to the agglomeration of the nanoparticles in the nanofluid coolant) causes scaling (fouling) of the heat exchanging surfaces and thus results in degradation of convective heat transfer. This study shows that the surface morphology plays a crucial role in determining the efficacy of convective heat transfer involving suspensions of nanoparticles in coolants (or nanofluids). Flow visualization and quantitative estimation of near-wall temperature profiles were performed using quantum dots and fluorescent dyes. This non-contact measurement technique for temperature and flow profiles in microchannels using quantum dots is expected to make pioneering contribution to the field of experimental flow visualization and to the study of micro/nano-scale heat transfer phenomena, particularly for forced convective heat transfer of various coolants, including nanofluids. Logical extensions of this study were explored and future directions were proposed. Preliminary experiments to demonstrate feasibility showed significant enhancement in the flow boiling heat flux values for nanofluids compared to that of pure solvent (DIW). Based on the novel phenomena observed in this study several other topics for future research were suggested, such as, using Surface Plasmon Resonance (SPR) platforms to monitor precipitation of nanoparticles on microchannel surfaces in real time (e.g., for generating surface isotherms). Advisors/Committee Members: Banerjee, Debjyoti (advisor), Annamalai, Kalyan (committee member), Datta-Gupta, Akhil (committee member), Mukherjee, Partha (committee member).
Yu, Jiwon 1982-. "Experimental Investigation of Forced Convection Heat Transfer of Nanofluids in a Microchannel using Temperature Nanosensors." 2012. Thesis, Texas A&M University. Accessed April 18, 2019. http://hdl.handle.net/1969.1/148235.
Yu, Jiwon 1982-. "Experimental Investigation of Forced Convection Heat Transfer of Nanofluids in a Microchannel using Temperature Nanosensors." 2012. Web. 18 Apr 2019.
Yu J1. Experimental Investigation of Forced Convection Heat Transfer of Nanofluids in a Microchannel using Temperature Nanosensors. [Internet] [Thesis]. Texas A&M University; 2012. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1969.1/148235.
20. Penniall, Christopher Leigh. Fischer-Tropsch Based Biomass to Liquid Fuel Plants in the New Zealand Wood Processing Industry Based on Microchannel Reactor Technology.
Penniall, Christopher Leigh. "Fischer-Tropsch Based Biomass to Liquid Fuel Plants in the New Zealand Wood Processing Industry Based on Microchannel Reactor Technology." 2013. Thesis, University of Canterbury. Accessed April 18, 2019. http://hdl.handle.net/10092/7884.
Penniall, Christopher Leigh. "Fischer-Tropsch Based Biomass to Liquid Fuel Plants in the New Zealand Wood Processing Industry Based on Microchannel Reactor Technology." 2013. Web. 18 Apr 2019.
Penniall CL. Fischer-Tropsch Based Biomass to Liquid Fuel Plants in the New Zealand Wood Processing Industry Based on Microchannel Reactor Technology. [Internet] [Thesis]. University of Canterbury; 2013. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/10092/7884.
21. Tunuguntla, Sri Priyanka. Numerical Study of Thermal Performance of Two-Layered Microchannel Heat Sink with Nanofluids For Cooling of Microelectronics.
▼ Liquid cooling technology is necessary to meet the ever-increasing thermal challenges in the field of microelectronics cooling. In liquid-cooling systems, flow through microchannel heat sinks provide high performance and compact cooling, but have a high pressure drop penalty. To address this issue, multi-layered/stacked microchannels have been proposed in the literature. Further, increase in cooling performance of multi-layered microchannels can be achieved using coolants such as nanofluids, having high thermal properties. In the present study, a finite-volume numerical code with SIMPLE algorithm was used to solve the flow and energy equations, to analyze the thermal performance of a two-layered microchannel with pure water as well as CuO-water nanofluid. Flow rates between from 50ml/min and 320ml/min were considered to study the effect of varyingow rate on the thermal performance. Also, different volume fractions of nanoparticles are considered to investigate their effect on the thermal performance. The results show that nanofluids enhance the thermal performance, but the increase is not substantial. Also, the effect of channel geometry on the thermal performance of the two-layered microchannel heat sink has been investigated at two constraints, namely, fixed flow rate and fixed pumping power. The results show that the channel height, channel width and fin width have a significant effect on the thermal performance according to the flow constraints applied. Based on the parametric study, an optimization is carried out to obtain minimal thermal resistance, taking into account realistic constraint of fixed pumping power. Optimal channel dimensions were found for a range of power values between 0.01W-0.8W, which is the current micropumping power range. The minimal thermal resistance is found to be, is 0:09K/W/cm2 with 4% CuO-water nanouid and at pumping power of 0.8W. The results demonstrate that nanouids do not appreciably enhance the thermal performance of two-layered microchannel heat sink. Advisors/Committee Members: Ghia, Urmila (Committee Chair).
Tunuguntla, Sri Priyanka. "Numerical Study of Thermal Performance of Two-Layered Microchannel Heat Sink with Nanofluids For Cooling of Microelectronics." 2011. Masters Thesis, University of Cincinnati. Accessed April 18, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307442807.
Tunuguntla, Sri Priyanka. "Numerical Study of Thermal Performance of Two-Layered Microchannel Heat Sink with Nanofluids For Cooling of Microelectronics." 2011. Web. 18 Apr 2019.
Tunuguntla SP. Numerical Study of Thermal Performance of Two-Layered Microchannel Heat Sink with Nanofluids For Cooling of Microelectronics. [Internet] [Masters thesis]. University of Cincinnati; 2011. [cited 2019 Apr 18]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307442807.
22. Zandi, Matthew A. Single Position Focusing of Cells in a Microchannel System.
▼ The ability to focus and separate cells is invaluable in the area of cellular research. Inertial microfluidics uses the intrinsic physical properties of cells for manipulation and separation. Previous microfluidic devices use external controls in order to achieve focusing of cells into a single position. In this thesis we have examined a microfluidic device that exhibits inertial lift force as the only control to manipulate cells into a single position. We demonstrated that this device could handle variation of cell size and still achieve high efficiency and throughput. The device was verified for efficiency, throughput, recovery, and cell viability. The efficiency was reported at 99%, the throughput was reported at 850 cells per second, the recovery was reported at 99% and the cell viability were shown by incubation post device run. The simplified device offers many advantages over current methods, due to the simplified geometry, the ability for modification, and the flexibility in sample size variation. Advisors/Committee Members: Ho, Chia Chi (Committee Chair).
Zandi, Matthew A. "Single Position Focusing of Cells in a Microchannel System." 2015. Masters Thesis, University of Cincinnati. Accessed April 18, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428066046.
Zandi, Matthew A. "Single Position Focusing of Cells in a Microchannel System." 2015. Web. 18 Apr 2019.
Zandi MA. Single Position Focusing of Cells in a Microchannel System. [Internet] [Masters thesis]. University of Cincinnati; 2015. [cited 2019 Apr 18]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428066046.
23. Yordanov, Stoyan. Total internal reflection fluorescence cross-correlation spectroscopy: theory and application for studying boundary slip phenomenon.
I present a new experimental method called Total Internal Reflection Fluorescence Cross-Correlation Spectroscopy (TIR-FCCS). It is a method that can probe hydrodynamic flows near solid surfaces, on length scales of tens of nanometres. Fluorescent tracers flowing with the liquid are excited by evanescent light, produced by epi-illumination through the periphery of a high NA oil-immersion objective. Due to the fast decay of the evanescent wave, fluorescence only occurs for tracers in the ~100 nm proximity of the surface, thus resulting in very high normal resolution. The time-resolved fluorescence intensity signals from two laterally shifted (in flow direction) observation volumes, created by two confocal pinholes are independently measured and recorded. The cross-correlation of these signals provides important information for the tracers' motion and thus their flow velocity. Due to the high sensitivity of the method, fluorescent species with different size, down to single dye molecules can be used as tracers. The aim of my work was to build an experimental setup for TIR-FCCS and use it to experimentally measure the shear rate and slip length of water flowing on hydrophilic and hydrophobic surfaces. However, in order to extract these parameters from the measured correlation curves a quantitative data analysis is needed. This is not straightforward task due to the complexity of the problem, which makes the derivation of analytical expressions for the correlation functions needed to fit the experimental data, impossible. Therefore in order to process and interpret the experimental results I also describe a new numerical method of data analysis of the acquired auto- and cross-correlation curves – Brownian Dynamics techniques are used to produce simulated auto- and cross-correlation functions and to fit the corresponding experimental data. I show how to combine detailed and fairly realistic theoretical modelling of the phenomena with accurate measurements of the correlation functions, in order to establish a fully quantitative method to retrieve the flow properties from the experiments. An importance-sampling Monte Carlo procedure is employed in order to fit the experiments. This provides the optimum parameter values together with their statistical error bars. The approach is well suited for both modern desktop PC machines and massively parallel computers. The latter allows making the data analysis within short computing times. I applied this method to study flow of aqueous electrolyte solution near smooth hydrophilic and hydrophobic surfaces. Generally on hydrophilic surface slip is not expected, while on hydrophobic surface some slippage may exists. Our results show that on both hydrophilic and moderately hydrophobic (contact angle ~85°) surfaces the slip length is ~10-15nm or lower, and within the limitations of the experiments and the model, indistinguishable from zero.
Yordanov, Stoyan. "Total internal reflection fluorescence cross-correlation spectroscopy: theory and application for studying boundary slip phenomenon." 2011. Doctoral Dissertation, Johannes Gutenberg Universität Mainz. Accessed April 18, 2019. http://ubm.opus.hbz-nrw.de/volltexte/2011/2896/.
Yordanov, Stoyan. "Total internal reflection fluorescence cross-correlation spectroscopy: theory and application for studying boundary slip phenomenon." 2011. Web. 18 Apr 2019.
Yordanov S. Total internal reflection fluorescence cross-correlation spectroscopy: theory and application for studying boundary slip phenomenon. [Internet] [Doctoral dissertation]. Johannes Gutenberg Universität Mainz; 2011. [cited 2019 Apr 18]. Available from: http://ubm.opus.hbz-nrw.de/volltexte/2011/2896/.
24. Lu, Bin. Metal-based microchannel heat exchangers : manufacturing and heat transfer testing.
▼ This dissertation focuses on improving the functionality of metal-based microchannel heat exchangers (MHEs), as well as pushing this technology toward real-world applications. Design optimization was carried out on MHEs for performance maximization. Double-layered microchannel layout was experimentally studied, and a significant reduction on liquid flow pressure drop penalty was achieved. Other than water, another commonly-used coolant, ethylene glycol, was applied to MHEs, and flow and heat transfer characteristics were quantified. Transient Liquid Phase (TLP) bonding was used for joining Cu structures. For further understanding of the MHE heat transfer, a detailed examination was carried out on the TLP bonding interface region. In real applications, an MHE is likely to work with a heat rejection device. Therefore, further study was done on MHEs in the context of a close-loop recirculating-liquid cooling system. An alternative roll molding method suitable for continuous fabrication of metal-based microchannel arrays was studied. This technology may serve as an enabler for large-scale manufacturing of metal-based microchannel devices in an economical fashion.
Lu, Bin. "Metal-based microchannel heat exchangers : manufacturing and heat transfer testing." 2013. Doctoral Dissertation, Louisiana State University. Accessed April 18, 2019. etd-07082013-020113 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1879.
Lu, Bin. "Metal-based microchannel heat exchangers : manufacturing and heat transfer testing." 2013. Web. 18 Apr 2019.
Lu B. Metal-based microchannel heat exchangers : manufacturing and heat transfer testing. [Internet] [Doctoral dissertation]. Louisiana State University; 2013. [cited 2019 Apr 18]. Available from: etd-07082013-020113 ; https://digitalcommons.lsu.edu/gradschool_dissertations/1879.
25. Zhang, Chengqi. Wetting of Bio-Inspired Complexly-Shaped Fibers and Channels.
▼ This Dissertation is centered on studying the wetting of complexly-shaped fibers and channels which is inspired by the Lepidopteran proboscis. From materials science and engineering standpoint, the Lepidopteran proboscis is a multifunctional microfluidic device. The unique materials organization, morphology, structure, and surface properties of the proboscis allows the Lepidopterans to feed on various food sources from highly viscous to very thin liquids while keeping its surface clean. Thus, the study on the proboscis wetting phenomena has drawn great interests of materials scientists and engineers. The shape of the Lepidopteran proboscis has a very special design combining complexly-shaped fibers and channels. However, it remains unknown how this unique shape benefits the multiple functions of the proboscis. In this Dissertation, we investigate the effect of shape on the wetting properties of proboscis by separately studying the wetting of complexly-shaped fibers and channels, and then, applying the gained knowledge to explain various wetting phenomena observed on the Lepidopteran proboscis. In Chapter I, the definition of wetting is introduced and the fundamental studies on wetting of fibers and channels are reviewed. Then the structure and function of Lepidopteran proboscis is introduced, and the motivation for conducting the research in this Dissertation is explained. In Chapter II, several wetting phenomena on the ribbon-like fiber, e.g. the morphological transitions of droplet configurations, stability of coating films, capillary rise of menisci on ribbon-like fiber, and wetting of the ribbon rail are studied experimentally and theoretically. This study sets up the foundation for investigating the wetting phenomena of other complexly-shaped fibers and channels. The developed experimental and theoretical methods are actively used throughout this Dissertation. In Chapter III, the instability of a thin coating film on the internal and external walls of a straight hollow elliptical fiber is studied, and the mechanisms of drop formation from the coating films and the droplet morphology is briefly discussed. Then the study is expanded to the ring made of a curved elliptical tube to cover a broad range of wetting phenomena associated with such complexly-shaped fibers by discussing the effect of ring radius of curvature and the cross-sectional ellipticity. In Chapter IV, a new method for studying the wetting of complexly-shaped channels is developed based on the Princen theory, and examined with the V-shaped channel. Then, the wetting/dewetting of C-shaped channel is systematically studied both experimentally and theoretically. In Chapter V, several wetting phenomena associated with the Lepidopteran proboscises, e.g. the food uptake from a pool of liquid or from a limited volume of liquid, the stability of liquid films deposited on proboscis after dipping it into a nectar source, and self-assembly of proboscis after the insect emerges from the pupa, are discussed based on the study… Advisors/Committee Members: Dr. Konstantin G. Kornev, Committee Chair, Dr. Igor Luzinov, Dr. Olga Kuksenok, Dr. Ulf D. Schiller.
Zhang, Chengqi. "Wetting of Bio-Inspired Complexly-Shaped Fibers and Channels." 2018. Doctoral Dissertation, Clemson University. Accessed April 18, 2019. https://tigerprints.clemson.edu/all_dissertations/2172.
Zhang, Chengqi. "Wetting of Bio-Inspired Complexly-Shaped Fibers and Channels." 2018. Web. 18 Apr 2019.
Zhang C. Wetting of Bio-Inspired Complexly-Shaped Fibers and Channels. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2019 Apr 18]. Available from: https://tigerprints.clemson.edu/all_dissertations/2172.
26. Heintz, Keely. Synthesis and evaluation of PEO-coated materials for microchannel-based hemodialysis.
▼ The marked increase in surface-to-volume ratio associated with microscale devices for hemodialysis leads to problems with hemocompatibility and blood flow distribution that are more challenging to manage than those encountered at the conventional scale. In this work, stable surface modifications with pendant polyethylene oxide (PEO) chains were produced on polycarbonate microchannel and polyacrylonitrile membrane materials used in construction of microchannel hemodialyzer test articles. These coatings were evaluated in relation to protein repulsion, impact on urea permeability through the membrane, and impact on bubble retention through single-channel test articles. PEO layers were prepared by radiolytic grafting of PEO-PBD-PEO (PBD = polybutadiene) triblock copolymers to microchannel and membrane materials. Protein adsorption was detected by measurement of surface-bound enzyme activity following contact of uncoated and PEO-coated surfaces with β-galactosidase. Protein adsorption was decreased on PEO-coated polycarbonate and polydimethyl siloxane (PDMS) materials by 80% when compared to the level recorded on uncoated materials. Protein adsorption on membrane materials was not decreased with PEO-PBD-PEO treatment; a PEI (polyethylene imide) layer exists on the AN69 ST membrane which is intended to trap heparin during membrane pre-treatment. It is still unclear how this PEI layer interacts with PEO-PBD-PEO. Neither the PEO-PBD-PEO triblocks nor the irradiation process was observed to have any effect on polyacrylonitrile membrane permeability to urea, nor did the presence of additional fibrinogen and bovine serum albumin (BSA) in the urea filtrate. The PEO-PBD-PEO treatment was not able to visibly reduce bubble retention during flow through single-channel polycarbonate test articles, however, the rough surfaces of the laser-etched polycarbonate microchannels may be causing this bubble retention. This surface treatment holds promise as a means for imparting safe, efficacious coatings to blood processing equipment that ensure good hemocompatibility and blood flow distribution, with no adverse effects on mass transfer. Advisors/Committee Members: McGuire, Joseph (advisor), Schilke, Karl F. (committee member).
Heintz, Keely. "Synthesis and evaluation of PEO-coated materials for microchannel-based hemodialysis." 2012. Masters Thesis, Oregon State University. Accessed April 18, 2019. http://hdl.handle.net/1957/32641.
Heintz, Keely. "Synthesis and evaluation of PEO-coated materials for microchannel-based hemodialysis." 2012. Web. 18 Apr 2019.
Heintz K. Synthesis and evaluation of PEO-coated materials for microchannel-based hemodialysis. [Internet] [Masters thesis]. Oregon State University; 2012. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/1957/32641.
27. Cai, Shanshan. Design of an Experimental Facility for Frost Growth Study in Microchannel Heat Exchangers.
▼ This report focused on the new experimental methodology developed to investigate the frost and defrost thermal hydraulic performances of louvered folded fin microchannel heat exchangers under initial frost cycle, defrost cycle, and subsequent re-frost cycles. The required laboratory conditions are 35/33 °F dry-/wet-bulb temperature, with the air velocity around 100 ~ 300 fpm. In the air side, the required conditions were reached by a humidification, a cooling and a re-heating process with a fan, a refrigeration coil, a humidifier and a re-heating coil. In the refrigerant side, the required inlet coolant temperature was controlled by an automatically controlled heater and a plate heat exchanger connected with the chiller. The frost accumulation was measured by a precision scale for frost weight, and a videoscope for frost thickness. Uncertainties on U and hout were investigated based on both precision and bias uncertainties. Advisors/Committee Members: Cremaschi, Lorenzo (advisor), Spitler, Jeffrey D. (committee member), Fisher, Daniel E. (committee member).
Cai, Shanshan. "Design of an Experimental Facility for Frost Growth Study in Microchannel Heat Exchangers." 2009. Thesis, Oklahoma State University. Accessed April 18, 2019. http://hdl.handle.net/11244/9906.
Cai, Shanshan. "Design of an Experimental Facility for Frost Growth Study in Microchannel Heat Exchangers." 2009. Web. 18 Apr 2019.
Cai S. Design of an Experimental Facility for Frost Growth Study in Microchannel Heat Exchangers. [Internet] [Thesis]. Oklahoma State University; 2009. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/11244/9906.
28. Hong, Tommy. Measurements of Frost Growth on Louvered Folded Fins of Microchannel Heat Exchangers.
▼ Microhannel heat exchangers with louvered folded fins are subjected to frequent frost and defrost cycles when used in outdoor evaporator coils of air-source heat pump systems. Despite their potential for heat transfer enhancements, understanding the root causes that penalize microchannel heat exchangers during frosting operating conditions is still an open question. This thesis presents a new experimental methodology to study frost growth on louvered folded fins of microchannel heat exchangers. The paper demonstrates the feasibility of the frost mass and frost thickness measurements and, through a series of controlled laboratory experiments, provides new data of frost growth on louvered fins. Fin surface temperature was directly measured during actual frosting operating conditions and relations with heat transfer rates, air-side pressure drops, and frosting cycle times are discussed. The experimental results suggested that the frost mass increased linearly with time and water vapor did not experience any measurable time delay before it began to frost and to accumulate on the fins. The air-side flow blockage due to frost accumulation on the front leading edge of the fins was strongly dependent on the fin surface temperature and the data confirmed that the flow blockage was the key factor for the heat transfer capacity degradation during frosting operation. Advisors/Committee Members: Cremaschi, Lorenzo (advisor), Fisher, Daniel E. (committee member), Lilley, David G. (committee member).
Hong, Tommy. "Measurements of Frost Growth on Louvered Folded Fins of Microchannel Heat Exchangers." 2011. Thesis, Oklahoma State University. Accessed April 18, 2019. http://hdl.handle.net/11244/9946.
Hong, Tommy. "Measurements of Frost Growth on Louvered Folded Fins of Microchannel Heat Exchangers." 2011. Web. 18 Apr 2019.
Hong T. Measurements of Frost Growth on Louvered Folded Fins of Microchannel Heat Exchangers. [Internet] [Thesis]. Oklahoma State University; 2011. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/11244/9946.
29. Burk, Bryan E. Computational examination of conjugate heat transfer during microchannel flow boiling using finite element analysis, A.
▼ As technology advances, electronic components continue to produce more heat while at the same time growing smaller and being arranged in ever more compact packages. This has created the need for new thermal management systems able to both dissipate the large heat loads and meet the diminishing size requirements. Microchannel heat exchangers have become an integral part of such advanced cooling systems as they provide an exceedingly large surface area over which heat transfer can occur while maintaining a diminutive size. Current microchannel devices primarily use single-phase flow to dissipate the heat. As heat loads increase, so too must flow rates. Due to associated issues with extremely large pressure drops and high pumping power requirements, the practical capacity of single-phase microchannel coolers has largely been met. One particularly promising avenue forward is to utilize flow boiling with similar microchannel heat exchanger designs. The very high latent heat of vaporization associated with phase change for many fluids allows for a large amount of heat to be dissipated in flow boiling using a relatively low flow rate as compared to single-phase systems, drastically reducing the issues related to pressure drop. Additionally, two-phase heat transfer is associated with much higher heat transfer coefficients, allowing for smaller heat transfer surface areas (and thus smaller overall devices) and lower driving temperature differences for the same heat removal rates. Microchannel flow boiling studies to date have assumed 1D heat conduction through the heat exchanger material and have developed correlations to predict average heat transfer coefficients. Unfortunately, with the high heat fluxes expected in the near future, and with heat loads being applied at small, localized hotspots, the 1D assumption is no longer valid. Conjugate heat transfer must be considered, and local heat transfer coefficient correlations are necessary for the design of future thermal management systems. This thesis describes a first of its kind computational model that uses finite element analysis to analyze the conjugate heat transfer problem, complete with local heat transfer coefficients. This work serves as both proof of concept and an evaluation of the predictive capabilities of five published heat transfer correlations when applied locally to a high heat flux microchannel heat exchanger that has been previously tested. Modeling results show highly variable local heat flux profiles along the microchannel walls, confirming the need to consider conjugate heat transfer. Significant heat spreading resulted in peak local heat fluxes of roughly 0.5× that of the uniformly applied heat flux with 31.4% - 64.1% of total applied heat dissipated outside the region projected directly above the heater. As determined via local temperature comparisons, the correlation from Agostini and Bontemps provides the best overall agreement with average root mean square temperature differences of 2.6°C, though trends suggest that this difference may increase… Advisors/Committee Members: Bandhauer, Todd M. (advisor), Windom, Bret C. (committee member), Henry, Charles S. (committee member).
Burk, Bryan E. "Computational examination of conjugate heat transfer during microchannel flow boiling using finite element analysis, A." 2019. Masters Thesis, Colorado State University. Accessed April 18, 2019. http://hdl.handle.net/10217/193110.
Burk, Bryan E. "Computational examination of conjugate heat transfer during microchannel flow boiling using finite element analysis, A." 2019. Web. 18 Apr 2019.
Burk BE. Computational examination of conjugate heat transfer during microchannel flow boiling using finite element analysis, A. [Internet] [Masters thesis]. Colorado State University; 2019. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/10217/193110.
30. Padhmanabhan, Sankaranarayanan K. Study of Frost Growth on Heat Exchangers Used as Outdoor Coils in Air Source Heat Pump Systems.
▼ During winter heating operation, the outdoor coil of a heat pump acts as an evaporator and when the ambient temperature is near freezing, the moisture in the atmospheric air freezes on the coil surface. The frost growth affects the air flow and also adds resistance to heat transfer thus reducing the capacity and the efficiency of the heat pump. An experimental facility is designed and built to test a small scale heat exchanger working in frosting conditions. Tests are carried out using small scale fin-tube and microchannel heat exchanger over a range of glycol inlet temperatures, air velocities and ambient air RH. A semi-empirical frost model based on a scaling approach is developed and applied to both fin-tube heat and microchannel heat exchangers. The model is developed to handle non-uniformities in both refrigerant and air side. The frost model is integrated with a segment-by-segment heat exchanger calculation algorithm and is validated against experimental data. Frost growth model is also incorporated in a quasi-steady state system simulation algorithm.Findings and Conclusions: From the experimental study it was observed that the temperature of the surface and air RH affected the rate of frost growth significantly while the air velocity did not have a great influence. It is demonstrated that a dry heat transfer correlation can be used during frost growth period by correctly accounting for frost thickness in the hydraulic diameter calculations. Ignoring the phenomenon of air redistribution was found to result in errors in the range of 20% to 50% in predicted frost thickness. Frost thickness predicted by the frost model is within 5% of the measured values for most of the cases. Frost mass accumulation predicted by the simple model is higher than the measured values due to a uniform thickness assumption in the model. An improved frost model based on 1-D finite volume discretization is also presented which improved the frost mass prediction to within 13% of measured values. The system simulation is validated against experimental results and found to match reasonable well. The discrepancy between simulation and experiments were due to the effects of system transience in the initial stages. Advisors/Committee Members: Fisher, Daniel (advisor), Spitler, Jeffrey (committee member), Cremaschi, Lorenzo (committee member), Johannes, A. H. (committee member).
Padhmanabhan, Sankaranarayanan K. "Study of Frost Growth on Heat Exchangers Used as Outdoor Coils in Air Source Heat Pump Systems." 2011. Thesis, Oklahoma State University. Accessed April 18, 2019. http://hdl.handle.net/11244/7817.
Padhmanabhan, Sankaranarayanan K. "Study of Frost Growth on Heat Exchangers Used as Outdoor Coils in Air Source Heat Pump Systems." 2011. Web. 18 Apr 2019.
Padhmanabhan SK. Study of Frost Growth on Heat Exchangers Used as Outdoor Coils in Air Source Heat Pump Systems. [Internet] [Thesis]. Oklahoma State University; 2011. [cited 2019 Apr 18]. Available from: http://hdl.handle.net/11244/7817.


text:
GAB Protects Thousands of Wisconsin Voters from Baseless Challenges at Polls
Voters Can't be Removed from Rolls or Challenged
on Election Day Because of HAVA Mismatch
MADISON – Despite the best efforts of JB Van Hollen and the Republicans to influence the election by disenfranchising thousands of voters, not a single voter can be removed from the rolls or challenged on Election Day simply because their names appear differently on two state databases, according to a formal opinion released by the Government Accountability Board.
"This is great news for Wisconsin voters who want to participate in this historic election without being held up by an unnecessary and partisan attempt to challenge the process," said Joe Wineke, Democratic Party of Wisconsin Chair. "Every eligible voter in Wisconsin has a right to exercise their most basic American right and now no one will be challenged or denied that right on Election Day simply because their name appears differently on two state voter lists."
In September, Van Hollen, who is state Co-Chair for John McCain's campaign, brought a politically motivated lawsuit in collusion with the Republican Party designed to disenfranchise voters and sway the election in favor of McCain. Van Hollen's lawsuit asked the GAB to crosscheck voter registration files back to 2006 and the Republican Party of Wisconsin demanded that the Court order the GAB to remove voters from the rolls simply because their names appear differently on two state databases, affecting up to 1 million voters. (Source: AP, 10/1/08)
Last week, the RPW, as party to Van Hollen's lawsuit, asked a DaneCounty Judge to require Milwaukee voters who failed a "HAVA" cross-check to be required to show ID at the polls or be forced to cast provisional ballots. (Source: MJS, 10/10/08) The RPW is also setting the stage to challenge these voters at the polls.
The GAB's recent opinion effectively nullifies the intent of both Van Hollen's lawsuit, and the RPW motion, by saying that no voter may be removed from the rolls or challenged on Election Day simply because of a HAVA mismatch. The opinion, which was issued in response to an inquiry from the Milwaukee Election Commission, reads in part:
The fact information in a voter's registration records do not match similar information in other databases is not sufficient grounds to disqualify an elector and remove his or her name from the voter list and does not provide a basis for a challenge to the elector's ballot under § 6.925, Stats., or under chapter GAB 9, Wis. Adm. Code, or to the elector's registration under § 6.48, Stats. (Source: GAB formal opinion to Milwaukee Board of Election Commissioners, 10/6/08)
Oct 17, 2008 News #17

redpajama_set_name: RedPajamaCommonCrawl


For those that saw the sad demise of Ken Ritchie's Dakota at Catton Park in 2005, she's risen from the debris like the intrepid Phoenix!
It is of course a Nick Ziroli plan, featuring a fibreglass nose unit from Nick Ziroli, and Colin utilised some of the parts from the damaged airframe under the guidance of Tony Nijhuis. (The Flying Dutchman) The rear of the old airframe was untouched from the trailing edge of the wing rearwards and was sweated onto a new front end, once again under the watchful eye of 'Nidge' using the same idea he uses for his 18' Lancaster. (It fits in his Volvo! Don't you know!)?
The retracts resembled a tangled ball of bent and broken tubes, until Mike Jackson kindly offered to, "straighten em out!" Superb job done, many thanks Mike!
Thanks also to Harold of the Catton Group for repairing the Zenoah 38's, look forward to picking them up at the AGM in November 2006.
If you are reading my (Colin's) scribbling and do not belong to the LMA, take it from me, superb Association, please give it some serious thought, and join us around the shows in 2006, you won't be disappointed.
See you around the shows in 2006.
Here is the model completed ready for test flying.


Fuel prices were reduced again on Thursday after remaining unchanged on Wednesday. The petrol price was cut by 40 paise to 43 paise per litre while diesel price was cut by 30 to 48 paise per litre in all major cities of the country.
In Delhi, petrol is being retailed at Rs 75. 97 per litre, while diesel costs Rs 70.97 per litre. In Noida, petrol was sold at Rs 74.62 and diesel was retailing at Rs 69.37 per litre.
In Mumbai, petrol is being sold at Rs 81. 50 per litre and diesel rates at Rs 74.34 litre.
In Kolkata, petrol costs Rs 78.88 per litre and diesel rates at Rs 73.13 per litre. In Chennai, petrol costs Rs 79.31 per litre, and diesel rates at Rs 75.31 per litre.
In early October, Brent crude rates have come down by almost 30 per cent from their recent peaks, weighed down by surging supply and a slowdown in demand growth. Today, Brent crude futures were trading nearly $63 per barrel mark in Asian trade.


The Chapel is located in the heart of Stow-on-the-Wold. A blue door at the bottom of the clock tower opens into a lobby area which is shared with neighbouring apartments.
Family bathroom: Contains an L-shaped bath with an overhead rain shower and shower attachment, a toilet, wash basin and heated towel rail.


text:
All Time Numerical Roster
Jeff McKnight
Tag Archive for Rajai Davis
Proof of Being 21
September 1, 2020 This Friggin Team, Uni Controversies, Who Is This Guy 5 comments
It's a little more than an hour before game time in Baltimore and the tension is thick.
With Todd Frazier reacquired and Billy Hamilton still on board (I think) who wears No. 21?
The Mets quietly added Frazier, along with his Texas teammate Robinson Chirinos and Baltimore reliever Miguel Castro, in deadline deals that illustrate that even unaccomplished, old and/or boring guys might make a difference on a Mets club that can do little right so far this year and still acts like it might be a playoff team.
Frazier was something a guy to be endured and not necessarily welcomed back but hopefully represents some right-handed power we'd been missing since Cespedes quit and Pete Alonso and Wilson Ramos are taking the year off more stealthily, and JD Davis hurt. Frazier, as I've probably noted here before has one of the ugliest swings in club history but I cannot deny he's a pro. The Mets list both Frazier and Hamilton in 21, the latter guy would seem to me to be on the verge of release, having encountered but not delivered on more than a few Rajai Davis Moments. Hammy could alternatively slide down to 15 or 7.
Chirinos, a 36-year-old catcher and career .231 hitter, I suppose is seen as an upgrade on Ali Sanchez or Tomas Nido as a reserve but I'm already confusing him with Ramon Castro and Rod Barajas and any number of chunky Latin backstops who've passed through. Wearing the No. 61 jersey most recently belonging to DFA'ed pitcher Walker Lockett could distinguish him; having never traded Kevin Plawecki for Lockett in the first place might have helped more.
And not to continue with the stereotypes but Miguel Castro–acquired for a legit lefthanded starting prospect, Kevin Smith–looks like your standard crooked-cap-wearing reliever with good strikeout figures and lousy stats otherwise. At 25 and with a contract that keep him on the club for another year cheaply, he'll get a look and could still succeed, and also, could not. Castro gets No. 50 and another Uni Controversy given tat's the number also assigned to Jeremy Accardo, the pitching coach. Stay tuned!
Finally I have no idea who the guy starting tonight is other than his name, Ariel Jurado. The Mets acquired him from Texas a few weeks ago when I was out of town and he's presumably been hanging out in Brooklyn with the Sewalds, the Stricklands and the Locketts. Jurado, a young Panamanian righty with a 5.85 career ERA over part6s of two seasons with the Rangers, gets No. 49, last worn these parts by the fake-news relief prospect Tyler Bashlor.
Let's Go Islanders, I mean, Mets!
Rajai and Out
May 27, 2019 Who Is This Guy No comments
Those unpredictable Mets keep on churning the roster and you never know what'll happen next.
This week, with Nimmo and Conforto out, we introduced Rajai Davis and Aaron Altherr as special guest outfielders and each of them hit a home run in their first plate appearance. Davis, who didn't get an R designation on his nameplate despite the team already employing two other members of the Davis family (JD & Chili) wore No. 18, and Altherr took the 23 jersey most recently belonging to Keon Broxton. The Mets in the meantime signed Matt Kemp to a minor-league contract, then DFA'ed Davis to make room for the returning Conforto.
Should Kemp make it up here–and signing a veteran All-Star is becoming something of a Mets tradition given the recent history of Jose Bautista and Adrian Gonzalez and James Loney–they'll need to find another uniform number than the 27 he's previously worn over 1,700 games for Los Angeles, San Diego, Atlanta and Cincinnati. Juerys Familia has already kept 27 from Carlos Gomez.
The new additions and subsequent roster crush has resulted not only in Davis' assignment but also cost Paul Sewald and Tim Peterson spots. The latter two escaped the scrutiny even of the Washington Nationals and have landed back in Syracuse.
Stepping Out of A Hole
May 23, 2019 This Friggin Team 2 comments
Well, what do you know.
Mickey Callaway hasn't been fired and the Mets have started winning again. Those things no doubt will change at some point, maybe soon, but let's enjoy it now while we can.
The injuries are slowly piling up, for example. Jed Lowrie and Yoenis Cespedes might never get here. Conforto is concussed, Nimmo is out with a sore neck and Cano might have hurt himself hustling. New Mets hero Rajai Davis is here and wearing No. 18; interesting inasmuch he was issued 11 in Spring Training, but that went to Adeiny Hechavarria. And with Seth Lugo joining Justin Wilson and Luis Avilan on the shelf, Hector Santiago arrived. He'll be wearing No. 33.
Along the way we can close the book on Keon Broxton, traded to Baltimore for draft money yesterday, and perhaps on Paul Sewald, one of those organization relievers whose champions, if he had them, left the building a while ago.
Poor Sewald. Of the six pitchers who wore No. 51 in team history none have seen more action than Sewald's 107 games and 128.2 innings, but all of them have at least as many wins, which is to say zero. He departs as the losingest pitcher (13) without a win in Mets history.
March 10, 2019 Met Mysteries, Opening Day, Wild Speculation 3 comments
So our old friend Carlos Gomez is in camp wearing No. 85, which happened to be the lowest number available, although roster cuts and reassignments should free up additional space as opening day nears. Already there's been 13 reassignments and yesterday news came that TJ Rivera had been cut and also released.
This is not a big surprise as Rivera was a one-tool longshot before he missed a year with an injury, but his release frees up No. 19 if anyone wants it. I assume it won't be long before Dilson Hererra is reassigned and coughs up No. 16; then there's Gregor Blanco (7) and Rajai Davis (11) who suddenly look more vulnerable now that Gomez is back. In case you've forgotten Gomez wore No. 27 in his first appearances as a Met back in 2007. His return suggests to me that Omar Minaya is possibly making the personnel decisions again and just relying on Brodie Van Wagenen to say the right things to the press about them. That's not a good feeling.
Among pitchers, keep an eye on No. 26, where nonroster invitee Arquimedes Caminero has a 16.20 ERA so far (in a really small sample) but appears to need to beat out one or more better-performing counterparts like Hector Santiago (46), Luis Avilan (43) and Rule 5er Kyle Dowdy (33) who's going to get every chance despite a Camineroesque ERA so far this spring.
Mets by the Numbers // Est. 1999
@Springer66 January 20, 2021
What's next for the black-eyed, brain-drained Mets and why Neil Allen, Ollie Perez and Dallas Green shall celebrate: mbtn.net/?p=3357
Impressed with @MarcCarig's interview fundies. Strong body language, expression that says "you have to answer for this."
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