About 1.4 billion household refrigerators and freezers are in use worldwide, and virtually all of them employ reciprocating compressors and operate based on the vapor compression refrigeration cycle
The compression cycle in reciprocating compressors is a transient phenomenon that occurs in a time scale of about milliseconds and for this reason experimental measurements are not simple. Therefore, it is common to employ CFD simulations to study the compression cycle, a procedure that has been continuously employed at POLO over the last 20 years. These simulations are usually conducted using commercially available software, and are focused on the compression chamber as well as on other compressor components, such as filters and gaps. POLO possesses the know-how of whole simulation process, from the geometry generation through the analysis of engineering results. Currently, two main activities regarding this subject are being conducted. The first is related to the simulation of the transient fluid flow and heat transfer inside the suction muffler, with focus on suction superheating. The second activity is a comparative analysis between two mesh models employed to simulate the compression cycle. One is widely spread in the literature and (Moving Mesh – CFX Software) while the other is a new type of mesh model (Automatic Mesh Refinement –Converge Software), which is intended to reduce the time spent to build and improve the mesh for engineering simulations. The objective is to evaluate if the AMR model produces results as reliable as the ones given by the MM model, which is more established in the technical literature.
Besides the works focused on the compression cycle, POLO also develops research activities with the objective of evaluating the performance of reciprocating compressors under real operating conditions in a refrigerator. In most refrigerators, the operation is typically transient and characterized by alternate periods at which the compressor is either operating (on) or idle (off), being therefore difficult to predict the real operating conditions of the compressor during the first design stages. Currently, experimental tests are being conducted to evaluate several parameters of interest in a compressor operating in a refrigerator. These parameters include the temperatures of several compressor components, the mass flow rate, power consumption, and indicated power, among others. The experimental data will be employed to validate a simulation model under development, which will allow the characterization of compressor performance under typical operating conditions of a refrigerator. Also in the numerical area, an object-oriented equation-based programming language, called Modelica, is being used to develop part of the model, which is based on the C++ language. The experimental and numerical results will allow a deep analysis on the performance of reciprocating compressors in refrigerators, with focus on the main thermodynamic, mechanical and electrical losses under real operating conditions.