Conference Year
2021
Keywords
compressor simulation, isentropic efficiency, energy losses.
Abstract
Due to several incentives for reducing energy consumption worldwide, there is an increasingly demand for high-efficiency compressors for refrigeration systems. During the design stage of a refrigeration compressor, the designer needs to identify the main energy losses so as to propose alternatives to increase the compressor efficiency. The energy losses associated with the compression cycle are typically evaluated from the indicated diagram, which allows an accurate estimate of viscous flow losses through the suction and discharge systems, but no clear identification of piston-cylinder leakage and heat transfer losses. This paper presents a theoretical method to assess the energy losses associated with the compression chamber based on the analysis of the first law of thermodynamics, in which losses are detached into heat transfer, leakage, valve backflow and others. For this purpose, a compressor simulation model based on a transient and lumped formulation of mass and energy conservation equations is applied to the compression chamber and is validated with experimental data. A study case is performed in which the energy losses of a baseline compressor is compared with those of a 4% higher isentropic efficiency compressor. It is concluded that the typical indicated diagram analysis does not allow a clear identification of the benefits that cause the increase of 4% in isentropic efficiency, whereas the approach proposed herein and based on the first law of thermodynamics indicates that the increase of isentropic efficiency is associated with reduction in heat transfer and leakage losses during expansion and discharge processes.