Computer-aided simulation of the energetic and exergetic efficiency of a two-stage cascade cooling cycle

Abstract

Refrigeration systems are of great importance in industry and are widely used in food preservation or air conditioning. Studies have been carried out in recent years in search of parameters to optimise the cycle by reducing losses, both to increase the COP and to reduce energy consumption, so that process improvements have been made from which different cycles are derived, such as the gas cooling cycle with regeneration, absorption cooling, gas liquefaction or multistage compression cooling systems. This document presents a combined refrigeration system consisting of two vapour compression refrigeration cycles linked by a heat exchanger that not only reduces the work of the compressor but also increases the amount of heat absorbed by the refrigerated space as a result of the cascade stages and improves the COP of a refrigeration system. The study was carried out under the assumption of a stationary flow, and without significant changes in the kinetic and potential energy, i.e. assuming an ideal process, carrying out several case studies with the help of UNISIM, evaluating the effect of varying the low temperature on the exergetic efficiency, the destroyed exergy of the condenser, the net input work and the COP, as well as the influence of the input pressure in the upper cycle compressor on the net input work and the COP.