Experimental Energetic Analysis of the Liquid Injection Effect in a Two-Stage Refrigeration Facility Using a Compound Compressor

The objective of this paper is to detail an experimental analysis of the energetic implications of using a liquid injection system to produce desuperheating between the compression stages in a two-stage refrigeration facility. The analysis is carried out by comparing the experimental performance of the two-stage cycle working with and without the liquid injection system. The experimental analysis of the two-stage refrigeration cycle is performed in an evaporating temperature range between −36°C and −20°C and in a condensing temperature range between 30°C and 47°C using R-404A as working fluid. The discussion compares the cycle working with liquid injection to the two-stage configuration without this intermediate system by using experimental data from condensing and evaporating pressure variation tests in a two-stage refrigerating plant driven by a compound compressor and working with one of the fluids most widely-used in Europe for low-temperature applications, R-404A. Both experimental and theoretical results show that the use of the liquid injection to produce desuperheating between compression stages produces an increment of the interstage pressure in the cycle, the consequences of which are variations of the cooling capacity and the absorbed power consumption of the two-stage cycle.