Design and Numerical Simulation of an Evaporator for a Compact Vapor Compression Refrigeration System

Abstract

A miniature plate-fin heat exchanger was designed for use in a compact Vapor Compression Refrigeration (VCR) system used for cooling electronic components in an Air Transportable Rack (ATR) chassis. The evaporator was designed to have a cooling capacity of 350 W and to use R236ea as the primary refrigerant and PAO as the secondary refrigerant. The final dimensions of the heat exchanger were 2.75 x 0.75 x 2.00 inches. A model of the evaporator was developed and incorporated into a full cycle analysis of the refrigeration system. Comparisons between existing experimental correlations and a numerical simulation of PAO flow through lanced offset strip fins was also completed. Thermal performance of lanced offset strip fins showed agreement between the two methods to within eight percent while the pressure drop behavior only had 50 percent agreement when comparing existing experimental correlations and numerical simulations. Local fin heat transfer analysis revealed that thermally fully developed conditions prevailed on the last half of each fin resulting in constant Nusselt numbers for the designed fin geometry and flow conditions.