Construction of Test Facility to Measure and Visualize Refrigerant Maldistribution in Multiport Evaporator Headers

Abstract

In a refrigeration cycle, condensed liquid refrigerant is expanded to a two-phase fluid entering the evaporator. In many applications, the evaporator paths are divided into a number of parallel sections to keep the pressure drop across the evaporator within a reasonable range and to maximize overall heat exchanger performance. Since the state of the refrigerant entering the evaporator is two-phase and its quality changes depending upon the operating conditions, the proper refrigerant distribution to individual sections is not an easy task. Nonuniform distribution, or maldistribution, will cause dry out at sections of lesser mass flow by superheating the refrigerant gas. This can result in nonuniform heat exchanger surface temperature distribution. Single-phase heat transfer coefficients (HTCs) are much lower than those of two-phase HTCs. When dryout occurs, both refrigerant-side HTCs and air-side HTCs are lower than those of wet surfaces. In addition to this, the temperature difference between the air and