Performance instability of a refrigerator with its evaporator controlled by a thermostatic expansion-valve

Abstract

An evaporator's time-constant ( t c) equation has been developed as part of a mathematical model describing the time-dependent behaviour of a refrigeration system. The magnitudes of the evaporator's t c were approximately 2 and 5 s, respectively for 100 and 50% loads imposed on the refrigerator. As a result of a step change in the inlet's water-temperature, the magnitudes of both t c and the two-phase heat-transfer coefficient ( f tp) for the refrigerant system were altered. Although a step decrease in the inlet-water's temperature led to large increase in t c, the system's behaviour stabilized quickly because f tp had also increased significantly. The predictions of this investigation showed that such an analysis is highly sensitive to the accuracy of the equations used to calculate both t c and f tp and this makes the experimental verification of this model desirable.