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

An evaporator's time-constant (t(c)) equation has been developed as part of a mathematical model describing the time-dependent behaviour of a refriger ation 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 r efrigerant system were altered. Although a step decrease in the inlet-water 's temperature led to large increase in t(c), the system's behaviour stabil ized quickly because f(tp) had also increased significantly. The prediction s 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 th is makes the experimental verification of this model desirable. (C) 2001 Pu blished by Elsevier Science Ltd. All rights reserved.