Peformance of a two-phase unglazed solar evaporator-collector

Abstract

In this study, the performance of a two-phase unglazed solar evaporator-collector in a heat pump solar cooling, water heating and drying system is investigated. This type of collector can be locally made and relatively much cheaper than the conventional collector. Refrigerant R-134a is used as the working fluid due to the better thermodynamic and environmental performance. A transient two-dimensional mathematical model of the evaporator-collector has been developed to predict temperature distribution and useful energy gain. A series of experiments were performed under the meteorological conditions of Singapore. Both experimental and analytical results show the fact that the two-phase unglazed solar evaporator-collector, instead of losing energy to the ambient, gained a significant amount due to low operating temperature of the collector. As a result, the collector efficiency attains a value greater than 1, when conventional collector equation is used. With this evaporator-collector, the system can be operated even in the absence of solar radiation. Experiments with a header type parallel tube evaporator-collector and serpentine collector indicate a better performance of serpentine one. This analysis shows that the two-phase unglazed solar evaporator-collector has good potential for application in the tropics.