Erratum to “Thermal modeling of a packed bed thermal energy storage system during charging” [Appl. Therm. Eng. 29 (4) (March 2009) pp. 695–705]

A multi-functional heat-pump system is proposed to efficiently utilize the gray water as heat source and sink for heating and cooling of residential buildings, respectively. Heat is reclaimed from the plate heat exchanger installed at the outlet of the compressor to provide sufficient hot water for residential use. To study the performance of this innovative system, laboratory testing is performed with a prototype consisting of an outdoor heat pump, an indoor air handler, a gray water tank and a hot water tank. This system is set in two environmental chambers that they represent: the outdoor and indoor environments, respectively. In this paper, the investigation of the system is mainly focused on the heating performance. The system is designed to allow four combinations of two heat sources that they are a water-source evaporator and an air-source evaporator. The four combinations consist of air source only, water source only, air source and water source in parallel and air source and water source in series, in the refrigerant cycle. Performance of the four combinations of heat sources is experimentally investigated at a typical indoor air temperature of 21.1 °C and various outdoor air temperatures at 1.1, 8.3, and 15.6 °C. The results show that the heat source combinations influence the heating capacity and coefficient of performance (COP) of the system. Also, the system performance and the optimal heat source combination depend on the outdoor temperature. As outdoor temperature decreases, the variation of system performance among different combinations becomes small. The system performance in modes of space heating and space heating plus hot water supply are compared and analyzed. The COP of the system in the space heating plus hot water supply mode increases in all heat source combinations, compared with that in space heating only mode. The performance of the system for heating hot water from 30 °C to 48.9 °C is also studied. This proposed system can provide significant energy savings in space heating and hot water supply. The optimal source combination is critical in pursuing the maximum energy savings.