Heat Pump Design for Simultaneous Cooling Space and Heating Water Coupled with Earth-Tube Heat Exchanger as Secondary Heat Sink

Abstract

A heat pump for simultaneous heating and cooling (HPS) is more efficient in energy and beneficial in use than a reversible heat pump which works in either direction to provide heating or cooling. A HPS is usually coupled with a thermal storage tank for possibly operating in 3 modes: heating mode, cooling mode, and simultaneous heating and cooling mode. To improve the HPS performance in heating mode or cooling mode, the HPS should be installed an auxiliary equipment in order to reject overheat in the system or to absorb supplemental heat into the system. This paper proposed a design of a HPS for cooling space and hot water production coupled with a horizontally shallow earth-tube heat exchanger as secondary heat sink for Thai residences in which the main components in the design are composed of the condenser and the earth tube heat exchanger. The coefficients of performance (COP) of the HPS were evaluated by the experiments. The results showed that it could work the best performance when it worked in simultaneous cooling and heating mode at the water flow rate of 6.0 L/min with the coefficient of performance (COP) of 6.3±3.1 %. The HPS had high efficiency and it worked continuously in cooling mode when it operated in the nighttime with the average COP of 4.3±14.5 %. However, an efficiency of the HPS was declined when heat gain in the conditioned room is significantly increased by high intensity of solar radiation in the daytime with the average COP of 2.5±14.5 %.