Comparison And Analysis Of Design Temperature Of Heat Carrier Fluid For Hybrid Ground-Coupled Heat Pump Systems

Ground-Coupled Heat Pump System (GCHPS) is drawing more and more attentionfor its environmentally-friendliness and energy-saving. After the hybrid ground-coupledheat pump system (HGCHPS) was brought up, it broke up the application limitation ofconventional GCHPS. In the hot summer and cold winter area of China, the mainapplication form of HGCHPS is cooling tower assisted ground-coupled heat pump system,whose cooling effect is significantly affected by the capacity of the cooling tower, whichis due to the summer design temperature of heat carrier fluid. So we need to make someoptimization for the design temperature.This paper chose Wuhan as the representive city of hot summer and cold winter areain China, and two kinds of buildings office building&hotel as the research objects.Weused TRNSYS(A Transient System Simulation Program) to establish the model ofHGCHPS, and simulated the operating conditions under different design temperatures ofheat carrier fluid. According to the statistics, we computed the average annual cost (ACC)of system and assessed the soil thermal equlibrium. In the end, the author compared theoutlet fluid temperature of underground heat exchanger (GHE), soil temperature andaccumulative heat extracted from or rejected to soil. The conclusions are as follows:(1) the capacity of cooling tower is significantly affected by the summer designtemperature of heat carrier fluid. When the design temperature rises, the EER of heatpump units would fall, and the available temperature difference between the GHE and soilrises, so the capacity of cooling tower falls.(2) The AAC of system would rise along with the design temperature’s rising of heatcarrier fluid; The soil temperature of hotel reached a stable value, while that of officebuilding increased with time’s forward, the average annual increasement was0.3℃, Theheat equilibriums of hotel and office building were both in a acceptable range. The bestdesign inlet and outlet temperature of heat carrier fluid is40/35℃in summer. (3) For the HGCHPS in Wuhan, the AAC of cooling tower’s first cost is the maininfluence factor of the total AAC, so a higher design temperature of heat carrier fluid isrecommended.The results from this study have some reference value in the design process ofHGCHPS...