24 June 2014

Key technology study on thermal balance of ground source heat pump in territories with a cold winter and a warm summer


The imbalance of heat extracted from the soil by the ground heat exchangers
(GHEs) in winter and its rejection in summer is expected to affect the long term performance of ground source heat pump (GSHP) in cooling load dominated area of China. This paper
presents a new method based on traditional HGSHP system that the parallel operation mode of GHE and cooling tower (CT) to share the condensing load during low cooling load period and the series operation mode of GHE and CT to achieve cool-stage into the soil in transition
season. According to this technology, the evaluation index for GHE system and cooling tower are constructed on the base of finite line heat source theory, the superposition principle and
the heat and humidity transfer theory of cooling tower. Then the year-round suitable conditions of CT is analysed through theoretical analysis, practical measurement and numerical simulation. Finally, an actual GSHP project in Nanjing is given as example for system optimization and the predictive result using this new method is studied. The results show that using the new method, the “thermal accumulation” problem can be well restrained, which can provide reference on optimized system design and energy-saving operation when
using GSHP system in the territories with a cold winter and a warm summer of China.