Numerical Simulation Study On The Typical Vertical Ground Source Heat Exchanger Of GSHP

Ground source heat pump (GSHP) technology is widely used in many countries due to the features of energy-saving, environmental friendly and sustainable. Ground coupled heat pumps (GCHP), which use vertical buried pipe as ground heat exchanger (GHE), have the advantages of small footprint and stable performance. So, it has been widely applied in our country.First, the development history of GSHP is reviewed, including the status of research and applications, the classic heat transfer model of vertical GHE, the classic theory and experimental methods of soil thermal response test.Second, the heat transfer of the typical vertical GHE in soil is investigated by numerical simulation. Different from the previous studies, the impact of the groundwater level is considered. Soil below the groundwater level is regarded as saturated soil, and, the part above the groundwater level is considered as unsaturated soil. Ignoring the surface irrigation and precipitation, the soil-water characteristic curve is used to determine the distribution of water content and thermal properties in the vertical direction of unsaturated soil. A three dimensional model for the typical vertical GHE is built, and the heat transfer in soil is simulated using commercial software FLUENT. The comparison between numerical and experiment result confirmed the validity of the model.Finally, based on the above model, the factors which affect the performance of the typical vertical GHE are investigated, such as:inlet temperatures of fluid, flow rates and operating conditions. Especially, the effect of groundwater level changes at specific length of GHE and the effect of different lengths of GHE at specific groundwater level are investigated. The results could be used to guide the design and management of GSHP in the regions with obvious changes of groundwater level.