Analysis Of Ground Temperature In GSHP System Based On Dynamic Simulation Of Building Load

Lack of energy is emerging in all industry as the development of world economy. Ground source heat pump (GSHP) system as a new technology, which is low-energy-consumption and green to environment, has been widely used all over the world. Ground soil, the heat source of GSHP system, has important effect on overall system performance. The quantity of heat absorbed from deep ground soil (HA) and exhausted to it (HE) is unconstant based on different characteristics of building load. Unbalance of HA and HE will cause a change of soil temperature, which will weaken the performance of ground heat exchanger (GHE) by accumulation. Predicting of soil temperature in given building and GSHP system is the key to HVAC system design and healthy operation in long time.Based upon the former research, soil temperature resuming has been considered into classic line source theory model. Long term time-step simulation used variable heat flow line source model can be done with the application of load aggregation. The GSHP soil temperature calculation software, which is based on improved model, can make a link to EnergyPlus, then find out the long time impact to soil temperature with variable building load condition easily and precisely.By the 7 days experiment in test borehole of Tianjin University palestra, the author obtained ground average soil heat conduction coefficient as 1.904W/m·K, ground initial temperature as 15.5℃, which are sent to improved model for calculation in the average temperature change of the fluid in GHE. With average error less than 6.2%, the simulation can show the actual fluid temperature change in GHE, and the improved model can be considered reliable.Ground temperature calculation of GSHP in different areas with 4 kinds of climate, using EnergyPlus and GSHP soil temperature calculation software, shows the more unbalance load in GHE, the more annual ground temperature change. Through a 15 days (around summer design day) research of buildings with different function, author figures out larger value in peak load and more durative load will result in bigger change of ground temperature in one operation season. Then a 15 days simulation of shopping mall and hotel adopting mix system with same capacity of cooling tower shows sharing load by cooling tower in peak load period is effective to control ground temperature change for the building with large value in peak load such as shopping mall and intermittent operation (cooling tower operates out of peak load period) for building with durative load such as hotel. The operation schedule of mix system should be fit for the building load characteristic. By the research above, a design and system optimizing method based on predicting ground temperature in GSHP system has been presented, which is easy and conveniency and propitious to the application of GSHP in China.