Soil Temperature Field And System Energy Consumption Research On Ground Source Heat Pump In Intermittent Cooling

With the continuous development of our country’s economy, energy is short of supply and energy-saving and emission reduction has become an important subject. China is still lack of comprehensive experimental test and data analysis on ground source heat pump system (GSHP). Therefore, according to practical engineering, each operation parameter of heat pump system has been tested on the spot; experimental researches and numerical simulation about vertically buried single-U-tube ground heat exchanger under different operation modes during the cooling period have been completed.Taking the GSHP used in Taijia highway toll station in Linxian of Shanxi province as research object in this paper. An experimental platform has been established to measure running condition which last nearly two months on cooling period.This paper also have made analysis and research on the following aspects:the change of drilling soil temperature at different depths under different running conditions of vertically buried single-U-tube ground heat exchanger; supply and return water temperature; single well heat exchange rate of buried ground heat exchanger, the recovery condition of soil temperature in transition seasons, energy consumption analysis of the system.On the basis of the experimental studies mentioned above, the author used FLUENT to simulate numerically a three-dimensional mold about the fluid flow in the vertical single U-tube heat exchanger and soil temperature field in the drilling. And then, with the mold validated using observed temperature distribution, single U-tube heat exchanger at different flow rates, different tube and different backfilling has been simulated numerically. The conclusions obtained play a guiding role both in optimizing operation and design and construction of GSHP.Stated thus, this paper has made a profound research on soil temperature field around the vertically buried single-U-tube ground heat exchanger and system performance under different operation conditions during cooling period; finally we obtained some conclusions that have guiding significance to construction and design for heat pump system. The conclusions include:heat transfer rate per meter of single tube has a certain guiding role for design of ground source heat pump system; the mode of running in the day and stopping operation in the night can plays a positive role in optimizing operation of the system in the future;recommending flow velocity of 0.3m/s-0.5m/s in the pipes of vertically buried single-U-tube ground heat exchanger; suggesting using high density polyethylene as the material of buried ground heat exchanger and utilizing material which have similar thermal physical properties with soil around drilling for backfilling;. These conclusions lay a theoretical foundation for the application and spread of ground source heat pump system in Shanxi and even in the whole nation.