Experimental Investigation On Underground Heat Transfer With Seepage Of Ground Source Heat Pump System

According to the character of the underground soil temperature is not obvious seasonal change, soil source heat pump system has many advantages compared with the common air source heat pump system, soil source heat pump system can input a small amount of electrical energy, the effective use of low grade of shallow geothermal heating or cooling for buildings.In the process of the practical application of ground-source heat pump system, the heat transfer performance of buried pipe system energy efficiency level is closely linked, so need to have enough knowledge of heat transfer characteristic of the underground buried pipe.This article through the design structures, micro ground-source heat pump system test bench, the experimental research under different working conditions underground heat transfer characteristics of ground-source heat pump system and the system energy efficiency features.And then to set up and optimize the design of ground-source heat pump system to run.This article first to the development course of ground-source heat pump system and summarized the research status quo, with emphasis on the experimental research of ground-source heat pump system is analyzed.Designed to build on the basis of the micro test bench, ground-source heat pump system for experimental study of underground heat seepage coupling heat transfer characteristics.Design for test bench, based on the heat transfer theory to reduce for large soil source heat pump system with similar miniature experiment system.Soil along the seepage in the upstream and downstream layout box buried two U tubes, seepage velocity by moving water tank position difference to adjust.Pipe of heat pump units, system, circulating water pump design and selection of main equipment parts in detail.For soil temperature, fluid temperature and pipe wall temperature measuring point layout in detail design, acquisition and calibration temperature and heat pump power measurement calibration by integration of computer control, and the error analysis was carried out on the experimental data.Then, using the design of the micro test bench experiment of 9 groups compared conditions run, get different positions under different operation condition of soil temperature import and export of buried pipes, water temperature, buried outside the tube wall temperature, the changes in the rate of heat exchange.Analyses the three factors (buried pipe buried pipe inlet water temperature, water flow speed, seepage velocity) on the influence of the underground heat transfer characteristics of ground-source heat pump system.The results showed that the winter conditions, buried pipe inlet water temperature is lower, or buried pipe flow rate, the greater the as well as the seepage velocity, the greater the will make the heat exchange performance enhancements.But the seepage causes the heat between upstream and downstream interference phenomenon, buried tube heat transfer rate is less than the upstream downstream buried tube heat exchange rate.Finally, through the design of 8 groups of seepage and seepage heat pump units under the condition of continuous or intermittent operation of experiment condition, to experimental research on different operation mode with different seepage flow conditions of heat transfer characteristics of buried pipes and system energy efficiency features.The results indicate that intermittent operation of the system for soil temperature recovery is advantageous, and avoids the system run continuously when the buried tube heat transfer rate and heat pump COP decreases.Also found that the seepage velocity is large, because of the heat pump units refrigerating capacity is limited, the buried tube water temperature rise, leading to buried tube heat transfer rate is reduced, in seepage velocity is large, suitable to choose larger refrigerating capacity of heat pump units to maintain the buried pipe in heat stability.