Simulation Study On Performance Of Air-ground Compound Source Heat Pump System

As a new air conditioning technology of energy conservation, the ground source heat pump has been widely applied in residential and office building. As the big difference between the heating load and cooling load in the hot summer and cold winter region, the ground source heat pump system's long-term operating would lead the soil energy to become unbalanced, make the soil temperature rising year by year, decrease coefficient of performance of the system, and finally reduce the service time of heat pump units. Based to above-mentioned problems, this paper presents a new air-ground compound heat pump system, obtaining the natural energy from summer to winter, increasing the COP of the system, and expanding the application range of ground source heat pump.The air-ground compound heat pump system put in this paper not only overcomes the disadvantages of single source heat pump system, but also solves the unbalanced heat quantity of soil in the hot summer and cold winter region. Comparing to the general cooling tower-ground source heat pump, the scale of this system is smaller, and the first investment is cheaper. In addition, the stability of the system is better. Firstly, this paper expounds the operating principle of the system. In winter, the air side heat exchanger does not work, providing the heat to indoor by ground side heat exchanger. In summer, we can choose different operating modes of the system according to the need.This paper takes a villa building as study object, using DeST(energy simulation software) calculate the building's heating load and cooling load every hour in a year, and studies the heat pump system's interval operating and continuous operating in winter and summer respectively. In cooling season, according to release the hot quantity to the oil being equal to 20%~100% of the total cooling load in summer, we can get the temperature demarcation point in the different conditions. According to the temperature demarcation point the heat pump operation mode can be switched. At the same time, we calculate coefficient of performance of the system. In heating season, the heat pump only taking heat from soil can satisfy the need of indoor heating load, and we also calculate coefficient of performance of the system. For comparing the COP of the system in the different operating mode, this paper calculates the single air source heat pump system in winter and summer respectively. The results show that the interval operating of the compound source heat pump is the best operating mode in summer. The interval operating of the single stage compression soil source heat pump is the best operating mode in winter and more suitable for the hot summer and cold winter region.