Design and Analysis of Shallow-Deep-Mixed Borehole Heat Exchanger Array

At present, the shallow ground source heat pump system often causes soil heat imbalance after long-term operation, and the combination of shallow borehole heat exchanger array and deep borehole heat exchanger array will effectively alleviate this phenomenon. Considering the increase of auxiliary heat source, the design of shallow-deep-mixed borehole heat exchanger array will meet the requirements of cooling load and heat load of buildings. Through the comparison of different schemes, the main design parameters of borehole heat exchanger array are determined, such as buried pipe depth, buried pipe quantity, buried pipe spacing and the position of middle-deep borehole heat exchanger array. In the cooling period, the middle-deep borehole heat exchanger array stops running, and the shallow borehole heat exchanger array bears all the cooling load. In the heating period, the middle-deep borehole heat exchanger array starts to run and some shallow borehole heat exchanger array may stop running. The results show that the shallow-deep-mixed borehole heat exchanger array can alleviate the problem of soil heat imbalance and prolong the efficient operation time of ground source heat pump system.