Heat transfer performance experiment of double pipe type ground heat exchangers

With a ground source heat pump system with galvanized double pipe type ground heat exchangers whose pipe buried depth is 60 m and a thermocouple temperature measurement system, experimentally studies the soil temperature, heat transfer performance of the heat exchanger and thermal impact of the heat exchanger on surrounding soil. The results show that the temperature of the soil below the ground 5 m to 60 m is 23.2 ℃ to 23.7 ℃ in Nanning city; the appropriate flow of Ф80 and Ф65 double pipe type heat exchangers is 1 500 L/h and 1 200 L/h separately, and the unit depth heat transfer quantity is 107.5 W/m and 81.4 W/m separately; the heat transfer coefficient of the inner tube has little effect on the heat transfer performance of double pipe type heat exchanger; the heat transfer performance in the flow mode of inside entering and outside leaving is superior to that in the mode of outside entering and inside leaving; intermittent operation is favourable to soil temperature recovery.