Abstract
For the purpose of using soil as heat sink and heat source, the quantity of heat exchanged with soil and variations of water temperature in a steel pile were measured. The steel pile was 400 mm in diameter and was installed vertically at a depth of 20 m in soil. Numerical calculation was done using a three-dimensional finite difference equation to predict water temperature and quantity of heat exchanged with soil. The results obtained were as follows. 1) The heat released to soil per unit length of the steel pile was 290 W/m during operation of the equipment, and 115-140 W/m was the average value over 24 hours. 2) During operation of the equipment, 60-70 % of the input heat by the equipment was released to soil. The ratio of released heat and input heat per day was 80-95 %. 3) Heat collected from soil was 230-405 W/m, during operation of the chiller, and 70-90 W/m was the average value over 24 hours. 4) During operation of the chiller, 50 % of the heat absorbed by the chiller was collected from soil. The ratio of collected heat and absorbed heat per day was 95 %. 5) The heat exchanged with soil per day was 58 kW as heat sink, and 31-42 kW as heat source. 6) The numerical results agreed well with the experimental results, which showed that the calculation method may predict variations in water temperature and heat exchanged with soil.
