Performance prediction of a sub-slab heat exchanger for geothermal heat pumps
Book
·
OSTI ID:483917
- Univ. of Idaho, Moscow, ID (United States). Dept. of Mechanical Engineering
A large portion of the installation cost of a ground-coupled heat pump system is for the excavation necessary for ground coil placement. One possible method of reducing this cost is to place the ground coils beneath the slab floor of the building. This configuration of ground coil placement has not been specifically addressed in previous research. Freezing of the soil must be avoided in such a system. To simulate the temperature response of the surrounding soil to heat pump operation, a computer model was developed which incorporates line source theory in the form of a system of rings. The fluid temperature change along the length of the coil was used to determine the distribution of the ground load throughout the ring system. The model includes an adiabatic upper boundary, seasonal soil temperature variation, and thermal interference throughout the system. This model was used to explore the effects of pipe spacing and flow direction on soil temperature response under various load conditions. Using these results, the minimum soil temperature over a season was predicted. Based on these results, design recommendations for ground coil installation are provided based on available area, soil type, heat extraction rate, depth of coil beneath the slab floor, and depth of slab floor below grade. These include recommendations for spacing between pipe loops, flow direction, and a method to determine whether this type of system is feasible for installation in a particular location.
- OSTI ID:
- 483917
- Report Number(s):
- CONF-961105--; ISBN 0-7918-1527-7
- Country of Publication:
- United States
- Language:
- English
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