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Performance prediction of a sub-slab heat exchanger for geothermal heat pumps

Journal Article · · Journal of Solar Energy Engineering
DOI:https://doi.org/10.1115/1.2888132· OSTI ID:316127
;  [1]
  1. 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. 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 pipe spacing, flow direction, and a method to determine whether this type of system is feasible for installation in a particular location.
Sponsoring Organization:
USDOE
OSTI ID:
316127
Journal Information:
Journal of Solar Energy Engineering, Journal Name: Journal of Solar Energy Engineering Journal Issue: 4 Vol. 120; ISSN JSEEDO; ISSN 0199-6231
Country of Publication:
United States
Language:
English