Experimental Ground Source Heat Pump System to Investigate Heat Transfer In Soil

Abstract

The earth is an energy resource which has more suitable and stable temperatures than air. Typical values for Coefficient of Performance (COP) of Ground Source Heat Pumps (GSHPs) are up to 8 while it is 4 of air source heat pumps. GSHPs were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. Design of GSHP systems in different regions of US and Europe is performed using data from an experimental model. However, there are many more techniques including some complex calculations for sizing GHEs. An experimental study was carried out to investigate heat transfer in soil. Measured fluid inlet temperatures were used in the numerical simulation and the fluid outlet temperatures were calculated. A parametrical study was conducted to investigate effects of soil thermal properties and geometrical parameters on heat transfer from ground heat exchanger. It is seen that the soil thermal conductivity has great importance on heat transfer. Also, burial depth and distance between pipes are other parameters to be considered for sizing GHEs.