Thermal analysis of a low-cost ground heat exchanger using laboratory simulator

Shallow depth of ground can be use as heat source in winter, and heat sinks through summer has shown, numerically and experimentally that it is able to produce potential cooling and heating throughout the year. The cooling and heating can be extracted / injected by means of a novel affordable thermal-pipe heat exchanger with heating medium (water/glycol) technique. To exploit effectively the heat capacity of the ground, a heat-exchanger system has to be designed and constructed to facilitate heat transfer to/from the ground. Because of the shallow depth of the soil around the thermal-pipe, the experiment has limitations in rapid change of input parameters. Thus, this paper presents the performance of the thermal-pipe ground heat exchanger (TP-GHE) based on experimental studies using a laboratory simulator. Different input parameters have been investigated such as heat medium (water/glycol) inlet temperature varies from 10 to 11°C, ground temperature (Tg) varies from 4 to 12°C and water/glycol flow rate at 0.01– 0.03 kg/s. The actual soil surrounding was created in a plastic tank and nine copper thermal pipes of 1m length and 0.125m pitch between them were used in the simulator. A chiller, was used to maintain the soil temperature constant. Results show that the flow rate of 0.03 kg/s and Tground of 13 °C gives the highest temperature lift with 6.62 °C or 26.5 % relative to the inlet temperature. The highest heat transfer rate at 308.3 W was obtained at a flow rate of 0.03 kg/s. The experimental results also have been validated with a field test from the industrial partner and were found to be in close agreement with, numerically analysis results.