Field study using the ground as a heat sink for the condensing unit of an air conditioner in Thailand

This paper reports on an investigation of the feasibility of using earth to absorb the heat normally rejected into the atmosphere by the condensing unit of a conventional air conditioner. To this end, a copper tube of about 67 m in length was buried at a depth of 1 m underground, where the temperature was constant at about 27°C year round. The copper coil of an air type condenser is about 22 m long. For the buried condenser, the R-22 refrigerant requirement was 5.8 kg as compared with 1.2 kg for the air condenser system. It was found that with this modified condensing unit, the coefficient of performance (COP) was much higher than that of a conventional one: it varied between 7.1 (daytime) and 8.1 (nighttime), compared to 2.8 and 3.1, respectively. The ground temperature near the buried copper coil did not increase, thus demonstrating the ability of the soil to dissipate the absorbed heat into the ground. Consequently, there is a high potential for contributing to environmental protection by using the ground as a heat sink. The elimination of the condensing fan is an additional advantage of the buried condenser system.