Experimental and thermodynamic analyses of a pilot-scale Earth–Air Refrigeration System designed for hot and dry climatic region

With accelerating climate change, reducing emissions due to heating/cooling built environment has become critical, as conventional vapour-compression heating/cooling systems are responsible for emissions of greenhouse gases due to both electricity use and refrigerant life-cycle. This work presents the design and analysis of an Earth–Air Refrigeration System (EARS) using earth–air heat exchanger (EAHE) as a low-Carbon alternative for space cooling in hot and dry climatic regions. A pilot-scale EARS system was designed for a 1 cubic-meter test hut and its performance has been analysed experimentally and thermodynamically using a one-dimensional transient heat-transfer model. The experimental results show a reduction in the indoor temperature of the hut by around 10 °C compared to the ambient air during the peak sun hours. Similar reduction has also been predicted by the thermodynamic model with deviation from experimental results within the range of – 2.41% to 6.39%. This validated the capability of the thermodynamic model developed and it has been further used to predict the performance of the EAHE using parametric studies on pipe materials, air flow rate, etc. The results of the studies show: (a) the marginal effect of variations in pipe materials on outlet air temperature, (b) the dominance of air-side convection and soil conduction in the overall heat transfer co-efficient of the EAHE, (c) the performance of EAHE is more sensitive to flow conditions and geometric configuration than to the choice of pipe material, (d) the optimum performance was observed at an air flow rate of 0.5–1.0 kg/s with the length of the and an EAHE length of 6–12 m when PVC was used as the pipe material.