Parametric optimization of earth-air heat exchangers (EAHEs) for central air conditioning

•EAHE system is combined with AHU to reduce the compressor power and annual cost.•Analytical model is built to evaluate the effect of different geometry parameters.•Optimum diameter is found to be 0.35 m and length depends on the number of pipes.•Maximum power saving is 44%, and the maximum cost reduction is 16.6%.•Payback period is ranged from 0.35–9.3 years depending on the number of pipes. This paper presents a thorough parametric analysis of an earth-air heat exchanger (EAHE) that reveals optimal parameters for minimizing the cost of central air conditioning in a hot and dry climate. A mathematical model with the aid of MATLAB is developed to optimize different parameters including length, diameter, and number of pipes. The performance of the selected cooling system is evaluated in terms of compressor power consumption, overall power savings, overall cost reduction, and payback period. As a case study for our analysis, a 25-TR air-conditioning system was chosen to cool an operation room in a hospital in Egypt. The maximum reduction in compressor power consumption is estimated to be 44%. Moreover, the reduction in the annual costs is estimated to be 16.6% with a payback period that increases as the number of pipes increases.