Thermal design of Earth-to-Air Heat Exchanger: Performance analysis of new transient semi-analytical model for short period of continuous operation

Abstract

This paper concerns the thermal design of Earth-to-Air Heat Exchanger (EAHE). The paper presents new transient semi-analytical models to estimate i) the disturbed soil thermal resistance of EAHE pipe as a function of duration of operation and ii) thermal performance of EAHE operating under transient conditions. The main aim of this study is to evaluate the parameter choices of this new model for short period of continuous operation of the system (less than 70 h). The results show that time discretization steps of 15 min and 1 h present and lead to appreciable results compared to the experiments. Therefore, the variation of the layer length step of the buried pipe does not alter simulation results. In terms of precision of the soil temperature profile, refined solutions were obtained by the decreasing of the disturbed soil radius and the increasing the number of roots of Bessel's functions. Furthermore, the effect of the variation of surrounding soil radius is discussed for short period of continuous operation of the system. The time step of 1 h and the interval of the surrounding soil radius of 0.4 m–1.1 m are found accurate for good results with a reasonable computational time.

Keywords

• Earth-to-air heat exchanger
• Transient semi-analytical model
• Short period of continuous operation
• Performance analysis