Numerical and Analytical Study of a Novel Hybrid Earth to Air Heat Exchanger with an Integrated Thermo-Electric Coolers for Arid Climates

Abstract

Abstract Sustainable cooling solutions in hot, arid climates are essential to reduce high energy consumption. Earth to Air Heat Exchanger (EAHE) offers a promising passive cooling strategy, however, its standalone performance is often insufficient to meet thermal comfort requirements. This thesis proposes and investigates a novel hybrid cooling system that integrates the EAHE with a Thermoelectric Cooler (TEC) to enhance cooling capacity, aiming to use the pre-cooled air from the EAHE to improve the TEC’s efficiency. To investigate this system, a comprehensive, transient numerical model was developed in FORTRAN. The model is based on a Finite Volume Method (FVM) for spatial discretization, an implicit Backward scheme for temporal discretization, and a Newton-Raphson method to solve the resulting coupled, non-linear equations. The model’s computational efficiency was optimized through a non-uniform mesh, and its credibility was established through grid and time-step independence studies and validation of the EAHE component against published experimental data. Initial analysis of the EAHE-TEC Case Base (CB) demonstrates a significant, short-term boost in cooling performance. However, this analysis also revealed a critical performance flaw under continuous operation, which was that the rejected heat by the TEC led to rapid thermal saturation of the surrounding soil, “Heat Trap”. This saturation quickly diminished the system’s cooling power, eventually causing it to perform worse than a standalone EAHE. By building on this finding, the system was enhanced by modifying its configuration and operational schedule, which led to substantial cooling capacity, though for a shorter duration. This thesis therefore provides a numerical tool for modelling, with its EAHE component validated, and an enhanced operational strategy for operating the hybrid EAHE-TEC system to improve cooling performance during peak thermal loads in arid climates, such as Saudi Arabia.