Simulation study of a horizontally installed compact helical earth-air heat exchanger for energy efficiency in buildings

This study presents a numerical investigation of a compact Horizontal Helical Earth–Air Heat Exchanger (EAHEHH), developed for the climatic and soil conditions of Viam˜ao, Brazil. The analysis focuses on the influence of the helical pitch (Ph) on the system’s thermal and fluid-dynamic behavior. Simulations were performed in ANSYS Fluent using the Finite Volume Method, and performance was assessed through the thermal potential (TP) and pressure drop (PD), combined in a multiobjective evaluation using the Technique for Order Preference by Similarity to Ideal Solution method (TOPSIS). Results show that the EAHE-HH is effective for air cooling during warm periods, while its heating capacity remains negligible under local winter conditions. Among the tested configurations, Ph = 100 mm provided the highest thermal performance, improving TP by approximately 10 % compared to Ph = 400 mm. Conversely, the largest pitch (Ph = 400 mm) reduced pressure drop by up to 66 % relative to Ph = 100 mm. The EAHE-HH displayed cooling performance comparable to other EAHE systems reported for the same region, supporting its applicability in areas with limited surface availability and reduced excavation requirements. The TOPSIS method has proven effective in evaluating the performance indicators TP and PD, identifying the best performance at opposite extremes of the geometric range under study.