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 (EAHE-HH), developed for the climatic and soil conditions of Viamão, Brazil. The analysis focuses on the influence of the helical pitch ( P h ) 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 multi-objective 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, P h = 100 mm provided the highest thermal performance, improving TP by approximately 10 % compared to P h = 400 mm. Conversely, the largest pitch ( P h = 400 mm) reduced pressure drop by up to 66 % relative to P h = 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. • This work presents a numerical investigation of a Horizontal Helical Earth-Air Heat Exchanger (EAHE-HH), accounting for the climatic conditions and soil properties specific to a locality. • The influence of different helicoidal pitches ( P h ) on the system's geometric configuration has been investigated. • The performance of the different EAHE-HH configurations is evaluated using two parameters: thermal potential ( TP ) and pressure drop ( PD ), thus constituting a multiobjective problem. • The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is employed to perform the multiobjective evaluation. • As a result, the EAHE-HH systems are shown to be suitable for air cooling during hot periods, although their heating capacity is negligible during cold periods. • The configuration with P h = 100 mm yielded the highest thermal performance, surpassing the P h = 400 mm case, the least efficient configuration, by approximately 10 %. • 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.