Preliminary Study of Helical Discrete Double-Inclined Ribs Tube with Various Backfill Materials on Horizontal Ground Heat Exchanger Performance

Ground heat exchanger (GHE) is a equipment for transferring heat in space heating or cooling by using geothermal as heat source or sink. Horizontal GHE is one of the preferred types of GHE if the GHE is viewed from the aspect of ease of installation and installation costs. However, horizontal GHE has worse thermal performance than vertical GHE. With the same heat transfer rate, Horizontal GHE requires longer dimensions than vertical GHE. Thus, this problem becomes an obstacle to utilize horizontal GHE. Discrete Double-Inclined Ribs (DDIR) is a method of increasing heat transfer by generating a longitudinal vortex. This study aims to enhance the thermal performance of Horizontal GHE by adding Helical DDIR on straight pipes. The heat-released performance in some backfill materials. The backfill materials are sandy-clay, dry-sand bentonite, and wet-sand bentonite. The study found that tubes modified with helical DDIR are better than smooth tubes in the first 60 minutes. The backfill material provides a significant increase of up to 80 W/m.