A new design of ground heat exchanger with insulation plate for effectively geothermal management. (November 2022)

• Record Type: Journal Article
• Authors: Ngo, Ich Long; Ngo, Van He
• Is Part Of: Geothermics. Volume 105(2022)
• Publication Date: 2022-11
• Subjects: Finite element method -- Geothermal system -- Ground heat exchanger -- Insulation material -- Low–Reynold flow; Hydrogeology -- Periodicals; Geothermal resources -- Periodicals; Énergie géothermique -- Périodiques; GEOTHERMAL ENGINEERING; GEOTHERMAL ENERGY; GEOTHERMAL EXPLORATION; Geothermal resources; Hydrogeology; Periodicals; Electronic journals; 621.44
• DOI: 10.1016/j.geothermics.2022.102512
• Languages: English
• ISSNs: 0375-6505

Abstract

Highlights: A new design of the ground heat exchanger with insulation plates is first proposed. This design can be developed for the other GHE prototypes, such as the double U–tube, the W–shaped tube, and the spiral tube. The outlet temperature is non–linearly proportional to Reynolds number (Re) and approaches a minimum value for a particular Re. The optimal design point where the outlet temperature is minimal moves toward the low Re when Prandtl number increases. The outlet temperature decreases with increasing the pipe depth, however, its variation becomes smaller and flatter when the pipe width increases. The thermal performance increases significantly with decreasing the thermal conductivity of insulation plate. The outlet temperature is up to 15% lower than that without an insulation plate. Abstract: This paper proposes a new design of the ground heat exchanger (GHE) with the insulation plate based on the numerical approach. The heat transfer problem is solved in non-dimensional fashion under the important effects of many characteristic parameters, such as Reynolds number (Re), Prandtl number (Pr), pipe width, pipe depth, particularly the thermal conductivity (TC) and the dimensions of insulation plate. The numerical model has a good validation due to its excellent agreement with the results obtained in the literature. It was found that the temperature at the outlet ( T out *) is non–linearly proportional to Re and approaches a minimum value for a particular Re. Furthermore, the optimal design point where T out * is minimal moves toward the low Re when Pr increases. The T out * also decreases with increasing the pipe depth, however, its variation becomes smaller and flatter when the pipe width increases simultaneously. Additionally, the thermal performance increases significantly with decreasing the TC of insulation plate. The T out * is up to 15 % lower than that without an insulation plate. In particular, the new design of the GHE prototypes with the insulation plate is first proposed. This idea can be developed not only for the U–shaped pipe, but also for the other GHE prototypes that are frequently used in practice, for example, the double U–tube, the W–shaped tube, and the spiral tube. The results obtained are very useful to effectively improve the thermal performance of the GHEs applied in the geothermal management.