Abstract
The slinky ground heat exchanger (GHE) is the most widely utilized horizontal-type GHE, however, this GHE has a low curvature coil. The GHE has poor thermal mixing, especially at a low flowrate. At this flowrate, the coil heat exchanger has similar performance to a straight tube heat exchanger. Discrete double-inclined ribs (DDIR) are well known for their good thermal mixing by generating a vortex in straight tubes. In this paper, a numerical analysis of thermal performance for the plain coil and DDIR coil is discussed. It was found that the thermal performance of the DDIR coil was slightly higher than that of the plain coil in laminar flow. In turbulent flow, the DDIR coil was superior to the plain coil only in the first 149-min operation. The first 60-min analysis shows that in laminar flow, the average heat transfer rate in the plain coil is 59 W/m and in the DDIR coil is 60.1 W/m. In turbulent flow, the average heat transfer rate is 62 W/m, and the plain coil is 62.3 W/m. The copper DDIR coil material produced a better heat transfer rate than that of the composite and High-Density Polyethylene (HDPE). Sandy clay has the highest heat transfer rate. The influence of ground thermal conductivity on the performance of the GHE is more dominant than convection in the DDIR coil.
Highlights
In recent decades, lack of energy, global warming, and air pollution are serious threats to the lives of living creatures in the world
This study aims to highlight the potential use of the Discrete double-inclined ribs (DDIR) coil in the slinky coil in ground heat exchangers under transient conditions in some different conditions
This study presents the results of numerical simulations of heat extraction from two types of horizontal slinky coil, namely the DDIR coil and the plain coil in laminar and turbulent flow
Summary
Lack of energy, global warming, and air pollution are serious threats to the lives of living creatures in the world. Several attempts have been made to reduce the impact of CO2 emissions by conserving energy [2,3,4]. To achieve this target, many researchers have focused on sustainable energy resources such as hydropower, geothermal energy [5,6], biomass, solar [7], and wind [8]. For the utilization of geothermal energy sources in shallow grounds, the ground source heat pump (GSHP). There are two types of GSHP, including open-loop systems using groundwater or surface water directly and closed-loop systems with ground heat exchangers [11,12].
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