Evaluating Groundwater Flow Effects for Enhancement of Ground-Source Heat Pipes in the Case of the Toyohira River Alluvial Fan, Japan

Yoshikata Sakata,Masataka Mochizuki,Katsunori Nagano,Johnson Chishimba

doi:10.3390/hydrology8030135

Abstract

The purpose of this study was to evaluate the potential enhancement of ground-source heat pipes by groundwater advection at two sites within an alluvial fan of Toyohira River, Sapporo. Two sites were selected: one in the fan toe, for negligible groundwater flow (Site 1), and the other in the apex for fast flows, the latter characterized by a specific discharge of 1.0 m/d from the losing river (Site 2). The evaporator section(s) of a single (double) heat pipe(s) was installed in a borehole at each site; the condenser section(s) on the ground was placed inside cooled brine at a set temperature, resulting in heat extraction under steady conditions. The single heat pipe experiments showed that the heat extraction rates ranged between 0.23 and 0.79 kW and were not clearly different at the two sites, considering some uncertainty. For double heat pipes, the heat extraction rates were unchanged at Site 1, but were about 146% higher at Site 2 compared to the single tests, due to groundwater advection. This study revealed that the number of ground-source heat pipes required could be reduced from three to two in areas near Site 2.

Highlights

Ground temperatures are the result of the thermal energy balance between the downward heat flux from solar radiation and the upward flux from the Earth’s interior [1].Generally, the ground temperature is almost equal to or several Kelvin higher than the average outdoor temperatures at a given location but is much less variable
If the cost-effective systems are designed with two or one heat a field experiment on ground-source heat pipes different pipes,This the study shapesdemonstrates of condensers under the pavements must be modified or theinfins must groundwater flow effects in the alluvial fan of ground-source heat be added to ensure the same efficiency of snow melting as with three condensers
Transient analysis of heat transfer in ground-source heat uncertainty was considered, single heat pipes at Site 2 showed no significant improvement pipes will be required to evaluate the thermal performance over the year, considering the in the heat extraction rates when compared to Site 1, because the heat energy supplied by change in climate and groundwater conditions

Summary

Introduction

The ground temperature is almost equal to or several Kelvin higher than the average outdoor temperatures at a given location but is much less variable. This stability can be confirmed in any location in the world during all seasons in each year, indicating a degree of thermal enthalpy underground and potential for renewable energy utilization. A heat pipe is an excellent thermal energy device that works on the principles of heat conduction and phase transition to effectively transfer thermal energy [2]. The geothermal energy is extracted through the evaporation of the working fluid and transported

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