Abstract
In this study, a mobile measuring device was developed and a thermal response test that applied a standing column well-type heat exchanger was conducted to obtain design parameters from field measurements. The main purpose of this study was to investigate the effects of thermal conductivity and geothermal resistance on site, including the flow and effects of natural convection of groundwater in boreholes. We compared, analyzed, and investigated the effective thermal conductivity of a borehole heat exchanger system and the effective thermal conductivity that was not applied when bleeding single-well standing column wells (SCWs), which is called an open-type standing column well geothermal heat exchanger system. We also investigated the heat transfer characteristics during the bleeding of two-well type SCWs, where water is injected from one clearing hole to the returning hole depending on the bleeding rate. Artificial recharging was used to inject the change of thermal conductivity from the bleeding rate of a geothermal heat exchanger into another SCW type. From the comparison results of the thermal conductivity of the multi-well and single-well underground heat exchangers, four times higher efficiency than the single-well was obtained. The reason for this is considered to be energy utilization utilizing groundwater energy.
Highlights
The development of alternative energy sources is becoming increasingly necessary in Korea to prepare for an era of hefty oil prices, as Korea faces energy and resource shortages and imports approximately 97% of its fossil fuels
The Korean government set up a plan in 2000 for stimulating the consumption of renewable energy in order to increase the renewable energy share of the total energy consumption to 5% by 2018 [4]
Many studies using single- and multi-well standing column wells were carried out recently, and studies reported that the efficiency is improved by using a plurality of SCW systems and using bleeding of water rather than a sealed heat exchanger
Summary
The development of alternative energy sources is becoming increasingly necessary in Korea to prepare for an era of hefty oil prices, as Korea faces energy and resource shortages and imports approximately 97% of its fossil fuels. It is necessary to select a test suitable for local conditions and prepare to compare the thermal performance of various BHE types of underground heat exchangers [14]. Standing column wells are in limited use since the development of geothermal heat pump systems; in recent years, overall performance improved in areas with adequate hydrological and geological conditions, attracting more attention [22,28–30]. Many studies using single- and multi-well standing column wells were carried out recently, and studies reported that the efficiency is improved by using a plurality of SCW systems and using bleeding of water rather than a sealed heat exchanger. SCW systems, which are more efficient than sealed type, are increasingly in areas where geological properties and groundwater utilization conditions are suitable [31,32].
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