Abstract
This study proposed a technology to improve the performance characteristics and coefficient of performance (COP) of a geothermal system by fundamentally preventing underground water discharge and maintaining a constant temperature of the underground heat exchanger composed of bleed discharge water that utilizes two balancing wells using cross-mixing methods. Using the standing column well (SCW) and cross-mixing balancing well underground heat exchanger, we compared and analyzed the effective thermal conductivity characteristics and COP characteristics during heating and cooling modes. Consequently, the cross-mixing balancing well underground heat exchanger exhibited more effective thermal conductivity than the SCW underground heat exchanger, with a high COP. Therefore, suggesting the performance was improved using groundwater flow rather than SCW. The comparison and analysis results of the effective heat map characteristics using the results of the SCW and balancing well system showed that the heating operation for the SCW underground heat exchanger had better thermal conductivity characteristics than the cooling operation. In addition, regarding a balancing well underground heat exchanger, the cooling operation exhibited superior thermal conductivity characteristics. Thus, the performance was considered to have improved due to the flow of activated groundwater in the ground and the rapid heat transfer without heat accumulation.
Highlights
The ground source heat pump system has been growing more than 10% annually in more than 30 countries over the past decade owing to its significant advantages utilizing renewable energy and high efficiency [1]
A geothermal heat pump system maintains a constant temperature throughout the year by using underground heat sources (15–16 ◦C), indicating a higher system efficiency than air heat pump systems that use outdoor heat sources, whose temperatures vary with the season
Infinite energy of the ground is utilized through activation of the aquifer developed in the ground. This method is similar to the method that is based on the bleed rate, but the difference is identified with the utilization of underground water
Summary
The ground source heat pump system has been growing more than 10% annually in more than 30 countries over the past decade owing to its significant advantages utilizing renewable energy and high efficiency [1]. The system energy efficiency was calculated as the ratio of the resultant value of the produced heat obtained by applying the liquid enthalpy test method of the heat source and load sides to the COP of the system to compare it with the existing SCW geothermal system. The linear source theory is well established and has been applied to thermal performance tests since 1980 [31] This approach has been extended to the comparative studies of energy losses in different heat exchanger arrays [32,33,34]. This is because the thermal properties of the underground heat absorption and dissipation are the same under actual loads, when the actual amount of heat that is intended to be used is injected into the ground, and the test can predict the thermal properties of the ground
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