• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.7 no.2
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• pp.23-29
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• 2011

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the plate heat exchanger with corrugation height by numerical analysis. Plate heat exchanger of three types was designed, which was corrugation height 3.1mm, 2.8mm and 2.5mm. The plate heat exchanger was numerically investigated for Reynolds number in a range of 950~3,380. The temperatures of the hot side were performed at $14.5^{\circ}C$ while that of the cold side was conducted at $4.5^{\circ}C$. The results show that the performance of heat transfer coefficient for corrugation height 2.5mm increases about 9.5~17.1% compared to that of corrugation height 3.1mm. On the other hand, the performance of pressure drop for corrugation height 2.5mm is remarkably higher than that of corrugation height 3.1mm, about 65.7~86.0%.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.172.2-172.2
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• 2010

This study was carried out in order to reduce the installation expense of heating system for greenhouse comparing to geothermal heat pump and develope the coefficient of performance (COP) for a heat pump. For getting plenty of heat flux from geothermal energy. Surface water in river channel was used for getting a lots of geothermal heat by penetrating water through underground soil layer of the river bank that make heat transmission to passing water. The range of water temperature after the process of Ground filtration is 13~18 degrees celsius which is very similar to low heat source of geothermal heat pump system and the plenty amount of heat source from that make the number of geothermal heat exchanging hole and the expense for geothermal heat exchanger construction reduced. Drainage well is also used for returning filtration water to the aquifer that keep the water good recirculation from losing geothermal heat and water resource. For the COP improvement of Heat pump, thermal storage tank with separating insulation plate according to the temperature difference make the COP of Heat pump that is similar to thermal storage tank with diffuser. Developed thermal storage tank make construction expense cheaper than customarily used one's. and that sand filter and oxidation sand (FELOX) are going to be used for improving ground filtration water quality that make heat exchanger efficiency better. All above developed component skill are going to be set on the Ground filtration water source heat pump system and applied for medium, large scale for protected greenhouse in riverside area and on-site experiment is going to do for optimizing the heating system function and overcome the problem happening in the process of on-site application afterward.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.6
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• pp.347-354
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• 2009

Experimental study on a cross-flow air-cooled plate heat exchanger (PHE) was performed. Two types of PHEs were manufactured either with single-wave plates or with double-wave plates in parallel. Cooling air flows through the PHEs in a crosswise direction against internal hot water. The heat exchanger aims to substitute open-loop cooling towers with closed-loop water circulation, which guarantees cleanliness and compactness. In this study, prototype single-wave and double-wave PHEs were designed and tested in a laboratory scale experiments. From the tests, the double-wave PHE shows approximately 50% enhanced heat transfer performance compared to the single-wave PHE. However, the double-wave PHE costs 30% additional pressure drop. For the commercialization, a wide channel design for air flow would be essential for performance and reliability.

• Smart Structures and Systems
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• v.34 no.1
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• pp.41-50
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• 2024

The accurate measurement of temperature in the ground source heat pump system is crucial for assessing the thermal response of the system and validating the numerical model for parametric study, which is necessary for the thermal performance evaluation of the geothermal energy system. Conventional temperature sensors have some disadvantages such as they are difficult to install, and their position can be shifted during the backfill process of the ground heat exchanger. In this study, Fiber Bragg Grating (FBG) sensors were used to measure the temperature change of a recently developed ground heat exchanger (Coil Column Unit, CCU). FBG sensors were first calibrated in a thermal chamber alongside a correlation sensor (RTD sensor). The calibrated sensors were then mounted on the pipe surface at each spiral of the CCU to measure how temperature changes during the in-door mockup thermal response test. Finally, the measurement results of the FBG sensors were verified with a finite element coded program. The results indicated that the temperature difference between the numerical analysis and the experiment was less than 1%, which is significantly lower than that of the previous study using the RTD sensors. Therefore, it is feasible to apply FBG sensors for temperature measurement during the operation of the TRT of the geothermal energy system.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.452-455
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• 2007

The geothermal heat pump system is designed for cooling and heating for three stories building (2,435 $m^2$) includes total 79 heat pumps. Therefore, the monitoring system is installed for each floor and the data is automatically transmitted to the monitoring system. Heat exchange rate and temperature of a geothermal heat pump system have been monitored for a long period. The seasonal operation of geothermal heat pump shows the different shape of heat exchange rate for cooling and heating. Ground water flow can influence on heat exchange rate and thermal storage of the system. In order to define the hydraulic characteristics and groundwater temperature variation, the relationships among air temperatures, groundwater temperatures, water table, and precipitation are analysed.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.2
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• pp.7-11
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• 2015

Recently, as the demand for sustainable energy sources is increasing, ground-source heat pump (GSHP) systems are receiving growing attention. However, the initial cost of GSHP system is higher than it of the conventional systems, especially, in small-size buildings. Therefore, for the application to the small-size building, it is necessary to develop small-size ground heat exchanger with small-size buildings. In this study, analysis of unit-type heat exchanger due to grouting materials. As a result, 1492.14 W of heat exchange rate was acquired in the condition of cement-silica sand-graphite materials.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.2
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• pp.1-6
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• 2016

A ground air heat exchanger (GAHX), also called earth air heat exchanger is a useful technology to be integrated with other renewable energy technologies. In this study, ground-air heat exchanger system for the air source heat pump is introduced. The purpose of this study is to design the volumetric flow rate and the length of GAHX system. A GAHX length model equation has been developed and used for calculation. GAHX thermal efficiency are recommended as 75% and 85% in order to optimize pipe length. $2,750m^3/h$, $2,420m^3/h$ of volumetric flow rate on 88.3m, 111.7m length are suggested for providing 7.5kW thermal capacity. And the number of path is recommended more than two to minimize pressure drop. For future study, advanced model equation study with ground thermal behavior and a more efficient GAHX design will be considered.

• Journal of Biosystems Engineering
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• v.32 no.1 s.120
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• pp.30-36
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• 2007

Geothermal heat pump systems use the earth as a heat source in heating mode and a heat sink in cooling mode. These systems can be used for heating or cooling systems in farm facilities such as greenhouses for protected horticulture, cattle sheds, mushroom house, etc. A horizontal type means that a geothermal heat exchanger is laid in the trench buried in 1.2 to 1.8 m depth. Because a horizontal type has advantages of low installation, operation and maintenance costs compared to a vertical type, it is easy to be adopted to agriculture. In this study, to heat and cool farm facilities and obtain basic data for practical application of horizontal geothermal heat pump systems in agriculture, a horizontal geothermal heat pump system of 10 RT scale was installed in greenhouse. Heating performance of this system was estimated. The horizontal geothermal heat pump used in this study had heating COP of 4.57 at soil temperature of 14$^{\circ}C$ for depth of 1.75m and heating COP of 3.75 at soil temperature of 7$^{\circ}C$ for the same depth. The stratification of water temperature in heat tank appeared during the whole heat rejection period.

• Korea Journal of Geothermal Energy
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• v.10 no.2
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• pp.25-31
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• 2014

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.2
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• pp.1-9
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• 2019

In a ground-source heat pump (GSHP) system, a vertical ground heat exchanger (GHE) is widely accepted due to a higher thermal performance. In the vertical GHE, grout (also called grouting material) plays an important role in the heat transfer performance and the initial installation cost of the GHE. Bentonite-based grout has been used in practice because of its high swelling potential and low hydraulic conductivity. This study evaluated the thermo-physical properties of the bentonite-based grouts through lab-scale measurements. In addition, we conducted performance simulation to analyze the effect of mixed ratio of grouts on the design length and thermal performance of the vertical GHE. The simulation results show that thermally-enhanced grouts improve the heat transfer performance of the vertical GHE and thus reduce the design length of GHE pipe.