• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.4 no.1
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• pp.11-19
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• 2008

Groundwater flow in confined aquifer and heat transport in underground geologic media are using same governing equation(line source) like well fuction. Therefore the conventional slope method using only later data obtained from in-situ thermal response test to determine the thermal conductivity of vertical geothermal heat exchanger(GHEX) is basically identical with one of Theis straight line method of aquifer test under artesian condition. In case that the pumping rate(Q, $m^3$/d) and drawdown(s,m) which are used for input data of existing hydrogeologic computer programs for aquifer test are replaced and converted to supplying heat energy per unit length of bore hole(Q/L,w/m or Kcal/h.m) and temperatures (T,$^{\circ}C$)measured at in and out-let of GHEX as in put data respectively, thermal conductivity around geothermal heat exchanger can be easily estimated without any special modification of the existing hydrogeologic computer program. Two numbers of time series temperature variation data obtained from in situ geothermal response test are analized using Theismethods(standard curve and straight line method) by using existing aquifer test program and conventional Slope method proposed by ASHRAE. The results show that thermal conductivity values estimated by two straight methods are identical and the difference of estimated values between standard curve methods and Slope method are also within acceptable ranges. In general,the thermal conductivity estimated from Theis straight linemethod gives more accurate value than the one of Slope method due to that Slope method uses only visual matching otherwise Theis method uses automatic curve matching estimation with reducing RSS.

• The Korean Journal of Pain
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• v.19 no.2
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• pp.137-141
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• 2006

Background: It has been known that melatonin is involved in the modulation of nociceptive transmission. However, the effect of melatonin administered spinally has not been examined. Therefore, we examined the effect of melatonin on the formalin-induced or thermal-induced nociception at the spinal level. Methods: Intrathecal catheter was inserted into the subarachnoid space of male Sprague-Dawley rats. Pain was assessed by formalin test (induced by injection of $50{\mu}l$ of a 5% formalin solution to the hindpaw) or Hot-Box test (induced by radiant heat application to the hindpaw). The effect of intrathecal melatonin was examined on flinching behavior in the formalin test or withdrawal response in Hot-Box test. Results: Intrathecal melatonin produced a limited, but dose-dependent reduction of the flinching response during phase 1 and 2 in the formalin test. In addition, melatonin delivered at evening also decreased the flinching response in both phases of the formalin test. Melatonin restrictively increased the withdrawal latency in Hot-Box test. Conclusions: These results suggest that melatonin is active against the formalin- and thermal-induced nocicpetion at the spinal level, but the effect is limited.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.93-99
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• 2014

Use of geothermal energy has been increased for its economical application and environmentally friendly utilization. Particularly, for energy piles, a spiral coil type ground heat exchanger (GHE) is more preferred than line type GHEs such as U and W shaped GHEs. A PHC energy pile with spiral coil type GHE was installed in an area of partially saturated dredged soil deposit, and a thermal response test (TRT) was conducted for 240 hours under a continuous operation condition. Besides, remolded soil samples from different layers were collected in the field, and soil specimens were reconstructed according to the field ground condition. Non-steady state probe methods were conducted in the lab, and ground thermal conductivity and thermal diffusivity were measured for the different soil layers. An equivalent ground thermal conductivity was calculated from the lab test results and it was compared with the field TRT result. The difference was less than 5%, which advocates the use of an equivalent ground thermal conductivity for the multi-layered ground. Furthermore, this paper also represents an equivalent ground thermal diffusivity evaluation method which is another very important design parameter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.4
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• pp.306-314
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• 2012

Several numerical or analytical models have been proposed to analyze the thermal response of vertical ground heat exchangers (GHEX). However, most models are valid only after several hours of operation since they neglect the heat capacity of the borehole. Recently, the short time response of the GHEX became important in system simulation to improve efficiency. In this paper, a simple new method to evaluate the short time response of the GHEX by using an analogy model of electric circuit transient analysis was presented. The new transient heat exchanger model adopting the concept of thermal capacitance of the borehole as well as the steady-state thermal resistance showed the transient thermal resistance of the borehole. The model was validated by in-situ thermal response test and then compared with the DST model of the TRNSYS program.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.168.2-168.2
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• 2010

The growing market for geothermal heat pump system requires great consideration of quality control and assurance in design and construction. The borehole heat exchanger of GHP system should be sustainable, economical and ecological. Thermal Response Test (TRT) is a useful method for site investigation to obtain reliable data for a optimal system design from the technical and economical aspect. Intensive researches combined with exchange of experiences on an international level within the IEA ECES Annex 21 improved the technology. Major subjects on the interpretation of TRT are development of improved evaluation models, evaluation of the TRT with respect to geological layers and investigation of the influence of ground water. Current status of TRT in South Korea, as well as a new version of the Korean TRT standard test procedure was presented. TRT is mostly used for governmental supported projects with corresponds to more than 100 GCHP systems per year. More than 200 tests are applied, mostly on single U-tube heat exchangers (about 95%). Bentonite is the most common grouting to be used. KIGAM (Korea Institute of Geoscience & Mineral Resources) is also keeping a GIS geological and geothermal database. In the institute also laboratory measurements of rock properties are carried out. About 90% of the laboratory measurements of the rock heat conductivity shows higher values than the in-situ TRT.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.33-38
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• 2008

A ground-loop heat exchanger in a ground source heat pump system is an important unit that determines the thermal performance of a system and its initial cost. The Size and performance of this heat exchanger is highly dependent on ground thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This study was performed to investigate the effect of some parameters such as borehole lengths, various grouting materials and U-tube configurations on ground effective thermal conductivity. In this study, thermal response tests were conducted using a testing device with 9-different ground-loop heat exchangers. From the experimental results, the length of ground-loop heat exchanger affects to the effective thermal conductivity. Among the various grouting materials, the bentonite-based grout with silica sand shows the largest thermal conductivity value.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.28-35
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• 2016

The in-situ thermal response test for the design of a ground heat exchanger of geothermal heat pumps have difficulty in predicting the outlet temperature according to the variation of conditions due to the expense and time. This paper suggests a 3-D CFD analysis method to predict the heat transfer performance of vertical type ground heat exchanger, which is mostly used in national, and the outlet temperature and the slope of two in-situ thermal response tests were compared to test the proposed CFD reliability. The results of CFD analysis showed that the outlet temperature was predicted to within $0.5^{\circ}C$ of the actual value and the slope was predicted to within 1.6%. The reliability of the CFD analysis method was confirmed using this process, and the outlet temperature prediction of the two in-situ thermal response tests was obtained by changing ${\pm}20%$ of the flow rate and the effective thermal conductivity conditions, respectively. The results of CFD analysis showed that the outlet temperature of Case 1 was 28.0 (-20%) and $29.6^{\circ}C$ (+20%) for the flow rate variation and $29.6^{\circ}C$ (-20%) and $28.0^{\circ}C$ (+20%) for the effective thermal conductivity variation, and the outlet temperature of Case 2 was 28.4 (-20%) and $29.8^{\circ}C$ (+20%) for the flow rate variation and $29.7^{\circ}C$(-20%) and $28.4^{\circ}C$(+20%) for the effective thermal conductivity variation.

• Journal of the Korean Solar Energy Society
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• v.31 no.4
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• pp.80-86
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• 2011

Investigation of the effective soil thermal conductivity(k) is the first step in designing the ground loop heat exchanger(borehole) of a geothermal heat pump system. Another important factor is the borehole thermal resistance($R_b$). Thermal response tests offer a good method to determine the ground thermal properties for the total heat transport in the ground. This is done by supplying a constant heat power into a borehole heat exchanger. There are two methods to supply a constant heat power. One is to employ the electricity provided by Korea Electric Power Corporation(KEPCO). The other is to use electricity generated by a generator. In this study, the power supply regulation was found to reduce when the electricity generated by the generator was used. This is because the generator evaluated with the power supply characteristically reduces the power supply regulation between an overload and a complex using. But it sometimes occurs a power supply regulation in In-situ thermal response test. In this case getting of k,$R_b$ requires delay times and restored normal state. However, the effect of the delay times and restored normal state on the soil thermal conductivity and borehole thermal resistance is very small. Therefore it is possible to use a generally accepted delay times and restored normal state in the analysis. In this work, it is also shown that an acceptable range of ${\Delta}k$, ${\Delta}R_b$ for normal state and regulation state might be approximately 0.01-0.16W/m k, and -0.004-0.007m K/W, respectively. Thus, restored normal state of power supply regulation is valuable to recommend.

• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.93-106
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• 2010

In performing a series of in-situ thermal response tests, the effective thermal conductivities of six vertical closed-loop ground heat exchangers were experimentally evaluated and compared one another, which were constructed in a test bed in Wonju. To compare thermal efficiency of the ground heat exchangers in field, the six boreholes were constructed with different construction conditions: grouting materials (cement vs. bentonite), different additives (silica sand vs. graphite) and the shape of pipe-sections (general U-loop type vs. 3 pipe-type). From the test results, it can be concluded that cement grouting has a higher effective thermal conductivity than bentonite grouting, and the efficiency of graphite better performs than silica sand as a thermally-enhancing addictive. In addition, a new 3 pipe-type heat exchanger provides less thermal interference between the inlet and outlet pipe than the conventional U-loop type heat exchanger, which results in superior thermal performance. Based on the results from the in-situ thermal response tests, a series of economic analyses have been made to show the applicability of the new addictives and 3 pipe-type heat exchanger.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.123.2-123.2
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• 2010

본 논문에서는 2008년 4월 이후 지열원 열펌프가 설치되어지는 현장에 시험공의 지중열전도도를 현장열응답법을 이용하여 측정하였으며, 그간에 측정된 지중열전도도를 이용하여 전국의 지중온도 및 지중열전도도의 산포도를 정리하였다. 지중열교환기의 심도가 150m일 때 지중온도 분포는 약 $12.0{\sim}19^{\circ}C$의 넓은 분포를 보였으나 대부분의 지중온도가 $15.0{\sim}17.0^{\circ}C$의 범위에 분포하였으며, 지중열전도도의 경우도 마찬가지로 1.50 ~ 9.00 W/mk 값으로 아주 넓은 분포를 보였으나 2.30 ~ 2.90W/mk 값이 가장 많이 나타냈다.