• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.195.1-195.1
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• 2011

This paper presents an experimental study on a new potential geothermal energy source obtained from tunnel structures. An "energy textile", which is a textile-type ground heat exchanger, was fabricated between a shotcrete layer and a guided drainage geotextile in the tunnel lining system. To examine the long-term thermal behavior of the energy textile, the difference in temperatures of the inlet and outlet fluid circulating through the heat exchange pipe within the energy textile was monitored using a constant-temperature water bath. Daily heat exchange rate of the energy textile during cooling operation was estimated from the measured temperatures of the inlet and outlet fluid through the energy textile. The air and ground temperature was also continuously monitored. The operation of the energy textile as a ground heat exchanger was simulated using a 3D numerical CFD model (Fluent). The thermal conductivity of shotcrete and concrete lining components and temperature variation of air in the tunnel were incorporated in the model. The numerical analysis shows a good agreement with the long-term monitoring result.

• Journal of Institute of Convergence Technology
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• v.4 no.2
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• pp.61-65
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• 2014

Pressure distribution around rotating impeller blades in centrifugal pump has been main issue for design of efficient and high performance automotive water pump. In addition, pressure losses of inlet water pipes should be considered to reduce additional pressure drop and design high performance engine cooling system. In this paper, pressure distribution inside water pump and pressure drop between inlet and outlet of water pump are investigated numerically to design plastic water pump for clean diesel engine application. And the inlet geometry of water pump was considered to analysis the effect of inlet water pipe geometry on pressure distribution around impeller blades and outlet pressure. The prediction results are compared with experimental data to validate and determine optimal operation condition without water pump cavitation. Major design parameters such as blade angle, volute geometry, system pressure, and coolant flow rate are considered to confirm applying possibility of plastic blades to the clean diesel engine.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.614-617
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• 2000

To get the maximum diffusion boundary of thermal effluent of Youngkwang Nuclear Power Plant, paths of TGPS Buoy and temperatures of surface water are obtained to 4 times at spring tide during 1 year. According to the paths of TGPS Buoy, the flumes of thermal effluent are moved about 12km from outlet to SW or WSW direction. After 3∼4 times of tidal period the waters are reached to Chilsan Island because the ebb flow is more predominant than the flood flow in this area. At the spring and fall season, a sudden drop of surface water temperature is detected around 5km radius from the outlet. At the summer season, it is measured about 10km. On the other hand the flumes are continuously cooled down by the atmosphere condition at winter season.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.733-741
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• 2002

If a part of the poor solution from the absorber outlet is recirculated to the absorber inlet, the solution temperature at the solution spray pump can be reduced, and the solution flow rate in the absorber is increased. We have performed the experiments on the influences of the absorption chiller performance according to the ratio of the recirculation, defined as the ratio of the recirculation flow rate to the total solution flow rate at the absorber outlet. As increasing the ratio of the recirculation, the absorption capacity of the solution can be deteriorated. On the other hand, due to the increasing flow rate, the heat transfer rate can be enhanced. As a result, the performance of the absorber and the cooling capacity of the absorption chiller have nothing to do with the recirculation ratio, and the lifetime of the spray pump will be maintained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.225-230
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• 2006

The overall performance and local flow fields of the fan, heat sink, and fan-sink were experimentally and numerically studied to investigate the flow characteristics of a fan-sink. The flow resistance of the heat sink was measured by small fan tester based on AMCA standards and compared with the CFD results to select available cooling fan for the fan-sink. The nonuniform velocity profile behind the fan outlet was shown by the flow visualization. The effects of nonuniform velocities on the performance of heat sink were discussed. To validate the commercial CFD code CFX-5.6, the predicted performance curve was compared with that of fan testing. The local flow fields of the fan-sink were analyzed by CFD results. MFR (multiple frame of reference) was used as a computational model combining rotating fan and stationary heat sink. Through the CFD results of the fan-sink, the flow patterns behind the fan outlet influenced the flow resistance and overall performance of the heat sink.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.2
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• pp.1-6
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• 2015

The horizontal earth-to-air heat exchanger (HEAHES) thermal performance is excellent on cooling and heating season in hot arid regions was reported. But the HEAHES thermal performance results is difficult to find on intermediate season. This paper was performed full scaled experiment to investigate HEAHES thermal performance on intermediate season (Oct. 10th ~ 12th Nov. 12th). When the air entering to HEAHES is the lowest $2.3^{\circ}C$, outlet air temperature from HEAHES is $15.95^{\circ}C$ through PVC pipe that buried length 60m and depth 3m. When the air entering to HEAHES is the highest $24.8^{\circ}C$, outlet air temperature from HEAHES is $22.05^{\circ}C$. During intermediate season, the HEAHES COP is 2.71 in daytime and 6.53 in evening.

• Korean Journal of Agricultural Science
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• v.17 no.1
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• pp.45-51
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• 1990

This study was conducted to obtain basic data for the design of cooling system by the test of engine performance of the power tiller being used widely in the rural area. Among the various factors affecting engine performance, the flow rate of cooling water was considered as the major factor in this study. Motoring loss, output, fuel consumption ratio, torque, heat absorption of cooling water, and thermal efficiency were measured and analyzed based on three flow rates of cooling water such as 15, 20, and $25{\ell}/min$. The results obtained were as follows : 1. Motoring loss of the engine was 1.371 kW at 2,200 rpm., and mechanical efficiency was 79.1% at rated output level. 2. Output power of the engine increased with the flow rate of cooling water increased. 3. BSFC was 282.9g/kW-h at the flow rate of $20{\ell}/min$, and the temperature of cooling water at outlet was $80.9^{\circ}C$. 4. There was a little variation of torque of the engine depending on the flow rate of cooling water. 5. Absorption of heat by cooling water was increased with the increase of flow rate. 6. The highest thermal efficiency of 32.3% at the flow rate of $20{\ell}/min$ was observed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1062-1070
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• 2016

The heat transfer and flow characteristics of gas turbine blade tip were investigated in this paper by using the conjugate heat transfer analysis. The rotor inlet boundary condition profile which was taken from the first stage nozzle outlet was used to analyse. The profile contained the velocity and temperature information. This study presents the influence of tip clearance about aerodynamic loss, heat transfer coefficient and film cooling effectiveness with the squealer tip designed blade model which tip clearance variation range from 1% to 2.5% of span. Results showed that the aerodynamic loss and the heat transfer coefficient were increased when the tip clearance was increased. Especially when the tip clearance was 2% of the span, the average heat transfer coefficient on the tip region was increased obviously. The film cooling effectiveness of tip region was increasing with decreasing of the tip clearance. There was high film cooling effectiveness at cavity and near tip hole region.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.316-326
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• 2017

Commercial buildings and institutions are predominantly cooled, thereby dissipating excess heat to a vertical ground heat exchanger (VGHE), than heat extracted over an annual cycle. Surface waters, such as lakes and ponds, provide a cost-effective means of reducing the VGHE length, and in balancing the thermal loads to the ground. This paper presents the measurement and analysis of the cooling performance of ground-coupled heat pump (GCHP) system, using surface water heat exchanger (SWHE) submerged in an artificial pond. In order to measure the performance of the system, we installed monitoring equipment, including sensors, for assessing the temperature and power consumption, after which the operation parameters were determined. The results from the thermal performance test for the SWHE indicate that the temperatures at the outlet of the SWHE and within the pond were affected by outdoor air temperature. In addition, the results reveal similar variation trends on temperatures; however, the peak temperatures of the SWHE were somewhat greater than those of outdoor air, due to the thermal capacity of the pond. Analyzing the cooling performance over the measurement period, the average coefficient of performance (COP) of heat pump was found to be 5.71, while that for the entire system was 2.99.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3403-3409
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• 2014

Hot-firing tests were carried out using a mixing head with 19 swirl coaxial injectors and a combustion chamber with internal cooling channels. The propellants of liquid oxygen and kerosene(Jet A-1) were burned in a range of chamber pressures (59~82 bar) and mixture ratios (2.0~3.0). The temperature of water used as the cooling fluid was measured at the inlet and outlet of the cooling channels, and the heat flux was calculated. The aim of this study was to examine the effect of combustion instability on heat transfer in a subscale thrust chamber, and detect the temperature variation of cooling water. During several hot-firing tests, combustion instability was encountered which caused a 5~20% increase in heat flux. The peak heat flux took place in the initial stages of combustion instability.