• Advances in Energy Research
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• 제6권2호
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• pp.161-172
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• 2019

The principal intention of this experimental work is to confer upon the exergy study of GSHP associated with horizontal earth heat exchanger for space heating. The exergy analysis recognizes the assessment of the tendency of various energy flows and quantifies the extensive impression of inefficiencies in the system and its components. Consequently, this study intends to provide the enlightenment for well interpretation of exergy concept for GSHP. This GSHP system is composed of heat pump cycle, earth heat exchanger cycle and fan coil cycle. All the required data were measured and recorded when the experimental set up run at steady state and average of the measured data were used for exergy investigation purpose. In this study the rate at which exergy destructed at all the subsystems and system has been estimated using the analytical expression. The overall rational exergetic efficiency of the GSHP system was evaluated for estimating its effectiveness. Hence, we draw the exergy flow diagram by using the various calculated results. The result shows that in the whole system the maximum exergy destruction rate component was compressor and minimum exergy flow component was earth heat exchanger. Consequently, compressor and earth heat exchanger need to be pay more attention.

• 설비공학논문집
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• 제18권3호
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• pp.193-201
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• 2006

Thermal performance model was developed for a cross-flow aluminum heat exchanger with relatively short passage. Appropriate heat transfer coefficient and friction factor equations for laminar channel flow were obtained considering developing regions. The heat exchanger was analyzed using the unmixed cross-flow ${\epsilon}$-NTU relationship considering leak-age between streams. Thermal contact between corrugations and plates was also considered. Tests were separately conducted for two samples - one made of non-treated aluminum sheets, and the other made of varnish-treated ones. The samples were made by stacking corrugations and plates one after another. The model adequately predicted the thermal performance and pressure drop of the non-treated heat exchanger. The thermal performance of the varnish-treated one was $7{\sim}12%$ overpredicted, and the pressure drop of the varnished-treated heat exchanger was $5{\sim}15%$ underpredicted. The air leakage ratio of the non-treated heat exchanger was $23{\sim}26%$. The ratio decreased to less than $10%$ with the varnish treatment.

• 한국유체기계학회 논문집
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• 제6권3호
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• pp.28-35
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• 2003

This paper presents analysis results for the effect of power control strategies on the part load performance of gas turbine based power generation systems utilizing exhaust heat of the gas turbine such as combined cycle power plants and regenerative gas turbines. For the combined cycle, part load efficiency variations were compared among different single shaft gas turbines representing various technology levels. Power control strategies considered were fuel only control and IGV control. It has been observed that gas turbines with higher design performances exhibit superior part load performances. Improvement of part load efficiency of the combined cycle by adopting air flow modulation was analyzed and it was concluded that since the average combined cycle performance is affected by the range of IGV control as well as its temperature control principle, a control strategy appropriate for the load characteristics of the individual plant should be adopted. For the regenerative gas turbine, it is likewise concluded that maintaining exhaust temperature as high as possible by air flow rate modulation is required to increase part load efficiency.

• 동력기계공학회지
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• 제11권1호
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• pp.70-75
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• 2007

Heat transfer coefficient and fin efficiency of a heat exchanger dispersed in the microelement of control volume were predicted with various flow patterns, conditions and material properties. A computational program was developed by using the method of efficiency-NTU(Number of transfer unit). The modelling was applied to heat exchangers, also was integrated in power pack cooling system in an armored vehicle. The compatibility and the generality were proved by comparing the prediction values with the test results. The developed program may be useful for the design of the cooling system in an armored vehicle.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권1호
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• pp.11-19
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• 2001

To establish optimum cycle of the inverter-driven heat pump with a variation of frequency, the bypass orifice, which was a short tube haying a bypass hole in the middle, was designed and tested. Flow characteristics of the bypass orifice were measured as a function of orifice geometry and operating conditions. Flow trends with respect to frequency were compared with those of short tube orifices and capillary tubes. Generally, the bypass orifice showed the best flow trends among them. and it would enhance the seasonal energy efficiency ratio of an inverter heat pump system, Based on experimental data, a semi-empirical flow model was developed to predict mass flow rate through bypass orifices. The maximum difference between measured data and model`s prediction was within $\pm$5%.

• 설비공학논문집
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• 제11권1호
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• pp.109-116
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• 1999

To establish optimum cycle of the inverter-driven heat pump with a variation of frequency, the bypass orifice, which is a short tube having a bypass hole in the middle, was designed and tested. Flow characteristics of the bypass orifice were measured as a function of orifice geometry and operating conditions. Flow trends with respect to frequency were compared with those of short tube orifices and capillary tubes. Generally, the bypass orifice showed the best flow trends among them, that will enhance the seasonal energy efficiency ratio of an inverter heat pump system. Based on experimental data, the semi-empirical flow model was developed to predict mass flow rate through bypass orifices. The maximum difference between measured data and model's prediction was within ${\pm}5%$.

• 수산해양교육연구
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• 제26권6호
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• pp.1352-1357
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• 2014

In the present study, the heat transfer performance on the heat recovery ventilator with rotary disk were experimentally investigated. The temperature of entrance and exit of the heat recovery ventilator, air flow distribution of high temperature air and low temperature air, heat flux and the overall heat transfer coefficients are estimated from the experimental results. As the number of revolution of rotary disk, the air flow distribution increase, heat flux and overall heat transfer coefficients increase.

• 한국산학기술학회논문지
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• 제18권1호
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• pp.702-708
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• 2017

함체 내의 발열은 이동통신기기의 회선 처리 능력이 증가함에 따라 계속 증가하고 있다. 이 열을 적절히 외부로 방출해 주지 않으면 중계기 내의 온도가 상승하여 전자장치 오작동의 원인이 된다. 본 연구에서는 통신 함체 냉각 모듈용 알루미늄 및 플라스틱 소자의 성능에 대해 실험을 수행하고 이론 해석 결과와도 비교하였다. 알루미늄 소자는 핏치 4.5 mm의 대향류 평행 채널로 구성되고 플라스틱 소자는 핏치 2.0 mm의 직교류 및 직교 대향류 삼각 채널로 구성되었다. 한편 직교류 소자의 크기는 알루미늄 소자와 동일하고 직교대향류 소자는 알루미늄 소자보다 33% 크다. 실험 결과 플라스틱 직교 대향류 소자의 전열량이 가장 크고 알루미늄 대향류 소자의 전열량이 가장 작게 나타났다. 또한 알루미늄 대향류 소자를 base 소자로 할 때 플라스틱 직교대향류 소자의 온도교환효율은 base 소자보다 평균 56% 크고 플라스틱 직교류 소자의 값보다는 평균 29% 크게 나타났다. 한편 플라스틱 직교대향류 소자와 base 소자의 압력손실은 유사하게 나타났다. 열교환 효율은 플라스틱 직교대향류 소자에서 가장 크고 플라스틱 직교류 소자에서 가장 작게 나타났다. 또한 이론 모델은 소자의 성능을 다소 과대 또는 과소 예측하였다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.91-100
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• 2004

Plate heat exchangers (PHE) have been widely used in different industrial applications, because of high heat transfer efficiency per unit volume. Basic study is performed for PHE to the application of intercooler in automobile. In order to understand the flow phenomena in the plate heat exchanger, a channel which was formed by the upper and lower plate in single plate was considered as calculation domains. Because chevrons attached on the upper plate are brazed with chevrons attached on the lower plate, the flow channel has very complex configuration. This complex geometry was analyzed by Fluent. In order to validate this methodology the proper experimental and theoretical data are collected and compared with numerical results. Finally, due to the lack of experimental values for PHE to the application of intercooler, various chevron angles and air velocities at inlet were tested in terms of physical phenomena. From this point of view, results of velocity vector, path lines, static pressure, heat flux, heat transfer coefficient, and Nusselt number are physically reasonable and accepted for the solutions. From these results, the correlations for pressure drop and Nusselt number with respect to chevron angle and Reynolds number in specific PHE are obtained for the design purpose. Thus, the methodology of the flow analysis in the full geometry of the channel was established for the predictions of performance in plate heat exchanger.

• 한국지열·수열에너지학회논문집
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• 제1권2호
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• pp.1-6
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• 2005

Ground water source heat pumps are clean, energy-efficient and environment-friendly systems for cooling and heating. Although the initial cost of ground water source heat pump system is higher than that of air source, it is now widely accepted as an economical system since the installation cost can be returned within a short period of time due to its high efficiency. In a ground water source heat pump system, the variation of the ground water temperature is an important factor that influences the system performance. In this study, variation of the ground water temperature of a single well system is studied experimentally for various operating conditions. When ground water flow exists in the underground, the returned water exchanges heat efficiently with the ground and the temperature of the ground water remains nearly constant. Hence the short circuit problem is minimized. If an active flow of ground water flow exists in the underground, a singe well heat pumps system will be free of short circuit problem and can operate with high performance.