• International Journal of Air-Conditioning and Refrigeration
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• 제12권1호
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• pp.1-9
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• 2004

The purpose of the present study is to examine the heat transport limitations in a screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6mm, and mesh numbers were 50, 100, 150, 200 and 250, and water was investigated as working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, the maximum heat transport limitations by capillary, entraintment, sonic and boiling were analyzed by a theoretical design method of heat pipe, including capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, etc. Based on the results, the capillary limitation in a small diameter of heat pipe is largely affected by mesh number and wick layer. Mesh number of 250 is desirable not to be used in pipe diameter of 6 mm, because capillary heat transport limitation decreases by the abrupt increase of liquid friction pressure due to the small liquid flow area. For the heat transport of 15 watt in 6mm diameter pipe, mesh number of 100 and one layer is an optimum wick condition, which thermal resistance is the smallest.

• 설비공학논문집
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• 제11권3호
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• pp.313-320
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• 1999

A PFC(Perfluorocarbon) heat pipe has been used recently for cooling of GTO(gate turn off) thyristors or diodes in electric commuter trains. The present study was conducted to determine heat transport limitation of a PFC heat pipe which is one of the important parameters in heat pipes design. The variables such as tube diameter, fill charge ratio, internal surface structure and operating temperature were examined by way of experiment. Experimental data showed that the heat transport limitation of PFC heat pipe was considerably low and mostly dependent on tube diameter, with the value of 440~500W for d$o$/=22.23mm and 150~200W for d$o$=15.88mm. The other parameters had negligible effects, except for the case of small charge ratio less than 30%. Some correlations proposed by previous studies were in agreement with data from this study within 10~30%.

• 설비공학논문집
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• 제14권9호
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• pp.725-733
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• 2002

In this study, the heat transport limitations of a two-phase closed thermosyphon were investigated. For the test, a two-phase closed thermosyphon ($L_t/: 600 mm,\;L_e:105mm,\;L_a:75mm,\;L_c:420mm,\;D_o:22.2mm,$ container: copper (inner grooved surface), working fluid: PFC ($C_6F_14$) was fabricated with a reservoir that can change the fill charge ratio. The following was imposed as the factors on the heat transport limitations of a two-phase closed thermosyphon. 1) Fill charge ratio of the working fluid. 2) Tilt angle of the longitudinal axis. From tile experimental data, some results were obtained as follows. When the fill charge ratio was relatively small ($\psi$20%), the heat transport limitation occurred about 100W by dry-out limitation. However over 40%, it shelved nearly constant value (500 W) by flooding limitation. The heat transport limitation according to the tilt angle increased smoothly until the tilt angle was $60^{\circ}$,/TEX>, after then decreased slowly.

• 한국추진공학회지
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• 제8권4호
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• pp.16-25
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• 2004

구리분말 소결윅 히트파이프의 열수송 한계를 예측하는 이론적 해석을 수행하였다. 히트파이프의 직경은 8 mm이고 물을 작동유체로 사용하였다. 입자의 직경을 대표적인 5 가지로 분류하여 각각의 유효 모세관 반경($r_c$) 기공률($\varepsilon$), 투파율(K)을 토대로 작동온도와 윅 두에 그리고 경사각에 따른 모세관압력과 열수송 한계, 열저항을 분석하였다. 소결윅의 모세관한계는 입자 직경이 크고 윅 두께가 증가하며 작동온도가 높을수록 증가했다 기공률과 모세관 반경이 증가할수록 열수송 한계가 높아졌으며, 윅 두께가 증가함에 따라 열저항이 크게 상승하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.317-322
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• 2005

This study is aimed to analyze the effects of heat pipe shape on the heat transfer in solar collector with a axial grooved heat pipe. In the design of a heat pipe. two of the most important criteria to be met are the operating temperature range and the maximum heat transport capacity, When the operating temperature range is known and the working fluid has been selected, the maximum heat transport capacity depends strongly on capillary pressure and liquid flow. The heat transport capacity of the heat pipe will depend on the geometry of the heat pipe, the wick structure. the vapor channel shape. groove number. cooling temperature. condenser length and pipe diameter. So various shapes are used for mathematical models of two-phase flow in grooved heat pipe. From the results. the adequate groove shape and scale are presented by considering the heat transport and capillary limitation.

• 한국항공우주학회지
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• 제33권9호
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• pp.97-103
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• 2005

본 연구에서는 소형 동-소결윅 히트파이프를 대상으로 소결윅의 구조적 인자들이 히트파이프의 열수송 한계에 미치는 영향을 이론적으로 분석하였다. 소결윅의 입자 크기의 균일성과 소결 조건이 전체적인 기공분포와 기공률을 포함한 물리적 특성에 지배적인 요소로 작용했으며, 윅 두께 및 기공의 작은 편차가 히트파이프의 열수송 한계에 대체로 큰 영향을 미치는 것으로 나타났다. 특히, 증기온도와 경사각에 따라서 윅 두께와 평균 입자 반경, 그리고 모세관반경의 미세한 변화가 히트파이프의 모세관한계를 현저하게 변화시켰다.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1711-1720
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• 2001

In this study, the heat transfer characteristics of a U-shape heat pipes were investigated. Heat is supplied to the U heat pipe through its middle zone(evaporator), and is released to the environment through its both arms(condensers). Both heat transfer coefficients and heat transport limitations were measured and compared with correlations previously developed for straight type heat pipes. Special concerns were focused to the cases, when each of condensers were submitted to a different cooling conditions, relatively. As a result. the heat transfer limitation of a U-shape heat pipe was found out to be 10∼15% less than the value for a straight heat pipe with an equivalent size.

• 에너지공학
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• 제13권4호
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• pp.267-274
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• 2004

스크린 메쉬윅 및 소결윅 히트파이프의 열수송 한계를 예측하기 위한 이론적 해석을 수행하였다. 히트파이프의 직경은 8mm이고 작동유체는 물을 사용하였다 250메쉬 조건에서, 각각의 유효 모세관 반경(r$_{c}$ ), 기공률($\varepsilon$), 투과율(K)을 토대로 작동온도와 윅 두께 그러고 경사각에 따른 모세관압력과 열 수송 한계, 열 저항을 분석하였다. 작동온도가 높고 윅 두께가 증가할수록 모세관한계가 높아졌으며, 대체로 소결윅이 스크린적보다 높은 열수송 한계를 나타냈다. 스크린윅의 열저항이 소결윅보다 높았으며, 두 가지 모두 윅 두께가 증가함에 따라 열저항이 선형적으로 상승하였다.

• 태양에너지
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• 제12권2호
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• pp.9-17
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• 1992

This is an experimental work concerning about an application of a heat pipe to an evacuated-glass-tube solar collector system. A methanol heat pipe with length of 0.7 m and diameter of 8 mm was manufactured and tested to compare its performance with that of freon thermosyphon which was originally used in a solar collector system fabricated at Thermomax Co.. Then this methanol heat pipe was utilized to be one component, i.e. heat transfer element, of the present experimental model of a solar collector. This model was performed the operation test as its absorber plate was irradiated by infrared lamps. The following results were obtained. (1) The methanol heat pipe was showed a stable operation when the variation of axial heat transport was $0{\sim}40$ watts and that of inclination angle was $30{\sim}90^{\circ}$. (2) The heat transport capability of the heat pipe was proved to be higher than that of the thermosyphon, because the heat transport limitation of the latter was occured at about 30 watt. (3) The heat pipe in a solar collector was also showed good performance as it transmitted absorbed energy.

• 한국군사과학기술학회지
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• 제9권2호
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• pp.127-135
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• 2006

Experimental studies of the cylindrical sintered-copper wick heat pipes were carried out to investigate the capillary heat transfer characteristics. Six models of the sintered-copper wick heat pipes were manufactured and tested to evaluate the heat transport limitations and the thermal characteristics. Also the performance of the heat pipes was analyzed theoretically and compared with the test results. The heat pipe models are divided into two sintered-wick groups and the nominal particle sizes are $180{\mu}m$(wick #1) and $200{\mu}m$(wick #2) respectively The experimental results showed that, the porosity of wick #1 was higher than that of wick #2, and also the wick #1 was generally superior than the wick #2 for the heat transport capability. The maximum heat transport rates were increased as the wick thicknesses and the vapor temperatures were increased.