• Journal of Energy Engineering
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• v.10 no.3
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• pp.214-222
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• 2001

The purpose of this research it to develop gas-air rotary heat exchanger using heat pipe and the performances were examined by way of the theoretical analysis and the experiment. Centrifugal force to return the working fluid in heat pipe elements with different radius was evaluated as a function of the revolution speed and inclination angle, and a rotary heat exchanger with 60 heat pipes in 3 rows was designed and manufactured. The inclination angle of a heat pipe relative to the revolving axis was designed to be 2$^{\circ}$and water was used as a working fluid. Experimental result showed the heat exchange rate was enhanced by 16% with compared to the calculated value.

• 보일러설비
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• s.69
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• pp.78-82
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• 1999

• Solar Energy
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• v.11 no.1
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• pp.78-86
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• 1991

Heat transfer characteristics of a rotating heat pipe have been studied numerically and experimentally with using water-ethanol mixture as working fluid. And triangular fins are attached inside the rotating heat pipe. Experimental results generally agreed with numerical results. According to increasing rpm and vapour pressure of the rotating heat pipe, the heat transfer rate increased. And also according to decreasing the concentration of ethanol, the heat transfer rate increased. In the case of using the pure ethanol as working fluid, the heat transfer rate was about 80% of using distilled water. The heat transfer rate and operating temperature difference of the rotating heat pipe was much influenced by ethanol concentration, and the optimum ethanol concentration was 0.2.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.2
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• pp.122-129
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• 1993

The heat transfer characteristics of the rotating heat pipe with a disc evaporator and a grooved condenser have been investigated by measuring temperature distributions of wall and vapor for various thermal inputs and revolutions per minute. The results showed that the heat transfer coefficients of all types are increased with thermal input and revolutions per minute. The heat transfer coefficient of evaporator with groove (pitch=2.5mm depth=1.5mm) is 25.8% higher than that of evaporator without groove at 500RPM, 150W.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1572-1581
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• 1994

Heat transfer characteristics in a rotating heat pipe with evaporator of the rotating disc and the condenser of the screwed groove is investigated by numerical method for various dimensionless film thicknesses, Re, C_{p}{\Delta}T/h_{fg}$, rotational speed and working fluids. The temperature difference between evaporator wall and vapor increases a little, but the temperature difference between condenser wall and vapor decreases rapidly as Re increases. As the dimensionless film thickness decreases, the temperature difference of evaporator and condenser decreases. As the rotational speed increases, the temperature difference between evaporator wall and vapor increases but the temperature difference between condenser wall and vapor decreases. The Nusselt number can be shown as a function of dimensionless film thickness and Re, that is $Nu=0.963\cdot(\delta^{-1}(\omega/\vpsilon)^{-1/2}{\cdot}Re^{0.5025})$.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.7-12
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• 2000

The purpose of this study is to develop heat transfer analysis program of heat pipe elements and design a revolving heat pipe exchanger by the performance experiment of hot air production by means of middle-temperature waste heat. Experimental variables are the revolution per minute, normal velocity of inlet air and the temperature of waste heat. The revolving heat exchanger has designed as $2^{\circ}$ in inclination angle of heat pipe bundle and as 20% in working fluid quantity and as water in working fluid. Experimental value of the total heat transfer coefficient was $20w/m^2-^{\circ}C$

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.13-25
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• 1996

The purpose of this paper is to study heat transfer characteristics of rotating heat pipe with tapered condensers by numerical analysis and experimental method. An experimental investigation has been carried out on thermal resistance between condenser wall and vapor region fo the rotating heat pipe with various taper 0, 1/11.4, 1/38. Heat transfer characteristics by analytical study were applied to describe various Nu numbers on the base of dimensionless condensate film, Re and Pr numbers in both condensers. Comparison between calculated results and experimental data showed qualitatively good agreement and the numerical analysis of this study can be utilized to predict the performance of a rotating heat pipe. The thermal resistance can be decreased by increasing the revolution per minute. Regardless of various dimensionless condensate film, Nu number was largely influenced by saturation temperatures of working fluid.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.129.1-129.1
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• 2011

최근 급격한 경제성장과 고도 산업사회로의 전환에 따라 에너지 수요가 크게 증가하고 있다. 이에 따라 석유, 가스 등 화석에너지의 소비량과 온실가스 배출량이 급격히 늘어나고 있는 실정이다. 따라서 화석에너지의 소비와 온실가스 배출을 저감시키기 위해 친환경적인 에너지를 이용하기 위한 많은 연구가 이루어지고 있다. 이와 같은 노력 중 하나가 바로 태양열에너지를 이용하는 방법이다. 태양열에너지는 자원 고갈의 우려가 없고, 에너지의 이용 과정에서 공해 물질을 배출하지 않아 대체 에너지원으로 각광을 받고 있다. 하지만 에너지 밀도가 낮고 에너지의 공급이 기상조건에 따라 큰 영향을 받으므로 태양열에너지를 이용하기 위해서는 효율적인 집열시스템이 필요하다. 따라서 본 연구에서는 우수한 열적특성을 가진 탄소나노유체를 히트파이프 작동유체에 적용하여, 태양열 집열기의 효율을 향상시키기 위해 탄소나노유체의 열전도도 및 점도특성을 비교분석하였다. 나노유체는 에탄올에 산화 다중벽 탄소나노튜브(Oxidized Multi-walled Carbon Nanotubes, OMWCNTs)를 혼합하고, 초음파 분산하여 제조하였다. 에탄올-산화탄소나노유체의 열전도도와 점도는 저온($10^{\circ}C$), 상온($25^{\circ}C$), 고온($70^{\circ}C$)에서 측정하여 비교분석하였으며, 열전도도는 전기 전도성 유체의 비정상 열선법(Transient Hot-wire Method)을 이용하여 측정하였고, 점도는 회전형 디지털 점도계를 이용하였다. 실험 결과 0.1 vol%의 에탄올-산화탄소나노유체의 열전도도는 기본 유체 대비 33.72%($10^{\circ}C$), 33.14%($25^{\circ}C$), 32.26%($70^{\circ}C$)가 향상되었으며, 점도 또한 기본유체보다 크게 증가하지 않아 히트파이프 작동유체로서 우수한 효과를 나타낼 수 있음을 확인하였다. 본 연구의 결과는 태양열 집열기 히트파이프의 효율 향상을 위한 기초자료로써 유용한 정보를 제공할 것이라 판단된다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1217-1228
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• 1998

In order to elucidate the operational characteristics of rotating heat pipes, the internal flow patterns and heat transfer performance are investigated. Flow patterns and its transition are studied with various rotational speeds by visualizing flows established inside a rotating tube. To verify those results of analysis, 2 heat pipes of the same geometries but fill charge rates of 7, 30% were manufactured and submitted to operating tests. Comparison of experimental results on heat transfer rate show a fairly good agreement with the analytical results. The analysis reveals that the optimum charge ratio is ranged in 4~7% depending on the quantity of thermal loads. but the heat pipe with 7% of fill charge ratio reached dry-out limitation at heat flux of $q^{{\prime}{\prime}}=6.2kW/m^2$ lower than that of analytic results. Transition of flow regime was well related to the correlation by Semena & Khmelev on transient centrifugal Froude Number Frc. But hysteresis phenomenon was observed in transition of flow regime, when the rotational speed was stepwisely changed in the way to undergo 1 cycle.

• Solar Energy
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• v.20 no.3
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• pp.75-84
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• 2000

The purpose of this research is to study on the heat transfer characteristics of separate type heat pipe with a rotor. The heat transfer characteristics of the rotor condenser are various on input heat of evaporator, rotational speeds of rotor, and working fluid amount. The results obtained from the study are as follows. 1. Magnetic fluid using seal of the rotor operated in stability by a variation of temperature and rotation speeds. The configuration of magnetic fluid seal assembly was adequate. 2. Steam ejector is effective in recovering working fluid condensate in the rotor. When steam ejector is operating, the heat flux of working fluid does not change, with the wall temperature in the rotor. 3. The optimum design conditions on working fluid amount and rotational speeds are effective in evaporator volume 50%, rotational speeds 200rpm, 300rpm, and operating temperature $80^{\circ}C$. With working fluid amount increasing, overall heat transfer coefficient decreases linearly.