• International Journal of Air-Conditioning and Refrigeration
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• 제9권4호
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• pp.27-36
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• 2001

A new two-phase non-boiling convective heat transfer correlation for turbulent flow $(Re_{SL}>4000)$ in vertical tubes with different fluid flow patterns and fluid combinations was developed using experimental data available from the literature. The correlation presented herein originates from a careful analysis of the major non-dimensional parameters affecting two-phase heat transfer. This model takes into account the appropriate contributions of both the liquid and gas phases using the respective cross-sectional areas occupied by the two phases. A total of 255 data points from three available studies (which included the four sets of data) were used to determine the curve-fitted constants in the improved correlation. The performance of the new correlation was compared with two-phase correlations from the literature, which were developed for specific fluid combinations.

• 설비공학논문집
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• 제4권2호
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• pp.137-145
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• 1992

coefficient precisely, experiments were carried out in three categories which contain the regime of (1) constant wire temperature (2) constant fluid temperature (3) constant temperature difference between wire and fluid. Measurements were made with electrically heated circular tungsten wire placed normal to air stream at the exit of jet. Heat transfer coefficient was increased with wire temperature increasing and decreased by fluid temperaure increasing and was not changed with varying both temperature if their difference were kept constant.

• 수산해양교육연구
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• 제26권3호
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• pp.639-646
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• 2014

A heat exchanger using two-phase loop thermosyphons was developed as a waste heat recovery system. An experimental study was carried out on the heat transfer characteristics of two-phase loop thermosyphons heat exchanger and the results from the experiments were used to see the possibility which the two-phase loop thermosyphons could be an alternate solution for waste heat recovery system. In the present work, R134a has been used as the working fluid and the filling rate do working fluid and heat flux have been used as the experimental parameters. The results show that the filling rate of working fluid and heat flux are very important factors for the operation of two-phase loop thermosyphons. The experimental results showed the provisional results as a waste heat recovery system.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1533-1542
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• 2003

In the present study, the characteristics of pressure oscillation and heat transfer performance in an oscillating capillary tube heat pipe were experimentally investigated with respect to the heat flux, the charging ratio of working fluid, and the inclination angle to the horizontal orientation. The experimental results showed that the frequency of pressure oscillation was between 0.1 Hz and 1.5 Hz at the charging ratio of 40 vol.%. The saturation pressure of working fluid in the oscillating capillary tube heat pipe increased as the heat flux was increased. Also, as the charging ratio of working fluid was increased, the amplitude of pressure oscillation increased. When the pressure waves were symmetric sinusoidal waves at the charging ratios of 40 vol.% and 60 vol.%, the heat transfer performance was improved. At the charging ratios of 20 vol.% and 80 vol.%, the waveforms of pressure oscillation were more complicated, and the heat transfer performance reduced. At the charging ratio of 40. vol.%, the heat transfer performance of the OCHP was at the best when the inclination angle was 90$^{\circ}$ the pressure wave was a sinusoidal waveform, the pressure difference was at the least, the oscillation amplitude was at the least, and the frequency of pressure oscillation was the highest.

• 대한기계학회논문집B
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• 제24권4호
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• pp.495-503
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• 2000

The present numerical study investigates flow characteristics and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The combined effect of temperature-dependent viscosity, buoyancy and secondary flow caused by second normal stress difference are all considered. The Reiner-Rivlin model is used as a viscoelastic fluid model to simulate the secondary flow and temperature-dependent viscosity model is adopted. Three types of thermal boundary conditions involving different combinations of heated walls and adiabatic walls are considered in this study. Calculated Nusselt numbers are in good agreement with experimental results in both the thermal developing and thermally developed regions. The heat transfer enhancement can be explained by the combined viscoelasticity-driven secondary flow, buoyancy-induced secondary flow and temperature-dependent viscosity.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3352-3357
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• 2012

본 논문은 열매체(Synthetic Heat Transfer Fluid) 보일러의 화재원인을 분석하기 위하여 3차원 자동설계 프로그램인 CATIA를 활용하여 설계하였다. 또한 3차원 유한요소 코드인 ANSYS를 활용하여 설계된 열매체보일러에 대하여 구조해석을 실시하였다. 구조해석을 통하여 열매체보일러의 정상상태와 화재 후의 최대온도(maximum temperature), 최대응력(maximum stress), 최대변형율(maximum strain) 등을 구하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.277-282
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• 2009

A temperature equation which is derived from an enthalpy transport equation by using an assumption of a constant specific heat is very attractive for analyses of heat and fluid flows. It can be used for an analysis of a solid-fluid conjugate heat transfer, and it does not need a numerical method to find temperature from a temperature-enthalpy relation. But its application is limited because of the assumption. A new method is derived in this study, which is a temperature-explicit formulation of the energy equation. The enthalpy form of the energy equation is used in the method. But the final discrete form of the equation is expressed with temperature. It can be used for a solid-fluid conjugate heat transfer and multiphase flows. It is found by numerical tests that it is very efficient and as accurate as the standard enthalpy formulation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 춘계 학술대회논문집
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• pp.79-84
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• 2005

The numerical solutions are examined on the effect of a centered heat conducting body on natural convection in a 2-D square cavity. The influences of the Rayleigh number, the dimensionless conducting body size, and the ratio of the thermal diffusivity of the body to that of the fluid have been investigated on the natural convection heat transfer in overall concerned region. The analysis reveals that the fluid flow and heat transfer processes are governed by all of them. Results for isotherms, vector plots and wall Nusselt numbers are reported for Pr = 0.71 and relatively wide ranges of the other parameters. Heat transfer across the cavity, in comparison to that in the absence of a body, are enhanced (reduced) in general by a body with a thermal diffusivity ratio less (greater) than unity. The heat transfer are also found to attain a minimum as the body size is increased.

• 전기학회논문지
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• 제59권6호
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• pp.1087-1094
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• 2010

We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.

• 신재생에너지
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• 제18권2호
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• pp.73-81
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• 2022

This study was aimed at designing a condenser, as a component of the organic Rankine cycle system for ships. The condenser was manufactured through press molding to achieve a bent shape to enhance the heat transfer performance, considering the shape of the heat transfer plate used in a brazing plate heat exchanger. The heat transfer plate was made of copper-nickel alloy. The required heat transfer rate for the condenser was 110 kW, and the maximum number of layers was set as 25, considering the characteristics of high-temperature brazing. Computational fluid dynamics techniques were used to perform the thermal fluid analysis, based on the ANSYS CFX (v.18.1) commercial program. The heat transfer rate of the condenser was 4.96 kW for one layer (width and length of 0.224 and 0.7 m, respectively) of the heat transfer exchanger. The fin efficiency pertaining to the heat transfer plate was approximately 20%. The heat flow analysis for one layer of the heat exchanger plate indicated that the condenser with 25 layers of heat transfer plates could achieve a heat transfer rate of 110 kW.