• Journal of Advanced Marine Engineering and Technology
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• 제33권2호
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• pp.244-251
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• 2009

Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.

• 대한기계학회논문집
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• 제11권1호
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• pp.105-109
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• 1987

본 연구는 열교환기의 설치 및 사용목적에 따라 전열관내유동이 경사류가 될 때 특히 자연순환(2*$10^{6}$＜Gr＜15*$10^{6}$)의 경우와 강제순환(3,000＜Re＜ 40,000)의 경우에 대해서 열전달특성과 유동마찰에 의한 손질을 규명하는데 있다. 사용되는 관은 평골관과 ribbed관이며 관경사각을 수평면에 대하여 0˚,22.5˚,45˚, 90˚로 변화시켰다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.277-278
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• 2018

Improvement of insulation performance of buildings is a major part. Adiabatic method The adiabatic method minimizes the heat loss of the building. External insulation uses insulation to prevent fire. Ambient air hazards are less prone to fire. When a fire occurs, a phenolic pattern is formed and bond strength with the wall increases. EPS insulation and phenol foam were used to compare external heat transfer and external heat transfer. The heat transfer properties of phenolic foam and styrofoam were evaluated as follows. In the mortar and styrofoam structure, the problem of styrofoam reaching the burning point occurred before the collapse of the mortar, and the phenol foam had a problem in that when the direct fire was continued on the phenol foam. The characteristics of continuous infiltration appeared. In the case of mortar and phenol foam + styrofoam, the heat penetrated into the interior due to the shrinkage due to the shrinkage of the carbon screen on the phenol foam. However, when reinforced with glass mesh on the outer surface, And to reduce infiltration.

• 에너지공학
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• 제26권4호
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• pp.57-66
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• 2017

열은 전력과 같이 이동속도가 빠르지 못하고 전력에 비해 손실이 비교적 크게 발생하므로 전력거래와 같이 한개의 운용센터를 두고 열 연계 시스템을 운용하는 것은 현실성이 없다. 현재 열 연계가 모두 이루어지고 있는 한국지역난방공사의 경우에도 인접한 2~4개 정도의 열병합발전소간에만 열 거래가 이루어지고 있는 실정이다. 따라서 본 논문에서는 열 거래를 위한 통합운용센터를 몇 개의 권역으로 나누어 각 권역마다 권역의 Hub 통합운용발전소를 두고 운용하는 것이 열매체의 특성을 반영하는데 적정하고 타당한 것으로 판단하여 집단에너지 사업자간 열 연계 메커니즘을 제안하였다. 제안된 메커니즘에 최적으로 열 거래를 행할 수 있는 알고리즘을 개발하고 이를 실제 사업자에 적용하여 제안한 알고리즘의 유용성을 검증하였다.

• 대한기계학회논문집B
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• 제27권10호
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• pp.1412-1419
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• 2003

Heat regenerator occupied by regenerative materials improves thermal efficiency of combustion system through the recovery of sensible heat of exhaust gases. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of regenerator with spherical particles, was numerically analyzed to evaluate the heat transfer and pressure losses and to derive the design parameter for heat regenerator. It is confirmed that the computational results, such as air preheat temperature, exhausted gases outlet temperature, and pressure losses, agreed well with the experimental data. The thermal flow in heat regenerator varies with porosity, configuration of regenerator and diameter of regenerative particle. As the gas velocity increases with decreasing the cross-sectional area of the regenerator, the heat transfer between gas and particle enhances and pressure losses decrease. As particle diameter decreases, the air is preheated higher and the exhaust gases are cooled lower with the increase of pressure losses. Assuming a given exhaust gases temperature at the regenerator outlet, the regenerator need to be linearly lengthened with inlet Reynolds number of exhaust gases, which is defined as a regenerator design parameter.

• KIEAE Journal
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• 제15권1호
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• pp.111-116
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• 2015

Heat loss from windows and condensation occuring on its surface due to its lower insulation value causes much discomfort to occupants. In this study, Heated glass was used to make a basic study on prevention of condensation on glass surface for its heating functionality through experimental measurement and simulation analysis of total heat flux on the interior and exterior surface of glass. Error between experimental results and three dimensional steady-state heat transfer analysis were caused firstly, beacuse in the experimental chambers, cold chamber and steady temperature and humidity chamber, air temperature setting was not constant but rather ON/OFF control, and secondly, due to error rate in heat flux meter due to heat flux direction even in stable conditions.

• 설비공학논문집
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• 제17권9호
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• pp.855-862
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• 2005

An experimental investigation has been carried out for aluminum foam heat sink inserted into the annulus to examine the feasibility as a heat sink for high performance forced water cooling in the annulus. The local wall temperature distribution, inlet and outlet pressures and temperatures, and heat transfer coefficients were measured for heat flux of 13.6, 18.9, 25.1, 31.4 $kw/m^2$ and Reynolds number ranged from 120 to 2000. Experimental results show that the friction factor is higher than clear annulus without aluminum foam, while the significant augmentation in Nu is obtained. This technique can be used for the compactness of the heat exchanger.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.184-191
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• 2015

As the power electronics system increases the frequency, the power loss and thermal management are paid more attention. This research presents a real time model of dissipation power with junction temperature response for 120kw IGBT inverter which is applied to the thermal management of high power IGBT inverter. Since the computational time is critical for real time simulation, look-up tables of IGBT module characteristic curve are implemented. The power loss from IGBT provides a clue to calculate the temperature of each module of IGBT. In this study, temperature of each layer in IGBT is predicted by lumped capacitance analysis of layers with convective heat transfer. The power loss and temperature of layers in IGBT is then communicated due to mutual dependence. In the dynamic model, PWM pulses are employed to calculation real time IGBT and diode power loss. Under Matlab/Simulink$^{(R)}$ environment, the dynamic model is validated with experiment. Results showed that the dynamic response of power loss is closely coupled with effective thermal management. The convective heat transfer is enough to achieve proper thermal management under guideline temperature.

• 대한기계학회논문집B
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• 제23권7호
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• pp.831-840
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• 1999

In this work, an aerothermodynamic calculation model for cooled axial flow turbine blades with trailing edge ejection is suggested and a mean line performance analysis of a turbine stage with nozzle cooling is carried out. A unique model regarding the interaction between coolant and main gas is proposed, while existing correlations are adopted to predict viscous loss and blade outflow angle. The interactions considered are the heat transfer from main gas to coolant and the temperature and pressure losses by the mixing of two streams due to the trailing edge coolant ejection. For a stator blade without ejection, trailing edge loss calculated by the trailing edge analysis is compared with that calculated by loss correlation. The effect of heat transfer effectiveness of coolant passage on the mixing loss is analyzed. For a model turbine stage with nozzle cooling, parametric analyses are carried out to investigate the effect of main design variables(coolant mass flow ratio, temperature and ejection area) on the stage performance.

• 대한기계학회논문집A
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• 제24권10호
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• pp.2428-2437
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• 2000

In general, it is known that the portion of leakage loss is more than 20 % of total loss in scroll compressor. So far many studies have been done to improve the leakage problem and volumetric efficiency. In order to do this it is necessary that the leakage is exactly evaluated for conventional scroll model. Almost all studies that have been done were assumed that the clearance remains constant while operating. But in actual operating conditions, scroll wrap is deformed due to elevated refrigerant gas temperature. And this makes the leakage clearance change, so the leakage mass flow and the volumetric efficiency are also changed. In this study we assumed the steady state operating condition and obtain the average temperature and convection heat transfer coefficient in terms of involute angle. With these results, using finite element method we analyzed the heat transfer of scroll wrap, then did thermal deformation analysis. Then we obtain the leakage clearance and do the leakage and volumetric efficiency analysis. Compared with undeformed feature, we examine the effect of the thermal deformation on the leakage. The results say that the leakage mass flow for the case of considering thermal deformation is less than that for the unconsidered one, and this means that the leakage clearance is reduced due to thermal deformation.