지하대수층을 이용한 축열시스템의 설계(II) : 열해석

이관수,이태희,송영길,Lee, K.S.,Lee, T.H.,Song, Y.K. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.3

The energy recovery efficiency(ERE) of an aquifer thermal energy storage system was calculated using curvilinear coordinate. The results of the calculation were compared with the experimental results, and agreed within 11% of the discrepancy. The variation of ERE was investigated as a function of the underground water natural velocity, the amount of the stored energy, and period of the energy recovery. The slower the natural velocity and shorter the recovery period, the higher ERE was yielded. Also it was found that increase in the amount of energy storage yields higher ERE, and carries out less influential ERE to the natural velocity. Reiterative usage of the aquifer as a thermal storage tends to gradually increase ERE. The result of this study implements that the aquifer thermal energy storage system is suitable for large cooling/heating loads, such as district cooling/heating.

착상조건하에서 핀-관 열교환기 성능에 관한 실험적 연구

이관수,박희용,이태희,이남교,이수엽,이명렬,Lee, K.S.,Pak, H.Y.,Lee, T.H.,Lee, N.G.,Lee, S.Y.,Lee, M.R. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.2

In this study, the experiment with 2rows-2columns fin-tube heat exchanger under forced convection and frosting condition is performed. The influence of each operating condition(the temperature of air, the humidity of air, the velocity of air, the temperature of coolant) on the growth of frost layer, air-side pressure drop, and characteristics of heat transfer is investigated. The experimental results show that the frost thickness increases rapidly in the early stage of frost formation and increases linearly after sometime. The frost thickness increases with the increase of the inlet air humidity and velocity and the decrease of inlet air temperature and coolant temperature. It is also found that the total energy transfer rate increases with the increase of inlet air temperature and velocity and with the decrease of inlet air humidity and coolant temperature.

서리층 성장 예측을 위한 수치적 모델

이관수,지성,이태희,Lee, K.S.,Jhee, S.,Lee, T.H. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.2

In this study, a numerical model for analyzing frost formation phenomena on a cold flat plate has been developed. Both regions of air flow and frost layer have been coupled to calculate the amount of the heat and mass transfer between air flow and frost layer. Experiments have been also conducted to validate the numerical model. The present numerical results show a good agreement with the experimental data. The present numerical model also provides some useful data such as the temperature distribution inside the frost layer which could not be obtained through the experiments.

전도와 복사를 고려한 전자 장비의 자연대류 냉각에 관한 연구

이관수,백창인,김우승,Lee, K.S.,Baek, C.I.,Kim, W.S. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.2

A numerical investigation on the conduction-natural convection-surface radiation conjugate heat transfer in the enclosure having substrate and chips has been performed. A 2-dimensional simulation model is developed by considering heat transfer by conduction, convection and radiation. The solutions to the equation of radiative transfer are obtained by the discrete ordinates method using S-4 quadrature. The effects of Rayleigh number and the substrate-fluid thermal conductivity ratio on the cooling of chip are analyzed. The result shows that radiation is the dominant heat transfer mode in the enclosure.

착상조건하에서 평행 평판 열교환기의 열 및 물질전달

이관수,이태희,김우승,Lee, K.S.,Lee, T.H.,Kim, W.S. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.2

In this study, the following factors are investigated from experiments for a vertical parallel plate heat exchanger under the frosting condition ; the growth of frost layer, the characteristics of heat and mass transfer, the change of mass flow rate of the air passing through the heat exchanger, and the pressure drop of the air in the heat exchanger. The amount of heat and mass flux of water vapor transferred from the air stream to the heat exchanger surface is large at the early stage of frosting and then decreases dramatically, and the extent of decreasing rate becomes moderate with time. The frost layer formed near the inlet of the heat exchanger is thicker and denser than that formed near the outlet. It is found that the gradient of the amount of frost along the flow direction increases with time. In the early period of frost formation, the thermal resistance between the air and the cooling plate increases dramatically and then the extent of change decreases with time. Initially the convective thermal resistance is dominant. Then, while the convective thermal resistance decreases with time, the conductive thermal resistance continues to increase with time and finally the conductive thermal resistance becomes dominant.

착상조건 하에서 핀-관 열교환기의 성능예측을 위한 컴퓨터 시뮬레이션

이관수,박희용,이욱용,이태희,이수엽,이명렬,Lee, K.S.,Pak, H.Y.,Lee, W.Y.,Lee, T.H.,Lee, S.Y.,Lee, M.R. 대한설비공학회 1995 설비공학 논문집 Vol.7 No.1

This study is concerned with the numerical analysis of performance on fin-tube heat exchanger under frosting condition. In this work, tube-by-tube method using LMED is employed. The present results are compared with O'Neal's experimental and numerical results. A standard evaporator model with 2rows-2columns is selected to investigate the effects of the various parameters such as fin pitch, air flow velocity, and humidity. The results show that frost thickness and the amount of frost per unit area decrease as fin-pitch becomes narrower. In the meantime, frost thickness and accumulation rate increase with higher inlet air humidity. It is shown that heat transfer rate increases during 30minutes and then it decreases. Heat transfer rate and the amount of frost increase with air velocity, however frost thickness does not increase over a certain velocity.

수평원관상의 LiBr-수용액에 수증기가 흡수될때의 열 및 물질전달

이관수,서석청,김영인,박동규,Lee, K.S.,Seo, S.C.,Kim, Y.I.,Park, D.K. 대한설비공학회 1988 설비저널 Vol.17 No.2

The problem of heat and mass transfer accompanying the absorption of water vapor into LiBr-$H_2O$ liquid solution flowing over the outside of the horizontal cylinder was theoretically studied to understand the absorption process occuring in the absorber of the absorption heat pump. Numerical results are presented for various quantities of interest relating to temperature, concentration, heat flux and mass flux. Also, the effects of mass flowrate, initial average velocity, and the radius of the cylinder were investigated.

핀-관 열교환기의 착상 거동에 대한 표면 접촉각의 영향

이관수,지성,이동욱,Lee, K. S.,Jhee, S.,Lee, D. W. 대한설비공학회 2000 설비공학 논문집 Vol.12 No.1

The effect of surface contact angle on the behavior of frost formation in a fin-tube heat exchanger is investigated experimentally. It is shown that both heat exchangers with hydrophilic and hydrophobic surfaces appear to have a better thermal performance than bare aluminium heat exchanger, but the improvements are very small. There is a little increase in the amount of the frost deposited onto the heat exchanger with both hydrophilic and hydrophobic surface. However, the effect of contact angle on the frost density is observed ; the frost with high density forms on the heat exchanger with hydrophilic surface ; and the frost with low density is deposited onto the heat exchanger with hydrophobic surface when compared with the frost deposited onto the heat exchanger with bare aluminium surface. This may be attributed to the fact that the shape of water droplets which condense on the surface of heat exchanger at the early stage of frosting varies with contact angle, and thus makes a difference on the structure of frost formation. From the experiments with different relative humidity of inlet air, it is shown that the variations of operating parameter make no influence on the effect of surface contact angle on the frosting behavior in the heat exchanger.

제상 현상 연구를 위한 눈 융해 과정 해석

이관수,고영우,Lee, K.S,Ko, Y.W. 대한설비공학회 1999 설비공학 논문집 Vol.11 No.1

An improved one-dimensional modeling of snow melting was obtained by considering both the effect of heat capacity and the decreasing influence of porosity. Using the improved model, the effects of initial snow temperature, initial snow density and the heat flux on the snow melting were investigated. It is found that the drainage starting time is delayed and the drainage rate becomes smaller with lower initial snow temperature. ResuIts also show that the drainage starts at the same time when an initial snow density is over a certain value. Melting efficiency increases linearly with an increasing initial snow temperature. With increasing the initial density of the snow and the amount of heat supplied, the melting efficiency increases, then converges to a constant value.

착상이란?

이관수,이태희,Lee, K.S.,Lee, T.H. 대한설비공학회 1995 설비저널 Vol.24 No.3