• 설비공학논문집
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• 제12권5호
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• pp.511-518
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• 2000

The present experimental study investigates the impact of porous fins on the pressure drop and heat transfer characteristics in plate-fin heat exchangers. Systematic experiments have been carried out in a simplified model of a plate-porous fin heat exchanger at a controlled test environment. Comparison of performance between the porous fins and the conventional louvered fins has been made. The experimental results indicate that friction and heat transfer rate are significantly affected by permeability as well as porosity of the porous fin. The porous fins used in the present study show a similar air-side performance to the louvered fin. The correlations of friction and modified j-factor are also given for the design of the plate-porous fin heat exchanger.

• 대한기계학회논문집
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• 제14권1호
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• pp.225-229
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• 1990

본 연구에서는 외부조건과 입력이 일정하게 주어져 있는 냉동 사이클에 대하 여 열교환기의 용량을 설계변수로 하여 출력과 효율이 최대가 되는 조건, 즉 최적 설 계조건을 살펴 보고자 한다. 아울러 이 조건과 엔트로피 생성 최소조건과의 관계와 비가역 사이클인 경우도 살펴보았다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.107-110
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• 2002

The present study deals with CFD analysis of 'The vortex generators on plastic plate heat exchanger'. When a vortex generator is placed on the heat transfer surface, the flow gets more complex because it entails complicated three-dimensional flows such as separation, reattachment, and recirculation. CFX-5.4, a commercial code utilizing unstructured mesh, has been used as a computational method for solving RANS(Reynolds-Averaged Wavier-Stokes) equations, and the applied turbulence model is $k-{\varepsilon}$ model. In addition, those computational analyses were implemented under various conditions , with or without the vortex generator between two plates, the number, form and the size of vortex generator, and different attack of angle. From the calculated temperature, velocity and pressure distribution, vorticity, wall heat flux and so on under those conditions, this study shows the effect of vortex on heat transfer.

• 한국생산제조학회지
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• 제20권5호
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• pp.547-552
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• 2011

Drying process, corresponding to a final process in the area of food engineering, requires a lot of heat energy. Thus, the energy efficiency is very important for dryers. Since the energy efficiency of heat pump dryers is much higher compared to that of electric dryers or other types of dryers, most of large-capacity dryers are adopting heat pump. In this study, shapes, positions and number of air-circulating fans, guide vanes, air inlet, outlet and top separator were varied for optimization of the flow of a large-capacity heat pump dryer. In addition, fans were modelled with performance curves and porous media were assumed for foods and heat exchangers. The simulation results were applied to the 12-ton dryer and the velocity distributions were experimentally examined. Finally, uniform drying in time was successfully accomplished through frozen pepper experiment.

• 설비공학논문집
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• 제16권4호
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• pp.349-354
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• 2004

Scale is formed when hard water is heated or cooled in heat transfer equipments such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. When the scale deposits in a heat exchanger surface, it is conventionally called fouling. The objective of the present study is to analyze the process of the fouling formation in a heat exchanger according to different types of water using visualization techniques. In order to experimentally investigate the formation of the fouling, this study built a lab-scaled heat exchanging system. Using the visualization techniques of Scanning Electron Microscopy (SEM) and X-Ray diffraction method, the three dimensional configurations of the fouling formation could be successfully obtained. Based on the experimental results, it was found that the configurations of the fouling formation were different when using tap water compared to river water.

• 설비공학논문집
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• 제13권8호
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• pp.730-738
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• 2001

This work discusses the pressure droop, heat and mass transfer of the finned-tube heat exchangers having 7 mm tubes and offset strips in dehumidifying applications. It focuses on the fin material saving and the reduction of pressure drop. The experiment was conducted using three times scaled-up models to simulate the performance of the prototype. Eight kinds of fins having different strips and S shape edges were tested. the area density of the strip was a major factor and its shape and the location were secondary factors on the pressure drop, the heat and mass transfer. The reduced-area fin can almost equal the non-reduced fin in the aspect of heat and mass transfer. The strip fins proposed in the present work can considerably reduce both the pressure drop and the fin material for similar thermal load.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.167-172
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• 2005

The purpose of this study is to present the simulation results and an overview of the performance assessment of the Ground-Source Heat Pump(GSHP) system. The calculation was performed for two design factors. the spacing between boreholes and the depth of the vertical ground heat exchangers. And the simulation was carried out using the thermal simulation code TRNSYS with new model o( water to water heat pump developed by this study. As a result, it was anticipated that the yearly mean COPs of heat pump for heating and cooling are about 3.7 and 5.8 respectively and the heat pump can supply 100% of heating and cooling load all the year around.

• 설비공학논문집
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• 제21권12호
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• pp.649-655
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• 2009

The purpose of the present study is to investigate the flow resistances and heat transfer characteristics of V-shaped circular fin-tube heat exchangers. Four types of V-shaped fins in which the fin areas are identical but the areas of the V-shaped portion are different have been tested numerically. The results obtained for heat transfer, pressure drop, and fin temperature are discussed in this paper. With increase in the area of the V-shaped portion, the pressure drop and heat transfer increase up to 40% and 24%, respectively, in the present test range.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2316-2321
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• 2008

This paper presents an improved performance of heat transfer for shell-and-tube and thermal analysis based on the Bell-Delaware method for single tube. Heat transfer has been compared for a smooth tube, helical tube and surface-coated tube. In general, the results showed that properly designed helical tube and surface-coated tube offer a significant improvement in heat transfer. The numerical results derived from the Bell-Delaware method for the shell-side heat transfer coefficient were verified with experimental results. The thermal analysis aids significantly in the solution of the design problem.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권3호
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• pp.113-122
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• 2004

In case of heat exchangers operating under frosting condition, the thermal resistance and the air-side pressure loss increase with a growth of frost layer. In this paper, a transient characteristic prediction model of the heat transfer for a multi-inverter heat pump with frosting on its surface was presented by taking into account the change of the fin efficiency due to the growth of the frost layer. This dynamic simulation program was developed for a basic air conditioning system composed of an evaporator, a condenser, a compressor, a linear electronic expansion valve, and a bypass circuit. The theoretical model was derived from measured heat transfer and mass transfer coefficients. We also considered that the heat transfer performance was only affected by the decrease of wind flow area. The calculated results were compared with the experimental results for frosting conditions.