• 오토저널
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• 제9권4호
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• pp.69-76
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• 1987

A conjugate conduction-convection analysis has been made for a plate fin which exchanges heat with its fluid environment by forced convection. The analysis is based on a one- dimensional model for the plate fin whereby the transient heat conduction equation for the fin is solved simultaneously with the conservation equations for mass, momentum, and energy in the fluid boundary layer adjacent to the fin. The forced convection heat transfer coefficient is not specified in advance but is one the results of the numerical solutions. Numerical results of the overall heat transfer rate, the local heat transfer coefficient, the local heat flux, the fin efficiency and the fin surface temperature distribution for Pr=0.7 are presented for a wide range of operating conditions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.13.1-13.1
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• 2005

• 설비공학논문집
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• 제27권5호
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• pp.254-262
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• 2015

Heat transfer rate can be increased by increasing the heat transfer area. In this study, wide louver fin-and-tube heat exchangers with $P_t/P_l=1.03$ were tested and compared with louver fin-and-tube heat exchanger with $P_t/P_l=0.6$. Results show that heat transfer capacities of wide louver samples are larger (9.8% at one row, 13.6% at two row and 4.1% at three row) than those of conventional louver samples. Considering the area ratio of 1.78, the increase of heat transfer capacity is rather small, possibly due to the smaller heat transfer coefficient and fin efficiency of the wide louver sample. The j factor of the louver fin was 67% larger at one row, 42% larger at two row and 52% larger at three row. The f factor of the louver fin was 81% larger at one row, 63% larger at two row and 60% larger at three row. The effect of fin pitch on j and f factors are not pronounced and the j factor decreased as the number of tube row increased.

• 설비공학논문집
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• 제10권6호
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• pp.649-657
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• 1998

In this study, the effects of the various conditions of frosting and defrosting on the behavior of defrosting in a fin-tube heat exchanger have been examined experimentally. The electric heater is used for defrosting in a fin-tube heat exchanger It is shown that there are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after the completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering the degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of the frost irrespective of the frosting condition. The defrosting behavior is affected by the frosting density as well as the frost accumulation, which vary with the experimental operating conditions during the frosting period. The heat loss to the surrounding air decreases, and the melting and defrosting efficiencies show high values with decreasing heat input.

• 설비공학논문집
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• 제15권1호
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• pp.73-85
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• 2003

Four different methods of reducing the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two different heat and mass transfer models and two different fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the data with the reduction methods revealed that the single potential heat and mass transfer model yielded the humidity independent heat transfer coefficients. Two different fin efficiency models - enthalpy model and humidity model - yielded approximately the same fin efficiencies and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.

• 대한설비공학회지:설비저널
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• 제16권5호
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• pp.504-515
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• 1987

This study conducts an analysis for the heat diffusion of an annular fin considering con-vection phenomena at the fin edge as well as along the fin perimeter. When the temperature of the fin base is given with an increasing exponential function, the exact series solutions of tem-perature distribution are obtained by laplace transformation in terms of dimensionless para-meters. From these solutions heat flux and fin efficiency can be obtained. These exact solu-tions converge rapidly for large values of dimensionless time, but slowly for small ones. To avoid this convergence difficulty, approximate solutions of the temperature distribution and heat flux for small values of dimensionless time are also presented. Substituting the variations of dimensionless parameters into the these exact solutions, the characteristics of these response are investigated.

• 대한기계학회논문집B
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• 제29권9호
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• pp.1032-1041
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• 2005

This study is performed to investigate the heat transfer characteristics of heat exchanger according to the arrangement of fins as well as fin configuration by using the four times enlarged model. Friction factor, Colburn j factor and goodness factors are compared to each other to estimate performance of each case for 4 different kinds of fins, which are plain, single side slit, double side slit and louver fin. Results show that heat transfer would be altered by fin arrangement and that friction loss is more affected by fin configurations than by the fin arrangements. In particular, heat transfer depends more on the shape of front row than that of rear row. The heat transfer rate of combined fin arrangement increases a lot more under the same pressure drop than that of conventional fin arrangement. This indicates that the heat exchanger of higher efficiency would be designed by the proper combination of fins, of different shapes.

• 한국정밀공학회지
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• 제32권2호
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• pp.219-227
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• 2015

A dehumidifier using a thermoelement has many advantages compare to a dehumidifier using compressor systems. However, it is crucial to optimize the performance of heat sink for improving heat dissipation problem on the heat generation part. In this study, we utilized computational fluid dynamics software to compare Nusselt number, temperature and system efficiency based on fin thickness, flow gap between fin and fin length. Moreover, slip flow on the boundary layer was applied for the further analysis. Our objective in this study is to suggest an optimal fin shape to improve heat transfer with the tendency of performance factor depending on change of the shapes. Our results on the optimization of fin shape and analysis of slip flow will be utilized to enhance the heat transfer in the heat sink which is important in the design of dehumidifier using a thermoelement.

• 설비공학논문집
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• 제25권8호
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• pp.457-463
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• 2013

Nowadays, adsorption chillers have been receiving considerable attention, as they are energy saving and environmentally benign systems. A fin tube type heat exchanger in which adsorption/desorption takes place is required with more compact size. The adsorption chiller is expected to have high energy efficiency in utilizing the waste heat exhausted from a process. The objectives of this paper are to scrutinize the effect of design parameters on the adsorption performance, especially the fin pitch of the fin tube, and to develop an optimal design fin tube heat exchanger in a silica gel/water adsorption chiller. From the numerical results, the fin pitch of 2.5 mm shows the highest adsorption rate, compared to other fin pitches, such as 5 mm, 7.5 mm and 10mm. Also, the adsorption rate is affected by the cooling water and hot water temperature.

• 한국산업융합학회 논문집
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• 제22권4호
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• pp.405-413
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• 2019

In this study, a progressive process was performed to fabricate the inner fin of a high-efficiency heat exchanger. A forming simulation was also carried out on the concavo-convex of the inner fin, forming a simulation based on elastic-plastic finite element method. The forming analysis where the speed of the press descended and ascended was set to five seconds showed that the effective stress was at a maximum of about 69 MPa in the curved portion where the bending occurred. Therefore, the die was designed based on the simulation results, and the inner fin die was installed on the 400-ton capacity press. After that, the inner fin fabrication experiment was conducted under the same condition as the simulation. Crack was not found from the curved portion of the concavo-convex of the inner fin. The profile of the concavo-convex of the prepared inner fin measured 6.7~6.8 mm in depth, 2.65~2.7 mm in width, and 0.3 mm in thickness.