• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.974-980
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• 2005

The optimization of design factors on the frosting performance of a fin-tube heat exchanger is carried out using Taguchi method. The fin spacings of the heat exchanger are selected as design factors. Optimum values of the design factors under operating conditions of a household refrigerator/freezer are proposed. The average heat transfer rate and operating time of the optimum models, compared to those of a reference model, are increased at most by $6.5\%$ and $12.9\%$, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.129-136
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• 2006

Optimal design of an air-to-liquid finned plate heat exchanger is considered theoretically in this study. Based on existing correlations for the pressure loss and the heat transfer in channel flows, the optimal configuration of the plate heat exchanger including the optimal plate pitch and the optimal fin pitch is obtained to maximize the heat transfer within the limit of the pressure drop for a given flow depth of the plate heat exchanger. It is found that the optimal fin pitch is about one ninth of the optimal plate pitch. In the optimal configuration, the flow and thermal condition in the channels is just at the boundary between the laminar developing and laminar fully developed states. It is also found when reducing the flow depth of plate heat exchangers for compactness, the heat transfer performance can be maintained exactly the same if the geometric parameters such as the plate thickness, plate pitch, fin thickness, and fin pitch are reduced proportional to the square root of the flow depth as long as the flow keeps laminar within the heat exchangers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.2
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• pp.250-261
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• 1999

Based on a set of performance plots relating the design variables to the imposed conditions, an easy-to-use and versatile design procedure for chevron-type multipass plate heat exchangers is developed. In order for the present procedure to cover multipass with unequal passes and non-unity ratio of heat capacity rate, each stream number of transfer unit is adopted as the basic design variable instead of the exchanger number of transfer unit. It is found that there exists a unique relation between the stream and exchanger number of transfer units regardless of the chevron angle and the plate length. In addition, for a given value of the pressure drop the heat transfer area per unit mass flow rate can be expressed in terms of the stream number of transfer unit only. These two relationships in the form of simple plots constitute the framework of design. The sample results in comparison with the available data indicate that the present procedure includes the previous ones as a subset, and that every design method is affected essentially by the selection of specific correlations for the heat transfer coefficient and the friction factor.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.146-152
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• 2000

As an improvement in the standard of living and economic growth the demand for air conditioning equipment is increasing rapidly. Nowadays air conditioning equipments are being used for industry large building house and car. Thess equipments was concentrated on improving heat efficiency of economic aspects while they design heat exchanger for cooling and heating,. These air conditioning equipments using heat exchanger cause a discomfort to user due to generating mist at the beginning of operating. Therefore the user demand air of high class and quality. In this experimental study to acquire elementary data for development of heat exchanger which be able to supply air of high quality that is to say possess a restraint effect of mist generation. We estimate an effect on cooling plate kind supply air velocity supply air temperature cooled plate temperature and supply air relative humidity which have an influence on outlet air condition of heat exchanger.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1068-1071
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• 2017

The turbine exhaust system consists of a turbine flange, heat exchanger, exhaust duct and thrust nozzle. Heat exchanger is used for the launch vehicle because of the advantage of reducing the weight of the helium gas and the storage tank by using the heat exchanger pressurization method compared to the cold gas pressurizing method. Since the gas generator is combusted in fuel-rich condition, the soot is contained in the combustion gas. Hence, the heat exchanger should be designed considering the reduction of the heat exchange efficiency due to the soot effect. In addition, the uncertainty of the heat exchange calculation and the evaluation of the influence of the combustion gas soot on the heat exchange can not be completely calculated, so the design requirements must include a structure that can guarantee and control the temperature of the heat exchanger outlet. In this paper, it is described that the component allocation, the design method considering the manufacture of internal structure, the advantages of new concept of nozzle design.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.12
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• pp.600-604
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• 2014

Longitudinal heat conduction is known to be an important factor in the design of a printed circuit heat exchanger(PCHE) for cryogenic applications. Parasitic heat conduction through the heat exchanger frame needs to be considered because it is known to decrease the effectiveness of the heat exchanger. In this paper, a conjugate heat transfer problem in a simple counter-flow PCHE is analyzed by a computational fluid dynamics simulation. The effect of longitudinal conduction in a straight channel is compared with the theoretical effectiveness-NTU relationship that assumes a "thin" heat exchanger frame. The calculation results suggest that the theoretical model is valid in the present calculation conditions where NTU is < 13.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.2
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• pp.183-190
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• 2014

Our lab designs a heat exchangers for air and carbondioxide gas. Coolant is water, thus it is very difficult to determine heat transfer parameters in this gas-liquid system. Repeated experiments gives overdesign value 35%, overall heat transfer coefficient $33.8(kcal/m2-hr-^{\circ}C)$ for carbondioxide. Another series of experiments determine overdesign 18.7%, overall heat transfer coefficient $21.4(kcal/m2-hr-^{\circ}C)$ for Air. These parameters are in same range of literature. Overdesign is increasing as tube length increases, also increases as wall thickness of heat exchanger increases. To get proper fluid linear velocity in heat exchanger, we change the diameter of tube and finally we can have optimum fluid linear velocity in the heat exchanger.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.189-194
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• 2009

In a gas engine based cogeneration system, heat is recovered from two parts, which are jacket water and exhaust gas. The heat from the jacket water is often recovered by a plate type heat exchanger and used for the room heating and/or hot water supply. Depending on the operating conditions of engine and heat recovery system, there should be imbalance in the flow rate and supply pressure between engine and heat recovery side of the heat exchanger. The imbalance cause the deformation of the plate, which affects the pressure drop characteristics. In the present study, the pressure drop inside the heat exchanger has been investigated in a 1/5 scaled test rig and compare with the experimental correlations, which are used for the design.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1028-1033
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• 2004

The heat and flow characteristics in a single-phase parallel-flow heat exchanger was examined numerically to obtain its optimal shape. A response surface method was introduced to predict its performance approximately with respect to design parameters over design domain. Design parameters are inflow and outflow angle of the working fluid and horizontal and vertical location of inlet and outlet. The evaluation of the relative priority of the design parameters was performed to choose three important parameters in order to use a response surface method. A JF factor was used as an evaluation characteristic value to consider the heat transfer and the pressure drop simultaneously. The JF factor of the optimum model, compared to that of the base model, was increased by about 5.3%.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.734-741
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• 2020

A new air-cooled waste heat removal system with a direct contact heat exchanger was designed for SMRs requiring 200 MW of waste heat removal. Conventional air-cooled systems use fin structure causing high thermal resistance; therefore, a large cooling tower is required. The new design replaces the fin structure with a vertical string type direct contact heat exchanger which has the most effective performance among tested heat exchangers in a previous study. The design results showed that the new system requires a cooling tower 50% smaller than that of the conventional system. However, droplet formation on a falling film along a string caused by Rayleigh-Plateau instability decreases heat removal performance of the new system. Analysis of Rayleigh-Plateau instability considering drag force on the falling film surface was developed. The analysis results showed that the instability can be prevented by providing thick string. The instability is prevented when the string radius exceeds the capillary length of liquid by a factor of 0.257 under stagnant air and 0.260 under 5 m/s air velocity.