• 연구논문집
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• s.26
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• pp.51-56
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• 1996

In the case of a heat exchanger, scale is made in the tube by the chemical reactions of Ca and Mg ions contained in the water, and heat transfer rate is reduced because of increment of heat resistance in the pipe of the heat flow. Thus it brings to reduce the energy efficiency and to make environmental pollution by the use of chemicals for the prevention and removement of scale. In this paper, we discussed the design of electronic generator for ultrasonic scale preventor and analyzed the fundamental characteristic for ultrasonic transducer.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.19-24
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• 2000

The objective of this study is to develope a computer simulation model and estimate theoretically the transient performance characteristics of heat exchangers in an automotive air-conditioning system. To do that, the mathematical modelling of heat exchangers, such as evaporator and condenser, is presented first of all. For detail calculation, evaporator and condenser are divided into many sub-sections. Each sub-section is an elemental volume for transient modelling. The elemental volume is assumed to consist of three components, refrigerant, tube with fin, and air, and various properties including temperatures of three components are determined step along sub-sections. The properties of refrigerant R134a and air are calculated directly in the program. The heat transfer coefficients and pressure drop in single or two phase are also calculated by suitable empirical correlations. The overall tendencies of the simulation results were agreed well with those of actual situation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.230-238
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• 2003

R407C is considered as alternative refrigerant of R22 for air conditioners. Experimental investigation is made to study the condensation heat transfer characteristics of slit fin-tube heat exchanger using alternative refrigerant, R407C. Experiments are carried out at condensation pressure of 2110 kPa and 1943 kPa with the degree of superheat of 1$0^{\circ}C$ and mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air condition is dry bulb temperature of 35$^{\circ}C$, relative humidity of 50% and air velocity varying from 0.8 to 1.6 m/s. Experiments show that pressure drop gets smaller at a higher condensation pressure especially when condensation pressure is raised from 1943 to 2110 kPa. Heat transfer rate gets smaller at a lower condensation pressure in the range of experimental condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.723-729
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• 2016

This study compared fin-tube and parallel-flow heat pipes for their sensible heat exchange rate, heat recovery amount, and air-side pressure drop. Tests were done with different refrigerant charging rates of 40-60% vol. and air flow rates of 300-1,400. The sensible heat exchange rate was highest for both types of heat pipes at a working fluid charge of 40% vol. and low flow rate. For the parallel-flow heat pipe, the 60% vol. charge is too high and results in a low sensible heat exchange rate. The reason is that the thicker liquid film of the tube wall deteriorates the heat transfer effect. Hence, the optimal charging rate is 40 to 50% vol. The evaporator heat pipe has a larger air-side pressure drop than the condenser section heat pipe. The reason is considered to be condensation water arising from the evaporator surface. Compared to the fin-tube heat pipe, the parallel-flow heat pipe showed better performance with a working fluid charging rate of 48%, volume of 41%, and an air-side pressure drop about 37%.

• Resources Recycling
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• v.24 no.2
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• pp.3-12
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• 2015

We researched characteristics of heat recovery rate and fouling according to structures and materials in heat exchangers like water preheater and air preheater. Economizer and air preheater have used in thermal electric power plant. we made small incinerator and heat exchangers to carry out simulated experiment. We observed fouling formation and change of heat recovery rate, combusting powdered coal for 24 hr. In economizer, fin tube type had the largest amount of fouling formation, followed by tube line type > pipe type > auto washing type according to structures. As heat recovery rate, fin tube showed highest recovery rate, followed by auto washing type > pipe type > tube line type. In air preheater, fin tube type had the largest amount of fouling formation, followed by fin plate type > pipe type > pipe type coated by teflon > pipe type coated by ceramic according to structures. And then, heat recovery rate showed the same oder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.765-766
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• 2012

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.753-758
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• 2003

In this study. an experiment has been performed to investigate distributions of static pressure around a circular cylinder in a uniform shear flow which is made by a specially designed wind tunnel. From the computation program(BLAYER), various boundary layer value are obtained depending on the shear flow rate. It is basical design data that boundary layer flow phenomenon of nuclear power plant heat exchanger tube surroundings. airfoil. and others flow fields.

• Proceedings of the SAREK Conference
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• 2007.06a
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• pp.207-207
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• 2007

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.982-991
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• 1991

본 연구에서는 냉방기에서 널리 이용되고 있는 평판핀이 연속적으로 부착된 다관식 증발 열교환기에 대하여 (1) 냉매의 열역학적 물성치의 변화 (2) 냉매와 공기 측 열전달 계수의 변화 (3) 냉매측 관 마찰 손실등을 고려한 시뮬레이션 프로그램을 작성하고 그 결과를 실험을 통하여 보정 완성하였다. 계산결과로 부터 공조기기의 설계조건, 공조계통 해석을 위한 기초자료를 제시하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.407-414
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• 2003

Analysis and experiment are performed to investigate the thermal performance of a heat pipe with axial grooves. The heat pipe was designed in a 6.5 mm I.D., 17 axial trapezoidal grooves. 1000 mm long tube of aluminium, and ammonia as working fluid. A mathematical equations fur heat pipe with axial grooves is formulated to obtain the capillary limitation on heat transport rate in a steady state. As a result, heat transport factor of heat pipe has the maximum at the operating temperature of 293K in 0m elevation. As the elevation of heat pipe increases. the heat transport factor of the heat pipe is reduced markedly, comparing with that of horizontal elevation of the heat pipe. It may be considered that such behavior of heat pipe is caused by the working fluid swarmed back to the condenser port due to gravity force and supercooled by a coolant of heat exchanger. Analytical results of heat transport factor are in a good agreement with those of experiment.