• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1143-1148
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• 2005

Experimental results for heat transfer characteristic and pressure gradient of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during condensing inside horizontal double pipe heat exchangers are presented. The test sections which have one tube diameter of 12.70 mm with 0.86 mm wall thickness, another tube diameter of 9.52 mm with 0.76 mm wall thickness are used for this investigation. The local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than those of R-22. The average condensing heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than those of R-22 in 12.7 mm and 9.52 mm. This results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.977-983
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• 2006

Experimental results for heat transfer characteristic and pressure gradient of hydrocarbon refrigerants (R-290, R-600a, R-1270) and HCFC refrigerant (R-22) during condensation inside horizontal double pipe heat exchangers are presented. The test sections which have one tube diameter of 12.70 mm with 0.89 mm, 9.52 mm with 0.76 mm, 6.35 mm with 0.13 mm wall thickness are used for this investigation, respectively. The local condensing heat transfer coefficients of hydrocarbon refrigerants were higher than those of R-22. The average condensing heat transfer coefficient increased with the increase of the mass flux. It showed the higher values in hydrocarbon refrigerants than R-22. Hydrocarbon refrigerants have higher pressure drop than R-22 in 10.92 mm, 8 mm and 6.1 mm inner diameters. These results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.852-858
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• 2011

This paper is aiming to estimate the mutual influence of the stack cooling performances with the operation modes of the thermal management system for the hydrogen fuel cell vehicles. The heat capacity of the thermal management system was measured by varying the operating modes such as stack cooling heat exchanger only (Mode 1), stack cooling and electric devices cooling heat exchangers (Mode 2), and stack cooling and electric devices cooling heat exchangers with an operation of the condenser (Mode 3).As the results, Performance of the thermal management system (TMS) at Mode 3 decreased up to 34.0%, compared with the result of the Mode 1. In addition, in order to optimize the performance of TMS, the entropy change of stack cooling heat exchanger using irreversibility analysis technique was analyzed with the relationship between entropy generation and entering air velocity of the thermal management system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.599-604
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• 2008

An experimental study has been performed to investigate the air-side capacity and pressure drop of the fin-tube heat exchanger for a fan coil unit under a cooling condition. The experimental data of five kinds of slit fin-tube heat exchangers were measured using an air-enthalpy calorimeter and a constant temperature water bath. Cooling capacities at the air and water rating flow rates were larger at the lower inlet water temperature. With increasing the water flow rate, the cooling capacity increased at the constant rate. Under the lower inlet water temperature, since the condensate was generated more on the fin-tube surface, the air-side pressure drop of the heat exchanger was larger.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.5
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• pp.533-539
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• 2005

Experimental results are presented for heat transfer and pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers. Two tubes with a tube diameter of 12.70mm and 9.52mm are used for this investigation. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7mm and 9.52mm. The results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.254-260
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• 2002

There have been many studies for the flow through internally finned tube, since the heat exchangers with fin device derive much attention in heat transfer enhance cent. In this study, analysis of laminar flow through the circular tube with longitudinal fins are investigated. The height and the number of fins are arbitrary. The flow field is assumed to be laminar and conformal mapping is used to obtain analytic solution. From the analytic solution, equi-velocity lines are shown, and the flow rate through the finned tube is calculated for various fin heights and numbers of fins. Darcy friction factor for this finned tube and shear stress distributions on the wall and fin are also considered.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1267-1271
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• 2009

In the present study, performance characteristics on environment change of A/C applied fin-tube and PF heat exchangers were experimentally investigated. Capacity and COP changing an outlet air velocity, an indoor/outdoor temperature and a relative humidity were obtained. Air－enthalpy calorimeter was used. As the air velocity, indoor temperature and relative humidity increase, capacity and COP increase. PF A/C has smaller refrigerant weight than the fin-tube A/C. The performance of PF-2 A/C with the squarer fin was more excellent than that of PF-1 A/C with the triangler fin.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.221-227
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• 2012

The CANDU 9 shield cooling system was designed and layout with the objective of promoting natural circulation on loss of forced flow. In the present study, the shield cooling natural circulation was analyzed using verified the thermal-hydraulic code when the coolant pump or the heat exchanger was lost. This study showed that thermosyphoning cooled the end shields and prevented the end shields and the reserve water tank from boiling for at least 8 hours on loss of the shield cooling pumps but the heat exchangers still operational. With the loss of both pumps and heat exchangers, the end shields remain subcooled for up to 4 hours. To enhance thermosyphoning, the bypass connection to the line from the reserve water tank should be relocated to a point as low as possible.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.181-185
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• 2008

The new concept for liquefaction of natural gas has been designed and simulated in this paper. Conventional liquefaction cycles are usually composed with Joule-Thomson valves at lower temperature refrigerant cycle. The new concept of natural gas liquefaction is discussed. The main difference with conventional liquefaction process is the presence of the turbine at low temperature of MR (mixed refrigerant) cycle. The turbine acts as expander but also as an energy generator. This generated energy is provided to the compressor which consumes energy to pressurize refrigerants. The composition of the mixed refrigerant is investigated in this study. Components of the refrigerant are methane, propane and nitrogen. Composition for new process is traced with Aspen HYSYS software. LNG heat exchangers are analyzed for the new process. Heating and cooling curves in heat exchangers were also analyzed.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.483-488
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• 2006

In this study, newly-developed slim electronic panel cooler with aluminum PF condenser and evaporator was tested and the results are compared with imported panel cooler with fin-tube heat exchangers. The PF heat exchangers significantly (approximately 45%) reduced the refrigerant charge. The air-side pressure drop was also reduced, which resulted in the reduction of the sound level of the panel cooler. The effect of the condenser size was also investigated.