• 한국전산유체공학회지
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• 제14권4호
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• pp.7-12
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• 2009

The purpose of the present study is to investigate the convective heat transfer characteristics and the validity of fin efficiency of the circular finned-tube heat exchanger by using commercial CFD code. The heat transfer coefficient obtained by using the laminar model was 22% overestimated to the experimental data. The fin surface temperature compared with the experimental data measured by the liquid crystal method. The fin efficiency by the present numerical experiment, defined as normalized and averaged fin surface temperature, was greater than the theoretical fin efficiency and the difference is increased at high value of the factor $mr{\phi}$.

• 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.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1161-1166
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non-inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• 설비공학논문집
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• 제20권1호
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• pp.75-80
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non~inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• 설비공학논문집
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• 제27권3호
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• pp.146-151
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• 2015

The heat transfer performance of heating medium oil fluidized bed heat exchanger was measured. The operation variables were air flow rate, air inlet temperature, moisture content, water flow rate and water inlet temperature. The outside heat transfer coefficient was determined from the heat exchanger experiment and its experimental correlation was determined as a function of air velocity and viscosity of heating medium oil. Effect of viscosity was well agreed with the previous studies. Errors of the correlation equation was less than about 10% for outside heat transfer coefficient developed in this study when compared with the measured value. Hot water with the temperature greater than $77^{\circ}C$ could be produced by using the heating medium oil fluidized bed heat exchanger.

• 융복합기술연구소 논문집
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• 제7권1호
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• pp.1-6
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• 2017

The Heat exchanger for deep geothermal system is very important to enhance the efficiency of the system. The co-axial heat exchanger is used due to the limitation of digging space. The heat transfer on the external surface of outer pipe should be high to receive a large amount of heat from the ground. However, the inner pipe should be insulated to reduce the heat loss and increase the temperature of discharge water. This study made experiment apparatus to describe the co-axial heat exchanger and measure the heat transfer coefficients on the internal and external surface. And the pin-fin was designed and fixed on the internal surface to increase the efficiency of heat exchanger. Finally, we calculated the temperature of discharge water using the heat transfer circuit of co-axial heat exchanger and heat transfer coefficient which from experimental results. The water temperature was reached the ground temperature at -500 m and following the ground temperature. When the water return to the ground surface, the water temperature was decreased due to heat loss. As the pin-fin case, the heat transfer coefficient on the internal surface was decreased by 30% and it mean that the pin-fin help to insulate the inner pipe. However, the discharge water temperature did not change although pin-fin fixed on the inner pipe.

• Journal of Advanced Marine Engineering and Technology
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• 제20권4호
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• pp.36-42
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• 1996

Analysis of heat transfer on small-size Diesel engine is required for the development of high performance and efficiency engine. This basic study aims to establish heat transfer technique for marine Diesel engine. The main results from this study are as follows : 1) Overall engine heat transfer correlation of Re-Nu. 2) Radiant heat flux as fraction of total heat flux over the load range of several different Diesel engine. 3) Characteristics of heating curves on piston, cylinder liner and head. 4) Surface heat flux versus injection timing.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.237-238
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• 2012

Recently, an energy-saving due to the energy utilisation efficiency enhancement is important. In order to improve the heat efficiency of the general residential boiler, We performed an experiment of condensation heat transfer to air pre-heat exchanger adhered to the condensing boiler. In this research, We analyze the heat transfer performance through the hydrophilic surface treatment(plasma, etching). The results of the research, On plasma and etching treated surface, Overall heat transfer coefficient is displayed the tendency to increase.

• 수산해양교육연구
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• 제27권6호
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• pp.1872-1879
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• 2015

The present study was conducted on the improvement of the heat transfer performance of double pipe heat exchangers with helical insert device. Double pipe heat exchangers with helical insert device were studied for improvement of the heat transfer performance of double pipe heat exchangers with helical insert device and plain double pipe heat exchangers were also studied to comparatively analyze heat transfer performance. Experimental results were derived on changes in the Reynold's numbers of the cooling water flowing in helical and plain double pipe heat exchangers and changes in the heat flux of the air. Thereafter, to verify the reliability of the experimental results, the theoretical total energy and the experimental total energy were comparatively analyzed and the following results were derived. The thermal energy of the calorie lost by the hot air and that of the calorie obtained by the cooling water were well balanced. The experiments of plain double pipe heat exchangers and double pipe heat exchangers with helical insert device were conducted under normal conditions and the theoretical overall heat transfer coefficient value and the experimental overall heat transfer coefficient value coincided well with each other. In both plain double pipe heat exchangers and double pipe heat exchangers with helical insert device, heat transfer rates increased as the cooling water flow velocity increased. Under the same experimental conditions, the heat transfer performance of double pipe heat exchangers with helical insert device was shown to be higher by approximately 1.5 times than that of plain double pipe heat exchangers.

• 설비공학논문집
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• 제12권4호
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• pp.422-429
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• 2000

Plate and shell heat exchanger(P&SHE) is widely applied as evaporators or condensers in the refrigeration and air conditioning systems for their high efficiency and compactness. In order to set up the database for the design of the P&SHE, heat transfer and pressure drop characteristics for single phase flow of water in a plate & shell heat exchanger are experimentally investigated in this study. Single phase heat transfer coefficients were measured for turbulent water flow in a plate and shell heat exchangers by Wilson plot method. The shell side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a plate side were obtained by Wilson plot method. Single-phase heat transfer correlations based on projected heat transfer area and friction factor correlations have been proposed for single phase flow in a plate and shell heat exchanger.