• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.1
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• pp.59-66
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• 2003

The purpose of this study is to analyze the characteristics (COP) of the heat pump system for various operating conditions with the use of seawater heat source and exhaust energy. To accomplish the goal, first of all, the computer simulation for heat pump system is carried out. The heat pump system model is made of a waste heat recovery system and a vapor compression refrigeration system, and the working fluid is R-22. The model calculated the change of COP with the variation of temperature and flow rate. The COP and the plate heat exchanger (PHE) area of the heat pump system are considered moderately high in the condensation temperature of $25^{\circ}^C$ and the evaporation temperature of $2^{\circ}^C$ in indoor culture system. The simulation results will be used effectively for the design and the performance prediction of heat pump system using unused energy in a land base aquaculture system.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.12-19
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• 2000

The increasing use of vehicles is causing air-pollution problems. Diesel vehicles are preferred to gasoline vehicles, because the diesel vehicles are superior to gasoline vehicles in terms of fuel consumption, durability, power and efficiency. But the emission reduction technologies for diesel vehicle are not developed well like those for gasoline vehicles. Moreover, the NOx and smoke emitted from diesel vehicle are recognized as a main source of the air-pollution in the urban areas. The emission reduction devices have been installed for each of the emission gas components. Using plasma(i.e. electrical energy)only, the emission gas was found to be reduced. The present paper investigate the effects of a low temperature plasma device in engine performance as well as in emission reduction with the change of the applied voltage and the loading rate of the engine.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.8
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• pp.648-655
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• 2002

For a discharge system of rotary compressor, analytical investigation on the discharge gas pulsation has been carried out. With the aid of four pole theory, acoustic impedance of the discharge system composed of muffler and cavities on both sides of motor with gas passages between them can be calculated using discrete acoustic elements described by transfer matrices, yielding the relationship between discharge mass flow rate and gas pulsation at the discharge port. This method of predicting the gas pulsation was validated by measurement data. Effects of change in discharge muffler geometries on the gas pulsation also were investigated, demonstrating that this method can be used for muffler design.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.11
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• pp.1106-1113
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• 2001

This paper presents experimental works on the ultrasonic influence during melting of ice and paraffin and compared the paraffin's result with ice's results. The experiments was carried out under two setting conditions.: 1) Heater without ultrasonic vibration, 2) heater with ultrasonic vibration. Experimental observations show that the ultrasonic vibration enhances significantly the phase-change process (melting) so that the melting time is reduced about 16∼25% compared to those of molting process without ultrasonics in the melting of both ice and paraffin. But the influence of ultrasonics was not significant to affect the reduction of the power consumption. In the case of paraffin, the reduction rate of power consumption was about 20%, but the reduction of the power consumption was increased about 0∼12%.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.7
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• pp.603-611
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• 2006

A variety of schemes were sought for a mitigation of thermal stratification phenomenon in the branch piping of domestic nuclear power plant. Several mechanisms of thermal stratification occurrence were introduced in this paper. A number of factors were selected to find out the schemes for thermal stratification mitigation and the computational analysis were performed. The length of vertical branch piping, the diameter, the radius of curvature of the elbow, the direction of connection between main piping and branch piping, the slope of branch piping, the leakage flow rate, the installation of additional valve, the change of the 1st valve position and another branch piping connected with branch piping were mentioned as factors in this paper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.8
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• pp.427-431
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• 2013

Ground heat pump systems utilize the annually stable underground temperature to supply heat for space heating and cooling. The underground temperature affects not only the underground ecosystem, but also the performance of these systems. However, in spite of the widespread use of these systems, there have been few researches on the effect of the systems on underground temperature. In this research, case studies with numerical simulation have been conducted, in order to estimate the effect of ground heat pump systems on underground temperature. The simulation was coupled with the ground water-ground heat transfer model and the ground surface heat transfer model. In the result, it was found that the underground change depends on the heat transfer from the ground surface, the heat exchange rate, and the heat conductivity of soil.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.3
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• pp.235-243
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• 2000

A theoretical model for laminar filmwise condensation along an isothermal vertical wall at constant pressure has been formulated on the basis of conservation laws and other fundamental physical principles. The model was applied to the prediction of the influences of variable thermophysical properties of liquid and vapor layers in the filmwise condensation of superheated vapor of Rl2, R134a, R142b and R152a. The dimensionless velocity component method was employed in the transformation of the governing equations and their boundary conditions, and the polynomial method was used for treating variable thermophysical properties of liquid and vapor. Physical quantities, such as the dimensionless thickness of the liquid layer, local heat transfer rate and mean heat transfer coefficient, were investigated for different values of the superheated temperature of the stagnant vapor far from the wall. It was found that the value of mean heat transfer coefficient of R134a was higher than other refrigerants for the change of the superheated temperature.

• Nuclear Engineering and Technology
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• v.33 no.1
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• pp.83-92
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• 2001

The properties of off-gas generated from vitrification process of ion-exchange resin were characterized. Theoretical composition and flow rate of the off-gas were calculated based on chemical composition of resin and it＇s burning condition inside CCM. The calculated off-gas flow rate was 67.9Nm$^3$/h at the burning rate of 40kg/h. And the composition of off-gas was avaluated as $CO_2$(41.4%), steam(40.0%), $O_2$(13.3%), NO(3.6%), and SO$_2$(1.6%) in order. Then, actual flow rate and composition of off-gas were measured during pilot-scale demonstration tests and the results were compared with theoretical values. The actual flow rate of off-gas was about 1.6 times higher than theoretical one. The difference between theoretical and actual flow rates was caused by the in-leakage of air to the system, and the in-leakage rate was evaluated as 36.3Nm$^3$/h. Because of continuous change in the combustion parameters inside CCM, during demonstration tests, the concentration of toxic gases showed wide fluctuation. However, the concentration of CO, a barometer of incompleteness of combustion inside CCM, was stabilized soon. The result showed quasi-equilibrium state was achieved two hours after feeding of resin.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.56-59
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• 2001

An effective method of detecting inter-turn short circuits on round rotor windings is described. Shorted-turns can have significant effects on a generator and its performance. A method of detecting inter-turn short circuits on rotor windings is described. The approach used is to measure the rate of change of the air-gap flux density wave when the rotor is at operating speed and excitation is applied to the field winding. The inter-turn short circuits sensor for synchronous generator's field winding has been developed. The sensor, installed in the generator air-gap, senses the slot leakage flux of field winding and produces a voltage waveform proportional to the rate of change of the flux. For identification of reliability for sensor, a inter-turn short circuits test was performed at the West-Inchon combined cycle power plant on gas turbine generator and steam turbine generator. This sensor will be used as a detecting of shorted-turn for field winding of synchronous generator. The purpose of this paper is to describe the design and operation of a sensitive inter-turn short circuits detector. In this paper, development of inter-turn short circuits sensor for field winding of synchronous generator and application in a field.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.801-808
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• 2021

In this paper, a numerical analysis was conducted on the effect of the flow control valve of a oscillation water column(OWC) type wave power generator turbine. The OWC wave power turbine operates with compressed air in the air chamber according to the change of wave height. When the wave height changes rapidly, a flow control valve is required due to overload of the turbine and reduced efficiency. Therefore, in this paper, a flow control valve with an opening angle of 60 degrees was installed in the front of the turbine, and the pressure drop, torque, and overall performance were calculated according to the change of turbine RPM and flow rate of turbine inlet. In conclusion, the flow control valve with an opening angle of 60 degrees affects when the turbine rotates at low rotation and the inlet flow rate is large. But it does not have a significant effect on overall turbine performance and it is necessary to find the optimal angle in the future works.