• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.5
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• pp.41-45
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• 2001

This paper presents an comparative study on the effect of STATCOM and UPFC to power flow analysis of power systems. The effect of STATCOM can be analyzed with PSS/E program which is generally used in power system analysis, while UPFC model for power flow analysis is not provided yet. Thus, UPFC is equivalently represented as a synchronous condenser and load, while the active and reactive power of the specific transmission line and the voltage of the bus is controlled appropriately. This procedure is implemented by IPLAN which is an external macro program of PSS/E. The simulation results show that UPFC is more effective to control the bus voltage than STATCOM, because UPFC can control not only the bus voltage where the parallel inverter is installed but also the active and reactive power flow in the transmission line where the series inverter is installed.

• 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%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.272-280
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• 1999

A cycle analysis was achieved to predict the characteristics by comprehensive modeling and simulation of an air-cooled, double-effect absorption system using a new $H_2O/LiBr+HO(CH_2)_3OH$ solution. The simulation results showed that the new working fluid may provide the crystallization limit 8% higher than the conventional $H_2O/LiBr$ solution. With a crystallization margin of 3wt%(weight%), the optimal solution distribution ratio was found in the range of 36 to 40%. Variation of cooling air Inlet temperature has a sensitive effect on the cooling COP and corrosion problem. The simulation of heat exchangers with UA value revealed that the absorber and the evaporator are relatively important for an air-cooled system compared with the condenser and the low temperature generator. The effect of cooling air flow rate, circulation weak solution flow rate and chilled water inlet temperature were also examined. The new working fluid may provide the COP approximately 5% higher than the conventional $H_2O/LiBr$ solution.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.44-56
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• 1998

Separate heat pipe exchanger is considered as the high thermal transportation equipment, because evaporator and condenser are separately positioned in the long distance. Its characteristics are that the working fluid is circulated naturally by the position height of two exchangers. But the operating characteristics are restricted by the temperature of hot and cold fluid, flow pattern and diameter of vapor line, etc. in this study, the vapor pressure and the minimum height of two exchangers are studied about the factors restricting the operating characteristics.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.148-157
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• 1998

This study presents test results of a residential window air-conditioner using R22 and two potential alternative refrigerants, R407C and R410B. A series of performance tests has been carried out for the basic and liquid-suction heat exchange cycles in a psychometric calorimeter test facility. For R407C, the same rotary compressor was used as in the R22 system. However, compressor for the R410B system was modified to provide the similar cooling capacity. The evaporator circuit was changed to get a counter-cross flow heat exchanger to take advantage of zeotropic mixture's temperature glide, and liquid-suction heat exchange cycle was also considered to improve the system performance. Test results were compared with those for the basic R22 system. The modified system with a liquid-suction heat exchanger increased cooling capacity and energy efficiency by up to 5%.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.203-211
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• 1998

The system performance of an automobile air conditioning system with variations of charging conditions has been investigated experimentally. An automobile air conditioning system was composed of laminated type evaporator, parallel flow type condenser, swash plate type com-pressor, externally equalized thermostatic expansion valve and receiver drier. The objective of this study was to quantify the influence of the refrigerant charge under the steady state operation of an automobile air conditioning system. The results indicated that a 10% undercharge caused a 10% reduction in the capacity of evaporator.

• Journal of Energy Engineering
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• v.7 no.2
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• pp.231-240
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• 1998

The global environmental problems such as CFC, energy losses in heat recovery system as well as summer peak time power demands, the development of high efficiency absorption refrigeration systems is one of the most promising method in this problems. The absorption refrigeration system to utilize treated sewage is available for environmental protection and energy conservation. Simulation analysis on the double-effect absorption refrigeration cucles with parallel or series flow type has been performed. LiBr+LiI+LiCl+LiNO$_3$ solution was selected as the new working fluid. The main purpose of this study is evaluating the possibilities of effective utilization of treated sewage as a cooling water for the absorber and condenser. The other purpose of the present study is to determine the optimum designs and operating conditions based on the operating constraints and the coefficient of performance in the parallel or series flow type. In this study, we found out the characteristic of new working solution through the cycle simulation and compared LiBr solution to evaluate. The absorption refrigeration machine using the new working fluid was obtained better results COP rise and compactness of system by comparison with LiBr solution.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.214-216
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• 2000

This paper presents an comparative study on the effect of STATCOM and UPFC to the power system static analysis. The effect of STATCOM can be analyzed with PSS/E program which is generally used in power system analysis, while UPFC model for static analysis is not provided yet. Thus, UPFC is equivalently represented as a synchronous condenser and load, while the active and reactive power of the specific transmission line and the voltage of the bus is controlled appropriately. This procedure is implemented by IPLAN which is an external macro program of PSS/E. The simulation results show that UPFC is more effective to control the bus voltage than STATCOM, because UPFC can control not only the bus voltage where the parallel inverter is installed but also the active and reactive power flow in the transmission line where the series inverter is installed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.222-229
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• 2009

This study presents comparison of heat transfer and air side friction characteristics in a condenser condition of air conditioner between Louver fin-tube heat exchangers and aluminum parallel heat exchangers. All experiments are performed using an air-enthalpy type calorimeter, which is designed based on the method described in ASHRAE standards. The air velocities crossing the heat exchanger tubes are varied from 0.7 to 1.6 m/s with 0.3 m/s interval, maintaining air dry temperature and relative humidity at $20^{\circ}C$ and 60% respectively. Water temperature and flow rate inside the tube are $70^{\circ}C$ and 10 LPM, respectively. Experimental results show that the heat transfer performances of aluminum heat exchangers are 17-163% higher than those of Louver fin-tube heat exchangers based on the data per unit volume, mass, and heat transfer area, whereas air side pressure drops of aluminum heat exchangers are 19-81% lower.