• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.2
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• pp.88-96
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• 2002

The present study was conducted to estimate the effect on fouling reduction in tubes of the condenser. It shows in detail how to calculate the fouling factor from the experimental results of refrigeration systems with or without the automatic cleaning system using sponge balls and to predict the variation of the factor with time. It also represents how to calculate the temperature and pressure decrease of the refrigerant vapor in the condenser and the load decrease of the compressor in the refrigeration system by fouling reduction.

• Transactions of the Korean hydrogen and new energy society
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• v.5 no.2
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• pp.91-98
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• 1994

In this study hydrogen gas and oxygen gas are used to make a pollution-free engine which is a closed system with the components such as a combustor, two turbines, a radiator and a compressor. One of the two turbines produces main power, and the other is used to drive a compressor to compress unburned gases and to return them to the combustor. Some of the water from the radiator is pumped to cool down the internal wall of the combustor and to be used as a working fluid which expands from liquid state to vapor state to get more expansion work. The possibility of operating the whole system is checked by the thermodynamic analysis to make the closed engine system. The calculations in the thermal analysis are based on the Brayton cycle and the Rankine cycle. The closed system in this study shows similar efficiency as usual internal combustion engines, but it produces water only without air pollution such as $NO_x$ and soot.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.2
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• pp.121-128
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• 2012

Improvement in the energy efficiency has been studied of the desiccant cooling system by applying a vapor compression type heat pump to modify the system into a hybrid system. The cycle simulation was performed and the results were compared between a reference desiccant cooling system composed of a desiccant rotor, a sensible rotor and a regenerative evaporative cooler, and a hybrid desiccant cooling system with the sensible rotor being replaced by a heat pump. Though the electric consumption increases as much as the compressor power consumption, the total cooling capacity increases and the thermal energy input decreases by the addition of the heat pump. Therefore, the total energy efficiency can be improved if the increase in the electric consumption can be compensated with the increase in the cooling capacity and the decrease in the thermal energy input. The results showed that the total energy efficiency is optimized at a certain heat pump capacity. When the heat from the CHP plant is used for the thermal energy input, the energy consumption of the hybrid system is reduced by 20~30% compared with the reference system when the heat pump shares 30~40% of the total cooling capacity.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.170-177
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• 2012

To apply the nanofluids into the general vapor compression cycle, basically have to know the thermal properties including thermal conductivity and dynamic viscosity. And needs to show the dispersion characteristics for various nanofluids and concentrations. So, firstly this study showed experimentally the thermal properties for various concentration (0.1%~0.7%, as mass balance) and temperature($20^{\circ}C{\sim}40^{\circ}C$) on $Al_2O_3$, $TiO_2$, and CuO nanofluids using base fluid as POE oil that has used in the scroll compressor for various refrigeration system. From the results, the dynamic viscosity of nanofluids was considerably changed from the base POE oil. And, the dispersion characteristics of various nanofluids using the simple methods like as analyzing the RGB value or measuring the sinking height of nanofluids were showed experimentally. Through the results, the dispersion characteristics of $Al_2O_3$ nanofluid was better than those of $TiO_2$, and CuO nanofluids not considering the real refrigeration cycle rurming conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.9
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• pp.809-816
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• 2010

An environmental control system is installed to dissipate the thermal load in avionic equipments that are mounted under an aircraft. The operating characteristics of the system change with variations in the control parameters. In this study, an environmental control system was designed and built using R-124 by adopting a vapor compression cycle. The operating characteristics of this system were observed by varying the control parameters, such as refrigerant charging amount, opening of the expansion device, compressor rotation speed, and blower rotation speed. The effect of the control parameters on the environmental control system was analyzed and an optimum control method was identified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.431-439
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• 2013

A cooling system is adopted to control the thermal load from the avionic equipments in an aircraft for stable operation. In this study, an avionic cooling system was designed and manufactured by adopting a vapor compression cycle with a closed-loop air-circulation system to investigate the operating characteristics of an alternative refrigerant. The performance characteristics of a cooling system adopting R236fa as an alternative refrigerant were experimentally determined by varying the refrigerant charging amount, expansion valve opening, and compressor rotation speed. The experimental results were analyzed and compared with those of a cooling system adopting R124 as a refrigerant. The possibility of the adoption of R236fa as an alternative refrigerant was verified, and design solutions were suggested to improve the system efficiency.