• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.1
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• pp.7-13
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• 2006

Because the usage of CFC and HCFC based refrigerants are restricted due to the depletion of ozone layer, the $NH_3$ gas, in the experiment is evaluated to the performance characteristics for the superheat control to improve the energy efficiency. The experiment is carried out about the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa through the degree of superheat from 0 to $10^{\circ}C$ at each condensing pressure. As a result, in the case of shell and tube type of heat exchanger, the COP is more efficient than other cases at the degree of superheat $1^{\circ}C$ at each condensing pressure. In the case of shell and disk type of heat exchanger, the COP is the most efficient at the degree of superheat 0.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.4
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• pp.297-302
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• 2005

Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the $NH_3$ gas to study the performance characteristics of $NH_3$ refrigeration system by the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa and for degree of superheat from $0^{\circ}C\;to\;10^{\circ}C$ at each condensing pressure. As a result of experiment, when the degree of superheat is $0^{\circ}C$ at each condensing pressure, the refrigeration system has the highest performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.377-383
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• 2006

Recently, production and use of Freon substances are restrained due to destruction of ozone layer and grobal warming. In this aspect of environmental problems, the best solution is to use the natural refrigerant such as ammonia. Thus, this study apply the $NH_3$ and R22 to study the performance characteristic from the superheat control and compare the energy efficiency of two refrigerants from the high performance. The condensing pressure of refrigeration system is increased from 1,500 kPa to 1,600 kPa and degree of superheat is increased from 0 to $10^{\circ}C$ at each condensing pressure. As the result of experiment, when comparing the each COP, we knew the $NH_3$ is suitable as the alternative refrigerant of the R22.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.713-718
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• 2015

The purpose of this study is to realize compressor-performance improvements in the fuel economy of an automotive air-conditioning system. We conduct cooling performance tests in a compressor calorimeter test stand. To improve the cooling performance, we investigate the increase in the suction flow rate and the decrease in the discharge dead volume. Based on the results of the test, we found that the cooling capacity and the coefficient of performance (COP) of the compressors were improved as follows. The cooling performance improved greater at high speeds than low speeds in the case of an increase in the suction flow rate increase, and it improved more at low speeds than at high speed when there was a decrease in the discharge dead volume. When both of the above factors were included, we observed that the improvement effects were generally balanced for both high- and low-speed modes, and there was a significant improvement in the discharge temperature. The improvement was found to be about 3.2% at low speed, 8.3% at high speed during in cooling performance improvement, about 5.8% at low speed and about 6.2% at high speed in COP improvement, and there was a decrease of about $3^{\circ}C$ at low speed and a $5^{\circ}C$ decrease at high speed in discharge temperature.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.80-83
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• 2008

As SOC (Social Overhead Capital) has been expanded, the highway road construction has been accelerated and city road system has been more complicated. So, long road tunnels have been increased and traffic flow rate also has been raised. Accordingly, the exhausting gas of vehicle cars seriously deteriorates the tunnel inside air quality and driving view. In order to improve tunnel inside air quality, we may need to introduce a compulsory ventilation system as well as natural ventilation mechanism. The natural ventilation mechanism is enough for short tunnels, meanwhile longer tunnels require a specific compulsory ventilation facility. Many foreign countries already have been devoting on development of effective tunnel ventilation system and especially, some European nations and Japan have already applied their developed tunnel ventilation system for longer road tunnels. More recently, as the quality of life improved, our concerns about safety of driving and better driving environment have been increased. In order to obtain clearer and longer driving view, we are more interested in EP tunnel ventilation system in order to remove floating contaminants and automobile exhaust gas. Evan though it's been a long time since many European countries and Japan applied more economical and environment-friendly tunnel ventilation system with their self-developed Electrostatic Precipitator, we are still dependant on imported system from foreign nations. Therefore, we need to develop our unique technical know-how for optimum design tools through validity investigation and continuous possibility examination, eventually in order to localize the tunnel ventilation system technology. In this project, we will manufacture test-run products to examine the performance of system in order to develop main parts of tunnel ventilation system such as electrostatic precipitator, high voltage power generator, water treatment system, etc.

• Journal of the Korea Convergence Society
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• v.2 no.3
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• pp.45-50
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• 2011

High performance heat transfer channel is necessary to discharge operating heat of computer and high integrated circuit, refrigerator and air conditioning system. Nano-Tube is useful module witch is able to cope with heat transfer problems. The purpose of this study is to develop the process and manufacturing system for Nano-Tube. Since the Nano-Tube which is used in our country is imported, this study will contribute the development of Nano-Tube technique and economic profits with import substitute effect. This study show the procedure of process and manufacturing system development.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.115-123
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• 2010

Cool-down performance after soaking is important because it affects passenger's thermal comfort. The cooling capacity of HVAC system determines initial cool down performance in most cases, the performance is also affected by location, and shape of panel vent, indoor seat arrangement. Therefore, optimal indoor designs are required in developing a new car. In this paper, initial cool down performance is predicted by CFD(computational fluid dynamics) analysis. Experimental time-averaging temperature data are used as inlet boundary condition. For more reliable analysis, real vehicle model and human FE model are used in grid generation procedure. Thermal and aerodynamic characteristics on re-circulation cool vent mode are investigated using CFX 12.0. Thermal comfort represented by PMV(predicted mean vote) is evaluated using acquired numerical data. Temperature and velocity fields show that flow in passenger's compartment after soaking is considerably unstable at the view point of thermodynamics. Volume-averaged temperature is decreased exponentially during overall cool down process. However, temperature monitored at different 16 spots in CFX-Solver shows local variation in head, chest, knee, foot. The cooling speed at the head and chest nearby panel vent are relatively faster than at the knee and foot. Horizontal temperature contour shows asymmetric distribution because of the location of exhaust vent. By evaluating the passenger's thermal comfort, slowest cooling region is found at the driver's seat.

• Journal of the Korean Solar Energy Society
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• v.34 no.6
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• pp.67-74
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• 2014

An inverter scroll compressor is used for the air conditioning in cars. Scrolls would be changed from the aluminum material to the magnesium material in order to satisfy the light weight trends of cars. The material changing influences on the scroll dimensions particularly the gap between two scrolls. Since the larger gap declines the performance of the compression, the gap between wraps of scrolls or the gap between wraps of scrolls to the plate of the opposite scroll is regarded as an important design variable. This paper is focused on the effects of the thermal stress due to the materials changing. The temperature difference between the inlet and the outlet is about 60 degrees and the highest operating temperature in the compressor is less than 110 degrees. The level of thermal stresses in the magnesium scroll is less than the result from aluminum one. The trend of the deformation is revealed that the normal directional deformation is 2 times lager than the in-plane directional deformation. Therefore the gap between the top of the wrap to the plate of the opposite scroll become more important than the other gaps. The orbiting scroll deforms larger than the fixed scroll by the thermal stresses. The deformation of the magnesium scroll is about 10% lager than that of the aluminum scroll. This value is similar to the ratio of the coefficients of thermal expansion of two materials. At the initial design stage, the results give many useful guides to engineers to propose gaps between parts.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.38-42
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• 2012

A scroll compressor used in the air conditioning in automobile consists of the fixed scroll and the orbiting scroll. Temperature gradient in the scroll compressor during the operation induces the thermal expansion of two scrolls. Therefore, the gap between scrolls in the initial stage is regarded as an important variable in structural design of the scroll compressor. The coupled thermal-stress analysis was carried out for the scrolls of a scroll compressor. The temperatures of major points of two scrolls in the steady states were referred by the literature of C. Lin. The sequentially coupled thermal-stress analysis is utilized to the heat transfer analysis and the thermal expansion analysis. In the thermal expansion analysis, the contact analysis was considered between the fixed and the orbiting scrolls in order to obtain the penetration distance and the contact pressure between two scrolls. The range of deformation was from 44 to $76{\mu}m$ according to the height of the scroll. The maximum penetration distance of $60{\mu}m$ occurred at the top surface of the fixed scroll in the center of the scroll parts.