• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1267-1275
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• 2002

An experimental study was performed to investigate adiabatic wall temperature and heat transfer coefficient around a module cooled by forced air flow. The flow angle of attack to the module were 0$^{\circ}$and 45$^{\circ}$. In the first method, inlet air flow(1~7m/s) and input power.(3, 5, 7W) were varied after a heated module was placed on an adiabatic floor(320$\times$550$\times$1㎣). An adiabatic wall temperature was determinated to use liquid crystal film. In the second method to determinate heat transfer coefficient, inlet air flow(1~7m/s) and the heat flux of rubber heater(0.031~0.062W/$m^2$) were varied after an adiabatic module was placed on rubber heater covering up an adiabatic floor. Additional information is visualized by an oil-film method of the surface flow on the floor and the module. Plots of $T_{ad}$ and $h_{ad}$ show marked effects of flow development from the module and dispersion of thermal wake near the module. Certain key features of the data set obtained by this investigation may serve as a benchmark for thermal-design codes based on CFD.

• Journal of Acupuncture Research
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• v.17 no.3
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• pp.277-285
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• 2000

By process of treatment for a case which diagnosed as suppurative arthritis and admitted from the 5th, October, 1999 to the 15th, November, 1999, the results are as follows. Method & Results : In the earlier days of admission, this patient was diagnosed as damp-heat(濕熱) and medicated Cheongyeolsaseup-tang(qingrexieshi-tang). As the result, heating, pain in both knees and heating in both lmees are improved. In the later days of admission, this patient was diagnosed as impairment of the liver and kidney(肝腎虛損) and medicated Samgi-eum(sanqi-yin). As the reslut, weakness in lower limbs is improved. Conclusion : I consider that the rate of recovery for other infectious diseases including suppurative arthritis can be maximized by accumulation of clinical experiences and continuous research through both western medical treatment and oriental medical treatment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.720-729
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• 1996

An analysis of convective boiling heat transfer for refrigerant mixtures is performed for an annular flow to investigate the degradation of the heat transfer rate. Annular flow is selected in this study because a great portion of the evaporator in the refrigeration and air conditioning system is known to be in the annular flow regime. Mass transfer effect due to composition difference between liquid and vapor is included in this analysis, which is considered to be one of driving forces for the mass transfer at the interface. Due to the concentration gradient at the interface the mass transfer is interfered, so is the evaporative heat transfer at the interface. The mass transfer resistance makes the interface temperature slightly higher and, as a result, the heat transfer coefficients decrease compared with those without mass transfer effects. The degradatioin of the heat transfer rate reaches its maximum at a certain composition. The composition difference between vapor core and vapor at the interface has a direct effect on the temperature difference between the vapor core and the interface and the degradation of the heat transfer rate. Correction factor $C_{F}$ for the mixture effects is added to the correlation for pure substances and the flow boiling heat transfer coefficients can be calculated using the modified equation.n.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.407-416
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• 2005

The kimchi refrigerator is the electric home appliance which is used for the maturing and preserving of the kimchi in domestic and foreign market. The kimchi refrigerator is composed in 3 main parts as insulation. kimchi container, machinery room. The heat exchanger of kimchi refrigerator is made of aluminum and the other parts are made of steel and polymer. Also, kimchi refrigerator is expensive and heavy as compared with same class of refrigerator until now. In the present study, the possibility to replace heat exchanger from aluminum to thermal conductive plastic was analyzed and experimented. The thermal conductive plastic has $10{\sim}100$ times heat conductivity than that of normal plastic. It is known that heat transfer process is dependent not only conduction but convection or radiation. Thermal conductivity of the applied material in this research is over than 2 W/mK, thermal conductivity doesn't play a vital role on heat transfer. In this study, temperature is the most important parameter on the kimchi refrigerator and the temperature of kimchi refrigerator's heat exchanger was measured and compared with the temperature calibrated by CFD analysis on the inside wall of the kimchi refrigerator. It is important to keep constantly the inside temperature of the Kimchi refrigerator. Besides numerical analyses for the new thermal conductive plastic for heat exchanger were executed with the various height of evaporation tube. A series of experiments were conducted to compare the performance of the two heat exchanger made of aluminum and thermal conductive plastic at the same condition and certified the possibility of the thermal conductive plastic. According to these results, it was confirmed that the conventional aluminium heat exchanger can be replaced by thermal conductive plastic successfully.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.107.1-107.1
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• 2012

Because of beautiful glossy and color, the value of gold leverage is very high in Europe. For improve the quality of white gold, we performed heat treatment on 14K white gold alloys at various age-hardening conditions. Age-hardening behavior and the related phase transformation changes were studied to elucidate the hardening mechanism of 14K white gold alloys. For solid solution treatment [ST], casted 14K white gold alloy specimens were treated at high temperature ($750^{\circ}C$) during 30 minute, and the specimens dropped to water for quenching immediately. For Age-hardening treatment [AT], the specimens were treated at various temperatures ($250^{\circ}C{\sim}300^{\circ}C$). After the heat treatment, we observed increased hardness from 144 Hv to 214 Hv by Vicker's hardness tester. Variation of the grain size measured by optical microscopy (OM) and scanning electron microscopy (SEM) images. By electron probe micro-analysis (EPMA) mapping analysis, we investigated that irregular particles were changed uniformly. After heat treatment, 14K white gold alloys showed improved hardness and became uniformity of grain size by age-hardening treatment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.482-490
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• 2002

This paper presents modelling and analyzing method of centrifugal chiller which has a rated capacity of 200 RT(703 kW) through on-site performance test. Field performance data of a chiller installed in a research building of KIST have been collected. Simple models were developed for predicting the heat exchanger and system performances by regression of chiller operation data during 5 days in August. The models proposed here account for the effect of variations of cooling capacity, temperatures and flew rates of secondary fluids. The proposed models can predict the actual performance data from June to September within $\pm$ 5% error. The COP of centrifugal chiller are estimated under the standard rating conditions and reduced mass flow rates of chilled and cooling water.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.303-315
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• 1997

The theoretical model for the transient probe method is the modified Jaeger model which is used perfect line source theory. The transient probe technique has been developed for the simultaneous determination of thermal conductivity, diffusivity and volumetric heat capacity of liquids. The Levenberg-Marquardt iteration method is adapted to obtain thermal property within nonlinear range. Experimental results of liquids were found to agree well with recommended thermal property data.

• Solar Energy
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• v.18 no.2
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• pp.105-113
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• 1998

In general, the thermo-diode is a device designed to allow heat to be transferred only in one direction. However, the bidirectional thermo-diode devised to change the heat flow in the desired direction can be used for the reduction of the heating load in winter as well as the cooling load in summer. In this study, a solar heating system using loop-type bidirectional thermo-diodes is designed and set up, also it is successfully applied to an outdoor test cell for the verification of its usefulness.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.7
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• pp.567-573
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• 2001

A real-time HVAC system is proposed which implements real-time control of thermal environment for virtual reality. It consists of a pair of hot and cold loops that serve as thermal reservoirs, and a mixing box to mix hot and cold air streams flowing if from loops. Their flow rates are controlled in real-time to meet a set temperature and flow rate. A cascade control algorithm along with gain scheduling is applied to the system and test results shows that the closed-loop response approached set values within 3 to 4 seconds.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.328-335
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• 1996

The one-dimensional flame analysis was carried out to understand the combustion phenomena in porous media. The downstream as well as upstream solution corresponding to upper and lower solutions could be obtained. While upper flame temperature gets higher, lower flame temperature gets lower, as the flame approaches the central part of the combustor. The reason why upstream flame and downstream flame exist at the same flow condition is that the regions where net heat recirculation is identical exist in upstream and downstream of the combustor. In order for the downstream flame to be stabilized, more heats needed to be recirculated towards upstream because of larger radiation loss of downstream flame.