• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.5
• /
• pp.716-723
• /
• 2002

Heat transfer in linear motor driven stages for surface mounting device applications was investigated. A simple one-dimensional thermal resistance model (TRM) was introduced. In order to reduce three-dimensional nature to one-dimensional, a few assumptions and simplifications were employed suitably. A good agreement with a finite element heat transfer analysis in temperature profile was obtained. For validation, the analysis was compared with the measurement with respect to motor driving power. Overall discrepancy was less than 7$^{\circ}C$. The influence of two high thermal resistance parts, insulation sheet and thermal contact between the coil assembly and the mounting plate, was examined through the analysis. Additionally, the thermal resistance analysis was applied to another stage including an internal cooling-air passage, and was found available for this system as well. After validation, the cooling effect was surveyed in terms of motor power, and cooling-air and -water flow rate.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.96-101
• /
• 2001

Heat transfer in linear motor driven stages for surface mounting device applications was investigated. A simple one-dimensional thermal resistance model was introduced. In order to reduce three-dimensional nature to one-dimensional, a few assumptions and simplifications were employed suitably. A good agreement with a finite element heat transfer analysis in temperature profile was obtained. For validation, the analysis was compared with the measurement with respect to motor driving power. Overall discrepancy was less than $7^{\circ}C$. The influence of two high thermal resistance parts, insulation sheet and thermal contact between the coil assembly and the mounting plate, was examined through the analysis. Additionally, the thermal resistance analysis was applied to another stage including an internal cooling-air passage, and was found available for this system as well. After validation, the cooling effect was surveyed in terms of motor power, and cooling-air flow rate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.7
• /
• pp.512-520
• /
• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the effective thermal conductivity of the ground and the effective thermal resistance of the borehole. To evaluate these heat transfer properties, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to circulating water. The line-source method is applied to the temperature rise in an in-situ test and extended to also give an estimate of borehole effective thermal resistance. The effect of increasing thermal conductivity of the grouting materials from 0.818 to $1.104W/m^{\circ}C$ resulted in overall increases in effective thermal conductivity by 15.8 to 56.3% and reductions in effective thermal resistance by 13.0 to 31.1%.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.11a
• /
• pp.135-144
• /
• 2009

In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.

• Journal of computational fluids engineering
• /
• v.15 no.1
• /
• pp.46-55
• /
• 2010

In this study, the heat transfer and fluid flow characteristics of a condenser for a refrigerator are analyzed with the numerical method. The main objective of the study is to obtain basic data in order to develop a new type of condenser focused on an influence of thermal resistance of air side and thermal contact resistance on the heat transfer performance. The CFD technique was used for whole study, and experiments were performed in order to verify the reliability of the numerical analysis and predict the thermal contact resistance. In this study, a heat exchanger sample was made of a part of condenser to make the experimental and numerical analysis simple and efficient. Water was used for the inner working fluid of the heat exchanger, and an experimental apparatus was composed concisely. A heat exchanger sample of tube type was used to verify the reliability of numerical analysis, and a heat exchanger of fin and tube type was used to predict the ratio of thermal contact resistance to the overall thermal resistance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.17 no.8
• /
• pp.695-703
• /
• 2005

The objective of this study is to determine the effective thermal conductivity and thermal resistance values in test boreholes with three different fill materials. To evaluate these heat transfer properties, in-situ tests on four vertical boreholes were conducted by adding a monitored amount of heat to water over various test lengths. Two parameter estimation models, line-source and numerical one-dimensional models, for evaluation of thermal response test data were compared when applied on the same four data sets. Results show that the average thermal conductivity deviation between measured data and these two models is in the range of $3.03\%$ to $4.45\%$. The effect of increasing grout thermal conductivity from 1.34 to 1.82 $W/m^{\circ}C$ resulted in overall increases in effective formation thermal conductivity by $11.1\%$ to $51.9\%$ and reductions in borehole thermal resistance by $11.6\%$ to $26.1\%$.

• International Journal of Internet, Broadcasting and Communication
• /
• v.7 no.2
• /
• pp.161-167
• /
• 2015

The performance of high power LEDs highly depends on the junction temperature. Operating at high junction temperature causes elevation of the overall thermal resistance which causes degradation of light intensity and lifetime. Thus, appropriate thermal management is critical for LED packaging. The main goal of this research is to improve thermal resistance by optimizing and comparing nano-pore silicon-based thermal substrate to insulated metal substrate and direct bonded copper thermal substrate. The thermal resistance of the packages are evaluated using computation fluid dynamic approach for 1 W single chip LED module.

• International Journal of Human Ecology
• /
• v.3 no.1
• /
• pp.55-72
• /
• 2002

The purpose of this study was to evaluate the thermal resistance of pesticideprotective clothing and to investigate its subjective wear performance. Three different nonwoven fabrics, which provide barrier properties against water and pesticide, were used to manufacture the experimental clothing: spunbonded nonwoven (SB), spunbonded/meltblown/spunbonded nonwoven (SM), and spunlaced nonwoven (SL). The thermal insulation values of the experimental clothing were measured with a thermal manikin, and other wear trials were performed on human subjects in a climate chamber at $28^{\circ}C$, with 70% R.H. and air movement at less than 0.15m/s. Our results found that the thermal resistance was lower in the SB experimental clothing than in the others; that the mean skin temperature of subjects who wore the experimental clothing made with SL was significantly lower than that of subjects who wore the SB and SM clothing; and that the microclimate temperature and humidity with SB were significantly higher than that of the others. Overall, the experimental clothing made with SL was more comfortable than the others in terms of subjective wear sensations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.3
• /
• pp.231-239
• /
• 2006

An experimental investigation of a Reversible Loop Heat Pipe (RLHP) was conducted to determine the operating limits and performance characteristics as functions of the thermophysical parameters, the heat input, and the cooling intensity. Variations in both temperature and heat transport capacity were measured and analyzed in order to accurately evaluate the transient operating characteristics. In addition, the maximum heat transport as a function of the mean evaporator temperature, the ratio of heat transport to heater input power as a function of the mean evaporator temperature, and the overall thermal resistance as a function of the overall heat transport capacity were examined as well. Results indicated that the cooling intensity played an important role on the operating characteristics and performance limitation. The maximum heat transports corresponding to cooling intensity $72W/^{\circ}C$ and $290W/^{\circ}C$ were 446 W and 924 W, respectively. Also, observation of the startup characteristics indicated that the mean evaporator temperature should be maintained between $40^{\circ}C$ and $60^{\circ}C$, and overall thermal resistance were measured as $0.02^{\circ}C/W$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.5
• /
• pp.348-355
• /
• 2001

The coupled conduction and convection heat transfer from a protruding heated module in a horizontal channel with a variation of channel height is experimentally investigated. The input power to the module is 3, 7W and thermal resistance of module support is 0.06 , 1.03 and 158K/W. the Reynolds number ranged from 350 to 4500 corresponding to the inlet velocity(0.4~1.3 m/s) and channel height(11~35 mm). The results were obtained that the decrease of thermal resistance of module support reduces the module temperature by redistributing the heat flux and the overall thermal resistance of the module. In the study the effect of channel height is very significant in the adiabatic condition, but negligible in the conjugate condition. Finally, correlations for Nusselt number and $Q_B$/Q with a variation of Reynolds number were developed respectively.