• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1071-1082
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• 1995

Numerical analyses have been performed to obtain the absorption heat and mass transfer coefficients and the absorption mass flux from a falling film of the LiBr aqueous solution which is cooled by cooling air. Heat flux at the wall is specified in terms of the heat transfer coefficient of cooling air and the cooling air temperature. Effects of operating conditions, such as the heat transfer coefficient, the cooling air temperature, the system pressure and the solution inlet concentration have been investigated in view of the local absorption mass flux and the total mass transfer rate. Effects of film thickness and film Reynolds number on the heat and mass transfer coefficients have been also estimated. Analyses for the constant wall temperature condition have been also carried out to examine the reliability of present numerical method by comparing with previous investigations.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1853-1859
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• 2019

The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.503-511
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• 2011

Water spray cooling is a significant technology for cooling of materials from high-temperature up to $900^{\circ}C$. The effects of cooling water temperature on spray cooling are mainly provided for hot steel plate cooling applications in this study. The heat flux measurements are introduced by a novel experimental technique that has a function of heat flux gauge in which test block assemblies are used to measure the heat flux distribution on the surface. The spray is produced by a fullcone nozzle and experiments are performed at fixed water impact density of G and fixed nozzle-totarget spacing. The results show that effects of water temperature on forced boiling heat transfer characteristics are presented for five different water temperatures between 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided to a benchmark data for the actual spray cooling of hot steel plate cooling applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.1-14
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• 1997

Natural convection cooling of discrete heaters located in a two-dimensional vertical open top cavity is investigated experimentally. The five discrete heaters with same heat generation are located on the wall of the cavity. The heaters are arranged in two configurations; flush-mounted on a vertical wall and protruding from the wall about 4.5 mm. The materials used for the vertical walls are copper and epoxy-resin, and air is used as the cooling fluid. The temperature and flow fields in the cavity were visualized by means of Mach-Zehnder interferometer and smoke-method. Also, local temperature measurements are made along the vertical wall. Results are obtained for cavity aspect ratios of 4.6, 7.5 and 9.5 and modified Rayleigh numbers ranging from 10$^{3}$ to 10$^{6}$ . Results indicate that the cooling efficiency for the copper wall is superior to that of the epoxy-resin. For the epoxy-resin wall, the protrusion of the heaters plays a role in decreasing the heat transfer performance. The location of maximum temperature is significantly influenced by the wall materials and heater configurations. Correlations relating the Nusselt number to the modified Rayleigh number are proposed.

• Journal of Environmental Health Sciences
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• v.33 no.3
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• pp.211-216
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• 2007

This study was to determine the effect of cooling part of the trunk without harm for the health. The results provide basic data for the development of clothing which could increase work efficiency and reduce body strain in hot environment. Eight males took part in the study. The experiment was conducted in a climate-chamber controlled with $37{\pm}1^{\circ}C,\;50{\pm}5%R.H$. The trunk was divided into six areas to be cooled: head, neck, chest, abdomen, the upper back, the lower back. According to preceding studies, permissible safety cooling limits of skin temperature, of each part of the trunk for four hours cooling were $25^{\circ}C$ on the head, $20^{\circ}C$ on the neck, $27^{\circ}C$ on the chest, $25^{\circ}C$ on the abdomen, $20^{\circ}C$ on the upper back, $20^{\circ}C$ on the lower back. So cooling temperatures of each region set up temperatures above mentioned. In conclusion, the head, the neck and the upper back cooling could reduce sweating amount, rectal temperature and heart rates and reduce the heat stress of workers exposing in the hot environment by decreased subjective sensations of heat and comfort. Thus, it was concluded that effectiveness of cooling among the trunk was best on the head and the neck.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1821-1829
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• 2023

The temperature distribution of the reactor pool under natural circulation induced by the RVACS operation was experimentally studied. According to the Bo' based similarity law, which could reproduce the temperature distribution of the working fluid under natural circulation, SINCRO-2D facility was designed based on the PGSFR. It was reduced to 1 : 25 in length scale, having water as a simulant of the sodium, which is the original working fluid. In general, temperature was stratified, however, effect of the natural circulation flow could be observed by the entrainment of the stratified temperature. Relative cooling contribution of the upper plenum (narrow gap) and lower plenum was approximately 0.2 and 0.8, respectively. In the range of decay heat from 0.2% to 1.0%, only the magnitude of the temperature was changed, while the normalized temperature maintained. Boundary temperature distribution change made a global temperature offset of the pool, without a significant local change. Therefore, the decay heat and cooling boundary condition had no significant effect on temperature distribution characteristics of the pool within the given range of the decay heat and boundary temperature distribution.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.175-180
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• 2001

In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about $900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the experimental results show that the velocity of wetting front increases with the increase of the droplet flow rate.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.721-727
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• 2003

Freezing of turbulent water flow between two horizontal cooled parallel plates with the separated region has been investigated experimentally. The flow separation was induced by vertical plates (two-dimensional plates) situated at the inlet of the rectangular channel. The degree of flow separation was varied by employing vertical thin plates with various heights. Three kinds of the vertical plates with 8.0, 9.8 and 12.5 mm in height were utilized. The Reynolds number and cooling temperature ratio were ranged from $3.45\times10^3 to 1.73\times10^4$ and 7.0 to 20.0 respectively, The measurements show that the flow separation influenced remarkably on the local ice formation characteristics. The location of the first ice layer and the average heat transfer at the ice surface were found be correlated as a function of the Reynolds number, the cooling temperature ratio, and the orifice height ratio.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.974-981
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• 2001

In this study, the minimum heat flux conditions are experimentally investigated for the spray cooling of hot plate. The hot plates are cooled down from the initial temperature of about$ 900^{\circ}C$, and the local heat flux and surface temperatures are calculated from the measured temperature-time history. The results show that the minimum heat flux point temperatures increase linearly resulting from the propagation of wetting front with the increase of the distance from the stagnation point of spray flow. However, in the wall region, the minimum heat flux point temperature becomes independent of the distance. Also, the velocity of wetting front increases with the increase of the droplet flow rate.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.66-70
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• 2005

Structural components for aerospace, electronics and automobile industry are the main applications for magnesium alloys due to their lightweight and high specific strength. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this paper, the authors aim to improve the formability of AZ31 magnesium alloy. For this, experiment and finite element analysis on used warm deep drawing process with a local heating and cooling technique were done. Both die and blank holder were heated at various warm temperature while the punch was kept at room temperature by cooling water.