• Journal of Energy Engineering
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• v.25 no.3
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• pp.59-65
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• 2016

MVR evaporation is a method of pressurizing the evaporating steam to raise its temperature with an electric compressor instead of burning fuel and reusing the heat source through the embraced heat exchanger to minimize energy use. MVR desalination system with wind power uses varying wind power instead of stable electricity and can flexibly control the volume of fresh water production. The present study introduces the design, construction and operation of a MVR desalination system of 30ton/day capacity. Experimental results, MVR compression ratio is higher than 1.5, temperature difference of the main heat exchanger is $5{\sim}7^{\circ}C$. This value shows the same performance as the designed value.

• Journal of Biosystems Engineering
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• v.30 no.2 s.109
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• pp.110-113
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• 2005

Relative humidity of air In the greenhouse has to be maintained at 70 to 80 percents to provide a better growth condition of crops. To control relative humidity of air in the greenhouse, a dehumidifier functioning by refrigeration cycle was designed and manufactured in this study. And, results of its performance test in the greenhouse site were reported. The developed dehumidifier has separated condenser and evaporator in the heat exchanger part in order to increase dehumidifying capacity at a low temperature condition. When the conditions of incoming air into the dehumidifier were temperature of $15\~25^{\circ}C$ and relative humidity of $0\~95\%$, quantity of condensed water per hour, ie, dehumidification rate was $4.7\~7.0\;kg/hr$. Relative humidity difference was not greater than 5 percents at various locations in the greenhouse due to proper distributing of dehumidified air through vinyl duct. Thermal energy output from the developed dehumidifier was about 8,5000 kcal/hr that was 7 percents of maximum greenhouse heating load of 10 a.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.283-292
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• 1999

Temperature prediction model was developed for on-line application to plate rolling mills of POSCO. The adequate boundary conditions of heat transfer coefficients were obtained by comparing the predicted temperature with the measured temperatures taken by measuring system in plate rolling mill of POSCO. In obtaining the boundary condition which minimize the mean and standard deviation of the difference between prediction and measurement, orthogonal array for experimental design was used to reduce the calculation time of large data set. To predict the temperature drop at four edge of plate in one dimensional model, the energy change by heat transfer though directions perpendicular to thickness direction was treated like that by deformation. And the heat transfer through four edge directions was inferred from that through thickness direction with two coefficients of depth and severity of temperature drop at the edge. The boundary condition for the depth and severity of temperature drop were also determined using the measured temperature.

• Journal of Biosystems Engineering
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• v.36 no.4
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• pp.273-278
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• 2011

This study was carried out to define the optimum drying conditions for Lycium chinense Miller as a useful healthy food, because recently the cultivation area and yield of this fruit are increased. The experiments of two varieties were performed at the temperature of $45^{\circ}C$, $50^{\circ}C$, $55^{\circ}C$ and $60^{\circ}C$. The drying ratio was the slowest and quality was the best at the drying temperature of $45^{\circ}C$. The drying temperature was higher, drying ratio was more faster and the quality became worse. The difference of drying ratios between the varieties was insignificant. The energy consumption per hour was the minimum at the drying temperature of $45^{\circ}C$, but the total energy consumption was the maximum for the long drying time. Also, the energy consumption at the drying temperature $50^{\circ}C$, $55^{\circ}C$ and $60^{\circ}C$ was not very different from others. Considering the drying ratio, quality and energy consumption, the drying time of 36 hours at the drying temperature of $50^{\circ}C$ was the most optimum condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1700-1716
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• 1996

The two-dimensional, unsteady, laminar conservation equations for mass, momentum, energy and species transport in the gas phase and mass, momentum and energy in the liquid phase are solved simultaneously in spherical coordinates in order to study heating and vaporization of a droplet entrained in the oscillating flow. The numerical solution gives the velocity and temperature distribution in both gas and liquid phase as a function of time. When the gas flow oscillates around an vaporizing droplet, the liquid flow circulates in the clockwise or counterclockwise direction and the temperature distribution in the liquid phase changes its shapes, depending on the gas fow direction. When the gas flow changes its direction of circulating liquid flow is opposite to the gas flow, forming two vortex circulating in the opposite direction. During the heating period, the difference in the maximum and minimum temperature is large, followed by the almost uniform temperature slightly below the boiling temperature. The mass and heat transfer from the droplet depend on the droplet temperature, droplet diameter and the magnitude of relative velocity, giving the droplet lifetime different from the d$^{2}$-law.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.18-23
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• 2012

The purpose of this study is to visually confirm on variation of temperature changes according to the basic of Kumdo by using infrared rays camera and to obtain the difference of temperature distribution according to the warm up procedure. We selected randomly two Kumdo players, and recorded twice continuously their actions of three basic(Head Hitting, Wrist Hitting, Waist Hitting) motions of Kumdo. In other to obtain the effect of warm up procedure, we recorded again their actions including warm-up motions. Four measuring points on the body were selected in each motion considering the error on continuous recoding. Temperature distributions of the before and after warming up procedure were analyzed at two measuring point. Skin temperature distributions of the players's body in two cases are shown a similar tendency. It can be predicted that the parts of large physical movement result in the large changes of temperature according to the warm up motion.

• Journal of Institute of Convergence Technology
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• v.2 no.1
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• pp.31-37
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• 2012

The purpose of this study is to visually confirm on variation of temperature changes according to the basic of Taekgyoen by using infrared rays camera and to obtain difference of temperature distribution according to the warm up procedure. We selected randomly two Taekgyeon players, and recorded twice continuously their actions of three basic motions of Taekgyeon. In other to obtain effect of warm up procedure, we recorded again their actions including warm-up motions. Four measuring points on the body were selected in each motion considering the error on continuous recoding. Temperature distributions of the before and after warming up procedure were analyzed at two measuring point. Temperature distributions of skin of players body in two cases are shown a similar tendency. It can be predicted that the parts of large physical movement result in the large changes of temperature according to the warm up motion.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.287-296
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• 2006

In this paper, optimal control strategy of the air-conditioning system with slab thermal storage was investigated based on the optimal control theory. An optimal heat output to the plenum chamber and the air-conditioned room was determined based on two kinds of criterion functions. The first one requires small deviation in room air temperature from a set-point value and low energy consumption. It is shown that the optimized control is to store heat through the whole storage time and to increase storage rate gradually with time. As the second case, a criterion that both a deviation of operative temperature from a set-point temperature and the energy consumption should be minimized was adopted. The room air temperature was a little high and the cooling load during storage time was reduced, compared with the results when a criterion function considering only the room air temperature is used.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.514-525
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• 2023

This study conducted numerical simulations with the purpose of analyzing the impact of variations in outlet pressure conditions under extreme temperature conditions on the fluid dynamics and performance of a check valve utilized in hydrogen refueling systems. Under the extreme temperature conditions, changes in outlet pressure conditions of the check valve were investigated to analyze velocity distributions, pressure distributions, and temperature distributions in the operational and connection regions. The analysis results indicated that changes in outlet pressure had a significant influence on the internal temperature variation of the check valve. Furthermore, due to density variations in the connection region caused by the cooling effect of excessively cooled hydrogen, a bias in the primary flow direction towards the lower part of the valve outlet was observed in the outlet area. Through a comparison of the results of the valve's inherent flow performance, represented by the flow coefficient, it was observed that when the pressure difference between the inlet and outlet was below 0.37 MPa, sufficient flow was not ensured.

• Journal of Biosystems Engineering
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• v.24 no.4
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• pp.335-342
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• 1999

Air and flue gas temperature distributions in the space heater for greenhouse were measured to develop a thermal design technology for the space heater. Also, the characteristics of the fan supplying air to the space heater were investigated. The temperature of the flue gas inside the flue gas tube was linearly decreased as the lenght of than those of the flue gas with the oxygen concentration of 8.25% at the last exit of the second flue gas tube. Thus, the operating efficiency of the space heater could be increased with low air ratio decreased exhausting gas temperature and saved the energy consumption with decreased excess air flow. The temperature of the air supplied by fan was increased slowly around the first flue gas tube, meanwhile, increased sharply around the second flue gas tube due to large LMTD (Logarithmic Mean Temperature Difference) at the first flue gas tube than which of the second flue gas tube.