• Journal of the Korean institute of surface engineering
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• v.52 no.3
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• pp.171-179
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• 2019

We have developed a numerical model to analyze flow dynamics and heat transfer characteristics of the cooling water in a circular rotating magnetron cathode by a moving boundary grid method realized in a commercial multiphysics package, CFD-ACE+. The numerical model is composed of a target, dual mass rotating cathode and cooling water connections. When the inlet and outlet of the cooling water are offset by the same distance from the rotation axis, the temperature at the center is higher by $50^{\circ}C$ at maximum. At 5 mm away from the target surface, the temperature profile showed typical center high characteristic. At heat input of 30 kW, the maximum temperature change of the cooling water hits $6^{\circ}C$ within 0.5 sec under 60 rpm. With a cooling water configuration of center in/edge out, the temperature of the center region of the target gets lowered. Within 100 seconds of plasma operation time, the cooling water temperature keeps getting higher.

• Journal of Bio-Environment Control
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• v.3 no.1
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• pp.36-41
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• 1994

The major objective of this study is to develop a method of zone cooling during summer day using heat pump for year- round cultivation. The efficiency of cold water cooling and fog cooling was investigated. In order to prevent the occurrence of blossom - end rot in tomato, cooling was induced together with air flow of the fruit treatment as well as promoting air circulation in the plant treatment was induced. The following results were obtained : 1) The temperature in the cold water cooling district was 1$0^{\circ}C$ lower than greenhouse temperature and the temperature in the fo8 cooling district was about 5$^{\circ}C$ lower than the greenhouse. 2) Regardless of cooling method, the treatment of air flow on fruit did not affect the fruit but prevent blossom-end rot. There was 34.5% occurrence rate of blossom -end rot in non-air flow district of cold water cooling 54.5% in non-air flow district of fog cooling and 78% in fog circulation cooling district. The cooling efficiency using cold water cooling method induced enough cooling at critical temperature for growth and development and the occurrence of blossom -end rot was lower than fog cooling. Fog cooling in culture district with air circulation did not induce and difference in temperature but caused an Increase in humidity resulting in 24% increase in the occurrence of blossom-end rot. Thus the occurrence of blossom-end rot in tomato caused by environmental factors can be attributed more to humidity than to temperature.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1300-1305
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• 2004

The purpose of this experiment is to study the radiant cooling effects by a plate directly viewing the nighttime sky. The measurements are performed at a rooftop of the Engineering building at the Dongguk University in Seoul during the month of August in 2004. The radiant cooling effects are compared using three different types of plate surfaces such as galvanized Iron, black painted, and aluminum film coated galvanized iron plate. Among these plates, the black painted surface show the lowest temperature that is lower than its ambient temperature. The maximum radiant cooling temperature difference, that is ambient temperature minus plate temperature, observed is about 5K..

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.25-32
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• 2000

In this paper, experiments investigating the high-temperature region heat transfer coefficients for the spray cooling of hot flat plates were performed by down spray water using flat spray nozzles. The heat transfer surface is made of copper and is 100mm in length and 40mm in width and 15mm in thickness. The experimental condition of spray are as follows: temperatures of the water droplets are T=20~$80^{\circ}C$ and droplets volume fluxes are D=0.001565~0.010438$m^3/m^2s$. Next, correlating equations for the heat transfer characteristics of spray cooling in the high temperature region are developed from the effects of droplets volume flux and the surface temperature of heat transfer plate.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1250-1254
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• 2004

To develop more compact and light generators which have high capacity, the most important thing that should be considered is the inner cooling system. Under all circumstances, the temperature of rotor and stator windings must be kept below the maximum temperature of insulation to maintain reliability and prolong durability of the machine. Therefore, the development of more effective cooling system and the exact prediction of windings are essential to produce our unique generator model which is reliable and competitive in international market. In this study, the flow of cooling air and the temperature distribution of winding is analyzed by using computational fluid dynamics. This analysis can lead to optimize the structure of cooling system and predict a local temperature rise.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.6
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• pp.605-610
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• 2005

The purpose of this experiment is to study the radiant cooling effects by a plate directly viewing the nighttime sky. The measurements are performed on a rooftop of the Engineering building at the Dongguk University in Seoul during the month of August in 2004. The radiant cooling effects are compared using three different types of plate sufaces, namely, galvanized iron, black painted, and aluminum film coated galvanized iron plate. Among these plates, the black Painted surface showed the lowest temperature that is lower than the ambient temperature. The maximum radiant cooling temperature difference, which is ambient temperature minus plate temperature, observed is about 5 K.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.126-133
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• 2008

The main objective of the present study is to achieve linear temperature distribution of cooling surface of plunger. K type thermocouples are attached at the surface of plunger to measure temperature. Nozzle and insulating material are inserted in the pin hole of the plunger for this study. Cooling water flow enters at one nozzle and leaves at three nozzles. Flow through nozzle can be activated in the pin hole, temperature of hot point around hole is decreased. Meanwhile, insulating material blocks off heat transfer, temperature of cold point around hole is increased. By combination of nozzle and insulation, heat transfer of hole is controlled effectively, as result its, temperature of plunger surface shows linear temperature distribution.

• Journal of Mechanical Science and Technology
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• v.18 no.5
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• pp.820-829
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• 2004

The In-Containment Refueling Water Storage Tank (IRWST), one of the design improvements applied to the APR -1400, has a function to condense the high enthalpy fluid discharged from the Reactor Coolant System (RCS). The condensation of discharged fluid by the tank water drives the tank temperature high and causes oscillatory condensation. Also if the tank cooling water temperature approaches the saturated state, the steam bubble may escape from the water uncondensed. These oscillatory condensation and bubble escape would burden the undue load to the tank structure, pressurize the tank, and degrade its intended function. For these reasons simple analytical modeling and experimental works were performed in order to predict exact tank temperature distribution and to find the effective cooling method to keep the tank temperature below the bubble escape limit (93.3$^{\circ}C$), which was experimentally proven by other researchers. Both the analytical model and experimental results show that the temperature distributions are horizontally stratified. Particularly, the hot liquid produced by the condensation around the sparger holes goes up straight like a thermal plume. Also, the momentum of the discharged fluid is not so strong to interrupt this horizontal thermal stratification significantly. Therefore the layout and shape of sparger is not so important as long as the location of the sparger hole is sufficiently close to the bottom of the tank. Finally, for the effective tank cooling it is recommended that the locations of the discharge and intake lines of the cooling system be cautiously selected considering the temperature distribution, the water level change, and the cooling effectiveness.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.908-912
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• 2013

Because of their longer operating times and larger size relative to conventional fans, the cooling fans mounted in buses consume larger amounts of energy. Most of the cooling fans mounted in a bus are connected to the engine by a viscous clutch. A viscous cooling fan's speed is determined by its fluid temperature, which is affected by the air flow through the radiator. The fan does not react immediately to the coolant temperature and in doing so causes unnecessary energy consumption. Therefore, the fuel economy of buses using viscous fans can be improved by changing to an electric cooling fan design, which can be actively controlled. In addition, electric power consumption is increased by using electric cooling fans. Thus, when electric fans are applied in conjunction with the alternator management system (AMS), the fuel economy is further enhanced. In this study, simulations were performed to predict coolant temperature and cooling fan speeds. Simulations were performed for both viscous and electric cooling fans, and power consumption was calculated. Additionally, fuel economy was calculated applying both the alternator management system and the electric cooling fan.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.55-60
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• 2009

The present study investigated temperature and thermal stress distributions in a film cooling system with normal injection cooling flow. 3D-numerical simulations using the FEM commercial code ANSYS were conducted to calculate distributions of temperature and thermal stresses. In the simulations, the surface boundary conditions used the surface heat transfer coefficients and adiabatic wall temperature which were converted from the Sherwood numbers and impermeable wall effectiveness obtained from previous mass transfer experiments. As a result, the temperature gradients, in contrast to the adiabatic wall temperature, were generated by conduction between the hot and cold regions in the film cooling system. The gradient magnitudes were about 10~20K in the y-axis (spanwise) direction and about 50~60K in the x-axis (streamwise) direction. The high thermal stresses resulting from this temperature distribution appeared in the side regions of holes. These locations were similar to those of thermal cracks in actual gas turbines. Thus, this thermal analysis can apply to a thermal design of film cooling holes to prevent or reduce thermal stresses.