• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.292-300
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• 2010

This study strives to develop an effective strategy to inhibit cavitation inception on hydrofoils by using local cooling technique. By setting up a temperature boundary condition and cooling a small area on the upper surface of a hydrofoil, the fluid temperature around the cooling surface will be decreased and thereby the corresponding liquid saturation pressure will drop below the lowest absolute pressure within the flow field. Hence, cavitation can never occur. In this paper, a NACA0015 hydrofoil at $4^{\circ}$ angle of attack was numerically investigated to verify the effectiveness of the proposed technique. The CFD results indicate that the cooling temperature and the cooling surface roughness are the critical factors affecting the success of such technique used for cavitation suppression.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.4
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• pp.356-361
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• 1986

An optimum design condition for a basic refrigeration cycle is defined as the condition which minimizes the total cost of heat exchanges (condenser and evaporator) and compressor for the refrigeration effect. Thermodynamic properties of ammonia (R717) are approximated by rational functions in order to obtain the optimum condition for a basic refrigeration cycle. Optimum condition depends on the heat capacity rates (mass flow rate times specific heat) of cooling water and brine used in condenser and evaporator. The difference between the cooling water temperature and condensation temperature at the optimum condition increases as the heat capacity rates and the coat of heat exchangers relative to the cost of compressor increase. Numerical examples of optimum conditions are obtained when the condensation temperature is $30^{\circ}C$ and the evaporator temperature is $-10^{\circ}C$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.160-164
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• 1991

The effect of various parameters, such as temperature, current density and operating valtage on the performance of phosphoric acid fuel cell stack was studied by using numerical analysis. The utilization ratio of reaction gas, inlet condition of reaction air and cooling air, inlet condition of cooling air flow latin were changed regularly, The results showed good agreements with the existing results and experimental ones.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.3
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• pp.214-220
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• 2002

A small air conditioner using thermoelectric module has been designed and built. Three types of cooling methods, such as air cooling, closed-loop water cooling, and evaporative cooling, for hot side of thermoelectric module have been investigated. Among three types of cooling method, the evaporative cooling method is seen to be the most effective to achieve the steady state operation of a thermoelectric air conditioner The system performance with evaporative cooling method are also studied in detail for several oprating parameters, such as input power to the thermoelectric module, water or air flow rate at the hot side, and air flow rate at the cold side. The results obtained indicate that the cooling capacity of a system is increased with an increase in the input power to the thermoelectric module while the system COP is decreased. It is also found that the optimal air flow rate as well as water flow rate at the hot side is needed for the best system performance at a liven operating condition. Both the system COP and cooling capacity are increased as the air flow rate at cold side is increased.

• Design & Manufacturing
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• v.12 no.1
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• pp.18-25
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• 2018

Both injection and injection molding dies have evolved into advanced technology. Product quality is also evolving day after day. Therefore, the conditions of the injection mold and the injection conditions are becoming important. In order to improve the quality of the product, the Hardware part of the mold has developed as an advanced technology, and the Software part has also developed with advanced technology. This study deals with the cooling part, which is part of the hardware. In addition to fluid cooling, which is commonly used in the industry, by using gas cooling identify the phenomena that appear on the surface of the product and the critical point strain of the product to find the optimal cooling. Electronic parts and automobile parts whose surface condition is important, the cooling process is important to such a degree that they are divided with good products and defective products according to the cooling process at the time of injection. By controlling this important cooling and reducing the injection time with additional cooling, the product quality can be increased to the highest production efficiency. In addition, high efficiency can be achieved without additional investment costs. This study was conducted to apply these various advantages in the field.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.99-100
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• 2012

Aggregate thermal properties and cooling methods are most important to evaluate the residual mechanical properties of concrete. In this study, we evaluate the residual mechanical properties of concrete according to the aggregate type and cooling method. We use the normal weight aggregate and light weight aggregate which have different thermal properties. After heating to the target temperature, we evaluate the mechanical properties according to the slow and fast cooling condition. As a result, normal weight aggregate concrete has higher effectiveness of cooling conditions than light weight aggregate concrete.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1183-1194
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• 1998

This paper describes a theoretical model developed for analyzing the heat transfer of automotive cooling systems. From the model, heat transfer rate of automotive cooling systems can be predicted, providing useful information at the early stages of the design and development. The aim of the study is to develop a simulation program for automotive cooling system analysis and a performance analysis program for analyzing heat exchanger. Heat release rate from combustion gas to coolant through cylinder wall in engine cylinder was analyzed by using a two zone combustion model. This paper studied how cooling condition would affect engine heat release rate and measured temperature distribution of coolant in water jacket.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.44-46
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• 2003

Nowaday it is trend to be one cooling radiator and cooling fan from separate engine radiator and air condition radiator in cars. For the cooling fan is developed a electrical motor which is limited in size. The motor should be working in silence and have no electromagnetic Problem and high efficiency. In this paper will be proposed some parameters for improvement of the efficiency of a BLDC motor which is developed for the cooling system after theoretical and experimental investigation.

• Journal of the Korean Solar Energy Society
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• v.29 no.6
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• pp.32-38
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• 2009

The effects of surface radiative properties on the radiant cooling of opaque surfaces under clear sky condition are studied. Two types of surfaces, one gray and the other selective, are compared. For the nighttime cooling, black surface gives the lowest plate temperature and on the other hand the ideal selective surface gives the highest temperature. The reverse is true when there is an insolation. Equivalent radiative heat transfer coefficient of radiant cooling without convection is about $1{\sim}7\;W/m^2-K$ for the range of values studied. The surface with black within the $6{\sim}13\;{\mu}m$ band else zero emissivity could be regarded as a black surface for the nighttime radiant cooling purposes. However, lower band limit of $4\;{\mu}m$ is preferred to $6\;{\mu}m$ for small insolation situations.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.623-628
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• 2009

Desiccant based air conditioning system offers a promising alternative to conventional one using vapour compression refrigeration for energy saving and greenhouse gas reduction. It is a heat driven cycle which has high potential for the use of low grade heat source such as the waste heat from the cogeneration plant or the solar thermal energy. In this study, the cooling performance of a desiccant cooling system incorporating a regenerative evaporative cooler was characterized in various operation conditions through numerical simulation. The cooling capacity and COP were evaluated at various outdoor conditions, regeneration temperatures, and supply flow rates. Based on the performance characteristics, the optimal control scheme was discussed to minimize the cooling cost at part load condition.