• Metals and materials international
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• v.24 no.6
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• pp.1422-1431
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• 2018

We investigated the additional (secondary) cooling effect of casted strips on the magnetic properties of Nd-Fe-B sintered magnets. The Nd-Fe-B sintered magnets were fabricated with the casted strips prepared without and with additional cooling. Additional cooling was achieved by blowing Ar gas at various pressures (0.1, 0.3, and 0.6 MPa) on the free-side surface of the strips during the strip-casting process. The higher magnetic properties of $H_c$, $B_r$, and $(BH)_{max}$ of the final Nd-Fe-B sintered magnets were obtained for 0.1 MPa rather than for 0.0 MPa. The best microstructure of the columnar grains in the casted strips was produced with the aid of a lower pressure of gas on the free-side surface. It was found that the microstructure of the strips affects the distribution of grains grown in the sintered magnets. This report demonstrates that the improved magnetic performance of Nd-Fe-B sintered magnets was achieved via additional gas cooling.

• 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.

• Journal of the Korean housing association
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• v.15 no.2
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• pp.107-115
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• 2004

The objective of this study is to show the system Integrations and control method for operation of the Radiant Floor Cooling. The systems for radiant floor cooling system consist of only using the radiant floor cooling and the radiant floor cooling integrated with a dehumidification system. And the study is suggested control method with composed radiant floor cooling system through simulations. Radiant floor cooling systems compose of four main parts: an existing radiant heating panel, manifold, cooling source and controller, and sensors. If dehumidifying or supplementary cooling is needed, additional equipments such as PAC and AHU are needed. Simulation results show that control method only using radiant floor cooling system can prevent condensation and set room air temperature with the exception of hot and humid periods and control method using the radiant floor cooling integrated with a dehumidification system is comfort thermal environments and can reduce the cooling load quickly, moreover, show comfort control method to meet various cooling operation situations.

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.121-121
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• 2017

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.6
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• pp.574-583
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• 2004

In this study, the operation strategy of the radiant floor cooling is evaluated in terms of indoor environmental conditions and energy consumption through simulations using the TRNSYS comparing the existing cooling operation. The operation strategy during continuously operated for cooling is proposed that a representative room had additional equipments and other rooms were operated with only a radiant floor cooling system and that system and control method for cooling are varied with period while intermittently operated for cooling. Specifically, when there are no people in the room, rooms were operated by only radiant floor cooling system using cooling storage and when people are occupied, rooms were operated by dehumidification and supplementary cooling device with radiant floor cooling system. The results of this study show that proposed operation strategy can stably maintain the set room air temperature and can reduce the energy consumption compared to the existing cooling method during continuously operated for cooling. While intermittently operated for cooling, the difference of set room air temperature by proposed operation strategy does not happen, satisfying comfort standards and the radiant floor cooling can expect to supply stable electric power because of decreasing demand for peak electric power of energy consumption.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.647-654
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• 2002

This study deals with the characteristic of quenching refrigerant for heat treatment deformation control of SM45C steel. Heat-treatment deformation must be controlled for the progress of production parts for landing gear. Most of deformation is occurred on inconsistent cooling. The inconsistent cooling is caused by a property of quenching refrigerant. When a heated metal is deposited in the quenching refrigerant, the cooling speed is so slow in early period of cooling because of a steam-curtain. After additional cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.341-344
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• 2006

In this analytical study on the engine coolant flow of a heavy-duty diesel engine with 4 valves and linear-type 8 liter 6 cylinders, the characteristics of pressure drop and engine cooling performance with the additional coolant passages between cylinder blocks have been investigated. Since the most part of pressure drop is caused by the coolant flow passages inside a cylinder head and cylinder blocks for this type of heavy-duty diesel engines, the advantage of pressure drop is just 2.6% and the characteristics of heat transfer and the distribution of coolant velocities in the head part show little differences in case of additional coolant passages. Thus the coolant flow passages between cylinder blocks make little contribution on the cooling performance of heavy-duty diesel engines

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.87-93
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• 2008

The $CO_2$ air conditioning system installed in fuel cell vehicles could be used either for stack cooling or for cabin cooling, and thus was used for the stack cooling when additional stack heat release was required over a fixed radiator capacity for high power generation. This study investigated the performance of the stack cooling system using $CO_2$ air conditioner at various operating conditions. Also, the heat releasing effectiveness and mutual interference were analyzed for the stack cooling system using an air conditioner and compared with the conventional radiator cooling system with/without cabin cooling. The heat release of the stack cooling system with the aid of $CO_2$ air conditioner increased up to 36% more than that of the conventional radiator cooling system with cabin cooling. Furthermore, the heat release of the stack cooling system using $CO_2$ air conditioner increased more by 7% than that of the conventional radiator cooling system without cabin cooling.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.83-88
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• 2003

An analytical study was carried out to evaluate the regenerative cooling characteristics in the liquid rocket engine of a 10tf-thrust level using kerosene as a fuel. As a supplementary cooling method, a radiative cooling was applied to the nozzle extension. It was found out from this work that the cooling system with the regenerative and radiation cooling only is not adaptable as a cooling method for the liquid rocket engine of a 10tf-thrust level using kerosene as a fuel for the 2nd stage of the space launch vehicle. So, additional cooling method, curtain cooling was introduced and analyzed. Curtain cooling was very effective to reduce the thermal and thermo-structural instability.

• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.2
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• pp.64-69
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• 2008

Electronic and telecommunication industries are constantly striving towards miniaturization of electronic devices. Miniaturization of chips creates extra space on PCBs that can be populated with additional components, which decreases the heat transfer surface area and generates very high heat flux. Even though an air-cooling technology for telecommunication equipment has been developed in accordance with rapid growth in electrical industry, it is confronted with the limitation of cooling capacity due to the rapid increase of heat density. In this study, liquid-cooling heat exchangers were designed and tested by varying geometry and operating conditions. In addition, air-cooling heat exchangers were tested to provide performance data for the comparison with the liquid-cooling heat exchangers. The liquid-cooling heat exchangers had twelve rectangular channels with different flow paths of 1, 2, and 12. Silicon rubber heaters were used to control the heat load to the heat exchangers. Heat input ranged from 293 to 800W, and inlet temperatures of working fluid varied from 15 to $27^{\circ}C$. The heat transfer coefficients were strongly affected by flow conditions. All liquid-cooling heat exchangers showed higher cooling performance than the air-cooling heat exchanger. The heat exchanger with 2-paths could provide more controllability on the maximum temperature than the others.