• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.17 no.3
• /
• pp.21-29
• /
• 2021

In this study, the current regulation of the water source energy, one of the renewable energy, was analyzed, and the improvement plan for the high efficient data center cooling system was suggested. In the improvement plan, the design and construction guidelines of the water source energy system permit to adopt the cooling and heating system with or without heat pump. In addition, it should also include the system operated in the cooling mode only all year-round. The domestic test standards to consider the water source operating conditions should be developed. Especially, it is highly recommended that the test standards to include the system with forced cooling and free cooling modes related with the enhanced data center cooling system adopting the water source energy.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.4
• /
• pp.350-355
• /
• 2004

This paper deals with the design of a heat dissipation system, which consists of a heat source of power semiconductor devices, a heat sink ;md a fan for the forced air cooling. It suggests the method of appropriately dividing the whole heat transfer system into analytical subsystems and also presents the correspondent analytic or experimental design equations for the subsystems. The experimental results on the designed heat dissipation system for the 400kW IGBT inverter show less than 10［%］ error with respect to the design temperature and therefore verify the validity of the proposed analytical design method in the steady state.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.4
• /
• pp.580-584
• /
• 2012

The insulating oils perform a cooling and insulation action in electric power transformer. The mineral oil has immanent fire dangerousness and environmental contamination problem. Vegetable insulating oil has higher ignition point, flash point and more excellent biodegradability than conventional mineral oil. In a real oil-filled transformers, some of the power is dissipated in the form of heat. And transformer require the heat to be removed from the winding and insulator by forced convection of the insulating oil. The flow electrification occurs when insulating oil was forced to be circulated. In this paper, influence of temperature, velocity of flow, and insulating pipe and diameter on streaming electrification of vegetable insulating oil was investigated using forced circulation apparatus. Temperature effects were most significant, and it showed a peak in the temperature $30^{\circ}C$ to $35^{\circ}C$ at insulating and copper pipe. The change of flow electrification according to area variety could be checked by change of diameter.

• Tribology and Lubricants
• /
• v.8 no.1
• /
• pp.70-77
• /
• 1992

Al-Pb-Si bearing alloys were produced by a forced stirring method and a rapid solidification process to study wear properties of bearing alloys. A homogeneous distribution of Pb particles in Al matrix could be obtained by means of the forced stirring and the rapid cooling during the casting. The wear properties of bearing alloys were tested by a pin-on-disc wear tester. The change in microstructure according to the alloy manufacturing variables was observed by the backscattered electron images. Al-Pb and Al-Si binary alloys showed a transition from mild to severe wear. The transition was not found in Al-Pb-Si ternary alloys. It could be concluded that the lubricatioin effect of Pb and the strengthening effect of Si in the ternary alloys enhanced the bearing properties. A Al-25%Pb-13%Si alloy showed the lowest coefficient of friction in this experiment. It indicated that the optimum concentration of alloy was 25% Pb and 13% Si when the forced stirring of melt and water-cooled-copper-mold solidification were adopted.

• Journal of Power System Engineering
• /
• v.10 no.2
• /
• pp.41-46
• /
• 2006

This study shows a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water by about $5^{\circ}C\;from\;25^{\circ}C$ or higher. In this research, to replace the present water cooling system, we focused on a water cooling system by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are depended on the vacuum pressure in the enclosed tank, and the cooling water is generated by latent head of evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{\sim}8$ mmHg using a steam driven ejector with jet condenser.

• Journal of Energy Engineering
• /
• v.21 no.3
• /
• pp.221-227
• /
• 2012

The CANDU 9 shield cooling system was designed and layout with the objective of promoting natural circulation on loss of forced flow. In the present study, the shield cooling natural circulation was analyzed using verified the thermal-hydraulic code when the coolant pump or the heat exchanger was lost. This study showed that thermosyphoning cooled the end shields and prevented the end shields and the reserve water tank from boiling for at least 8 hours on loss of the shield cooling pumps but the heat exchangers still operational. With the loss of both pumps and heat exchangers, the end shields remain subcooled for up to 4 hours. To enhance thermosyphoning, the bypass connection to the line from the reserve water tank should be relocated to a point as low as possible.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2043-2052
• /
• 2008

The increasing heat generation rates in CPU of notebook computers motivate a research on cooling technologies with low thermal resistance. This paper develops a closed-loop two-phase cooling system using a micropump to circulate a dielectric liquid(PF5060). The cooling system consists of an evaporator containing a boiling enhancement microstructure connected to a condenser with mini fans providing external forced convection. The cooling system is characterized by a parametric study which determines the effects of volume fill ratio of coolant, existence of a boiling enhancement microstructure and pump flow rates on thermal performance of the closed loop. Experimental data shows the optimal parametric values which can dissipate 33.9W with a film heater maintained at $95^{\circ}C$.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.2
• /
• pp.34-39
• /
• 2018

A cryogenic cooling system is designed for a 154 kV/ 2 kA three-phase hybrid type superconducting fault current limiter (SFCL). The superconducting modules of the SFCL have the operating condition of 71 K at 500 kPa. The total heat load of the SFCL including the cooling system is estimated at 9.6 kW. The cooling system of the closed loop is configured to meet the operating condition, depending on cooling methods of forced flow cooling and re-liquefaction cooling. The cooling system is composed of three cryostats with superconducting modules, cryocoolers, liquid nitrogen circulation pumps, a subcooler and a pressure builder. The basic cooling concept is to circulate liquid nitrogen between three SFCL cryostats and the cryocooler, while maintaining the operating pressure. The design criterion for the cooling system is based on the operation results of the cooling system for a 154 kV/2 kA single-phase hybrid SFCL. The specifications of system components including the piping system are determined according to the design criterion.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.1
• /
• pp.97-102
• /
• 2005

The procedure of semi-solid forming is composed of heating a billet, forming, compression holding and ejecting step. There are several methods to heat a billet during semi-solid forming process such as electric heating and induction heating. Usually in semi-solid forming process, induction heating has been adopted to achieve more uniform temperature of semi-solid material. Although induction heating is better method than any others, however, there is still difference of temperature between internal part and surface part of semi-solid material. Worse yet, in case of high liquid fraction of semi-solid material, liquid of the billet will flow down though solid of the billet still remains, which is very difficult to handle. In the present study, induction heating of semi-solid material with compulsive surface cooling has been performed to obtain uniform distribution of temperature. Distribution of temperature of the billets was measured and compared with that of conventional distribution of temperature. By this new induction heating method, not only temperature over the whole billet become uniform, but also control of temperature is possible.

• Horticultural Science & Technology
• /
• v.32 no.2
• /
• pp.202-209
• /
• 2014

This study was conducted to investigate the effects of low temperature shipping condition and precooling treatments (forced air and room cooling) on everbearing strawberry through export simulation of 'Goha' and 'Flamenco' cultivars. After harvest, it took two days to prepare export procedure such as precooling, sorting, storage, transportation, quarantine and handling, and then everbearing strawberry was carried out shipping at room ($20-25^{\circ}C$) or low ($8^{\circ}C$) temperature conditions. In the case of shipping at room temperature, weight losses of both cultivars were increased up to 10% after 2 days where 'Goha' being 2% higher than that of ' Flamenco'. In 'Flamenco' cultivar, shipping temperature and precooling treatment were not effective in firmness and soluble solids contents during transporting periods. However, in 'Goha' cultivar, room cooling treatment and low shipping temperature were effective in maintaining firmness until 4 days after shipping. Especially titratable acidity was affected by shipping temperature ($P{\leq}0.001$) and precooling treatments ($P{\leq}0.05$) in 'Goha' cultivar. Also shipping temperature under $8^{\circ}C$ delayed coloring and decay incidence of both strawberry cultivars, and precooling treatments of both forced air and room cooling reduced frequency of decay. The shelf life of everbearing strawberry at low shipping temperature was extended more than 4 days compared with shipping at room temperature. Precooling treatment including forced air or room cooling will be useful for the two cultivars when they are transported at low temperature. In 'Flamenco' cultivar, the effect of forced air and room cooling was similar, whereas in 'Goha' room cooling was more effective.