• 한국유체기계학회 논문집
• /
• 제13권5호
• /
• pp.22-28
• /
• 2010

A study has been made of cool-down process on an incompressible fluid contained in a periodically oscillating cylinder when an abrupt cooling of wall temperature is imposed. Characteristics of flow and heat transfer are investigated along the variations of oscillating frequency and amplitude. One found the flow regimes are divided into 4-modes : 1 thermal island mode, 2 thermal island mode, 4 thermal island mode and asymmetry mode. Comprehensive analysis for each mode are given with a physical mechanism on cool-down process.

• 동굴
• /
• 제8호
• /
• pp.55-64
• /
• 1998

Many of the familiar roadside signs advertising caves open to the public carry the phrase, “Come underground and cool off”. This is reasonable advice, for during the heat of summer the temperature of these caves is indeed pleasantly cool. If the principal tourist season were in the winter instead of the summer, however, the signs would probably read, “Come underground and warm up”, for in winter these same caves are far warmer than the surface. Cave temperatures are nearly constant throughout the year.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집D
• /
• pp.683-688
• /
• 2001

Cryogenic LNG(Liquefied Natural Gas) which is stored in the cylindrical storage tanks of $100,000m^{3}$ has very complex flow phenomena and the changes of thermal properties with exterior conditions and operation mdoes. These complex thermofluid behaviors are affected by the storage, exterior conditions of LNG, design specifications and heat transfer characteristics of tanks, Also, those have influence on the stable storage and supply of LNG in the storage tanks. Thus this study performed the analysis on the 2-D heat transfer of the tank with exterior conditions, on the Cool Down Process in order to cool down the LNG Storage Tank at the initial normal state, and on the Filling Process considered for incoming and rising of LNG. The analysis on the Mixing LNG Storage was studied too. At last, the visualized program on the complex thermofluidodynamic analysis was developed on the basis of the above analyses. The development of this program becomes to be used to the basic design of the commercial tanks as well as to assure technical skill of the analysis on the thermal stability of the stored LNG in the LNG Storage Tank.

• 한국의류산업학회지
• /
• 제2권5호
• /
• pp.411-415
• /
• 2000

To be able to work safely and efficiency, the Threshold Limit Values (TLV) for work in the heat are widely used. Since these TLV are only applicable to workers in regular clothing, TLV should be adjusted when applied to the asbestos removal workers who wear extra impermeable protective clothing. Although abbreviated guidelines for heat stress exposure have been proposed, literature advocating their use in the asbestos removal industry is limited. Therefore, we planed a survey to evaluate the workload of asbestos abatement workers in summer, and an experiment with climatic chambers to evaluate the effects of resting in a cool environment between work periods. From these studies, we got following conclusions. There is a high risk of suffering from heat illness by asbestos abatement work in summer in Japan. It is proposed to create a cool room inside the workplace of asbestos abatement work to reduce thermal stress.

• 설비공학논문집
• /
• 제10권5호
• /
• pp.600-609
• /
• 1998

The experimental investigation of thermal response characteristics by the air flow through the porous media has been carried out. The packed spheres of steel or glass were considered as the porous media in the present study. Temperature distributions of the fluid in the porous media as well as pressure drops through the porous media were measured. The transient temperature variations in the porous media are compared favorably with the analytical results in the high Reynolds number ranges. However, in the low Reynolds number ranges, the experimental data deviate from the analytical results, due to the dominant heat conduction penetration to the upstream direction, which is not considered in the analytical model. The cool-down response of porous media is found to be dependent upon the specific dimensionless time considering the material property and air velocity. The heat discharge process is recommended to be operated until a certain time, considering the cost efficiency.

• 설비공학논문집
• /
• 제1권3호
• /
• pp.203-209
• /
• 1989

This paper is an experimental study on the pleasantly suitable cool/warm air conditioning system in order to minimize the energy consumption by attaching the electronic-controlled device to the heat pump air conditioning system.While the cool/warm air conditioning, the air temperatures in the entrance and exit of the indoor heat exchangers should be checked and when the surface of heat exchanger is reached to the dew point temperature, a speed of the compressor is to be automatically controlled by anti-dewing system in order to minimize the energy consumption.At the result of this study, the energy consuming amount is saved about 5% more than that of the conventional air conditioning system by prevent unnecessary dew forming.

• 한국전기전자재료학회논문지
• /
• 제16권9호
• /
• pp.842-850
• /
• 2003

The suspension insulators are subjected to harsh environments in service for a long time. The long-term reliability of tile insulators is required for both mechanical and electrical performances. This study describes some basic performance tests and accelerated aging test by cool-heat cycling methods and thermal mechanical performance test methods on alumina porcelain insulators (new and aged) used for transmission line in KOREA. There was no fail in electrical and mechanical performance tests such as a high voltage strength, a flashover voltage, and an impact strength in all samples. But in the case of accelerating aging tests which have above 9$0^{\circ}C$ temperature gradient, fracture phenomena was happened by a thermal shock in tile aged sample(sample A) with low alumina porcelain body. It was indicated that sample A was more severely aged than other samples. According to results of HRB test and microstructural analysis, it was reasoned that insulator bodies with the matrix reinforced with alumina crystalline phase have advantages over the suppression of crack advance. And cool-heat aging and mechanical thermal ageing tests shows that a temperature gradient is more effective to accelerating than a cycling number.

• 설비공학논문집
• /
• 제16권10호
• /
• pp.889-894
• /
• 2004

Infrared (IR) detectors are widely used for many applications, such as temperature measurement, intruder and fire detection, robotics and industrial equipment, thermoelstic stress analysis, medical diagnostics, and chemical analysis. Quantum detectors commonly need to be refrigerated below 80 K, and thus a cooling system should be equipped together with the detector system. The cooling load, which should be removed by the cooling system to maintain the nominal operating temperature of the detector, critically depends on the insulation efficiency of the cryochamber housing the detector. Thermal analysis of cryochamber includes the conduction heat transfer through a cold well, the gases conduction and gas outgassing, as well as radiation heat transfer, The transient cooling characteristics of an infrared detector cryochamber are investigated experimentally in the present study. The transient cooling load increases as the gas pressure is increased. Gas pressure becomes significant as the cooling process proceeds. Cool down time is also increased as the gas pressure is increased. It is also found that natural convection effects on cool down time become significant when the gas pressure is increased.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
• /
• pp.483-486
• /
• 2006

The fan is widely used to cool high heat flux generated as of the electronic communication device consoles. It, however, makes a lot of noises that interfere considerably with the operation environment. This study was conducted to obtain the cooling design technology of the consoles through being equipped with the Heat Pipe Heat Exchangers (HPHE) together with low revolution fans in place of existing fans for the cooling technology of the forced convection. Not only the sealed type consoles but the HPHE were also designed so as to cool effectively the heat generated from the inside of the console. The simulation was conducted by computational numerical analysis along with its experiments. The results of the numerical analysis and experiments were compared in order to improve the cooling technology of the consoles mounted with the HPHE. Consequently, instead of loud fan noise generated as of existing forced convection methods, the cooling technology of HPHE can remarkably improve many problems such as the operation environment, indoor dust, malfunction caused by pollution sources and so on.

• 대한기계학회논문집B
• /
• 제27권1호
• /
• pp.125-134
• /
• 2003

The present paper is concerned to the thermal analysis during the cool-down period of 138,000 m$^3$class GTT MARK-III membrane type LNG carrier servicing with LNG from the Middle East to Korea. It is the cool-down period that cools the insulation wall and the gas in LNG tank to avoid the thermal shock as the start of loading of -162$^{\circ}C$ LNG. For six hours of the standard cool-down period, the temperature of NG falls down from -4$0^{\circ}C$ to -13$0^{\circ}C$ and especially the mean temperature of the 1st barrier in the top side insulation wall falls down from -38.38$^{\circ}C$ to -122.42$^{\circ}C$ in case of IMO design condition. By the 3-D numerical calculation about the cargo tank and the cofferdam, the temperature variation in hulls and insulations is precisely predicted in this paper. And the mean temperature variation of gas is calculated as the function of the spraying rate by the heat balance model during the cool-down period.