• Title, Summary, Keyword: Vertical Heater

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A NUMERICAL STUDY ON MHD NATURAL CONVECTIVE HEAT TRANSFER IN AN AG-WATER NANOFLUID FILLED ENCLOSURE WITH CENTER HEATER

  • NITHYADEVI, N.;MAHALAKSHMI, T.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.21 no.4
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    • pp.225-244
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    • 2017
  • The natural convective nanofluid flow and heat transfer inside a square enclosure with a center heater in the presence of magnetic field has been studied numerically. The vertical walls of the enclosure are cold and the top wall is adiabatic while the bottom wall is considered with constant heat source. The governing differential equations are solved by using a finite volume method based on SIMPLE algorithm. The parametric study is performed to analyze the effect of different lengths of center heater, Hartmann numbers and Rayleigh numbers. The heater effectiveness and temperature distribution are examined. The effect of all pertinent parameters on streamlines, isotherms, velocity profiles and average Nusselt numbers are presented. It is found that heat transfer increases with the increase of heater length, whereas it decreases with the increase of magnetic field effect. Furthermore, it is found that the value of Nusselt number depends strongly upon the Hartmann number for the increasing values of Rayleigh number.

An Experimental Study on the Fire Hazards in Electric Heater (전기히터의 화재위험성에 관한 실험연구)

  • Hong, Sung-Ho;Lee, Bock-Young;Park, Sang-Tae;Yu, Hyun-Jong
    • Journal of the Korean Society of Safety
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    • v.22 no.2
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    • pp.36-40
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    • 2007
  • This study presents on the analysis fire hazards of electric heater. In order to analyze fire hazards fire experiment is conducted. The fire experiment is conducted to simulate normal condition and abnormal condition. The abnormal condition experiment is simulated in which combustibles are placed near by electric heater. Vertical burning test(UL 94) is conducted for the fire retardant experiment. The results show that fire hazard is high in case of abnormal condition. And Material of electric heater has not fire retardant performance. In this paper, we suggest to add temperature fuse in electric heater for reducing fire hazard.

Development of an Integrated Controller to the Control Vertical Agitation Heater and Facilities (수직교반히터 및 시설물 제어를 위한 통합 제어기 개발)

  • Kim, Jin-Ha;Yoo, Seung-Hyeok;Kim, Eung-Kon
    • The Journal of the Korea institute of electronic communication sciences
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    • v.15 no.4
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    • pp.753-758
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    • 2020
  • In this paper, we intend to develop a control system that can apply the developed vertical stirring heater to the facility house and control the other facilities (circulating fan, ventilation fan, window using a switching motor, ceiling, and dehumidification). Through this, it is intended to increase the cultivation efficiency of crops and improve storage environment of crops held by non-heated storage or storage warehouses to increase the storage period and freshness. In addition, ICT monitoring technology is added to enable users to easily solve problems when there is a problem due to changes in the cultivation and storage environment with Real Time Control (RTC).

Natural convection cooling of discrete heaters with same heat generation in a vertical open top cavity (상부가 개방된 수직 캐비티내에 장착된 불연속 균일 발열체의 자연대류 냉각)

  • Yu, Gap-Jong;Chu, Hong-Rok;Kim, Byeong-Ha;Choe, Byeong-Cheol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.1
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    • pp.1-14
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    • 1997
  • Natural convection cooling of discrete heaters located in a two-dimensional vertical open top cavity is investigated experimentally. The five discrete heaters with same heat generation are located on the wall of the cavity. The heaters are arranged in two configurations; flush-mounted on a vertical wall and protruding from the wall about 4.5 mm. The materials used for the vertical walls are copper and epoxy-resin, and air is used as the cooling fluid. The temperature and flow fields in the cavity were visualized by means of Mach-Zehnder interferometer and smoke-method. Also, local temperature measurements are made along the vertical wall. Results are obtained for cavity aspect ratios of 4.6, 7.5 and 9.5 and modified Rayleigh numbers ranging from 10$^{3}$ to 10$^{6}$ . Results indicate that the cooling efficiency for the copper wall is superior to that of the epoxy-resin. For the epoxy-resin wall, the protrusion of the heaters plays a role in decreasing the heat transfer performance. The location of maximum temperature is significantly influenced by the wall materials and heater configurations. Correlations relating the Nusselt number to the modified Rayleigh number are proposed.

Analysis of Air Circulation in Oyster Mushroom Farm

  • Jeong, Won-Geun;Lim, Hack-Kyu;Kim, Tae-Han
    • Journal of Biosystems Engineering
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    • v.37 no.2
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    • pp.75-81
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    • 2012
  • Oyster mushroom farm which could not meet optimum temperature range yields non-uniform sized, low quality products. Thus, this study, utilizing STAR CCM+, one of the computational fluid dynamics (CFD) programs, analyzed the impact of air circulation and temperature distribution. Methods: After we visited numerous mushroom farms, we measured the temperature at the discharge ports of heaters, fan capacity, and the locations of the air circulators in the farms. According to the data, most mushroom growers installed the heaters near the entrance and discharge ports of the heaters at the third growing bed on the same height as the heaters in the entrance. The temperature at the discharge port of heater was $1,26^{\circ}C$, and the fan capacity was 4,500 $m^3$/hr. The air circulator was placed in the center of the mushroom farm 50cm above the ground, and its capacity of inlet port was 1,100 $m^3$/hr and discharge port 1,600 $m^3$/hr. The mushroom farm was insulated. Results: According to the analysis of the temperature distribution in the vertical plane of the entrance side, no air circulation causes the high temperature zone of 296~299K at the discharge port of the heater to take up 34% of area while the operation of air circulators causes it to occupy only 9%. This means that not using air circulators leads to a concentration of high temperature at the discharge port near the entrance. In addition, with the results of the analysis of the temperature distribution in the vertical planes of the center, no air circulation causes the temperature zone of 295~298K at the discharge port of the heater to take up 48% of area while the operation of air circulators causes it to occupy 80%. This shows that the high outlet port temperature disseminated to the center. Conclusions: After ninety minute operation of both heater and air circulator, the interior temperature became stabilized in the mushroom farm. Air circulation made the high temperature at the discharge port disseminate to the center and exit in the farm and equalize the temperature distribution.

A Study on the Wall Thinning Range according to modified Extraction Nozzle Design in High Pressure Feedwater Heater (고압 급수가열기 추기노즐 설계변경에 따른 감육 범위 연구)

  • Park, Sang-Hoon;Yoo, Il-Gon;Kim, Kyung-Hoon;Hwang, Kyeong-Mo
    • Proceedings of the SAREK Conference
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    • pp.847-852
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    • 2009
  • Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feed-water heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare wall thinning range according to change entrance nozzle diameter and position with reference numerical analysis model's wall thinning range, various numerical analysis models applied. In case of changing diameter, four different diameter is applied. And a side of nozzle position, two different position-vertical type and parallel type-is applied. And then this paper describes operation of numerical analysis which is composed similar condition with real feed water heater. In conclusion, this study shows effective design for shall wall thinning by changing nozzle diameter and position.

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The optimal array of various heat-generating heaters located on one wall of a vertical open top cavity (상부가 개방된 수직 캐비티내의 한쪽면에 배열된 다양한 발열조건을 갖는 발열체의 최적배열)

  • Riu, Kap-Jong;Choo, Hong-Lock;Choi, Byung-Cheol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.1
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    • pp.15-23
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    • 1997
  • An experimental investigation of two-dimensional steady natural convection cooling in a vertical open top cavity with conducting side walls of finite thickness is presented. The various heat-generating discrete heaters are located on one vertical wall of the cavity. When each heater dissipates different amount of power, the purpose of the work is to obtain the optimal array condition of the heaters. The four cases of non-uniform heating conditions are considered. The temperature fields in the cavity were visualized by the interferometer and local temperatures of the vertical wall were measured by thermocouples. The heaters were arranged in two configurations: flush-mounted on a vertical wall or protruding from the wall about 4.5 mm. The vertical wall was constructed out of copper or epoxy-resin sheet. Experiments have been conducted for air with constant Prandtl number(Pr=0.7), the aspect ratio of 4.6, 7.5, 9.5, power input in the range of 0.9 W ~ 4.2 W. For the enhancement of the cooling effectiveness, the upper and lower of vertical wall would give the better position for the heaters of higher heat flux.

Crystal growth from melt in combined heater-magnet modules

  • Rudolph, P.;Czupalla, M.;Dropka, N.;Frank-Rotsch, Ch.;KieBling, F.M.;Klein, O.;Lux, B.;Miller, W.;Rehse, U.;Root, O.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.19 no.5
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    • pp.215-222
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    • 2009
  • Many concepts of external magnetic field applications in crystal growth processes have been developed to control melt convection, impurity content and growing interface shape. Especially, travelling magnetic fields (TMF) are of certain advantages. However, strong shielding effects appear when the TMF coils are placed outside the growth vessel. To achieve a solution of industrial relevance within the framework of the $KRISTMAG^{(R)}$ project inner heater-magnet modules(HMM) for simultaneous generation of temperature and magnetic field have been developed. At the same time, as the temperature is controlled as usual, e.g. by DC, the characteristics of the magnetic field can be adjusted via frequency, phase shift of the alternating current (AC) and by changing the amplitude via the AC/DC ratio. Global modelling and dummy measurements were used to optimize and validate the HMM configuration and process parameters. GaAs and Ge single crystals with improved parameters were grown in HMM-equipped industrial liquid encapsulated Czochralski (LEC) puller and commercial vertical gradient freeze (VGF) furnace, respectively. The vapour pressure controlled Czochralski (VCz) variant without boric oxide encapsulation was used to study the movement of floating particles by the TMF-driven vortices.

Numerical Study on Simultaneous Heat and Mass Transfer in a Falling Film of Water-Cooled Vertical Plate Absorber

  • Phan, Thanh-Tong;Song, Sung-Ho;Moon, Choon-Geun;Kim, Jae-Dol;Kim, Eun-Pil;Yoon, Jung-In
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.41-47
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    • 2002
  • A model of simultaneous heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled vertical plate absorber was developed. The model can predict temperature and concentration profiles as well as the absorption heat and mass fluxes, the total heat and mass transfer rates and the heat and mass transfer coefficients. Besides, the effect of operating condition on absorption mass flux has been investigated, with the result that the absorption mass flux is increased as the inlet cooling water temperature decreases, the system pressure increases and the inlet solution concentration increases. And among the effects of operating parameters on absorption mass flux, the effect of inlet solution concentration is dominant.

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Three Dimensional Analysis for the Performance of the Corrugated Louver Fin for a Vehicle Heat Exchanger (차량용 열교환기의 주름진 루터 휜에 대한 3차원 성능해석)

  • 박봉수;조재헌;한창섭
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.2
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    • pp.116-126
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    • 2002
  • A three dimensional numerical analysis of the corrugated louver fin for a vehicle heat exchanger was performed. The heat transfer rate and the air pressure drop of the corrugated louver fins for a slim heater were compared with experimental results at the same operating conditions. As for the slim heater fin, we found an optimum fin pitch at certain operating conditions. As the fin pitch increased, the air pressure drop decreased. The vertical or flat top fin was superior to the common declined fin in the aspect of heat transfer performance. As the louver length increased, both the heat transfer rate and the air pressure drop increased.