• Title/Summary/Keyword: Square hot body

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Natural Convection Heat Transfer from a Hot Body in s Square Enclosure (정사각형 밀폐공간 내에 있는 고온부로부터의 자연대류 열전달)

  • Kwon, S.S.;Chung, T.H.;Kwon, Y.I.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.4 no.3
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    • pp.147-154
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    • 1992
  • Laminar natural convection heat transfer from a hot body in a square enclosure has been studied for various center positions of a hot square at Grashof number $Gr=1.5{\times}10^5$, Prandtl number Pr=0.71 and dimensionless thermal conductivity $k_g/k_f=14710$. The natural convection at the center position of a hot square; $X_c$, $Y_c=0.5$, 0.2 shows the most strong and at $X_c$, $Y_c=0.5$, 0.7 the most weak. The total mean Nusselt number at $X_c$, $Y_c=0.5$, 0.2 was 7.4% higher than that at $X_c$, $Y_c=0.2$, 0.5. The total mean Nusselt number at $X_c$, $Y_c=0.5$, 0.7 was 5.0% lower than that at $X_c$, $Y_c=0.3$, 0.5.

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The Effect of Balneotherapy on Children Autonomic Nervous System Function and Body Composition (온천이 소아의 체성분과 자율 신경 기능에 미치는 영향에 관한 연구)

  • Jo, Min-Seo;Lee, Nam-Heon;Han, Jae-Kyung
    • The Journal of Pediatrics of Korean Medicine
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    • v.25 no.3
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    • pp.77-84
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    • 2011
  • Objectives: This study was performed to investigate the effect of hot spring therapy on children weight, body composition and heart rate variability. Methods: The study was carried out from 30 children who visited the spa from August 1, 2011 to August 31, 2011. We measured the change of weight, body composition, and heart rate variability after hot spring therapy for an hour per day. Results: The subject was consisted of 13 boys and 17 girls. This study revealed that their weight got lost from a hot spring therapy, which was statistically significant. Their body mass index(BMI) was decreased in from a hot spring therapy, which was not statistically significant. Total body water, muscle, protein, and mineral were decreased from a hot spring therapy, which was statistically significant. We measured HRV(heart rate variability) before and after the hot spring therapy. The mean HRT was increased, which was statistically insignificant. SDNN(standard deviation of the NN interval) and RMSSD(square root of the mean of the sum of the square of differences) were not different before and after the hot spring therapy. ln TP was decreased insignificantly. ln VLF was not affected before and after hot spring therapy. ln LF and ln HF was decreased, LF norm was increased, and HF norm was decreased, which were not statistically significant. Also, LF/HF ratio was increased insignificantly. Conclusions: From these results, we concluded that the weight, total body water, muscle, protein, and mineral got lost from the hot spring therapy. However, the HRV was not affected from the hot spring therapy.

Natural convection heat transfer from a hot body in the square enclosure with different boundary conditions (다른 경계조건을 갖는 밀폐공간 내에 존재하는 고온부로부터의 자연대류 열전달)

  • 권순석;정태현;권용일
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.12
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    • pp.2395-2406
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    • 1992
  • Laminar natural convection heat transfer from a hot body in a square enclosure has been studied for various center positions of a hot body at Grashof number Gr=1.5$\times$10/sup 5/, Prandtl number Pr=0.71 and dimensionless thermal conductivity K/sub s//K/sub f/= 14710. In case of vertical cold walls, the natural convection at the dimensionless center position of a hot body, X/sub c/Y/sub c/=0.2, 0.5 shows the most strong and at X/sub c/, Y/sub c/=0.5, 0.8 the most weak. In case of horizontal cold walls, the natural convection at the dimensionless center position of a hot body ; X/sub c/ Y/sub c/=0.5, 0.2 shows the most strong and at X/sub c/, Y/sub c/=0.2, 0.5 the most weak.

Natural Convection Heat Transfer from a Hot Body in an Inclined Square Enclosure (경사진 정사각형 밀폐공간 내에 있는 고온부로부터의 자연대류 열전달)

  • Kwon, Sun-Sok;Chung, Tae-Hyun
    • Solar Energy
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    • v.12 no.1
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    • pp.25-33
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    • 1992
  • Laminar natural convection heat transfer from a hot body in a square enclosure has been stooled for various inclination angles at $Gr=1.5{\times}10^5$, Pr= 0.71 and $k_s/k_f=14710$. The area of a hot body is 1/25 of the enclosure and the aspect ratio is 1.0. The total mean Nusselt number decreases as the inclination angle increases and in case of ${\theta}=90^{\circ}$ is 14% lower than that of ${\theta}=0^{\circ}$.

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Theoretical Analysis on the Hot Surface Ignition of a Rectangular-Shape Solid Fuel

  • Kim, Se-Won
    • Journal of Energy Engineering
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    • v.4 no.2
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    • pp.297-302
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    • 1995
  • Ignition of a reactive solid in a shape of square corner by a hot surface is studied theoretically. Ignition time and the location of ignition point are determined as a function of dimensionless parameters, with the use of the homogeneous model of ignition. The effect of geometry on the ignition of solid fuel results in the local characteristics: the reaction is initiated in a hot point in depth of the substance. It is shown that ignition time is proportional to the dimensionless initial temperature, whereas for the ignition of the semiinfinite body this dependence was quadratic.

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Measurement of Developing Turbulent Flows in a 90-Degree Square Bend with Spanwise Rotation

  • Choi Young Don;Kim Dong Chul;Lee Kun Hee
    • Journal of Mechanical Science and Technology
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    • v.19 no.7
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    • pp.1503-1516
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    • 2005
  • Mean flow and turbulence properties of developing turbulent flows in a 90 degree square bend with span-wise rotation are measured by a hot-wire anemometer. A slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and the Reynolds stress components. Combined effects of the centrifugal and Coriolis forces due to the curvature and the rotation of the bend on the mean motion and turbulence structures are investigated experimentally. Results show that the two body forces can either enhance or counteract each other depending on the flow direction in the bend.

Numerical Study on Convective Heat Transfer in a Compartment Fire - I. Evaluation of Numerical Method and Natural Convection- (실내화재에 있어서의 대류열전달에 관한 수치연구 - I. 수치법 검증과 자연대류-)

  • 박외철;고경찬
    • Journal of the Korean Society of Safety
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    • v.14 no.2
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    • pp.26-31
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    • 1999
  • In a compartment fire, convective heat transfer dominates spread of the fire and smoke movement before flash-over occurs, and natural convection is very important in particular when there are no openings. The finite volume method with SIMPLE algorithm was applied to a square cavity similar to a compartment without an opening. The objectives of this study are to evaluate the method and to simulate natural convection from a hot body in the cavity. The results without the hot body showed an excellent agreement with those of previous studies. Streamlines, isotherms and Nusselt numbers were computed for different Rayleigh numbers.

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Experimental Study on the Natural Convection in an Enclosure with an Adiabatic Body Using the Two-Color LIF Method (Two-color LIF 기법을 이용한 단열체가 있는 밀페계 내에서의 자연대류에 관한 실험적 연구)

  • Kwo S. H.;Jeong E. H.;Min Y. U.;Kim K. C.
    • Journal of the Korean Society of Visualization
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    • v.3 no.1
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    • pp.90-96
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    • 2005
  • Most of the previous studies on natural convection were based on the numerical analysis, and some experimental studies considered the classic case of thermal convection. In this study, an adiabatic square body was located at the center of an enclosure between the bottom hot and top cold walls. And the measurement of the detailed temperature fields was conducted by the method of two-color Laser Induced Fluorescence using a Nd:Yag laser. As a result, heat transfer characteristics of natural convection with an adiabatic body was estimated as a function of time over a range of Rayleigh numbers.

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Experimental study on the natural convection in an enclosure with an adiabatic body using the two-color LIF method (Two-color LIF 기법을 이용한 단열체가 있는 밀폐계 내에서의 자연대류에 관한 실험적 연구)

  • Kwon Su Hyun;Jeong Eun Ho;Kim Kyung Chun
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.104-107
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    • 2004
  • Most of the previous studies on natural convection were based on the numerical analysis, and some experimental studies considered the classic case of thermal convection. In this study, an adiabatic square body was located at the center of an enclosure between the bottom hot and top cold walls. And the measurement of the detailed temperature fields was conducted by the method of two-color Laser Induced Fluorescence using a Nd:Yag laser. As a result, heat transfer characteristics of natural convection with an adiabatic body was estimated as a function of time over a range of Rayleigh numbers.

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Measurement of Developing Turbulent Flows in a 90-Degree Square Bend with Spanwise Rotation (횡방향으로 회전하는 90도 정사각 단면 곡덕트에서 발달하는 난류유동의 측정)

  • Kim, Dong-Chul;Choi, Young-Don;Lee, Kun-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.2
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    • pp.206-214
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    • 2003
  • Mean flow and turbulence properties of developing turbulent flows in a 90 degree square bend with spanwise rotation were measured by a hot-wire anemometer. A slanted wire is rotated into 6 orientations and the voltage outputs from them are combined to obtain the mean velocity and Reynolds stress components. The combinative effects of the centrifugal and Coriolis forces due to the curvature and the rotation of bend on the mean motion and turbulence structures are investigated experimentally. Results show that the two body forces can either enhance or counteract each other depending on the flow direction in the bend.