• Title/Summary/Keyword: Convective Heat Transfer

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The Comparison Study of Radiative and Convective Heat Transfer in a Room Air Ventilation (환기구를 가진 실내공간에서 복사 및 대류열전달의 비교 연구)

  • 정효민;정한식;김경근
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.3
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    • pp.229-235
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    • 1997
  • The comparison of radiative and convective heat transfer in a room air ventilation is investi¬gated by a numerical simulation. The room air temperature distributions with radiation are appeared more uniform than without radiation at Gr= 1460 and Re=50. The mean Nusselt number in the radiative heat transfer shows less value than convective heat transfer. The total mean Nusselt number is found Wall 1> Wall 3${\fallingdotseq}$Wall 2 7 Wall 4.

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Numerical Analysis on the Thermal and Fluid in Air Conditioning Duct for Marine Offshore (해양 구조물용 공조덕트 열유동에 관한 수치해석)

  • Yi, Chung-Seob;Lee, Byung-Ho;Chin, Do-Hun
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.2
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    • pp.7-13
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    • 2019
  • This study is about distributions of heat transfer in air conditioning duct used for marine and oil drilling ship. As the convective heat transfer coefficient increased, heat transfer was conducted dynamically to inside as it exited to the outlet of duct. So, it was checked that the amount of heat transfer generated at duct increased as the convective heat transfer coefficient increased. In case the convective heat transfer coefficient was low, the temperature of duct showed the relatively high temperature distribution due to the temperature influence of internal fluid as the heat transfer between the outside and inside of the duct. In case of temperature distribution generated the volume of the duct along the change of the convective heat transfer coefficient, it was found out that the temperature descended as heat transfer was promoted and the convective heat transfer coefficient increased.

Numerical Estimation of Heat flux on the Deck Exposed to the High Temperature Impinging Jet of VTOL Vehicle (수직 이착륙기의 고온 고속 배기열에 의한 함정 갑판의 열유속 계산을 위한 수치모델)

  • Jang, Hosang;Hwang, Seyun;Choi, Wonjun;Lee, Jang Hyun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.21 no.1
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    • pp.74-85
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    • 2018
  • This study has analyzed the convective heat transfer on the deck exposed to the high-temperature impingement exhausting from a VTOL vehicle. The heat flow of the impingement on the deck is modeled by the convection heat transfer. The convective heat flux generated by the hot impinging jet is investigated by using both convective heat transfer formulation and conjugate heat transfer formulation. Computational fluid dynamics(CFD) code was used to compute the heat flux distribution. The RANS equation and the k-e turbulence model were used to analyze the thermal flow of the impinging jet. The heat flux distribution near the stagnation zone obtained by the conjugate heat transfer analysis shows more reasonable than the convective heat transfer analysis.

Numerical Analysis of Convective Heat and Mass Transfer around Human Body under Strong Wind

  • Li, Cong;Ito, Kazuhide
    • International Journal of High-Rise Buildings
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    • v.1 no.2
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    • pp.107-116
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    • 2012
  • The overarching objective of this study is to predict the convective heat transfer around a human body under forced strong airflow conditions assuming a strong wind blowing through high-rise buildings or an air shower system in an enclosed space. In this study, computational fluid dynamics (CFD) analyses of the flow field and temperature distributions around a human body were carried out to estimate the convective heat transfer coefficient for a whole human body assuming adult male geometry under forced convective airflow conditions between 15 m/s and 25 m/s. A total of 45 CFD analyses were analyzed with boundary conditions that included differences in the air velocity, wind direction and turbulence intensity. In the case of approach air velocity $U_{in}=25m/s$ and turbulent intensity TI = 10%, average convective heat transfer coefficient was estimated at approximately $100W/m^2/K$ for the whole body, and strong dependence on air velocity and turbulence intensity was confirmed. Finally, the formula for the mean convective heat transfer coefficient as a function of approaching average velocity and turbulence intensity was approximated by using the concept of equivalent steady wind speed ($U_{eq}$).

Measuring Convective Heat Transfer Coefficient Around a Heated Fine Wire in Cross Flow of Nanofluids (나노유체의 수직유동 속에 놓인 가는 열선주위의 대류열전달계수 측정)

  • Lee, Shin-Pyo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.2
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    • pp.117-124
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    • 2008
  • Recent researches on nanofluids have mainly focused on the increase of thermal conductivity of nanofluids under static condition. The ultimate goal of using nanofluids, however, is to enhance the heat transfer performance under fluid flow. So it has been highly necessary to devise a simple and accurate measuring apparatus which effectively compares the heat transfer capability between the base and nanofluids. Though the convective heat transfer coefficient is not the complete index for the heat transfer capability, it might be one of useful indications of heat transfer enhancement. In this article, the working principles of experimental system for convective heat transfer coefficient around a heated fine wire in cross flow of nanofluids and its application example to three samples of nano lubrication oils are explained in detail.

Forced convective boiling heat transfer for a ternary refrigerant mixture inside a horizontal tube (수평관내 3성분 혼합냉매의 강제대류비등 열전달)

  • 오종택
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.6
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    • pp.912-920
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    • 1999
  • The forced convective boiling heat transfer coefficients of R-407C were measured inside a horizontal tube 6.0mm I.D. and 4.0m long. The heat transfer coefficients increased according to an increase in heat flux at constant mass flux. Because nucleation was completely suppressed in the two-phase flow region with high quality, heat transfer coefficients in forced convective evaporation were higher than those in nucleate boiling region. Average heat transfer coefficients of R-407C were about 30 percent lower than the pure refrigerant correlation, due to mass transfer resistance at the gas-liquid interface. However, the total experimental data shows an agreement with the predicted data for ternary refrigerant mixtures with a mean deviation of 30%.

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Numerical Analysis on the Thermal and Fluid in Air Conditioning Duct for Marine Offshore (해양 구조물용 공조덕트 열유동에 관한 수치해석)

  • Yi, Chung-Seob;Lee, Byung-Ho;Chin, Do-Hun
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.17 no.5
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    • pp.23-29
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    • 2018
  • This study is about the distribution of heat transfer in air conditioning ducts used for marine vessels and oil drilling platforms. As the convective heat transfer coefficient increased, heat transfer was conducted dynamically to inside as it exited to the outlet of duct. The experiment was to determine if the amount of heat transfer generated at the duct exit increased as the convective heat transfer coefficient increased. When the convective heat transfer coefficient was low, the temperature of the duct showed a relatively high temperature difference between the outside and inside of the duct due to the temperature influence of the internal fluid. In case of temperature distribution generated the volume of the duct along the change of the convective heat transfer coefficient, the temperature descended as heat transfer was promoted and the convective heat transfer coefficient increased.

A Study on the Laminar Flow Field and Heat Transfer Coefficient Distribution for Supercritical Water in a Tube (초임계상태의 물에 대한 관 내 층류유동장 및 열전달계수 분포특성에 관한 연구)

  • 이상호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.9
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    • pp.768-778
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    • 2003
  • Numerical analysis has been carried out to investigate laminar convective heat transfer in a tube for supercritical water near the thermodynamic critical point. Fluid flow and heat transfer are strongly coupled due to large variations of thermodynamic and transport properties such as density, specific heat, viscosity, and thermal conductivity near the critical point. Heat transfer characteristics in the developing region of the tube show transition behavior between liquid-like and gas-like phases with a peak in heat transfer coefficient distribution near the pseudocritical point. The peak of the heat transfer coefficient depends on pressure and wall heat flux rather than inlet temperature and Reynolds number, Results of the modeling provide convective heat transfer characteristics including velocity vectors, temperature, and the properties as well as the heat transfer coefficient. The effect of proximity to the critical point is considered and a heat transfer correlation is suggested for the peak of Nusselt number in the tube.

A Numerical Study on the Laminar Flow Field and Heat Transfer Coefficient Distribution for Supercritical Water in a Tube

  • Lee Sang-Ho
    • International Journal of Air-Conditioning and Refrigeration
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    • v.13 no.4
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    • pp.206-216
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    • 2005
  • Numerical analysis has been carried out to investigate laminar convective heat transfer at zero gravity in a tube for supercritical water near the thermodynamic critical point. Fluid flow and heat transfer are strongly coupled due to large variation of thermodynamic and transport properties such as density, specific heat, viscosity, and thermal conductivity near the critical point. Heat transfer characteristics in the developing region of the tube show transition behavior between liquid-like and gas-like phases with a peak in heat transfer coefficient distribution near the pseudo critical point. The peak of the heat transfer coefficient depends on pressure and wall heat flux rather than inlet temperature and Reynolds number. Results of the modeling provide convective heat transfer characteristics including velocity vectors, temperature, and the properties as well as the heat transfer coefficient. The effect of proximity on the critical point is considered and a heat transfer correlation is suggested for the peak of Nusselt number in the tube.

Measuring Convective Heat Transfer Coefficient of Nanofluids Considering Effect of Film Temperature Change over Heated Fine Wire (막온도 변화를 고려한 가는 열선주위 나노유체의 대류열전달계수 측정 실험)

  • Lee, Shinpyo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.8
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    • pp.725-732
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    • 2013
  • This study examined the convective heat transfer characteristics of nanofluids flowing over a heated fine wire. Convective heat transfer coefficients were measured for four different nano-engine-oil samples under three different temperature boundary conditions, i.e., both or either variation of wire and fluid temperature and constant film temperature. Experimental investigations that the increase in the convective heat transfer coefficients of nanofluids in the internal pipe flow often exceeded the increase in thermal conductivity were recently published; however, the current study did not confirm these results. Analyzing the behavior of the convective heat transfer coefficient under various temperature conditions was a useful tool to explain the relation between the thermal conductivity and the boundary layer thickness of nanofluids.