Turbulent Heat Transfer

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A Rabienataj A Darzi - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Heat Transfer of al2o3 water nanofluid inside helically corrugated tubes numerical study
    International Communications in Heat and Mass Transfer, 2013
    Co-Authors: A Rabienataj A Darzi, Mousa Farhadi, Kurosh Sedighi, Shahriar Aallahyari, Mojtaba Aghajani Delavar
    Abstract:

    Abstract Turbulent Heat Transfer in Heated helically corrugated tube was investigated numerically for pure water and water–alumina nanofluid using two phase approach. The study was carried out for different corrugating pitch and height ratios at various Reynolds numbers ranging from 10,000 to 40,000. The effect of nano-particles in Heat Transfer augmentation for smooth tube and helically corrugation tubes (HCT) was discussed and their relative Nusselt number was compared. Results show that the Heat Transfer enhancement is promoted extremely by increasing the volume fraction of nano-particles. Adding 2% and 4% nano-particles by volume to water enhances the Heat Transfer by 21% and 58%, respectively. Also, the overall enhancement in Heat Transfer using two mechanisms simultaneously compared to using pure fluid within smooth tube exceeds over 330%. A correlation is given based on curve fitting from numerical data. Results indicate that using nano-particles yields different enhancement in Heat Transfer of tube for different corrugation height and pitch.

  • experimental investigation of Turbulent Heat Transfer and flow characteristics of sio2 water nanofluid within helically corrugated tubes
    International Communications in Heat and Mass Transfer, 2012
    Co-Authors: A Rabienataj A Darzi, Mousa Farhadi, Kurosh Sedighi, Rouzbeh Shafaghat, Kaveh Zabihi
    Abstract:

    Abstract Experiments were conducted to investigate the effect of nanofluid on Turbulent Heat Transfer and pressure drop inside concentric tubes. Water and SiO 2 with mean diameter of 30 nm were chosen as base fluid and nano-particles, respectively. Experiments were performed for plain tube and five roughened tube with various heights and pitches of corrugations. Results show that adding the nano-particles in tube with high height and small pitch of corrugations augments the Heat Transfer significantly with negligible pressure drop penalty. It is discussed on relative Nusselt number and thermal performance of Heat exchanger.

Smith Eiamsaard - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Heat Transfer enhancement in a Heat exchanger using helically corrugated tube
    International Communications in Heat and Mass Transfer, 2011
    Co-Authors: S Pethkool, Smith Eiamsaard, Sutapat Kwankaomeng, Pongjet Promvonge
    Abstract:

    Abstract The augmentation of convective Heat Transfer in a single-phase Turbulent flow by using helically corrugated tubes has been experimentally investigated. Effects of pitch-to-diameter ratio (P/DH = 0.18, 0.22 and 0.27) and rib-height to diameter ratio (e/DH = 0.02, 0.04 and 0.06) of helically corrugated tubes on the Heat Transfer enhancement, isothermal friction and thermal performance factor in a concentric tube Heat exchanger are examined. The experiments were conducted over a wide range of Turbulent fluid flow of Reynolds number from 5500 to 60,000 by employing water as the test fluid. Experimental results show that the Heat Transfer and thermal performance of the corrugated tube are considerably increased compared to those of the smooth tube. The mean increase in Heat Transfer rate is between 123% and 232% at the test range, depending on the rib height/pitch ratios and Reynolds number while the maximum thermal performance is found to be about 2.3 for using the corrugated tube with P/DH = 0.27 and e/DH = 0.06 at low Reynolds number. Also, the pressure loss result reveals that the average friction factor of the corrugated tube is in a range between 1.46 and 1.93 times over the smooth tube. In addition, correlations of the Nusselt number, friction factor and thermal performance factor in terms of pitch ratio (P/DH), rib-height ratio (e/DH), Reynolds number (Re), and Prandtl number (Pr) for the corrugated tube are determined, based on the curve fitting of the experimental data.

  • Turbulent Heat Transfer enhancement by counter co swirling flow in a tube fitted with twin twisted tapes
    Experimental Thermal and Fluid Science, 2010
    Co-Authors: Smith Eiamsaard, Chinaruk Thianpong, Petpices Eiamsaard
    Abstract:

    Abstract In the present study, the influences of twin-counter/co-twisted tapes ( counter / co-swirl tape ) on Heat Transfer rate ( Nu ), friction factor ( f ) and thermal enhancement index ( η ) are experimentally determined. The twin counter twisted tapes ( CTs ) are used as counter-swirl flow generators while twin co-twisted tapes ( CoTs ) are used as co-swirl flow generators in a test section. The tests are conducted using the CTs and CoTs with four different twist ratios ( y / w  = 2.5, 3.0, 3.5 and 4.0) for Reynolds numbers range between 3700 and 21,000 under uniform Heat flux conditions. The experiments using the single twisted tape ( ST ) are also performed under similar operation test conditions, for comparison. The experimental results demonstrate that Nusselt number ( Nu ), friction factor ( f ) and thermal enhancement index ( η ) increase with decreasing twist ratio ( y / w ). The results also show that the CTs are more efficient than the CoTs for Heat Transfer enhancement. In the range of the present work, Heat Transfer rates in the tube fitted with the CTs are around 12.5–44.5% and 17.8–50% higher than those with the CoTs and ST , respectively. The maximum thermal enhancement indices ( η ) obtained at the constant pumping power by the CTs with y / w  = 2.5, 3.0, 3.5 and 4.0, are 1.39, 1.24, 1.12 and 1.03, respectively, while those obtained by using the CoTs with the same range of y / w are 1.1, 1.03, 0.97 and 0.92, respectively. In addition, the empirical correlations of the Heat Transfer ( Nu ), friction factor ( f ) and thermal enhancement index ( η ) are also reported.

M A Abdou - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation of Turbulent Heat Transfer of high prandtl number fluid flow under strong magnetic field
    Fusion Science and Technology, 2007
    Co-Authors: Takehiko Yokomine, Tomoaki Kunugi, Shinichi Satake, J Takeuchi, Hiroyuki Nakaharai, N B Morley, M A Abdou
    Abstract:

    An investigation of MHD effects on Flibe simulant fluid (aqueous potassium hydroxide solution) flows has been conducted under the U.S.-Japan JUPITER-II collaboration program using "FLIHY" pipe flow facility at UCLA. Mean and fluctuating temperature profiles in a conducting wall pipe were measured for low Reynolds number Turbulent flows using a thermocouples probe at constant Heat flux condition. It is suggested that the temperature profiles are characterized by interaction between turbulence production, turbulence suppression due to magnetic field and thermal stratification occurred even under the situation where quite small temperature difference exists in the pipe cross-section.

  • the influence of a magnetic field on Turbulent Heat Transfer of a high prandtl number fluid
    Experimental Thermal and Fluid Science, 2007
    Co-Authors: Hiroyuki Nakaharai, Tomoaki Kunugi, Shinichi Satake, Takehiko Yokomine, J Takeuchi, N B Morley, M A Abdou
    Abstract:

    The influence of a transverse magnetic field on the local and average Heat Transfer of an electrically conducting, Turbulent fluid flow with high Prandtl number was studied experimentally. The mechanism of Heat Transfer modification due to magnetic field is considered with aid of available numerical simulation data for Turbulent flow field. The influence of the transverse magnetic field on the Heat Transfer was to suppress the temperature fluctuation and to steepen the mean temperature gradient in near-wall region in the direction parallel to the magnetic field. The mean temperature gradient is not influenced compared to the temperature fluctuation in the direction vertical to the magnetic field.

Pongjet Promvonge - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Heat Transfer enhancement in a Heat exchanger using helically corrugated tube
    International Communications in Heat and Mass Transfer, 2011
    Co-Authors: S Pethkool, Smith Eiamsaard, Sutapat Kwankaomeng, Pongjet Promvonge
    Abstract:

    Abstract The augmentation of convective Heat Transfer in a single-phase Turbulent flow by using helically corrugated tubes has been experimentally investigated. Effects of pitch-to-diameter ratio (P/DH = 0.18, 0.22 and 0.27) and rib-height to diameter ratio (e/DH = 0.02, 0.04 and 0.06) of helically corrugated tubes on the Heat Transfer enhancement, isothermal friction and thermal performance factor in a concentric tube Heat exchanger are examined. The experiments were conducted over a wide range of Turbulent fluid flow of Reynolds number from 5500 to 60,000 by employing water as the test fluid. Experimental results show that the Heat Transfer and thermal performance of the corrugated tube are considerably increased compared to those of the smooth tube. The mean increase in Heat Transfer rate is between 123% and 232% at the test range, depending on the rib height/pitch ratios and Reynolds number while the maximum thermal performance is found to be about 2.3 for using the corrugated tube with P/DH = 0.27 and e/DH = 0.06 at low Reynolds number. Also, the pressure loss result reveals that the average friction factor of the corrugated tube is in a range between 1.46 and 1.93 times over the smooth tube. In addition, correlations of the Nusselt number, friction factor and thermal performance factor in terms of pitch ratio (P/DH), rib-height ratio (e/DH), Reynolds number (Re), and Prandtl number (Pr) for the corrugated tube are determined, based on the curve fitting of the experimental data.

K. V. Sharma - One of the best experts on this subject based on the ideXlab platform.

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