Effect of Prandtl Number on the Heat Transfer From a Rotating Disk: An Experimental Study

2016 ◽  
Author(s):  
Christian Helcig ◽  
Stefan aus der Wiesche
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Prandtl Number ◽  
Rotating Disk ◽  
Boundary Layer Theory ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heated Disk ◽  
Correlation Exponent ◽  
Experimental Apparatus

Heat transfer coefficients were experimentally determined for a free rotating disk in still air and water. These were obtained with an electrically heated disk placed in a cylindrical pool. The accuracy of the employed experimental apparatus was assessed by heat transfer measurements in air. For this fluid, an excellent agreement with reliable literature data was found. Essentially new experimental data were obtained for water as fluid. Based upon the experimental data, the validity of theoretical correlations and the effect of the Prandtl number on the convective heat transfer from a rotating disk were discussed. It was found that in laminar water flow, the value of the correlation exponent for the Prandtl number is practically identical to 1/2 as theoretically predicted in 1948 by Dorfman. In turbulent flow, its value is better given by 1/3 as in case of the classical turbulent boundary layer theory.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Yantao Li ◽  
Yulong Ji ◽  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Bulk Liquid ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

Calibration of External Heat Transfer Coefficients During Cooling of a Partially-Filled Water Tank Using Measured Temperature-Time Data

2018 ◽  
Author(s):  
Vishal Ramesh ◽  
Sandip Mazumder ◽  
Gurpreet Matharu ◽  
Dhaval Vaishnav ◽  
Syed Ali ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Measured Temperature ◽  
Water Tank ◽  
Time Data ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Temperature Time

A combined Computational Fluid Dynamics (CFD) and experimental approach is presented to determine (calibrate) the external convective heat transfer coefficients (h) around a partially-filled water tank cooled in a climactic chamber. A CFD analysis that includes natural convection in both phases (water and air) was performed using a 2D-axisymmetric tank model with three prescribed average heat transfer coefficients for the top, side and bottom walls of the tank. The commercial CFD code ANSYS-Fluent™, along with User-Defined Functions (UDFs), were utilized to compute and extract temperature vs. time curves at five different thermocouple locations within the tank. The prescribed h values were then altered to match experimentally obtained temperature-time data at the same locations. The calibration was deemed successful when results from the simulations exhibited match with experimental data within ±2°C for all thermocouples. The calibrated h values were finally used in full-scale 3D simulations and compared to the experimental data to test their accuracy. Predicted 3D results were found to agree with experimental results within the error of the calibration, thereby lending credibility to the overall approach.

Conjugate Heat Transfer in a Rotor-Stator System With Through-Flow

2002 ◽  
Author(s):  
Reby Roy ◽  
B. V. S. S. S. Prasad ◽  
S. Srinivasa Murthy
Keyword(s):  
Heat Transfer ◽  
Boundary Layer Thickness ◽  
Conjugate Heat Transfer ◽  
Rotating Disk ◽  
Thermal Boundary Layer Thickness ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Commercial Code ◽  
Through Flow

The conjugate heat transfer in a stationary cylindrical cavity with a rotating disk and fluid through-flow is analysed at various rotational speeds ranging from 10000 to 50000 rpm by using a finite volume commercial code. The numerical model and code are validated for a problem, which involves rotation and fluid through-flow. A reduction of the thermal boundary layer thickness and increase in the heat transfer coefficients are observed with increase in the rotational speed. Marked differences are noticed between the Nusselt numbers obtained from the conjugate and constant temperature analyses.

Heat Transfer in Rotating Multi-Pass Rectangular Smooth Channel With and Without a Turning Vane in Hub Region

2013 ◽  
Author(s):  
Jiang Lei ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Density Ratio ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
Rotation Numbers ◽  
Smooth Channel ◽  
Turn Region

This paper experimentally investigates the effect of a turning vane on hub region heat transfer in a multi-pass rectangular smooth channel at high rotation numbers. The experimental data were taken in the second and the third passages (Aspect Ratio = 2:1) connected by an 180° U-bend. The flow was radial inward in the second passage and was radial outward after the 180° U-bend in the third passage. The Reynolds number ranged 10,000 to 40,000 while the rotation number ranged 0 to 0.42. The density ratio was a constant of 0.12. Results showed that rotation increases heat transfer on leading surface but decreases it on the trailing surface in the second passage. In the third passage, the effect of rotation is reversed. Without a turning vane, rotation reduces heat transfer substantially on all surfaces in the hub 180° turn region. After adding a half-circle-shaped turning vane, heat transfer coefficients do not change in the second passage (before turn) while they are quite different in the turn region and the third passage (after turn). Regional heat transfer coefficients are correlated with rotation numbers for multi-pass rectangular smooth channel with and without a turning vane.

Performance of One- and Two-Row Tube and Plate Fin Heat Exchangers

1984 ◽  
Vol 106 (3) ◽  
pp. 627-632 ◽  
Author(s):  
E. C. Rosman ◽  
P. Carajilescov ◽  
F. E. M. Saboya
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchangers ◽  
Local Heat Transfer ◽  
Heat Transfer Analysis ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Fin Efficiency ◽  
Heat Transfer Coefficients ◽  
Experimental Apparatus

Heat exchangers consisting of finned tubes are commonly employed in air conditioning systems, air heaters, radiators, etc. Local measurements of mass transfer coefficients on fins, obtained by Saboya and Sparrow, are very nonuniform. In the present work, an experimental apparatus was set up to measure overall heat transfer coefficients for two-row tube and plate fin heat exchangers. The obtained results, together with Shepherd’s results for one-row exchangers, are used to transform the local mass transfer coefficients into local heat transfer coefficients. A numerical two-dimensional heat transfer analysis has been performed in order to obtain the temperature distribution and fin efficiency. The influences of the Reynolds number and fin material are also analyzed.

On the Influence of the Thickness and Thermal Properties of Heating Walls on the Heat Transfer Coefficients in Nucleate Pool Boiling

1975 ◽  
Vol 97 (2) ◽  
pp. 173-178 ◽  
Author(s):  
U. Magrini ◽  
E. Nannei
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Atmospheric Pressure ◽  
Metal Layer ◽  
Pool Boiling ◽  
Transfer Coefficients ◽  
Heating Wall ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient ◽  
Zinc Nickel

An experimental investigation was conducted under conditions of saturated pool boiling of water at atmospheric pressure on thin, horizontal, cylindrical walls of different metals and thicknesses, electrically heated. The heating walls, ranging in thickness from 5 to 250 μm, were obtained by plating copper, silver, zinc, nickel, and tin on nonmetallic rods. Experiments showed that the heat transfer coefficient can be affected, in particular conditions, by the heating wall thickness. In particular, it resulted that the smaller the thermal conductivity of the metal layer, the higher the influence of the thickness. A semiempirical correlation of the form ΔT = (q/A)nf(κd, √κρc) suitable to correlate the experimental data within ±15 percent in the whole range of variables here investigated is proposed.

A New Correlation for Heat Transfer Coefficient Prediction of Supercritical Pressure Water Flowing in Vertical Upward Tubes

2016 ◽  
Author(s):  
Xiangfei Kong ◽  
Huixiong Li ◽  
Changjiang Liao ◽  
Xianliang Lei ◽  
Qian Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Supercritical Pressure ◽  
Good Prediction ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
New Correlation ◽  
Pressure Water ◽  
Supercritical Pressure Water

Supercritical pressure water has been widely used in many industrial fields, such as fossil-fired power plants and nuclear reactors because mainly of its high thermal efficiencies. Although many empirical correlations for heat transfer coefficients of supercritical pressure water have been proposed by different authors based on different experimental data base, there exist remarkable discrepancies between the predicted heat transfer coefficients of different correlations under even the same condition. Heat transfer correlations with good prediction performance are of considerable significance for developing supercritical (ultra-supercritical) pressure boilers and SCWRs. In this paper, the experimental data (about 7389 experimental data points) and 30 existing empirical correlations for heat transfer of supercritical pressure water (SCW) flowing in vertical upward tubes are collected from the open literatures. Evaluations of the prediction performance of the existing correlations are conducted based on the collected experimental data, and a detailed multi-collinearity analysis has been made on different correction factors involved in the existing correlations, and then based on the collected experimental data, a new heat transfer correlation is developed for the supercritical pressure water flowing in vertical upward tubes under normal and enhanced heat transfer mode. Compared with the existing correlations, the new correlation exhibits good prediction accuracy, with a mean absolute deviation (MAD) of 9.63%.

The Correlation of Heat Transfer Coefficients for the Laminar Natural Convection in a Circular Finned-Tube Heat Exchanger

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Hie Chan Kang ◽  
Se-Myong Chang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Laminar Natural Convection

This study proposes an empirical correlation for laminar natural convection applicable to external circular finned-tube heat exchangers with wide range of configuration parameters. The transient temperature response of the heat exchangers was used to obtain the heat transfer coefficient, and the experimental data with their characteristic lengths are discussed. The data lie in the range from 1 to 1000 for Rayleigh numbers based on the fin spacing: the ratio of fin height to tube diameter ranges from 0.1 to 0.9, and the ratio of fin pitch to height ranges from 0.13 to 2.6. Sixteen sets of finned-tube electroplated with nickel–chrome were tested. The convective heat transfer coefficients on the heat exchangers were measured by elimination of the thermal radiation effect from the heat exchanger surfaces. The Nusselt number was correlated with a newly suggested composite curve formula, which converges to the quarter power of the Rayleigh number for a single cylinder case. The proposed characteristic length for the Rayleigh number is the fin pitch while that for the Nusselt number is mean flow length, defined as half the perimeter of the mean radial position inside the flow region bounded by the tube surface and two adjacent fins. The flow is regarded as laminar, which covers heat exchangers from a single horizontal cylinder to infinite parallel disks. Consequently, the result of curve fitting for the experimental data shows the reasonable physical interpretation as well as the good quantitative agreement with the correction factors.

Prediction of Jet Impingement Heat Transfer Using a Hybrid Wall Treatment With Different Turbulent Prandtl Number Functions

1996 ◽  
Vol 118 (3) ◽  
pp. 562-569 ◽  
Author(s):  
G. K. Morris ◽  
S. V. Garimella ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Prandtl Number ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Maximum Deviation ◽  
Turbulent Prandtl Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Numerical Predictions

The local heat transfer coefficient distribution on a square heat source due to a normally impinging, axisymmetric, confined, and submerged liquid jet was computationally investigated. Numerical predictions were made for nozzle diameters of 3.18 and 6.35 mm at several nozzle-to-heat source spacings, with turbulent jet Reynolds numbers ranging from 8500 to 13,000. The commercial finite-volume code FLUENT was used to solve the thermal and flow fields using the standard high-Reynolds number k–ε turbulence model. The converged solution obtained from the code was refined using a post-processing program that incorporated several near-wall models. The role of four alternative turbulent Prandtl number functions on the predicted heat transfer coefficients was investigated. The predicted heat transfer coefficients were compared with previously obtained experimental measurements. The predicted stagnation and average heat transfer coefficients agree with experiments to within a maximum deviation of 16 and 20 percent, respectively. Reasons for the differences between the predicted and measured heat transfer coefficients are discussed.

Theoretical Model for Nucleate Boiling Heat and Mass Transfer of Binary Mixtures

2003 ◽  
Vol 125 (6) ◽  
pp. 1106-1115 ◽  
Author(s):  
Ju¨rgen Kern ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Binary Mixtures ◽  
Phase Interface ◽  
Nucleate Boiling ◽  
Interfacial Thermal Resistance ◽  
Transfer Coefficients ◽  
Total Heat Flow ◽  
Heat Transfer Coefficients ◽  
Liquid Vapor

A model is presented to calculate nucleate boiling heat transfer coefficients of binary mixtures. The model includes the governing physical phenomena, such as the variation of the phase interface curvature, the adhesion pressure between wall and liquid, the interfacial thermal resistance as well as the local variation of composition and liquid-vapor equilibrium. Marangoni convection is considered, too. The theoretical background of these phenomena is described and their implementation is explained. The model is verified by comparing calculated heat transfer coefficients of hydrocarbon mixtures with experimental data. Computational and experimental data are in good agreement. In the examples a considerable amount of the total heat flow passes through a tiny thin film area, called micro region, where the liquid-vapor phase interface is attached to the wall. Very high spatial gradients of heat flux and mixture concentration occur interacting with overall heat transfer performance.

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