Screening and Correlating Data on Heat Transfer to Fluids at Supercritical Pressure

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
J. Derek Jackson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convection Heat Transfer ◽  
Correlated Data ◽  
Supercritical Pressure ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Convection Heat ◽  
Fluid Properties ◽  
Ratio Correction

A simple criterion for screening experimental data on turbulent heat transfer in vertical tubes to identify those not significantly influenced by buoyancy was proposed by the author many years ago and found to work quite well for water and air at normal pressures. However, it was recognized even then that the ideas on which the criterion was based were too simplistic to be suitable for use in the case of fluids at supercritical pressure. With the passage of time and tremendous advancement in data processing capability using present-day computers, it is now possible to contemplate adopting a refined approach specifically designed to be suitable for such fluids. The present paper describes a semi-empirical model of buoyancy-influenced heat transfer to fluids at supercritical pressure, which takes careful account of nonuniformity of fluid properties. It provides a criterion for determining the conditions under which buoyancy influences are negligibly small. Thus, the extensive databases now available on heat transfer to fluids at supercritical pressure can be reliably screened to eliminate those affected by such influences. Then, the many correlation equations that have been proposed for forced convection heat transfer can be evaluated in a reliable manner. These equations mostly relate Nusselt number to Reynolds number, Prandtl number, and simple property ratio correction terms. Thus, they should be evaluated using only experimental data that are definitely not influenced by buoyancy. A further outcome of the present paper is that it might now prove possible to correlate the buoyancy-influenced data in such databases and fit the equation for mixed convection heat transfer yielded by the model to the correlated data. If this can be done, it will represent a major advancement in terms of providing thermal analysts with a valuable new tool.

Influence on Convection Heat Transfer of Unsteady Flow in a Tube

2010 ◽  
Author(s):  
Lei Chen
Keyword(s):  
Heat Transfer ◽  
Thermophysical Properties ◽  
Convection Heat Transfer ◽  
Turbulent Heat Transfer ◽  
Transfer Model ◽  
Turbulent Heat ◽  
Convection Heat ◽  
Transient Effects ◽  
Basic Features ◽  
Temperature Factors

Turbulent convection heat transfer with monotonously time-increasing mass flux in a tube with consideration of variable thermophysical properties was investigated numerically. The turbulent heat transfer model was based on the equation of eddy shear stress and for unsteady process. The numerical calculations were compared with experimental data. It is shown that the basic features of the processes discussed in the present paper are the same as for the fluids with constant properties investigated earlier. However variable thermophysical properties increase the transient effects especially at high temperature factors.

Turbulent Heat Transfer in a Revolving Square-Sectioned Tube

1980 ◽  
Vol 22 (2) ◽  
pp. 95-101 ◽  
Author(s):  
W. D. Morris ◽  
F. M. Dias
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Turbulent Heat Transfer ◽  
Electrical Machine ◽  
Turbulent Heat ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Parallel Axis ◽  
Correlating Equation

An investigation of turbulent heat transfer in a revolving square-sectioned tube is reported in this paper. It is demonstrated that rotation about a parallel axis enhances the customary forced convection heat transfer, and a correlating equation for assessing this effect is proposed. The range of parameters covered in the experiments permit the results to have application for the assessment of heat transfer in certain gas-cooled electrical machine rotors.

scholarly journals FRACTAL-STRUCTURAL ANALYSIS OF CONVECTION HEAT TRANSFER IN A TURBULENT MEDIUM

2020 ◽  
Vol 17 (2) ◽  
pp. 61-68
Author(s):  
A.Zh. Turmukhambetov ◽  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Structural Analysis ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Convective Heat Exchange ◽  
Spherical Body ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat

The features of convective heat transfer of bodies in a turbulent environment are considered. The results of experimental research by one of the authors are discussed. Experimental data show that the heat transfer of a spherical body is affected by natural convection, the thermo-physical properties of the medium, the tightness of the flow, the turbulent flow regime, etc. Due to these factors, the formula for calculating convective heat transfer, which includes many experimental constants, becomes cumbersome and inconvenient for practical application. The paper presents the results of applying fractal-structural analysis methods to describe experimental data on convective heat exchange of badly streamlined (cylinder and sphere) bodies in a channel. Quantitative relations are obtained that link the intensity of turbulent heat transfer with the criteria for the degree of self-organization.

Simulation of mixed convection heat transfer to carbon dioxide at supercritical pressure

2004 ◽  
Vol 218 (11) ◽  
pp. 1281-1296 ◽  
Author(s):  
S He ◽  
W S Kim ◽  
P X Jiang ◽  
J D Jackson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Carbon Dioxide ◽  
Mixed Convection ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Supercritical Pressure ◽  
Convection Heat ◽  
Computational Simulations ◽  
Mixed Convection Heat Transfer

Computational simulations of turbulent mixed convection heat transfer experiments using carbon dioxide at supercritical pressure have been performed by solving the Reynolds averaged transport equations using an elliptic formulation. A number of two-equation low Reynolds number turbulence models have been used and the results have been compared directly with the experimental data. It has been shown that most of the models were to some extent able to reproduce the effects of the very strong influences of buoyancy on heat transfer in these experiments. However, the performance of the models varied significantly from one to another in terms of the predicted onset of such effects.

Deteriorated turbulent heat transfer (DTHT) of gas up-flow in a circular tube: Experimental data

2008 ◽  
Vol 51 (13-14) ◽  
pp. 3259-3266 ◽  
Author(s):  
J.I. Lee ◽  
P. Hejzlar ◽  
P. Saha ◽  
P. Stahle ◽  
M.S. Kazimi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Circular Tube ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat

scholarly journals 3D Numerical simulation of turbulent heat transfer and Fe3O4/nanofluid annular flow in sudden enlargement

2021 ◽  
Vol 321 ◽  
pp. 04014
Author(s):  
Hussein Togun
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transport ◽  
Annular Flow ◽  
Volume Concentration ◽  
Convection Heat Transfer ◽  
Turbulent Heat Transfer ◽  
Recirculation Region ◽  
Convection Heat

In this paper, 3D Simulation of turbulent Fe3O4/Nanofluid annular flow and heat transfer in sudden expansion are presented. k-ε turbulence standard model and FVM are applied with Reynolds number different from 20000 to 50000, enlargement ratio (ER) varied 1.25, 1.67, and 2, , and volume concentration of Fe3O4/Nanofluid ranging from 0 to 2% at constant heat flux of 4000 W/m2. The main significant effect on surface Nusselt number found by increases in volume concentration of Fe3O4/Nanofluid for all cases because of nanoparticles heat transport in normal fluid as produced increases in convection heat transfer. Also the results showed that suddenly increment in Nusselt number happened after the abrupt enlargement and reach to maximum value then reduction to the exit passage flow due to recirculation flow as created. Moreover the size of recirculation region enlarged with the rise in enlargement ratio and Reynolds number. Increase of volume Fe3O4/nanofluid enhances the Nusselt number due to nanoparticles heat transport in base fluid which raises the convection heat transfer. Increase of Reynolds number was observed with increased Nusselt number and maximum thermal performance was found with enlargement ratio of (ER=2) and 2% of volume concentration of Fe3O4/nanofluid. Further increases in Reynolds number and enlargement ratio found lead to reductions in static pressure.

Forced Convection Heat Transfer of Nanofluids: A Review

2017 ◽  
Author(s):  
Aditya Kuchibhotla ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat

Stable homogeneous colloidal suspensions of nanoparticles in a liquid solvents are termed as nanofluids. In this review the results for the forced convection heat transfer of nanofluids are gleaned from the literature reports. This study attempts to evaluate the experimental data in the literature for the efficacy of employing nanofluids as heat transfer fluids (HTF) and for Thermal Energy Storage (TES). The efficacy of nanofluids for improving the performance of compact heat exchangers were also explored. In addition to thermal conductivity and specific heat capacity the rheological behavior of nanofluids also play a significant role for various applications. The material properties of nanofluids are highly sensitive to small variations in synthesis protocols. Hence the scope of this review encompassed various sub-topics including: synthesis protocols for nanofluids, materials characterization, thermo-physical properties (thermal conductivity, viscosity, specific heat capacity), pressure drop and heat transfer coefficients under forced convection conditions. The measured values of heat transfer coefficient of the nanofluids varies with testing configuration i.e. flow regime, boundary condition and geometry. Furthermore, a review of the reported results on the effects of particle concentration, size, temperature is presented in this study. A brief discussion on the pros and cons of various models in the literature is also performed — especially pertaining to the reports on the anomalous enhancement in heat transfer coefficient of nanofluids. Furthermore, the experimental data in the literature indicate that the enhancement observed in heat transfer coefficient is incongruous compared to the level of thermal conductivity enhancement obtained in these studies. Plausible explanations for this incongruous behavior is explored in this review. A brief discussion on the applicability of conventional single phase convection correlations based on Newtonian rheological models for predicting the heat transfer characteristics of the nanofluids is also explored in this review (especially considering that nanofluids often display non-Newtonian rheology). Validity of various correlations reported in the literature that were developed from experiments, is also explored in this review. These comparisons were performed as a function of various parameters, such as, for the same mass flow rate, Reynolds number, mass averaged velocity and pumping power.

Sign in / Sign up

Export Citation Format

Share Document