Characteristics of heat transfer during the turbulent flow of supercritical helium

Results are shown of an experimental study concerning the heat transfer during the turbulent flow of supercritical helium through small tubes, as a function of the pressure, the temperature, the velocity, and the thermal flux density.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 5, pp. 814–819, November, 1972.     

A pumped supercritical helium flow loop for heat transfer studies

The construction and operation of a flow loop is described in which a 0.5 ls^? centrifugal pump circulates supercritical helium through a 1 m long, 18 mm id heated test section instrumented with 18 carbon resistance thermometers. Based on the heat transfer measurements obtained (published in detail elsewhere) some observations are made on deviations from the standard Dittus Boelter heat transfer correlation caused by helium's variable properties, and on possible buoyancy induced reductions in heat transfer particularly for radially inward flow in rotating machines.     

Numerical study of flow and heat transfer of superfluid helium in capillary channels

A modified two-fluid model is adopted to study flow and heat transfer of superfluid helium in a microchannel with a diameter as small as that of a superleak in a fountain effect pump. Variable properties of superfluid helium and energy dissipations due to the two-fluid mutual friction and the friction at the channel wall are fully taken into consideration. It is found that the normal fluid component flow is not trivial even in a channel with diameter of a micrometre, and that there exists an optimum diameter for the maximum mass flow rate. The flow of superfluid helium through a channel with different temperatures at the ends differs considerably from that of a Newtonian fluid. The strong dependence of the thermodynamic properties on temperature and pressure, as well as the internal-convection mechanism are found to be the causes of the unique flows.     

Pseudoboiling and heat transfer in a turbulent flow

Experimental data characterizing the onset of pseudoboiling in relation to flow rate, pressure, and tube diameter are presented for diisopropylcyclohexane (DICH).     

Simulation of turbulent heat transfer in application to natural-convection wall flow

As a result of analysis of experimental data for developed turbulent natural-convection flow on a vertical heated plate, algebraic models are suggested of turbulent thermal diffusivity and turbulent viscosity for the inner and outer regions. The parameters of the models are determined by comparing the experimental data with the results of calculations using the equations of natural-convection boundary layer. Relevant approximations are given in the form of functions of the value of the ratio between the thermal and dynamic scales of velocity. Comparison is made of the experimentally obtained and calculated profiles of temperature and velocity in the neighborhood of the wall. As a result of calculations using the suggested model, the inference is made of the need to use the model of turbulent temperature diffusivity in problems of this class along with the model of turbulent viscosity.     

Rough estimate of the heat transfer coefficient in laminar and in turbulent flow through flat channels

Approximate formulas are proposed for estimating the coefficient of convective heat transfer in laminar and in turbulent flow at the entrance to a flat channel.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 4, pp. 612–617, October, 1972.     

Applicability of various correlations for the prediction of turbulent heat transfer of supercritical helium

The workability of six heat transfer correlations for turbulent pipe flows of supercritical liquids when used for supercritical helium is tested by comparisons with reference experimental data. It is recommended to use for nonitteration heat transfer prediction in the cases of 1st kind (a given T_wJ and 2nd kind (a given q_w) boundary conditions, the correlations of ENIN and the correlation of Petukhov et al. respectively.     

Flow and heat transfer of finely dispersed turbulent flows in channels

Equations for the second moments of the velocity and temperature fluctuations are used to study the effect of particles on the rate of turbulent momentum and heat transfer in the flow of a gas suspension in circular pipes.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 740–751, November, 1987.     

On the transient heat transfer in liquid helium in narrow horizontal channels

The results of an experimental investigation into transient heat transfer from a horizontal flat copper strip surface both to an opened volume of liquid helium and to different crosssection cooling channels placed below the heated surface are given. The copper strip of 0.2 mm thickness is heated by passing the electrical current through it. The temperature in the centre of the strip is measured by a copper-iron versus copper thermocouple. The thermocouple junction to be measured is placed into the vacuum.     

Heat transfer to near-critical helium in horizontal channels

Experimental results on heat transfer and pressure losses during a forced motion of helium of near-critical state parameters in a horizontal channel are reported. A method of calculation of temperature and pressure distributions along the channel is proposed.     

Fluid flow and heat transfer in horizontal wavy channels

Summary The equations governing the fluid flow and heat transfer have been solved subject to the relevant boundary conditions by assuming that the solution consists of two parts: a mean part and a perturbed part. To obtain the perturbed part of the solution, use has been made of the long-wave approximation. The mean part of the solution has been found to be in good agreement with that of the plane Poiseuille flow. The perturbed part of the solution is the contribution from the waviness of the walls. The mean part, the perturbed part and the total solution of the problem have been evaluated numerically for several sets of values of the parameters. Certain qualitatively interesting properties of the fluid flow and heat transfer, along with the changes in the fluid pressure on the wavy walls, are recorded in § § 5 and 6.

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Strömung und Wärmeübergang in horizontalen, welligen Kanälen

Zusammenfassung Die Grundgleichungen des Problems werden für das Stromfeld und den Wärmeübergang unter den gegebenen Randbedingungen gelöst. Dabei wird angenommen, daß die Lösung aus zwei Anteilen besteht: einem Mittelwert und den Störgrößen. Der Störanteil wird ermittelt durch eine Approximation im Sinne langer Wellen. Der Mittelwert des Stromfeldes stimmt gut mit der ebenen Poiseuille-Strömung überein. Der Störanteil rührt von der Welligkeit der Wände her. Die Gesamtströmung wurde numerisch für zahlreiche Werte der eingehenden Parameter bestimmt. Zahlreiche interessante Eigenschaften der Strömungsgrößen sowie des Wärmeüberganges sowie der Druckverteilung längs der welligen Wand werden in § § 5 und 6 besprochen.

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With 12 Figures     

Entrance section heat transfer in flow of helium at supercritical pressure

It is shown that heat transfer in the entrance section depends on the flow parameters (inlet pressure and temperature), distance from the inlet, and gas heating level.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 4, pp. 546–551, April, 1985.     

Prediction of friction and heat transfer for viscoelastic fluids in turbulent pipe flow

Experimental measurements of the friction factor and the dimensionless heat-transfer j-factor were carried out for the turbulent pipe flow of viscoelastic aqueous solutions of polyacrylamide. The studies covered a wide range of variables including polymer concentration, polymer and solvent chemistry, pipe diameter, and flow rate. Degradation effects were also studied. It is concluded that the friction factor and the dimensionless heat transfer are functions only of the Reynolds number, the Weissenberg number, and the dimensionless distance, provided that the rheology of the flowing fluid is used.Nomenclature cp Specific heat of fluid, J · kg^–1 · K^–1 - d Diameter of tube, m - f Fanning friction factor, _w/(V²/2) - h Convective heat-transfer coefficient, q _w(T _w{T _b), W · m^–2 · K^–1 - k Thermal conductivity of fluid, W · m^–1 · K^–1 - j _H Heat-transfer j-factor, StPr _a ^2/3 - L _e Entrance length, m - Nu Nusselt number, hd/k - Pr _a Prandtl number based on apparent viscosity at the wall, c _p/k - q _w Heat flux at the wall, W · m^–2 - Re _a Reynolds number based on apparent viscosity at the wall, Vd/ - St Stanton number, Nu/(Re _a Pr _a) - T Temperature, K - T _b Bulk temperature of fluid, K - T _w Inside-wall temperature, K - V Average velocity, m · s^–1 - Ws Weissenberg number, V/d - x Axial coordinate, m Greek symbols g Shear rate, s^–1 - Apparent viscosity evaluated at the wall, P⁵ - ₀ Zero shear-rate viscosity, P⁵ - Apparent viscosity at infinite shear rate, P⁵ - Characteristic time of fluid, s - Density of fluid, kg · m^–3 - _w Wall shear stress, N · m^–2 Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Investigation of turbulent heat transfer and nanofluid flow in a double pipe heat exchanger

In present study, heat transfer and turbulent flow of water/alumina nanofluid in a parallel as well as counter flow double pipe heat exchanger have been investigated. The governing equations have been solved using an in-house FORTRAN code, based on finite volume method. Single-phase and standard k-ε models have been used for nanofluid and turbulent modeling, respectively. The internal fluid has been considered as hot fluid (nanofluid) and the external fluid, cold fluid (base fluid). The effects of nanoparticles volume fraction, flow direction and Reynolds number on base fluid, nanofluid and wall temperatures, thermal efficiency, Nusselt number and convection heat transfer coefficient have been studied. The results indicated that increasing the nanoparticles volume fraction or Reynolds number causes enhancement of Nusselt number and convection heat transfer coefficient. Maximum rate of average Nusselt number and thermal efficiency enhancement are 32.7% and 30%, respectively. Also, by nanoparticles volume fraction increment, the outlet temperature of fluid and wall temperature increase. Study the minimum temperature in the solid wall of heat exchangers, it can be observed that the minimum temperature in counter flow has significantly reduced, compared to parallel flow. However, by increasing Reynolds number, the slope of thermal efficiency enhancement of heat exchanger gradually tends to a constant amount. This behavior is more obvious in parallel flow heat exchangers. Therefore, using of counter flow heat exchangers is recommended in higher Reynolds numbers.     

Heat and mass transfer for turbulent flow of chemically reacting gas in eccentric annular channels

An algorithm is proposed for calculating the velocity, temperature, and concentration fields under conditions of cooling of a cylindrical heat-releasing rod, placed off-center in a circular casing pipe, by a longitudinal flow of chemically reacting gas [N₂O₄].Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 2, pp. 186–191, August, 1987.     

Properties of nonsteady-state heat transfer to superfluid helium

Results are presented from an experimental study of heat transfer from a cylindrical specimen to a volume of superfluid helium with thermal loading in the form of an impulsive step. Unique features of He II as a cooling agent as compared to He I are noted and discussed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 6, pp. 950–956, June, 1988.     

Skin friction and heat transfer in turbulent flow of structurally viscous fluids

Relations which contain no new empirical turbulence constants are proposed for calculation of the resistance coefficient and the Nusselt number in turbulent flow of structurally viscous fluids.     

Direct numerical simulation of turbulent heat transfer modulation in micro-dispersed channel flow

Summary The objective of this paper is to study the influence of dispersed micrometer size particles on turbulent heat transfer mechanisms in wall-bounded flows. The strategic target of the current research is to set up a methodology to size and design new-concept heat transfer fluids with properties given by those of the base fluid modulated by the presence of dynamically-interacting, suitably-chosen, discrete micro- and nano-particles. We ran direct numerical simulations for hydrodynamically fully developed, thermally developing turbulent channel flow at shear Reynolds number Re _τ = 150 and Prandtl number Pr = 3, and we tracked two large swarms of particles, characterized by different inertia and thermal inertia. Preliminary results on velocity and temperature statistics for both phases show that, with respect to single-phase flow, heat transfer fluxes at the walls increase by roughly 2% when the flow is laden with the smaller particles, which exhibit a rather persistent stability against non-homogeneous distribution and near-wall concentration. An opposite trend (slight heat transfer flux decrease) is observed when the larger particles are dispersed into the flow. These results are consistent with previous experimental findings and are discussed in the frame of the current research activities in the field. Future developments are also outlined. Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday It is our great pleasure to take part in this Festschrift Issue dedicated to the celebration of the 70th birthday of Professor Franz Ziegler. To honour his activity and his scientific achievements, we prepared this paper, crafted with friendship and respect. We wish Franz many more productive, enjoyable and happy years and a solid and long collaboration as Editors of Acta Mechanica.