Coupling Between Heat and Momentum Transfer Mechanisms for Drag-Reducing Polymer and Surfactant Solutions

1999 ◽  
Vol 121 (4) ◽  
pp. 796-802 ◽  
Author(s):  
G. Aguilar ◽  
K. Gasljevic ◽  
E. F. Matthys
Keyword(s):  
Heat Transfer ◽  
Momentum Transfer ◽  
Direct Coupling ◽  
Surfactant Solutions ◽  
Wide Range ◽  
Momentum And Heat Transfer ◽  
Local Measurements ◽  
Friction Measurements ◽  
Heat And Momentum Transfer ◽  
Transfer Mechanisms

Drag-reducing solutions exhibit simultaneous friction and heat transfer reductions, yet it has been widely believed that there is no direct coupling between the two. In this work, we have conducted a study to re-examine this issue, using measurements of friction and heat transfer over a wide range of flow conditions from onset to asymptotic, various pipe diameters, and several polymer and surfactant solutions. Contrary to some earlier suggestions, our tests show that no decoupling of the momentum and heat transfer mechanisms was seen at the onset of drag reduction, nor upon departure from the asymptotes, but rather that the friction and heat transfer reductions change simultaneously in those regions. For asymptotic surfactant and polymer solutions, the ratio of heat transfer and drag reductions was seen to be constant over a large range of Reynolds numbers, if modified definitions of the reduction parameters are used. In the nonasymptotic region, however, the ratio of heat transfer to drag reductions is higher and is a function of the reduction level, but is approximately the same for polymer and surfactant solutions. This variation is consistent with the concept of a direct coupling through a nonunity constant Prt, as also suggested by our local measurements of temperature and velocity profiles. We also saw that our diameter scaling technique for friction applies equally well to heat transfer. These findings allow us to predict directly the heat transfer from friction measurements or vice versa for these drag-reducing fluids, and also suggest that a strong coupling exists between the heat and momentum transfer mechanisms.

Transport Phenomena Through Gaseous Mixtures in Microchannels

2007 ◽  
Author(s):  
Felix Sharipov
Keyword(s):  
Heat Transfer ◽  
Momentum Transfer ◽  
Couette Flow ◽  
Poiseuille Flow ◽  
Transport Phenomena ◽  
Gaseous Mixture ◽  
Slip Coefficient ◽  
Gaseous Mixtures ◽  
Flow And Heat Transfer ◽  
Heat And Momentum Transfer

In practice, one deals with gaseous mixtures more frequently than with a single gas. However, very few papers about the transport phenomena through a mixture of rarefied gases were published. The aim of this work is to present a general approach to calculations of mass, heat and momentum transfer through gaseous mixtures over the whole range of the gas rarefaction. Results on some classical problems such as slip coefficient, Poiseuille flow, Couette flow and heat transfer are given for a gaseous mixture. A comparison with results corresponding to a single gas is carried out. Such a comparison shows the peculiarities of the transport phenomena in mixtures.

The Effect of Varying Fiber Characteristics on the Simultaneous Measurement of Heat and Momentum Transfer to Flowing Fiber Suspensions

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
S. N. Kazi ◽  
G. G. Duffy ◽  
X. D. Chen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Momentum Transfer ◽  
Pulp Fiber ◽  
Fiber Suspensions ◽  
Experimental Conditions ◽  
Good Correspondence ◽  
Fiber Flexibility ◽  
Heat And Momentum Transfer

Heat transfer and pressure loss measurements were obtained simultaneously for a range of wood pulp fiber suspensions flowing in a pipeline. Data were obtained over a selected range of flow rates and temperatures from a specially built flow loop. It was found that the magnitude of the heat transfer coefficient was above water at equivalent experimental conditions and at very low fiber concentrations, but progressively decreased until it was below water at slightly higher concentrations. Similar trends were obtained for the pressure drop measurements obtained simultaneously, showing good correspondence between the two sets of data. It was found that both heat and momentum transfer are affected in a closely similar way by varying fiber properties, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment, the variation of fibers from different parts of the tree, as well as the different pulping methods used to liberate the fibers from the wood structure. Drag reduction increased and heat transfer coefficient decreased with increasing fiber flexibility as found by previous workers.

scholarly journals The ultimate state of turbulent permeable-channel flow

2021 ◽  
Vol 931 ◽  
Author(s):  
Shingo Motoki ◽  
Kentaro Tsugawa ◽  
Masaki Shimizu ◽  
Genta Kawahara
Keyword(s):  
Heat Transfer ◽  
Momentum Transfer ◽  
Channel Flow ◽  
Large Amplitude ◽  
Large Scale ◽  
Ultimate State ◽  
Local Pressure ◽  
Permeable Channel ◽  
Permeable Walls ◽  
Heat And Momentum Transfer

Direct numerical simulations have been performed for heat and momentum transfer in internally heated turbulent shear flow with constant bulk mean velocity and temperature, $u_{b}$ and $\theta _{b}$ , between parallel, isothermal, no-slip and permeable walls. The wall-normal transpiration velocity on the walls $y=\pm h$ is assumed to be proportional to the local pressure fluctuations, i.e. $v=\pm \beta p/\rho$ (Jiménez et al., J. Fluid Mech., vol. 442, 2001, pp. 89–117). The temperature is supposed to be a passive scalar, and the Prandtl number is set to unity. Turbulent heat and momentum transfer in permeable-channel flow for the dimensionless permeability parameter $\beta u_b=0.5$ has been found to exhibit distinct states depending on the Reynolds number $Re_b=2h u_b/\nu$ . At $Re_{b}\lesssim 10^4$ , the classical Blasius law of the friction coefficient and its similarity to the Stanton number, $St\approx c_{f}\sim Re_{b}^{-1/4}$ , are observed, whereas at $Re_{b}\gtrsim 10^4$ , the so-called ultimate scaling, $St\sim Re_b^0$ and $c_{f}\sim Re_b^0$ , is found. The ultimate state is attributed to the appearance of large-scale intense spanwise rolls with the length scale of $O(h)$ arising from the Kelvin–Helmholtz type of shear-layer instability over the permeable walls. The large-scale rolls can induce large-amplitude velocity fluctuations of $O(u_b)$ as in free shear layers, so that the Taylor dissipation law $\epsilon \sim u_{b}^{3}/h$ (or equivalently $c_{f}\sim Re_b^0$ ) holds. In spite of strong turbulence promotion there is no flow separation, and thus large-amplitude temperature fluctuations of $O(\theta _b)$ can also be induced similarly. As a consequence, the ultimate heat transfer is achieved, i.e. a wall heat flux scales with $u_{b}\theta _{b}$ (or equivalently $St\sim Re_b^0$ ) independent of thermal diffusivity, although the heat transfer on the walls is dominated by thermal conduction.

An Analysis of Heat Transfer for Fully Developed Turbulent Flow in Concentric Annuli

1968 ◽  
Vol 90 (1) ◽  
pp. 43-50 ◽  
Author(s):  
N. W. Wilson ◽  
J. O. Medwell
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Maximum Velocity ◽  
Dimensionless Form ◽  
Temperature Distributions ◽  
Wide Range ◽  
Fully Developed Turbulent Flow ◽  
Heat And Momentum Transfer

The heat and momentum transfer analogy is employed to analyze the heat transfer phenomena for turbulent flow in concentric annuli. A modification of the velocity distribution due to Van Driest is assumed and equations in dimensionless form are developed to predict: (a) the position of maximum velocity in the annulus; (b) the friction factor-Reynolds number relationship, and (c) temperature distributions and heat transfer relations over a wide range of Reynolds number and Prandtl modulus.

Boiling Heat Transfer for Freon R21 in Rectangular Minichannel

2006 ◽  
Author(s):  
V. V. Kuznetsov ◽  
A. S. Shamirzaev
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Patterns ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Modified Model ◽  
Wide Range ◽  
Nucleation Boiling ◽  
The Heat Transfer Coefficient ◽  
Transfer Mechanisms

In this paper we study the boiling heat transfer of upward flow of R21 in a vertical mini-channel with size 1.6×6.3 mm. The heat transfer coefficient was measured as a function of heat flux for a wide range of vapor quality and for two levels of mass flow rate, G = 215 kg/m2s and G = 50 kg/m2s. The temperature dispersions over channel perimeter and in time were calculated. Different heat transfer mechanisms were revealed for different flow patterns. We distinguish the dominant nucleation boiling and the joint mode of nucleation boiling and convective evaporation. We also found the modes when the evaporation of thin liquid films makes the main contribution to heat transfer. The modified model of Liu and Winterton describes the experimental data for the flow patterns when the nucleation boiling and convective transfer make the most contribution to the heat transfer.

Modeling of Intensified Heat Exchangers with Different Fluid Viscosities

2021 ◽  
Vol 628 (6) ◽  
pp. 44-50
Author(s):  
A. G. Laptev ◽  
◽  
E. A. Lapteva ◽  
A. A. Akhmitshin ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mathematical Model ◽  
Heat Exchangers ◽  
Transformer Oil ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Industrial Enterprises ◽  
Wide Range ◽  
Momentum And Heat Transfer

Equations are derived for mean friction and heat transfer coefficients to solve problems of updating industrial plants for getting oil fractions based on application of approximate method of modeling momentum and heat transfer in heat exchangers with surface intensifiers. The Dyssler and Van-Driest turbulent boundary-layer model is used for the turbulent viscosity function for a flat smooth wall. An equation for the Stanton number is written using Chilton-Colborne hydrodynamic analogy and agreement with the known analogy is shown. Identical local properties of turbulent motion in a boundary layer on a plate and in a near-wall layer of a tube and the conservative properties of the laws of friction and heat transfer to turbulences, which are taken account of parametrically, are used for modeling momentum and heat transfer in channels with surface intensifiers. An equation for mean tangential stress in channels with intensifiers and, further, an equation for the Nusselt number is derived using a dissipative model. The results of calculations and comparison with the known experimental investigations are given for tubes with surface wire inserts, with spiral finning and rectangular projections for transformer oil at Reynolds numbers 200 < Re <2000. Thus, the adequacy of the developed mathematical model is proved in a wide range of operating and design parameters and thermophysical properties of fluids and gases. Further, the hydraulic resistance of the channel is the key experimental information about the object of modeling. Examples of use of mathematical model for designing and commissioning heat exchangers in petroleum fuels fractionating plants at industrial enterprises in the Russian Federation and abroad are given.

Some Correlations for Resistances to Heat and Momentum Transfer in the Viscous Sublayer at Rough Walls

1969 ◽  
Vol 91 (4) ◽  
pp. 488-494 ◽  
Author(s):  
N. S. Sood ◽  
V. K. Jonsson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Momentum Transfer ◽  
Three Dimensional ◽  
Viscous Sublayer ◽  
Wall Friction ◽  
Temperature Profiles ◽  
Boundary Layer Equations ◽  
Heat And Momentum Transfer ◽  
Resistance To Heat

Functions for the resistance to heat and momentum transfer in the region near the wall have been defined for flows with various geometries, and correlations from available literature on rough wall friction and heat transfer have been made for these functions. The functions may then be used in the expressions for velocity and temperature profiles to solve the turbulent boundary-layer equations for flows over rough surfaces. Roughnesses such as those formed by machined grooves, piston-rings, wires, and three-dimensional elements have been included in the correlations.

Thermal Transport From a Heated Moving Surface

1986 ◽  
Vol 108 (4) ◽  
pp. 728-733 ◽  
Author(s):  
M. V. Karwe ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Thermal Transport ◽  
Conjugate Problem ◽  
Moving Surface ◽  
Practical Applications ◽  
Thermal Fields ◽  
Heated Body ◽  
Wide Range ◽  
Surface Heat Transfer Coefficient ◽  
Transfer Mechanisms

A numerical and analytical study of the transport process arising due to the movement of a continuous heated body has been carried out. The relevant heat transfer mechanisms are of interest in a wide variety of practical applications, such as continuous casting, extrusion, hot rolling, and crystal growing. The conjugate problem, which involves a coupling between the heat transfer in the moving material and the transport in the fluid, is considered. The thermal fields in the material and in the fluid are computed. The temperature level is found to decay gradually with distance along the moving material, as expected. Results are obtained for a wide range of governing parameters, particularly the Peclet number Pe and the parameter R, which depends on the properties of the fluid and the material. The results obtained are compared with those for the idealized cases of an assumed surface heat transfer coefficient and of a moving isothermal surface. Of particular interest were the nature of the flow generated by the moving surface and the resulting thermal transport. The results obtained are also considered in terms of the underlying physical processes in the problem.

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