scholarly journals The effect of mixed convection on the thermal field of horizontal channel flow

2018 ◽  
Vol 180 ◽  
pp. 02019 ◽  
Author(s):  
Jakub Devera ◽  
Tomáš Hyhlík
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Thermal Field ◽  
Water Film ◽  
Temperature Fields ◽  
Bottom Surface ◽  
Complex Flow ◽  
Transient Behaviour ◽  
Speed Flow ◽  
Simultaneous Heat

An experimental study was conducted to investigate the thermal field of low-speed flow of moistair in a horizontal rectangular duct, uniformly heated from below (Poiseuille–Benard flow). Averaged temperature fields were measured in vertical mid-plane using thermocouples. The buoyancy-induced secondary flow is interacting with forced Poiseuille flow which leads to complex flow behaviour with flow reversal along the top surface. Two types of bottom boundary conditions were examined: aluminium plate (only heat transfer) and water film (simultaneous heat and mass transfer) heated to the same temperature. Presence of mass transfer causes stronger transient behaviour above the bottom surface and enhancing of heat transfer, but the overall character of the thermal field remains the same as in case of heat transfer only.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

Measurements of Flow Modification by Particle Deposition Inside a Packed Bed Using Time-Resolved PIV

2008 ◽  
Author(s):  
Elvis E. Dominguez-Ontiveros ◽  
Carlos Estrada-Perez ◽  
Yassin A. Hassan
Keyword(s):  
Heat Transfer ◽  
Velocity Field ◽  
Flow Structure ◽  
Particle Deposition ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Temperature Fields ◽  
Complex Flow ◽  
Flow Modification ◽  
Complex Flow Structure

In the Advanced Gas Cooled Pebble Bed Reactors for nuclear power generation, the fuel is spherical coated particles. The energy transfer phenomenon requires detailed understanding of the flow and temperature fields around the spherical fuel pebbles. Detailed information of the complex flow structure within the bed is needed. Generally, for computing the flow through a packed bed reactor or column, the porous media approach is usually used with lumped parameters for hydrodynamic calculations and heat transfer. While this approach can be reasonable for calculating integral flow quantities, it may not provide all the detailed information of the heat transfer and complex flow structure within the bed. The present experimental study presents the full velocity field using particle image velocity technique (PTV) in a conjunction with matched refractive index fluid with the pebbles to achieve optical access. Velocity field measurements are presented delineating the complex flow structure.

Enhancement of Combined Heat and Mass Transfer in a Vertical-Tube Heat and Mass Exchanger

1986 ◽  
Vol 108 (1) ◽  
pp. 70-75 ◽  
Author(s):  
R. L. Webb ◽  
H. Perez-Blanco
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Mass Transfer ◽  
Water Film ◽  
Vertical Tube ◽  
Transfer Coefficients ◽  
Interface Heat Transfer ◽  
Friction Performance ◽  
Predicted Values

This paper studies enhancement of heat and mass transfer between a countercurrent, gravity-drained water film and air flowing in a vertical tube. The enhancement technique employed is spaced, transverse wires placed in the air boundary layer, near the air-water interface. Heat transfer correlations for turbulent, single-phase heat transfer in pipes having wall-attached spaced ribs are used to select the preferred wire diameter, and to predict the gas phase heat and mass transfer coefficients. Tests were run with two different radial placements of the rib roughness: (1) at the free surface of the liquid film, and (2) the base of the roughness displaced 0.51 mm into the air flow. The authors hypothesize that the best heat/mass transfer and friction performance will be obtained with the roughness at the surface of the water film. Experiments conducted with both roughness placements show that the authors’ hypothesis is correct. The measured heat/mass transfer enhancement agreed very closely with the predicted values. A unique feature of the enhancement concept is that it does not require surface wetting of the enhancement device to provide enhancement.

Simultaneous Heat and Mass Transfer From a Two-Dimensional, Partially Liquid-Covered Surface

1991 ◽  
Vol 113 (4) ◽  
pp. 874-882 ◽  
Author(s):  
Y.-X. Tao ◽  
M. Kaviany
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Surface Temperature ◽  
Heat And Mass Transfer ◽  
Solid Surface ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Ambient Air ◽  
Simultaneous Heat

Simultaneous heat and mass transfer from partially liquid-covered surfaces is examined experimentally using a surface made of cylinders with the voids filled with liquid. The steady-state evaporation rate, surface temperature of the liquid and exposed solid, and location of meniscus are measured for various ambient air velocities and temperatures. Using these, we examine the effect of the extent to which the liquid covers the surface on the evaporation mass transfer rate resulting from the convective heat transfer from the ambient gas to this surface. The results show strong Bond and Reynolds number effects. For small Bond and Reynolds numbers, the presence of dry (exposed solid) surface does not influence the mass transfer rate. As the Bond or Reynolds number increases, a critical liquid coverage is found below which the mass transfer begins to decrease. Heat transfer from the exposed solid to the liquid is also examined using the measured surface temperature, a conduction model, and an estimate of the liquid and solid surface areas (using a static formation for the liquid meniscus). The results show that at the liquid surface an analogy between heat and mass transfer does not exist.

The CFD Simulation and Experimental Study of the Plate-Type Evaporative Condenser

2008 ◽  
Author(s):  
Dongsheng Zhu ◽  
Yuanxi Li ◽  
Jingwei Zhang ◽  
Xiang Jiang
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Experimental Study ◽  
Cfd Simulation ◽  
Water Film ◽  
Enhanced Heat Transfer ◽  
Air Velocity ◽  
Two Phase ◽  
Fluent Software ◽  
Plate Type

This paper presents a simulation of two operations—upwind, downwind with two-phase flowing in the plate bundles of the plate-type evaporative condenser, by means of the FLUENT software, which provide a direct illustration of the influence of the water film flowing on spray water flow, air velocity, air direction in the plate bundles. The result of simulation demonstrates the advantages of air-water parallel-flow over countercurrent in making use of enhanced heat transfer and mass transfer of fluid film.

Heat and mass transfer in rectification of binary mixtures at turbulent vapour flow

1983 ◽  
Vol 48 (7) ◽  
pp. 1820-1828 ◽  
Author(s):  
Václav Kolář ◽  
Jan Červenka
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Binary Mixtures ◽  
Reflux Ratio ◽  
Hydrodynamic Conditions ◽  
Transfer Coefficients ◽  
Mass Transfer Mechanism ◽  
Simultaneous Heat ◽  
Theoretical Results

Theoretical analysis of the heat and mass transfer mechanism in rectification of binary mixtures was made at the use of earlier obtained relations for the heat and mass transfer coefficients. Theoretical results were applied to the mixture methanol-water and have revealed that the effect of simultaneous heat transfer on mass transfer is insignificant and is little affected by both the reflux ratio and hydrodynamic conditions.

Simultaneous Heat and Mass Transfer in Inclined Channel With Asymmetrical Conditions

2010 ◽  
Author(s):  
Othmane Oulaid ◽  
Brahim Benhamou ◽  
Nicolas Galanis
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Mass Fraction ◽  
Numerical Study ◽  
Water Film ◽  
Ambient Air ◽  
The Body ◽  
Parallel Plates ◽  
Inclined Channel ◽  
Simultaneous Heat

This work deals with a numerical study of simultaneous heat and mass transfer with phase change in an inclined channel formed by two parallel plates. The lower one is covered by a thin liquid water film and the upper one is considered impermeable. The plates are maintained at a constant temperature TW. Ambient air with uniform dry bulb temperature Tin and relative humidity φin enters the channel with a uniform upward velocity Uin. The liquid film is assumed to be extremely thin and its temperature is equal to the wall temperature. Steady state conditions are considered and the flow is assumed to be laminar. Viscous dissipation, radiation heat transfer and other secondary effects (pressure work, energy transport by the inter-diffusion of species, Dufour and Soret effects) are neglected. The physical properties are taken constant except for the density in the body forces, which is considered to be a linear function of temperature and mass fraction. Results show that buoyancy forces have an important effect on the hydrodynamic, thermal and mass fraction fields and this effect depends on the channel inclination. A flow reversal chart and analytical correlations for the corresponding critical values of the thermal and solutal Grashof numbers are presented for different channel inclinations.

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