A study of electroconvection in the presence of a gravitational field

1996 ◽  
Vol 74 (9-10) ◽  
pp. 568-579
Author(s):  
M. F. Haque ◽  
Sigurds Arajs
Keyword(s):  
Heat Transfer ◽  
Gravitational Field ◽  
Electric Fields ◽  
Colloidal Suspension ◽  
Empirical Correlation ◽  
Distilled Water ◽  
Correlation Relation ◽  
Transfer Data ◽  
Rayleigh Numbers ◽  
Ac Fields

Measurements were made of the electroconvective heat transfer coefficient in gases (Ar, O2, N2O, and Freon-22); liquid (distilled water); and a colloidal suspension (α-Fe2O3 in distilled water) from a single Pt wire (diameter = 0.025 mm) mounted along the axis of a Cu cylinder (diameter = 53 mm). The measurements were carried out as functions of electric fields (dc and ac) and pressure in the Earth's gravitational field. The measurements reveal a complicated interaction between the electric-field gradient and thermal convection. Measured heat-transfer data are correlated by dimensional analysis. The data are compared with the empirical correlation relation and analytical expression and are well correlated over the range of Rayleigh numbers from 1.2 × 107 to 4.5 × 108. An empirical correlation relation has, also been proposed to evaluate the efficiency of convection and the results for dc and ac fields are presented.

On free convection experiments in inclined air layers heated from below

1980 ◽  
Vol 96 (3) ◽  
pp. 461-479 ◽  
Author(s):  
Douglas W. Ruth ◽  
K. G. T. Hollands ◽  
G. D. Raithby
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Convective Motion ◽  
Secondary Transition ◽  
Transfer Data ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Air Layers ◽  
Rayleigh Numbers ◽  
Theory And Experiment

The heat transfer and free convective motion, in inclined air layers heated from below, for angles of incidence 0 [les ] ϕ [les ] 30°, and Rayleigh numbers 100 < Ra cos ϕ < 10000, are studied experimentally. Results of both heat-transfer measurements and flow-visualization studies are reported. The purpose of the study was to investigate the fact, first noted by Hollands et al. (1976), that the experimental heat-transfer data, for ϕ > 20°, is not a function of the product Ra cos ϕ only, as expected from theoretical consideration. This discrepancy between theory and experiment is here attributed to a hypothesized secondary transition in the convective motion, due primarily to perturbation velocities in the upslope direction. This secondary transition appears to be the same as that predicted theoretically by Clever & Busse (1977); qualitative agreement with their theory is observed.

Electrohydrodynamic Condensation Heat Transfer

1968 ◽  
Vol 90 (1) ◽  
pp. 98-102 ◽  
Author(s):  
H. Y. Choi
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Liquid Film ◽  
Electric Fields ◽  
Vertical Tube ◽  
Condensation Heat Transfer ◽  
Instability Waves ◽  
Condensing Heat Transfer ◽  
Electrohydrodynamic Force ◽  
Rayleigh Numbers

This paper describes the results of an investigation of the effects of strong electric fields on condensation heat transfer. Freon-113 is condensed inside a vertical tube, and the condensate interface is stressed by a radial d-c field. The effect of the field on condensing heat transfer can be summarized as follows: (a) The condensing heat transfer coefficient increases significantly with the electric field; (b) the increase is related to the appearance of instability waves at the liquid film interface. These effects suggest that the average liquid film thickness is significantly reduced at high electric field intensities. A tentative correlation is presented for the high field data. The correlation is presented in terms of modified Nusselt and Rayleigh numbers in which the characteristic length is the most unstable wavelength in the system, and the driving force acting on the film is an equivalent electrohydrodynamic force.

WAVE CHARACTERISTICS OF LIQUID FILMS - CORRELATION OF HEAT TRANSFER DATA WITH VISUAL OBSERVATIONS

Equipment ◽  
2006 ◽  
Author(s):  
C. Philipp ◽  
A. Doeg ◽  
S. Kufaas Tellefsen ◽  
U. Gross
Keyword(s):  
Heat Transfer ◽  
Liquid Films ◽  
Transfer Data ◽  
Wave Characteristics ◽  
Visual Observations

Film boiling heat transfer on a completely wettable surface with atmospheric saturated distilled water quenching

2016 ◽  
Vol 93 ◽  
pp. 67-74 ◽  
Author(s):  
Jun-young Kang ◽  
Seol Ha Kim ◽  
HangJin Jo ◽  
Gunyeop Park ◽  
Ho Seon Ahn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Water Quenching ◽  
Film Boiling ◽  
Distilled Water

Effect of Insulated/Uninsulated Channel Walls on Heat Transfer From a Horizontal Finned Tube in a Vertical Channel

1987 ◽  
Vol 109 (2) ◽  
pp. 388-391 ◽  
Author(s):  
E. M. Sparrow ◽  
M. A. Ansari
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Vertical Channel ◽  
Finned Tube ◽  
Radiation Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Metallic Sheet ◽  
Rayleigh Numbers ◽  
Metal Wall

Measurements were made of the combined natural convection and radiation heat transfer from a horizontal finned tube situated in a vertical channel open at the top and bottom. In one set of experiments, both walls of the channel were heavily insulated, while in a second set of experiments, one of the insulated walls was replaced by an uninsulated metallic sheet. In general, the heat transfer coefficients were found to be lower with the metal wall in place, but only moderately. With the finned tube situated at the bottom of the channel, the differences in the heat transfer coefficients corresponding to the two types of walls were only a few percent. When the tube was positioned at the mid-height of the channel, larger differences were encountered, but in the practical range of Rayleigh numbers, the differences did not exceed 5 percent.

scholarly journals The Single-Blow Problem Including the Effects of Longitudinal Conduction

1964 ◽  
Author(s):  
C. P. Howard
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Conduction ◽  
Transient Behavior ◽  
Step Change ◽  
Graphical Form ◽  
Compact Heat Exchanger ◽  
Fluid Temperature ◽  
Transfer Data ◽  
Method Of Calculation

The results are presented from a numerical finite-difference method of calculation for the transient behavior of porous media when subjected to a step change in fluid temperature considering the case where the longitudinal thermal heat conduction cannot be neglected. These results, given in tabular and graphical form, provide a useful means for evaluating the heat-transfer data obtained from the transient testing of compact heat-exchanger surfaces.

Heat and Mass Transfer in an Incompressible Turbulent Boundary Layer

1972 ◽  
Vol 94 (1) ◽  
pp. 23-28 ◽  
Author(s):  
E. Brundrett ◽  
W. B. Nicoll ◽  
A. B. Strong
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Porous Plate ◽  
Mixing Length ◽  
Two Dimensional ◽  
Transfer Data ◽  
Incompressible Turbulent Boundary Layer ◽  
Wide Range ◽  
Incompressible Boundary

The van Driest damped mixing length has been extended to account for the effects of mass transfer through a porous plate into a turbulent, two-dimensional incompressible boundary layer. The present mixing length is continuous from the wall through to the inner-law region of the flow, and although empirical, has been shown to predict wall shear stress and heat transfer data for a wide range of blowing rates.

Analysis of disagreement between numerically predicted and experimental heat transfer data of impinging jet

2006 ◽  
Vol 13 (5) ◽  
pp. 486-490 ◽  
Author(s):  
Ping Zhou ◽  
Liang-chun Ye ◽  
Jie-min Zhou ◽  
Ying Yang
Keyword(s):  
Heat Transfer ◽  
Impinging Jet ◽  
Transfer Data ◽  
Experimental Heat ◽  
Experimental Heat Transfer
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