Heat Transfer in Two-Component Dispersed Flow

1981 ◽  
Vol 103 (2) ◽  
pp. 300-306 ◽  
Author(s):  
K. Mastanaiah ◽  
E. N. Ganic´
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Gas Flow ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Two Phase ◽  
Dispersed Flow ◽  
Wall Superheat ◽  
Two Phase Heat Transfer ◽  
Thermal Entrance

Measurements have been made of heat transfer near atmospheric pressure in the post dryout region of air-water dispersed flow in an electrically heated 12.95 mm i.d. vertical stainless steel tube with a length of 889 mm. The mass velocity ranges from 30 to 83 kg/m2·s, and the average wall heat flux is varied from 6.4 to 36.2 kW/m2 in the experiments. Correlation of a theoretical analysis with the measured wall temperatures suggests that the effectiveness of wall-to-drop heat transfer depends mainly on the wall superheat for surface temperatures below the minimum film boiling temperature. The local two-phase heat transfer coefficient decreases with increasing wall temperature. It is also found that the thermal entrance length for two-phase dispersed flow exceeds that of the single-phase gas flow, and that it decreases with an increase in wall temperature.

Evaporation of Ammonia in a Smooth Horizontal Tube: Heat Transfer Measurements and Predictions

1999 ◽  
Vol 121 (1) ◽  
pp. 89-101 ◽  
Author(s):  
O. Zu¨rcher ◽  
J. R. Thome ◽  
D. Favrat
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Two Phase

Experimental test results for flow boiling of pure ammonia inside horizontal tubes were obtained for a plain stainless steel tube. Tests were run at a nominal saturation temperature of 4°C, nine mass velocities from 20–140 kg/m2 s, vapor qualities from 1–99 percent and heat fluxes from 5–58 kW/m2. Two-phase flow observations showed that the current test data covered the following regimes: fully stratified, stratified-wavy, intermittent, annular, and annular with partial dryout. The Kattan-Thome-Favrat flow boiling model accurately predicted the local heat transfer coefficients measured in all these flow regimes with only two small modifications to their flow map (to extend its application to G < 100 kg/m2 s). Their flow boiling model was also successfully compared to the earlier ammonia flow boiling data of Chaddock and Buzzard (1986). The Gungor-Winterton (1987) correlation instead gave very poor accuracy for ammonia.

Numerical Solution for Transient Conjugate Two-Phase Heat Transfer With Heat Generation in the Pipe Wall

2002 ◽  
Vol 124 (6) ◽  
pp. 1213-1218 ◽  
Author(s):  
Yuri V. Fairuzov ◽  
Hector Arvizu
Keyword(s):  
Heat Transfer ◽  
Numerical Solution ◽  
Heat Generation ◽  
Two Phase ◽  
Convective Boiling ◽  
Wall Superheat ◽  
Boiling Flow ◽  
Rigorous Model ◽  
Two Phase Heat Transfer ◽  
Transient Boiling

A method developed earlier for modeling conjugate two-phase heat transfer in flashing flows was used to obtain a numerical solution for transient boiling flow in heated pipes or channels. Two criteria of applicability of the solution obtained were proposed and numerically tested using a more rigorous model, which accounts for the effects of heat conduction with heat generation in the wall and forced convective boiling. The solution obtained provides a simple and reliable alternative to more rigorous methods for modeling transient two-phase flow in heated channels when the material of the wall bounding the flow has a high thermal conductivity and the wall superheat is small.

Boiling Heat Transfer From a Horizontal Tube in an Upward Flowing Two-Phase Crossflow

1984 ◽  
Vol 106 (4) ◽  
pp. 849-855 ◽  
Author(s):  
M. E. Wege ◽  
M. K. Jensen
Keyword(s):  
Heat Transfer ◽  
Vertical Channel ◽  
Horizontal Tube ◽  
Nucleate Boiling ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Average Deviation ◽  
Wall Superheat ◽  
Two Phase Heat Transfer

An experimental investigation has been performed to determine the effects of a low-quality (≤ 20 percent) upward flowing mixture on the nucleate boiling on a single horizontal lube. An electrically heated, 12.7-mm-dia tube was centered in a plane wall vertical channel, the width of which resulted in channel width-to-tube diameter ratios (w/d) of 1.16 and 1.95. The working fluid was R-113. The two-phase heat transfer data showed a variety of effects. For a fixed w/d, pressure (P), and quality (x), the average heat transfer coefficients (h) increased with increasing mass velocity (G), but the effect of G decreased as the wall superheat (ΔT) increased. For a fixed w/d, G and x, h increased as the pressure increased except at low ΔT’s where the reverse was found. For fixed w/d, P and G, h increased with increasing quality with the effect appearing to be more pronounced at the lower pressure. At a fixed P, G and x, h was at larger w/d ratios at small ΔT’s, but as the wall superheat increased an inversion occured and h became smaller at the larger w/d ratio. The behavior exhibited in this experiment can be explained in terms of the velocity of the fluid flowing past the test section. The data were successfully predicted to within an average deviation of ±11.6 percent using a Chen-type correlation. Data from the literature also were predicted well.

Convective Boiling in Vertical Channels With Different Offset Strip Fin Geometries

1989 ◽  
Vol 111 (1) ◽  
pp. 156-165 ◽  
Author(s):  
G. D. Mandrusiak ◽  
V. P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Flow ◽  
Nucleate Boiling ◽  
Two Phase ◽  
Wall Superheat ◽  
Annular Film ◽  
Two Phase Heat Transfer ◽  
Offset Strip Fin

Newly obtained local heat transfer data are presented for flow boiling of liquids in two partially heated vertical channels with different offset strip fin geometries operating at low to moderate wall superheat levels. Experiments were conducted in special test sections that permitted direct visual observation of the boiling process while simultaneously measuring the heat transfer coefficient along the channel. Data for which nucleate boiling appeared to be completely suppressed were analyzed together with similar results for other offset fin geometries to assess the effects of channel geometry variations on the two-phase heat transfer coefficient during annular film-flow evaporation. For all geometries considered, the data for annular film-flow evaporation were found to correlate well in terms of modified versions of the F and Martinelli parameters used by Bennett and Chen (1980) to correlate similar data for round tubes. For fin matrices of similar size and configuration, the forced convective component of the two-phase heat transfer coefficient was found to be well represented by a single F-parameter correlation curve. However, F-factor correlations for matrices having significant differences in fin and channel dimensions were found to differ substantially. An approximate superposition method for including the contribution of nucleate boiling to the two-phase heat transfer coefficient at low to moderate wall superheat levels is also proposed.

MICROSCALE TWO PHASE HEAT TRANSFER ENHANCEMENT IN POROUS STRUCTURES

Equipment ◽  
2006 ◽  
Author(s):  
Leonid L. Vasiliev ◽  
A. Zhuravlyov ◽  
A. Shapovalov ◽  
L. L. Vasiliev, Jr
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Porous Structures ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Two Phase Heat Transfer
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