Flow Boiling in Horizontal Tubes: Part 3—Development of a New Heat Transfer Model Based on Flow Pattern

1998 ◽  
Vol 120 (1) ◽  
pp. 156-165 ◽  
Author(s):  
N. Kattan ◽  
J. R. Thome ◽  
D. Favrat
Keyword(s):  
Heat Transfer ◽  
Annular Flow ◽  
Flow Boiling ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Two Phase ◽  
Horizontal Tubes ◽  
High Vapor ◽  
Coefficient Versus ◽  
The Heat Transfer Coefficient

A new heat transfer model for intube flow boiling in horizontal plain tubes is proposed that incorporates the effects of local two-phase flow patterns, flow stratification, and partial dryout in annular flow. Significantly, the local peak in the heat transfer coefficient versus vapor quality can now be determined from the prediction of the location of onset of partial dryout in annular flow. The new method accurately predicts a large, new database of flow boiling data, and is particularly better than existing methods at high vapor qualities (x > 85 percent) and for stratified types of flows.

A New Thermodynamic and Heat Transfer Model for Nanolubricants and Refrigerant Heat Transfer Processes in Smooth Copper Tubes

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Pratik S. Deokar ◽  
Lorenzo Cremaschi ◽  
Andrea A. M. Bigi
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Single Phase ◽  
Flow Boiling ◽  
Heat Transfer Model ◽  
Forced Flow ◽  
Transfer Model ◽  
Phase Flow ◽  
Two Phase

Abstract In air conditioning systems, lubricating oil leaves the compressor and circulates through the other system components. This lubricant acts as a contaminant affecting heat transfer in heat exchangers. The literature indicated that mixtures of refrigerants and nanolubricants, that is, nanoparticles dispersed in the lubricant oils, have potentials to augment heat transfer exchange effectiveness. However, the nanoparticle mechanisms leading to such heat transfer changes are still unclear and not well included in the models. In this work, an existing single-phase forced flow convective heat transfer model, originally developed for water-based nanofluids, was modified to include the effects of diffusion and mass balance of different shape nanoparticles within the laminar sublayer and turbulent layer of the flow. A new physics-based superposition heat transfer model for saturated two-phase flow boiling of refrigerant and nanolubricants was also developed by integrating the modified forced flow convective heat transfer model and a semi-empirical pool boiling model for nanolubricants. The new model included the several physical effects that influenced heat transfer, such as slip mechanisms at the nanoparticles and base fluid interface and its influence on the laminar sublayer thickness, momentum transfer from the nanoparticles to the growing bubbles, and formation of lubricant excess concentration at the tube surface and its influence on bubble growth and tube wetting. The new model was validated for single-phase convective heat transfer and two-phase flow boiling of refrigerant R410A with two nanolubricants, having nonspherical ZnO nanoparticles and spherical Al2O3 nanoparticles.

A General Heat Transfer Model for Two-Phase Annular Flow

2019 ◽  
pp. 193-198
Author(s):  
G. Sun ◽  
W. H. G. T. Chan ◽  
G. F. Hewitt
Keyword(s):  
Heat Transfer ◽  
Annular Flow ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Two Phase

Theoretical Post-Dryout Heat Transfer Model

2018 ◽  
Vol 1 (1) ◽  
pp. 142-150
Author(s):  
Murat Tunc ◽  
Ayse Nur Esen ◽  
Doruk Sen ◽  
Ahmet Karakas
Keyword(s):  
Heat Transfer ◽  
Droplet Diameter ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Operating Pressure ◽  
Vertical Pipe ◽  
Two Phase ◽  
Experimental Values ◽  
Reactor Operating ◽  
Coolant System

A theoretical post-dryout heat transfer model is developed for two-phase dispersed flow, one-dimensional vertical pipe in a post-CHF regime. Because of the presence of average droplet diameter lower bound in a two-phase sparse flow. Droplet diameter is also calculated. Obtained results are compared with experimental values. Experimental data is used two-phase flow steam-water in VVER-1200, reactor coolant system, reactor operating pressure is 16.2 MPa. On heater rod surface, dryout was detected as a result of jumping increase of the heater rod surface temperature. Results obtained display lower droplet dimensions than the experimentally obtained values.

scholarly journals Experimental Investigation of Flow Condensation in Microgravity

2013 ◽  
Author(s):  
Hyoungsoon Lee ◽  
Ilchung Park ◽  
Christopher Konishi ◽  
Issam Mudawar ◽  
Rochelle I. May ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Condensation Heat Transfer ◽  
Interfacial Structure ◽  
Sensible Heat ◽  
Two Phase ◽  
The Heat Transfer Coefficient

Future manned missions to Mars are expected to greatly increase the space vehicle’s size, weight, and heat dissipation requirements. An effective means to reducing both size and weight is to replace single-phase thermal management systems with two-phase counterparts that capitalize upon both latent and sensible heat of the coolant rather than sensible heat alone. This shift is expected to yield orders of magnitude enhancements in flow boiling and condensation heat transfer coefficients. A major challenge to this shift is a lack of reliable tools for accurate prediction of two-phase pressure drop and heat transfer coefficient in reduced gravity. Developing such tools will require a sophisticated experimental facility to enable investigators to perform both flow boiling and condensation experiments in microgravity in pursuit of reliable databases. This study will discuss the development of the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS), which was initiated in 2012 in collaboration between Purdue University and NASA Glenn Research Center. This facility was recently tested in parabolic flight to acquire condensation data for FC-72 in microgravity, aided by high-speed video analysis of interfacial structure of the condensation film. The condensation is achieved by rejecting heat to a counter flow of water, and experiments were performed at different mass velocities of FC-72 and water and different FC-72 inlet qualities. It is shown that the film flow varies from smooth-laminar to wavy-laminar and ultimately turbulent with increasing FC-72 mass velocity. The heat transfer coefficient is highest near the inlet of the condensation tube, where the film is thinnest, and decreases monotonically along the tube, except for high FC-72 mass velocities, where the heat transfer coefficient is enhanced downstream. This enhancement is attributed to both turbulence and increased interfacial waviness. One-ge correlations are shown to predict the average condensation heat transfer coefficient with varying degrees of success, and a recent correlation is identified for its superior predictive capability, evidenced by a mean absolute error of 21.7%.

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