Investigation of flow boiling in horizontal tubes: Part II—Development of a new heat transfer model for stratified-wavy, dryout and mist flow regimes

2005 ◽  
Vol 48 (14) ◽  
pp. 2970-2985 ◽  
Author(s):  
Leszek Wojtan ◽  
Thierry Ursenbacher ◽  
John R. Thome
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Flow Regimes ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Horizontal Tubes ◽  
Mist Flow

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.

An Experimental Investigation of Flow Patterns During Condensation of HFC Refrigerants in Horizontal Micro-Fin Tubes

2019 ◽  
Vol 27 (01) ◽  
pp. 1950010
Author(s):  
Sanjeev Singh ◽  
Rajeev Kukreja
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Flow Regimes ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Regime Map ◽  
Fin Tubes ◽  
Flow Regime Map

Condensation heat transfer coefficients and flow regimes in two different horizontal micro-fin tubes are examined during the condensation of refrigerants R-134a and R-410A. The present investigation has focused on determination and prediction of condensation heat transfer coefficients and finding the interrelation between heat transfer coefficients and the prevailing flow regimes. During flow visualization, flow regimes have been captured using borosilicate glass tube at inlet and outlet of the test condenser using high speed digital camera. Stratified, stratified wavy, wavy annular, annular, slug and plug flows have been observed at different mass fluxes and vapor qualities of the refrigerants. The observed flow regimes are compared with the existing flow regime maps proposed by Breber et al. [Prediction of horizontal tube side condensation of pure components using flow regime criteria, J. Heat Transfer 102 (1980) 471–476], Tandon et al. [A new flow regime map for condensation inside horizontal tubes, J. Heat Transfer 104 (1982) 763–768.] and Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] flow regime map shows good agreement with experimental data.

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.

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