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Numerical Simulation of Boiling from a Single Reentrant-Cavity

Dietl, Jochen and Stephan, Peter (2014):
Numerical Simulation of Boiling from a Single Reentrant-Cavity.
In: The 15th International Heat Transfer Conference, [Online-Edition: http://dx.doi.org/10.1615/IHTC15.pbl.008590],
[Conference or Workshop Item]

Abstract

In this paper, results from numerical simulations of pool boiling of R-134a from single reentrant-cavities are presented. The simulations allow to study heat transfer and flow characteristics inside the cavities. Simulations were performed in 2D with circular cavities for several bubble cycles until a quasi steady-state was obtained and in 3D with square cavities for one bubble cycle. The results show that liquid films inside the cavities can significantly increase heat transfer performance. With circular cavities, no liquid backflow into the cavities was observed for all pore diameters and dryout occurred after one bubble cycle. With square cavities, thin liquid films establish in the edge regions due to capillary forces. These films connect the liquid pool with the liquid inside the cavities and allow backflow of liquid even during bubble growth. For boiling processes being governed by evaporation from thin liquid films in the vicinity of the three-phase contact line, heat transfer coefficients decrease with increasing heat flux. The results suggest that with careful design significant improvements of heat transfer coefficients are possible, not only with structures with subsurface tunnels as employed on tubes in industrial heat exchangers, but also with single reentrant-cavities.

Item Type: Conference or Workshop Item
Erschienen: 2014
Creators: Dietl, Jochen and Stephan, Peter
Title: Numerical Simulation of Boiling from a Single Reentrant-Cavity
Language: German
Abstract:

In this paper, results from numerical simulations of pool boiling of R-134a from single reentrant-cavities are presented. The simulations allow to study heat transfer and flow characteristics inside the cavities. Simulations were performed in 2D with circular cavities for several bubble cycles until a quasi steady-state was obtained and in 3D with square cavities for one bubble cycle. The results show that liquid films inside the cavities can significantly increase heat transfer performance. With circular cavities, no liquid backflow into the cavities was observed for all pore diameters and dryout occurred after one bubble cycle. With square cavities, thin liquid films establish in the edge regions due to capillary forces. These films connect the liquid pool with the liquid inside the cavities and allow backflow of liquid even during bubble growth. For boiling processes being governed by evaporation from thin liquid films in the vicinity of the three-phase contact line, heat transfer coefficients decrease with increasing heat flux. The results suggest that with careful design significant improvements of heat transfer coefficients are possible, not only with structures with subsurface tunnels as employed on tubes in industrial heat exchangers, but also with single reentrant-cavities.

Divisions: 16 Department of Mechanical Engineering > Institute for Technical Thermodynamics (TTD)
Exzellenzinitiative > Clusters of Excellence > Center of Smart Interfaces (CSI)
16 Department of Mechanical Engineering
Zentrale Einrichtungen
Exzellenzinitiative
Exzellenzinitiative > Clusters of Excellence
Event Title: The 15th International Heat Transfer Conference
Date Deposited: 17 Mar 2015 14:35
Official URL: http://dx.doi.org/10.1615/IHTC15.pbl.008590
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