Increased Cooling Power with Nucleate Boiling Flow in Automotive Engine Applications

Subcooled boiling flow was simulated by combining the two-fluid model of the CFX-4.4 code and a Lagrangian bubble-tracking model. At present, both models are coupled “off-line” via the local bubble Sauter diameter. The two-fluid model simulation with the CFX-4.4 code provides local values of turbulent kinetic energy field of the liquid phase, which is used as an input for the bubble-tracking model. In the bubble-tracking model, vapour is distributed in the liquid in the form of individually tracked bubbles. The result of the Lagrangian simulation is a non-homogeneous distribution of local Sauter diameter, which is used in the two-fluid model to predict the interfacial forces and interfacial transfer rates of mass and heat transfer. The coupled approach requires a few iterations to obtain a converged solution. The results of the proposed approach were validated against boiling flow experiments from the literature. A good agreement between measured and calculated radial profiles of void fraction and bubble diameter was obtained.

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Advanced Computational Modeling of Multiphase Boiling Flow and Heat Transfer

Volume 7: Fluid Flow, Heat Transfer and Thermal Systems, Parts A and B ◽

10.1115/imece2010-38785 ◽

2010 ◽

Cited By ~ 2

Author(s):

Huiying Li ◽

Sergio A. Vasquez ◽

Peter Spicka

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Critical Heat Flux ◽

Volume Fraction ◽

Nucleate Boiling ◽

General Purpose ◽

Phase Changes ◽

Pressurized Water ◽

Flow And Heat Transfer ◽

Boiling Flow

Numerical simulation of boiling flow and heat transfer presents a number of unique challenges in both theoretical modeling and developing robust numerical methodology. The major difficulty arises due to the heat transfer and phase changes between heated walls and fluid (liquid and vapor). Furthermore, modeling of the liquid-vapor interfacial transfers of momentum, heat and mass proves to be equally challenging. The multiphase boiling modeling approach described in this paper has been found to be capable of addressing these issues and is therefore suitable for inclusion in an advanced general purpose CFD solver. In the present approach, boiling flows are modeled within the framework of the Eulerian multifluid model. The governing equations solved are phase continuity, momentum and energy equations. Turbulence effects can be accounted for using mixture, dispersed or per-phase multiphase turbulence models. Wall boiling phenomena are modeled using the baseline mechanistic RPI model for nucleate boiling, and its extensions to non-equilibrium boiling and critical heat flux regime. A range of sub-models are considered to account for the interfacial momentum, mass and heat transfer, and flow regime transitions. An advanced numerical scheme has been developed for solving the model equations which can handle the heat partition between heated walls and fluid, provide for wall and interfacial mass transfer source terms in phase volume fraction equations, and address the coupling between the phase change rates and the pressure correction equation. The wall boiling models and numerical algorithm have been implemented in an advanced, general-purpose CFD code, FLUENT. Validations have been carried out for a range of 2D and 3D boiling flows, including pressurized water through a vertical pipe with heated walls, R-113 liquid in a vertical annulus with internal heated walls, a 3D BRW core channel geometry with vertical heated rods, and water in a vertical circular pipe under critical heat flux and post dry-out conditions. The results demonstrate that the wall boiling models are able to correctly predict the wall temperature and vapor volume fraction distribution. The predictions in all the cases are in reasonable good agreement with available experiments. Tests also indicate that the present implementation is fast and robust, as compared to previous approaches. All the cases are able to be simulated with the use of the FLUENT steady-state multiphase solver with reasonable numbers of iterations.

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NUMERICAL ANALYSIS OF NUCLEATE BOILING FLOW IN A PILOT-SCALE THERMOSIPHON

10.5380/simproc4.2019.art04 ◽

2020 ◽

Author(s):

Bruna Iten Bittelbrunn ◽

Roberto Fischer Junior ◽

Harlley Henrique Parno ◽

Henry França Meier ◽

Jaci Carlos Schramm Câmara Bastos

Keyword(s):

Numerical Analysis ◽

Nucleate Boiling ◽

Pilot Scale ◽

Boiling Flow

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Subcooled Boiling Flow Heat Transfer From Plain and Enhanced Surfaces in Automotive Applications

Journal of Heat Transfer ◽

10.1115/1.2780178 ◽

2008 ◽

Vol 130 (1) ◽

Cited By ~ 14

Author(s):

Franz Ramstorfer ◽

Helfried Steiner ◽

Günter Brenn ◽

Claudius Kormann ◽

Franz Rammer

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Nucleate Boiling ◽

Heated Wall ◽

Transfer Model ◽

Subcooled Boiling ◽

Cooling Systems ◽

Porous Coatings ◽

Transfer Rates ◽

Boiling Flow

The requirement for the highest possible heat transfer rates in compact, efficient cooling systems can often only be met by providing for a transition to subcooled boiling flow in strongly heated wall regions. The significantly higher heat transfer rates achievable with boiling can help keep the temperatures of the structure on an acceptable level. It has been shown in many experimental studies that special surface finish or porous coatings on the heated surfaces can intensify the nucleate boiling process markedly. Most of those experiments were carried out with water or refrigerants. The present work investigates the potential of this method to enhance the subcooled boiling heat transfer in automotive cooling systems using a mixture of ethylene-glycol and de-ionized water as the coolant. Subcooled boiling flow experiments were carried out in a vertical test channel considering two different types of coated surfaces and one uncoated surface as a reference. The experimental results of the present work clearly demonstrate that the concept of enhancing boiling by modifying the microstructure of the heated surface can be successfully applied to automotive cooling systems. The observed increase in the heat transfer rates differ markedly for the two considered porous coatings, though. Based on the experimental data, a heat transfer model for subcooled boiling flow using a power-additive superposition approach is proposed. The model assumes the total wall heat flux as a nonlinear combination of a convective and a nucleate boiling contribution, both obtained from well-established semiempirical correlations. The wall heat fluxes predicted by the proposed model are in very good agreement with the experimental data for all considered flow conditions and surface types.

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Advances in Modeling Critical Heat Flux in LWR Boiling Flows With the NEK-2P CFD Code

Volume 8: Computational Fluid Dynamics (CFD); Nuclear Education and Public Acceptance ◽

10.1115/icone26-81910 ◽

2018 ◽

Author(s):

Adrian Tentner ◽

Prasad Vegendla ◽

Ananias Tomboulides ◽

Aleks Obabko ◽

Elia Merzari ◽

...

Keyword(s):

Heat Flux ◽

Critical Heat Flux ◽

Vertical Channel ◽

Nucleate Boiling ◽

Heated Wall ◽

Transfer Model ◽

Axial Distribution ◽

Two Phase ◽

Wide Range ◽

Boiling Flow

The paper focuses on the extension of the NEK-2P Wall Heat Transfer model, which was initially developed for the analysis of Critical Heat Flux (CHF) under Dryout (DO) conditions to the simulation of CHF under Departure from Nucleate Boiling (DNB) conditions. The paper presents results of recent NEK-2P analyses of several CHF experiments including both DO and DNB conditions. The CHF experiments analyzed have measured the axial distribution of wall temperatures in two-phase boiling flow in a vertical channel with a heated wall. The axial distribution of the calculated wall temperatures is compared with the corresponding experimental data. Reasonably good agreement with measured data is obtained in predicting the CHF location and post CHF wall temperature magnitudes illustrating the ability of the NEK-2P code and Extended Boiling Framework (EBF) models to simulate the CHF phenomena for a wide range of thermal-hydraulic conditions.

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