A THERMODYNAMIC NON-EQUILIBRIUM SLUG FLOW MODEL EXPLAINS ENHANCEMENT OF BOILING HEAT TRANSFER IN WATER AT LOW PRESSURES

Equipment ◽  
2006 ◽  
Author(s):  
Geoffrey Hewitt ◽  
J. R. Barbosa, Jr.
Keyword(s):  
Heat Transfer ◽  
Slug Flow ◽  
Boiling Heat Transfer ◽  
Flow Model ◽  
Low Pressures ◽  
Non Equilibrium

A homogeneous flow model for boiling heat transfer calculation based on single phase flow

2009 ◽  
Vol 50 (7) ◽  
pp. 1862-1868 ◽  
Author(s):  
Guo-xiang Li ◽  
Song Fu ◽  
Yun Liu ◽  
Yong Liu ◽  
Shu-zhan Bai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Flow Model ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Homogeneous Flow ◽  
Heat Transfer Calculation

Use of Two-Phase CFD Simulations to Develop a Boiling Heat Transfer Prediction Method for Slug Flow Within Microchannels

2015 ◽  
Author(s):  
Mirco Magnini ◽  
John R. Thome
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Slug Flow ◽  
Boiling Heat Transfer ◽  
Prediction Method ◽  
Liquid Slug ◽  
Modeling Framework ◽  
Cfd Simulations ◽  
Two Phase ◽  
Elongated Bubble

This work presents a new boiling heat transfer prediction method for slug flow within microchannels, which is developed and benchmarked against the results of two-phase CFD simulations. The proposed method adopts a two-zone decomposition of the flow for the sequential passage of a liquid slug and an evaporating elongated bubble. The heat transfer is modeled by assuming transient heat conduction across the liquid film surrounding an elongated bubble and sequential conduction/convection within the liquid slug. Embedded submodels for estimating important flow parameters, e.g. bubble velocity and liquid film thickness, are implemented as “building blocks”, thus making the entire modeling framework totally stand-alone. The CFD simulations are performed by utilizing ANSYS Fluent v. 14.5 and the interface between the vapor and liquid phases is captured by the built-in Volume Of Fluid algorithm. Improved schemes to compute the surface tension force and the phase change due to evaporation are implemented by means of self-developed functions. The comparison with the CFD results shows that the proposed method emulates well the bubble dynamics during evaporation, and predicts accurately the time-averaged heat transfer coefficients during the initial transient regime and the terminal steady-periodic stages of the flow.

Modifications and Extensions to the Annular Flow Model

2006 ◽  
Author(s):  
Priyadarshan U. Patankar ◽  
Bhalchandra P. Puranik
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Annular Flow ◽  
Flow Model ◽  
Heat Sinks ◽  
Phase Flow ◽  
Uniform Heating ◽  
Two Phase

Boiling heat transfer to fluid flow in microchannel heat sinks is being looked upon as a promising solution to the problem of cooling microprocessors with large power densities. In the present work, an annular flow model [1] is implemented to investigate the boiling heat transfer and two-phase flow characteristics in microchannel heat sinks. A modification in the model for the deposition mass transfer coefficient is proposed to better compare the existing experimental data [2]. The deposition mass transfer coefficient affects the distribution of liquid in the form of entrained droplets and the liquid film. The liquid film thickness is the most significant parameter in the determination of the heat transfer coefficient. The suggested change ensures consistent results for the behavior of the entrained fraction. We further report pressure drop results obtained using the modified annular flow model and a comparison with existing experimental data. Finally, we present results predicted by the annular flow model for non-uniform heating of a microchannel, in an effort to simulate hot spots on a microprocessor chip. A few preliminary results obtained from the modified model to simulate boiling and two-phase flow in a parallel microchannel device with non-uniform heating are presented.

Two-Phase Flow Phenomena for Boiling in Two Parallel Microchannels

2004 ◽  
Author(s):  
H. Y. Li ◽  
P. C. Lee ◽  
F. G. Tseng ◽  
Chin Pan
Keyword(s):  
Heat Transfer ◽  
Slug Flow ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Nucleate Boiling ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Silicon Bulk ◽  
Flow Phenomena

Boiling heat transfer and corresponding two-phase flow phenomena are of significant interest for the design of a compact evaporator. The present work investigates experimentally, using a high-speed digital CCD camera, the two-phase flow phenomena for boiling in a silicon-based, two parallel trapezoid microchannels, which were prepared by the combination of silicon bulk micro machining and Pyrex-silicon wafer bonding. Onset of nucleate boiling, bubbly flow, slug flow, and partial dry out slug flow are typically observed along the flow direction. The appearance of the partial dryout slug flow may degrade the nucleate boiling heat transfer in the microchannel. At a low flow rate, reversed vapor flow is observed. In such a flow pattern, liquid droplets are formed intermittently on the inner wall of top Pyrex glass due to vapor condensation. Moreover, the reversed vapor flow usually accompanies with large magnitude two-phase flow oscillations.

Deterioration of boiling heat transfer on biphilic surfaces under very low pressures

2020 ◽  
Vol 113 ◽  
pp. 110026 ◽  
Author(s):  
Biao Shen ◽  
Tomosuke Mine ◽  
Naoki Iwata ◽  
Sumitomo Hidaka ◽  
Koji Takahashi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Low Pressures

CFD Simulation of Boiling Heat Transfer Using OpenFOAM

2014 ◽  
Author(s):  
Mehrdad Shademan ◽  
Ram Balachandar ◽  
Ron Barron
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boiling Heat Transfer ◽  
Flow Model ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Adiabatic Flow ◽  
Heat Transfer Phenomenon

An Eulerian-Eulerian two-phase flow model has been developed to simulate the boiling heat transfer phenomenon in a pipe flow. The model was implemented in the OpenFOAM source code. The code development process was divided into two sections. In the first step, an adiabatic two-phase flow model which takes into account the effect of interfacial forces was developed. In the second step, the energy equation was activated to account for non-adiabatic conditions. In order to include the boiling effect, several different subroutines which model evaporation and condensation phenomena were attached to the solver. Results of the two-phase adiabatic flow and from the boiling model are compared with available numerical and experimental data. The simulation predictions are in reasonable agreement with the experimental data and show significant improvement relative to previous numerical results, which suggests the validity of the developed model for boiling heat transfer problems.

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