Effect of an electrolyte (MgSO4) on the boiling flow regime and heat transfer for water at low heat flux and low pressure

2021 ◽  
Author(s):  
A. Holmes ◽  
A. Toic ◽  
D. Ewing ◽  
N. Fujisawa ◽  
C. Y. Ching
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Regime ◽  
Low Pressure ◽  
Boiling Flow

scholarly journals Numerical investigation on saturated boiling flow and heat transfer of mixture refrigerant in a vertical rectangular mini-channel

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 617-627
Author(s):  
Jie Chen ◽  
Weihua Cai ◽  
Shulei Li ◽  
Yan Ren ◽  
Hongqiang Ma ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Liquefied Natural Gas ◽  
Gas Field ◽  
Flow And Heat Transfer ◽  
Boiling Flow ◽  
Saturated Boiling

Plate-fin heat exchanger with rectangular minichannels, as a type of high-perfor- mance compact heat exchangers, has been widely used in liquefied natural gas field. However, the studies on saturated boiling flow and heat transfer for mixture refrigerant in plate-fin heat exchanger have been scarcely explored, which are helpful for designing more effective plate-fin heat exchanger using in liquefied natural gas field. Therefore, in this paper, the characteristics of saturated boiling flow and heat transfer for mixture refrigerant in rectangular minichannels of plate-fin heat exchanger were studied numerally based on validated model. Then, the effect of different parameters (vapor quality, mass flux, and heat flux) on heat transfer coefficient and frictional pressure drop were discussed. The results indicated that the boiling heat transfer coefficient and pressure drop are mainly influenced by quality and mass flux while heat flux has little influence on them. This is due to the fact that the main boiling mechanisms were forced convective boiling and the evaporation of dispersed liquid phase while nucleate boiling is slight.

Analysis on Heat Transfer and Phase Change for Two-Phase Boiling Flow in Quenching Process

2019 ◽  
Author(s):  
Lu Wang ◽  
Nobuyuki Oshima ◽  
Sangwon Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Wall Temperature ◽  
Computational Domain ◽  
Heating Wall ◽  
Two Phase ◽  
Phase Form ◽  
Quenching Process ◽  
Boiling Flow

Abstract A series of numerical simulations using “interThermalPhaseChangeFOAM” solver with improved VOF multiphase flow model in OpenFOAM were conducted to investigate the heat transfer and phase change characteristics for liquid-vapor boiling flow in quenching process. The computational domain is a cuboid with the heating wall at the bottom for both the variable and fixed wall temperature cases. The results for the variable wall temperature case with the heating wall temperature Twall = 150K show that the boiling phenomenon can be divided into the vapor film stage, the boiling stage and the convection stage. Then the fixed wall temperature cases with Twall = 110K, 120K and 140K are analyzed. It is found that 140K case is the most stable one, in which bubble formation is regular such as the bubble at the corner, resulting in the steady variation of heat flux. 120K case is the most unstable one, since the liquid phase and gas phase form the cross-interface shape and maintain this for a long time, leading to the fluctuations in heat flux. Finally, the influence of computational sizes on predicting the properties of boiling phenomenon is investigated. Although the variations of heat flux are not exactly same, the whole tendency is similar.

A semi-analytical model of heat transfer and pressure drop in annular flow regime for flow boiling in a horizontal microtube at uniform heat flux

2020 ◽  
Vol 44 (3) ◽  
pp. 362-384
Author(s):  
Amen Younes ◽  
Ibrahim Hassan ◽  
Lyes Kadem
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Regime ◽  
Analytical Model ◽  
Annular Flow ◽  
Present Model ◽  
Flow Boiling ◽  
Uniform Heat Flux ◽  
Two Phase

A semi-analytical model for predicting heat transfer and pressure drop in annular flow regime for saturated flow boiling in a horizontal microtube at a uniform heat flux has been developed based on a one-dimensional separated flow model. More than 600 two-phase heat transfer, 498 two-phase pressure drop, and 153 void fraction experimental data points for annular flow regime were collected from the literature to validate the present model. The collected data were recorded for various working fluids, R134a, R1234ze, R236fa, R410a, R113, and CO2, for round macro- and microsingle horizontal tubes with an inner diameter range of 0.244 mm ≤ Dh ≤ 3.1 mm, a heated length to diameter ratio of 90 ≤ Lh/Dh ≤ 2000, a saturation temperature range of –10 ≤ Tsat ≤ +50 °C, and liquid to vapor density ratios in the range 6.4 ≤ ρf/ρg ≤ 188. The model was tested for laminar and turbulent flow boiling conditions corresponding to an equivalent Reynolds number, 1900 ≤ Reeq ≤ 48 000, and confinement number, 0.27 ≤ Cconf ≤ 3.4. Under the annular flow regime, the present model predicted the collected data of the heat transfer, pressure drop, and void fraction with mean absolute errors (MAE) of 18.14%, 23.02%, and 3.22%, respectively.

Evaporative Annular Flow in Micro/Minichannels: A Simple Heat Transfer Model

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Zan Wu ◽  
Bengt Sundén ◽  
Wei Li ◽  
Vishwas V. Wadekar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Regime ◽  
Annular Flow ◽  
Bubble Flow ◽  
New Model ◽  
Error Band ◽  
Data Points

The present study collected and analyzed flow boiling data points which fall in the annular flow regime with an increasing heat transfer coefficient h - vapor quality x trend (h increases with increasing x) in small diameter channels (0.1 < dh < 3.1 mm) for halogenated refrigerants, CO2 and water. In this annular flow regime, heat transfer coefficient also depends on both heat flux and mass flux. It is proposed that the heat flux dependence comes mainly through its effect on interfacial waves and the fact that bubble growth and coalescence in isolated bubble flow and elongated bubble flow propagate oscillations downwards into the annular flow. In other words, heat flux affects the heat transfer coefficient in the annular flow regime by upstream effects or historical effects. A semi-empirical model for annular flow was developed by starting with pure thin film evaporation and then corrections were applied based on the Boiling number and the liquid Reynolds number. The resulting simple model can predict about 89.1% of the entire database within a ± 30% error band. Almost all data points can be predicted within a ± 50% error band. It is shown that the parametric trends are well captured by the new model. Besides, no noticeable macro-to-micro/miniscale transition was observed for the entire database of annular flow. Therefore, the new model can be applied to model annular flow covering from microchannels to relatively large channels.

Advanced Computational Modeling of Multiphase Boiling Flow and Heat Transfer

2010 ◽  
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.

Downflow Post-Critical Heat Flux Heat Transfer to Low Pressure Water

1982 ◽  
Vol 56 (1) ◽  
pp. 134-140
Author(s):  
Paul Robershotte ◽  
Peter Griffith
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Low Pressure ◽  
Pressure Water

Influence of Flow Regime, Heat Flux, and Mass Flux on Electrohydrodynamically Enhanced Convective Boiling

2000 ◽  
Vol 123 (2) ◽  
pp. 355-367 ◽  
Author(s):  
J. E. Bryan ◽  
J. Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Flow Regime ◽  
Mass Flux ◽  
Electrode Design ◽  
Convective Boiling ◽  
R 134A ◽  
The Heat Transfer Coefficient

The influence of quality, flow regime, heat flux, and mass flux on the electrohydrodynamic (EHD) enhancement of convective boiling of R-134a in a horizontal smooth tube was investigated in detail. The EHD forces generated significant enhancements in the heat transfer coefficient, but the enhancements were highly dependent on the quality, flow regime, heat flux, and mass flux. The experimental data provided evidence that an optimum EHD enhancement exists for a given set of these variables with a specific electrode design. However, experimental data also provided evidence that the EHD forces can drastically reduce the rate of heat transfer at certain conditions

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