Numerical Simulation of Bubble Growth and Heat Transfer During Flow Boiling in a Surface-Modified Microchannel

2013 ◽  
Vol 35 (5) ◽  
pp. 501-507 ◽  
Author(s):  
Woorim Lee ◽  
Gihun Son
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Bubble Growth ◽  
Flow Boiling ◽  
Surface Modified

Confined Bubble and Heat Transfer during Flow Boiling in a High Aspect Ratio Mini-Channel

2011 ◽  
Vol 312-315 ◽  
pp. 548-553 ◽  
Author(s):  
Yuan Wang ◽  
Khellil Sefiane
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Bubble Growth ◽  
Flow Boiling ◽  
Critical Time ◽  
Heat Fluxes ◽  
Equivalent Radius ◽  
Mass Fluxes ◽  
Transfer Mechanisms ◽  
Working Liquid

Single vapour bubble growth and heat transfer mechanism during flow boiling in a rectangular horizontal mini-channel were experimentally investigated. The hydraulic diameter of the channel was 1454 μm, with an aspect ratio (Win/din) of 10. Degassed FC-72 was used as the working liquid. In this paper, bubble equivalent radius was found to increase linearly till a critical time, beyond which the growth turned into exponential. Bubble growth rate increases with increasing heat flux. Heat transfer mechanisms of the bubble growth at different heat fluxes and mass fluxes were discussed. In addition, the relation between thermal and flow conditions with bubble temporal geometry was explored.

Numerical Simulation of Subcooled Flow Boiling Heat Transfer in Helical Tubes

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Jong Chull Jo ◽  
Woong Sik Kim ◽  
Chang-Yong Choi ◽  
Yong Kab Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Steam Generator ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Heat Transfer Analysis ◽  
Normal Operation ◽  
Phase Flow ◽  
Two Phase ◽  
Side Flow

This paper addresses the numerical simulation of two-phase flow heat transfer in the helically coiled tubes of an integral type pressurized water reactor steam generator under normal operation using a computational fluid dynamics code. The shell-side flow field where a single-phase fluid flows in the downward direction is also calculated in conjunction with the tube-side two-phase flow characteristics. For the calculation of tube-side two-phase flow, the inhomogeneous two-fluid model is used. Both the Rensselaer Polytechnic Institute wall boiling model and the bulk boiling model are implemented for the numerical simulations of boiling-induced two-phase flow in a vertical straight pipe and channel, and the computed results are compared with the available measured data. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. Both the internal and external turbulent flows are simulated using the standard k-ε model. From the results of the present numerical simulation, it is shown that the bulk boiling model can be applied to the simulation of two-phase flow in the helically coiled steam generator tubes. In addition, the present simulation method is considered to be physically plausible in the light of discussions on the computed results.

Numerical Analysis of Vapor Bubble Growth and Wall Heat Transfer During Flow Boiling of Water in a Microchannel

2005 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Vapor Bubble ◽  
Bubble Growth ◽  
Stokes Equations ◽  
Flow Boiling ◽  
Navier Stokes ◽  
Channel Cross Section ◽  
Wall Heat Transfer ◽  
Wall Superheat

The present study is performed to analyze the wall heat transfer mechanisms during growth of a vapor bubble inside a microchannel. The microchannel is of 200 μm square cross section and a vapor bubble begins to grow at one of the walls, with liquid coming in through the channel inlet. The complete Navier-Stokes equations along with continuity and energy equations are solved using the SIMPLER method. The liquid vapor interface is captured using the level set technique. The bubble grows rapidly due to heat transfer from the walls and soon turns into a plug filling the entire channel cross section. The average wall heat transfer at the channel walls is studied for different values of wall superheat and incoming liquid mass flux. The results show that the wall heat transfer increases with wall superheat but is almost unaffected by the liquid flow rate. The bubble growth is found to be the primary mechanism of increasing wall heat transfer as it pushes the liquid against the walls thereby influencing the thermal boundary layer development.

Numerical Simulation of Subcooled Flow Boiling Heat Transfer in Helical Tubes

2006 ◽  
Author(s):  
Jong Chull Jo ◽  
Woong Sik Kim ◽  
Chang-Yong Choi ◽  
Yong Kab Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Steam Generator ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Heat Transfer Analysis ◽  
Normal Operation ◽  
Phase Flow ◽  
Two Phase ◽  
Pressurized Water

This paper addresses the numerical simulation of two phase flow heat transfer in the helically coiled tubes of an integral type pressurized water reactor steam generator under normal operation using a CFD code. The single phase flow which flow downward direction in the shell side is also calculated together. For the calculation of tube side two-phase flow the inhomogeneous two-fluid model is used. Both the RPI (Rensselaer Polytechnic Institute) wall boiling model and the bulk boiling model are implemented for the numerical simulation and the computed results are compared with the available measured data. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. Both the internal and external turbulent flows are simulated using the standard k-ε model From the results of present numerical simulation, it is shown that the bulk boiling model can be applied to the simulation of two-phase flow in the helically coiled steam generator tubes. The results also show that the present simulation method is considered to be physically plausible when the computed results are compared with available previous experimental and numerical studies.

Numerical Simulation of Saturated Flow Boiling Heat Transfer of Ammonia/Water Mixture in Bubble Pumps for Absorption–Diffusion Refrigerators

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Soo W. Jo ◽  
S. A. Sherif ◽  
W. E. Lear
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Water Mixture ◽  
Saturated Flow ◽  
Ammonia Water ◽  
Flow Boiling Heat Transfer ◽  
Bubble Pump

This paper addresses a multidimensional numerical simulation of the saturated flow boiling heat transfer in bubble pumps of absorption–diffusion refrigeration cycles. The bubble pump with a shape of vertical tube is subjected to a uniform heat flux from the tube outer wall surface along the entire pump length. As the bubble pump wall is heated, a nonazeotropic mixture of saturated strong ammonia/water entering into the bubble pump transforms to ammonia vapor and diluted ammonia/water mixture. The weaker ammonia/water mixture is lifted by the buoyant force created by the ammonia vapor. The present multidimensional numerical simulation was performed using the two-fluid model with the equilibrium phase change model and the standard k-ε turbulence model. The numerical model designed for the present simulation was validated through a comparative study referring to available experimental data. The present numerical model was compared with the one-dimensional model to assess its applicability for numerical simulation of the saturated flow boiling heat transfer in bubble pumps. As a result, it is seen that the present numerical model predicts the performance of ammonia/water bubble pumps more realistically than the one-dimensional model. In addition, the effects of the bubble pump's geometrical dimension and heat input on the pump performance were investigated using the present numerical approach.

scholarly journals Simulation of flow boiling of nanofluid in tube based on lattice Boltzmann model

2019 ◽  
Vol 23 (1) ◽  
pp. 159-168
Author(s):  
Shouguang Yao ◽  
Tao Huang ◽  
Kai Zhao ◽  
Jianbang Zeng ◽  
Shuhua Wang
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann ◽  
Bubble Growth ◽  
Growth Process ◽  
Flow Boiling ◽  
Lattice Boltzmann Model ◽  
Lateral Acceleration ◽  
Bubble Flow ◽  
The Right ◽  
Boltzmann Model

In this study, a lattice Boltzmann model of bubble flow boiling in a tube is established. The bubble growth, integration, and departure of 3% Al2O3-water nanofluid in the process of flow boiling are selected to simulate. The effects of different bubble distances and lateral accelerations a on the bubble growth process and the effect of heat transfer are investigated. Results showed that with an increase in the bubble distance, the bubble coalescence and the effect of heat transfer become gradual. With an increase in lateral acceleration a, the bubble growth is different. When a = 0.5e?7 and a = 0.5e?6, the bubble growth includes the process of bubble growth, coalescence, detachment, and fusion with the top bubble and when a = 0.5e?5 and a = 0.5e?4, the bubbles only experience growth and fusion, and the bubbles do not merge with the top bubble directly to the right movement because the lateral acceleration is too large, resulting in the enhanced effect of heat transfer in the tube.

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