Numerical Study of Bubble Instability During Microchannel Flow Boiling

2015 ◽  
Author(s):  
Matthew Blomquist ◽  
Arman Khalighi ◽  
Abhijit Mukherjee
Keyword(s):  
Heat Exchangers ◽  
Heat Dissipation ◽  
Numerical Study ◽  
Flow Boiling ◽  
Microchannel Flow ◽  
Electronic Components ◽  
Vapor Interface ◽  
Compact Size ◽  
Convection Cooling ◽  
Liquid Vapor

In recent years, the forced convection cooling for the heat dissipation of electronic components has become a significant area of research. Many high-end computing applications, from consumer gaming to scientific research, encounter performance limitations due to heat generation in micro-electronic components. Micro heat exchangers can offer an ideal cooling solution for these applications due to their compact size and heat dissipation characteristics. Single-phase heat exchangers are widely used in both industry and consumer applications, but are limited by operational temperature ranges as well as the working fluid’s thermo physical properties. Two-phase, convection cooling systems, however, can further increase the capabilities of micro-heat exchangers. In the present study, a model has been created to investigate bubble growth and the values of wall superheat, contact angle, and Reynolds number that cause instability at the liquid-vapor interface during microchannel flow boiling. The results show how bubble instability is caused by the transfer of heat being restricted by the liquid-vapor interface.

A Numerical Study of Single Bubble Dynamics During Flow Boiling

2004 ◽  
Author(s):  
Ding Li ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Flow Boiling ◽  
Forced Flow ◽  
Single Bubble ◽  
Horizontal Line ◽  
Vapor Interface ◽  
Single Bubble Dynamics ◽  
Liquid Vapor

Nucleate flow boiling is a liquid-vapor phase-change process associated with high heat transfer rates. A complete 3D numerical simulation of single bubble dynamics on surfaces inclined at 90°, 45° and 30° to the horizontal line and subjected to forced flow parallel to the surface is performed in this work. The continuity, momentum and energy equations are solved with finite difference method and the level-set method is used to capture the liquid-vapor interface. The heat transfer contribution of the micro-layer between the solid wall and evolving liquid-vapor interface is included in this numerical analysis. The effect of dynamic contact angle is also included. The numerical result of bubble growth and sliding distance have been compared with experimental data.

Bejan’s Constructal Theory Analysis of Gas-Liquid Cooled Finned Modules

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Giulio Lorenzini ◽  
Simone Moretti
Keyword(s):  
Thermal Behavior ◽  
Heat Exchangers ◽  
High Performance ◽  
Numerical Study ◽  
Constructal Theory ◽  
Electronic Components ◽  
Theory Analysis ◽  
Pressure Losses ◽  
Different Types ◽  
Overall Performance

High performance heat exchangers represent nowadays the key of success to go on with the trend of miniaturizing electronic components as requested by the industry. This numerical study, based on Bejan’s Constructal theory, analyzes the thermal behavior of heat removing fin modules, comparing their performances when operating with different types of fluids. In particular, the simulations involve air and water (as representative of gases and liquids), to understand the actual benefits of employing a less heat conductive fluid involving smaller pressure losses or vice versa. The analysis parameters typical of a Constructal description (such as conductance or Overall Performance Coefficient) show that significantly improved performances may be achieved when using water, even if an unavoidable increase in pressure losses affects the liquid-refrigerated case. Considering the overall performance: if the parameter called Relevance tends to 0, air prevails; if it tends to 1, water prevails; if its value is about 0.5, water prevails in most of the case studies.

A Modified Correlation for Flow Boiling Heat Transfer in Plate Heat Exchangers

2019 ◽  
Author(s):  
Tong Lv ◽  
Boren Zheng ◽  
Wei Li ◽  
Zahid Ayub
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Plate Heat ◽  
Error Band ◽  
Flow Boiling Heat Transfer ◽  
Compact Size ◽  
Wide Range ◽  
Data Points

Abstract Corrugated plate heat exchangers are increasingly used in two-phase flow applications for their flexible and compact size and the efficient heat transfer performance. This paper presents a review of recent studies on the subject and creates a database containing 533 data points from experiment studies. The collected database covers seven working fluids, a wide range of vapor quality (both mean and local) 0.01–0.94, heat flux 0.5–46 kW m−2, mass flux 5.5–137 kg m−2 s−1, chevron angle 30°–70°, and hydraulic diameter 1.7–4.0 mm. Based on the database a brief comparison between several previous correlations are discussed. A new prediction method for flow boiling heat transfer coefficient is generated by multiple regression analysis and modifying an existing correlation. It was observed that the modified correlation shows a better agreement and predicts 74.3% of data points within ±30% error band and 94.9% within ±50% error band.

Force Analysis of Bubble Dynamics in Flow Boiling Silicon Nanowire Microchannels

2016 ◽  
Author(s):  
Tamanna Alam ◽  
Wenming Li ◽  
Fanghao Yang ◽  
Ahmed Shehab Khan ◽  
Yan Tong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Silicon Nanowire ◽  
Bubble Nucleation ◽  
Force Analysis ◽  
Vapor Interface ◽  
Liquid Vapor

In microchannel flow boiling, bubble nucleation, growth and flow regime development are highly influenced by channel cross-section and physical phenomena underlying this mechanism are far from being well-established. Relative effects of different forces acting on wall-liquid and liquid-vapor interface of a confined bubble play an important role in heat transfer performances. Therefore, fundamental investigations are necessary to develop enhanced microchannel heat transfer surfaces. Force analysis of vapor bubble dynamics in flow boiling Silicon Nanowire (SiNW) microchannels has been performed based on theoretical, experimental and visualization studies. The relative effects of different forces on flow regime, instability and heat transfer performances of flow boiling in Silicon Nanowire microchannels have been identified. Inertia, surface tension, shear, buoyancy, and evaporation momentum forces have significant importance at liquid-vapor interface as discussed earlier by several authors. However, no comparative study has been done for different surface properties till date. Detailed analyses of these forces including contact angle and bubble flow boiling characteristics have been conducted in this study. A comparative study between Silicon Nanowire and Plainwall microchannels has been performed based on force analysis in the flow boiling microchannels. In addition, force analysis during instantaneous bubble growth stage has been performed. Compared to Plainwall microchannels, enhanced surface rewetting and critical heat flux (CHF) are owing to higher surface tension force at liquid-vapor interface and Capillary dominance resulting from Silicon Nanowires. Whereas, low Weber number in Silicon Nanowire helps maintaining uniform and stable thin film and improves heat transfer performances. Moreover, force analysis during instantaneous bubble growth shows the dominance of surface tension at bubble nucleation and slug/transitional flow which resulted higher heat transfer contact area, lower thermal resistance and higher thin film evaporation. Whereas, inertia force is dominant at annular flow and it helps in bubble removal process and rewetting.

scholarly journals Optimization study on Electrical Enclosure with Forced Convection cooling using Computational Fluid Dynamics

2020 ◽  
pp. 34-42
Author(s):  
Mohammed Nabeel Ahmed ◽  
B. Meghanath ◽  
Mayur Laxman Kesarkar ◽  
Lakshminarasimha. N
Keyword(s):  
Heat Dissipation ◽  
Cfd Simulation ◽  
Internal Heat ◽  
Electronic Components ◽  
Ansys Fluent ◽  
Optimization Study ◽  
Convection Cooling ◽  
Electronic Parts ◽  
Significant Structure ◽  
Inlet Opening

Any electronic walled in area comprises of heat creating electronic components, as heat produced by the electronic parts in a fenced in area decreases the life of electronic segments prompting serious harm or disappointment of the framework. Research shows that each 10°c rise above room temperature of the enclosure, the life of the electronic parts decreases. Thus for any electronic frameworks, cooling turns into a significant structure interest, practical and ideal answer for hold the electronic parts to its working limit. Therefore, in the present work CFD simulation has been carried out using ANSYS Fluent by considering a typical Aluminum Electrical enclosure of volume (150mm X 600mm X 250mm) with total internal heat dissipation of 84W. With those values into consideration the surface area of enclosure, enclosure temperature rise, air flow requirement in an enclosure is calculated and based on which the fan is selected. Also optimization study has been carried out by changing the inlet opening position, exhaust fan location and providing baffle at inlet opening location. The results obtained from analysis are validated with analytical results.

Simulation of Single Bubble Growth in a Planar Microchannel With Temperature Recovery Model

2017 ◽  
Author(s):  
Yang Luo ◽  
Jingzhi Zhang ◽  
Wei Li ◽  
Zhengjiang Zhang ◽  
Jincai Du ◽  
...  
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Bubble Growth ◽  
Flow Boiling ◽  
Wall Heat Flux ◽  
Recovery Model ◽  
Vapor Interface ◽  
Wall Superheat ◽  
Temperature Recovery ◽  
Liquid Vapor

In the study numerical simulations are performed to investigate the saturated fluid flow through a two dimensional microchannel (1000μm×200μm, with a superheated bottom wall) by building a comprehensive physical method and updating the standard solver in the OpenFOAM software package. On basis of previous numerical study, most of the numerical methods for the micro-scale flow boiling emphasizes the mass transfer and interfacial heat exchange. Simultaneously, geometric reconstruction technology for liquid-vapor interface is widely used, which evidently captures the interfacial boundary characteristic accurately but costs lots of computational resources. In the present study, the temperature recovery model is adopted to maintain the liquid-vapor interface temperature, and an interface-cell searching algorithm is added into the model, while the geometric interface reconstruction technology is abandoned. For the validation of the new codes developed in OpenFOAM, 1-d Stefan Problem and the experimental results of Mukherjee are both utilized to compare with our simulation results. The growth process of a single bubble in the laminar flow regime is studied in order to explore the underlying mechanism of flow boiling in microchannels. The qualitative investigation for effects of wall superheat, Reynolds number, contact angle and surface tension on heat transfer are comprehensively discussed. In general, heat flux of the bottom wall increases because of the motion of liquid-vapor interface. Wall superheat determines the rate of bubble growth on the heated wall, which is roughly proportional to wall heat flux due to the Fourier’s Law. The distribution of velocity and temperature fields in the channel refresh progressively with increasing inflow Reynolds number, which speeds up the evolution of interface position and augments the wall heat flux significantly. Furthermore, the area of thin liquid film between the wall and the bubble is enlarged by reducing the contact angle, thus augmenting the wall heat flux by several times compared with the single phase microchannel flow. However, surface tension and gravitational acceleration are found to be negligible in the present study.

Two Phase Boiling Heat Transfer of Water in Minichannel

2017 ◽  
Author(s):  
Ye Tian ◽  
Wei Huang ◽  
Pengfei Li ◽  
Simin Cao ◽  
Yan Sun
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Absolute Error ◽  
Nuclear Industry ◽  
Working Fluid ◽  
Two Phase ◽  
Compact Heat Exchangers ◽  
Compact Size

Printed Circuit Heat Exchangers (PCHE) is a new type of compact heat exchangers, it will be widely used for nuclear industry due to its higher heat transfer area density, compact size, and design flexibility. The hydraulic diameter of PCHE tubes ranges from 1mm to 2mm which belongs to mini-channel according to Kandlikar and Grande (2003)’s study.[1] In this paper, two-phase flow boiling heat transfer of water in mini-channel is discussed. The most of previous literatures in this field mainly focused on flow boiling of refrigerants, but the main working fluid in PCHE tubes is water. A composite correlation of flow boiling of water through mini-channel has been developed on basis of a database of water in this paper. Mean absolute error (MAE) method is used to evaluate relative error. Comparing with the experimental data, the MAE of the new correlation is 23.4%.

Improved Radial Plane Fins Heat Sink for Light-Emitting Diode Lamps Cooling

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
António M. G. Lopes ◽  
Vítor A. F. Costa
Keyword(s):  
Heat Sink ◽  
Numerical Study ◽  
Light Emitting Diode ◽  
Heat Sinks ◽  
Electronic Components ◽  
Turning Operation ◽  
Light Emitting ◽  
Radial Plane ◽  
Convection Cooling ◽  
Main Ideas

Abstract A numerical study is conducted concerning the improvement of radial plane fins heat sinks for natural convection cooling of light-emitting diode (LED) lamps. The main objective is to maintain the temperature of the heat sink base below a prescribed threshold for a given released heat flux at the heat sink, minimizing its mass and maintaining at a reasonably simple level the manufacturing processes and operations required for its production. Starting from a previously optimized heat sink for the same purpose, constituted by complete rectangular radial plane fins, the present study aims at further improvements by considering incomplete rectangular radial plane fins. The main objective of this study is to find the best profile for the turning operation to obtain the radial plane fins lighter configuration. It is found that this can be achieved by removing part of the upper internal corners of the rectangular fins, more specifically shaping a curved cut, leading to heat sink mass reduction up to 32.4%. The geometry of the improved heat sink is of cylindrical nature, obtained from cutting an aluminum extruded bar comprising a cylindrical central core and a number of uniformly distributed rectangular radial plane fins, followed by a simple turning operation to remove their upper internal corners. Even if results concern a particular LED lamp, the main ideas and approach prevail to improve other types of heat sinks for general light and/or electronic components cooling.

A Modified Correlation for Flow Boiling Heat Transfer in Plate Heat Exchangers

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Wei Li ◽  
Boren Zheng ◽  
Tong Lv ◽  
Zahid Ayub
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Dimensionless Number ◽  
Plate Heat ◽  
Flow Boiling Heat Transfer ◽  
Compact Size ◽  
Wide Range ◽  
Data Points

Abstract Corrugated plate heat exchangers are increasingly used in two-phase flow applications for their flexible compact size and efficient heat transfer performance. This paper presents a brief review of recent studies on the flow boiling in plate heat exchangers and creates a database containing 533 data points from previous experimental studies. The collected database covers seven working fluids, a wide range of vapor quality (both mean and local) 0.01–0.94, heat flux 0.5–46 kW m−2, mass flux 5.5–137 kg m−2 s−1, chevron angle 30–70 deg, and hydraulic diameter 1.7–4.0 mm. Based on the database a brief comparison between several previous correlations are discussed. A new prediction method for flow boiling heat transfer coefficient is developed by multiple regression analysis and modifying an existing correlation. A criterion proposed by Li and Wu about the transition from micro- to macroscale was introduced with a combined dimensionless number Bd·Rel0.5 which attempts to comprehensively consider four types of forces during flow boiling. It was observed that the modified correlation shows a better agreement and predicts 74.3% and 94.9% of total data points within ±30% and ±50% error bands, respectively.

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