THE EFFECT OF INLET SUBCOOLING ON SUSTAINED AND TRANSIENT BOILING FLOW INSTABILITIES IN A SINGLE CHANNEL UPFLOW SYSTEM

1978 ◽  
Author(s):  
Sadik Kakac ◽  
T. Nejat Veziroglu ◽  
H. S. Ergur ◽  
I. Ucar
Keyword(s):  
Single Channel ◽  
Flow Instabilities ◽  
Boiling Flow ◽  
Transient Boiling

Transient boiling flow instabilities in a multi-channel upflow system

1977 ◽  
Vol 10 (3) ◽  
pp. 175-188 ◽  
Author(s):  
S. Kakaç ◽  
T. N. Veziroğlu ◽  
N. Özboya ◽  
S. S. Lee
Keyword(s):  
Flow Instabilities ◽  
Boiling Flow ◽  
Transient Boiling

Transient boiling flow in 5 × 5 rod bundle under non-uniform rapid heating

2018 ◽  
Vol 340 ◽  
pp. 447-456 ◽  
Author(s):  
Hiroki Takiguchi ◽  
Masahiro Furuya ◽  
Takahiro Arai ◽  
Kenetsu Shirakawa
Keyword(s):  
Rapid Heating ◽  
Rod Bundle ◽  
Boiling Flow ◽  
Transient Boiling

Active Flow Instability Control for Transient Two-Phase Electronics Cooling

2010 ◽  
Author(s):  
Tie Jun Zhang ◽  
Yoav Peles ◽  
John T. Wen ◽  
Michael K. Jensen
Keyword(s):  
Active Control ◽  
Flow Instability ◽  
Cooling System ◽  
Flow Instabilities ◽  
Future Research ◽  
Two Phase ◽  
Control Schemes ◽  
Boiling Flow ◽  
Flow Oscillations ◽  
Two Phase Cooling

Because of increasing power densities, refrigeration systems are being explored for two-phase cooling of ultra high power electronic components. Flow instabilities are potential problems in any two-phase refrigeration cooling system especially in transient applications. Oscillatory two-phase flow in a boiling channel can trigger transition to the critical heat flux (CHF). Active control methods can help better dynamic thermal management of electronic systems, even though transient two-phase boiling flow mechanisms are complicated. This paper presents a framework for the transient analysis and active control of pressure-drop flow instabilities under varying imposed heat loads. The first part of the paper is to study the external effects on boiling flow characteristics and the boiling oscillatory flow responses to transient heat load changes. Then based on the theoretical analysis of boiling flow oscillations, a set of active control schemes are developed and studied to suppress flow oscillations and, therefore, to increase the CHF. With the available control devices (i.e., inlet valve and supply pump), different active control schemes are studied to improve the transient two-phase cooling performance. Finally, a discussion is included to address potential future research.

Boiling Flow Interaction Between Two Parallel Microchannels

2006 ◽  
Author(s):  
Roger D. Flynn ◽  
David W. Fogg ◽  
Jae-Mo Koo ◽  
Ching-Hsiang Cheng ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Transfer ◽  
Liquid Flow ◽  
Heat Exchangers ◽  
Single Channel ◽  
Flow Boiling ◽  
Parallel Channel ◽  
Flow Interaction ◽  
Boiling Flow ◽  
Parallel Microchannels ◽  
Channel Configuration

Microchannel heat exchangers predominately use a parallel channel configuration to maximize heat transfer with minimal pump demand. Previous work optimized bulk performance of liquid flow heat exchangers but noted that upon boiling, flow redistributed among parallel channels, and they ultimately found that this instability caused an uncontrollable operating condition. This work predicts and measures fully coupled boiling flow interaction in a simplified two microchannel system. A series of silicon microfabricated devices enable piecewise study of the coupled fluidic and heat transfer interactions, first uniting the fluid inlets of thermally isolated channels, then connecting neighboring channel walls to allow heat transfer between channels. Multiple combinations of boiling and liquid flow, each satisfying system boundary conditions, are identified using flow demand curves assembled from single channel data. Each unique flow condition is experimentally demonstrated and found to be heavily dependent on the prior state of the channels. Connecting channel walls, thermally, is shown to lessen the number of allowed solutions and increase instability in the two channel system, allowing distinction between purely fluidic instabilities and fluidic instabilities coupled to heat transfer between channels. This work in describing interaction between two channels is a necessary step as work continues toward characterizing flow boiling in more complex parallel channel heat sinks.

Suppression of Two-Phase Flow Instabilities in Parallel Microchannels by Using Synthetic Jets

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Ruixian Fang ◽  
Jamil A. Khan
Keyword(s):  
Two Phase Flow ◽  
Flow Boiling ◽  
Synthetic Jets ◽  
Flow Instabilities ◽  
Phase Flow ◽  
Microchannel Flow ◽  
Two Phase ◽  
Boiling Flow ◽  
Parallel Microchannels ◽  
Flow Reversals

Two-phase flow instabilities in microchannels exhibit pressure and temperature fluctuations with different frequencies and amplitudes. An active way to suppress the dynamic instabilities in the boiling microchannels is to introduce synthetic jets into the channel fluid. Thus, the bubbles can be condensed before they clog the channel and expand upstream causing flow reversal. The present work experimentally investigated the effects of synthetic jets on microchannel flow boiling. An array of synthetic jets was introduced into the microchannel flow. The strength and frequency of the jets were controlled by changing the driving signals of the piezoelectric driven jet actuator. It is found that the bubbles were effectively condensed inside the jet cavity. The boiling flow reversals were notably delayed by the synthetic jets. Meanwhile, the pressure fluctuation amplitudes were suppressed to some extent. It was also observed that synthetic jets can help to uniformize the heat sink temperature distribution.

Numerical Solution for Transient Conjugate Two-Phase Heat Transfer With Heat Generation in the Pipe Wall

2002 ◽  
Vol 124 (6) ◽  
pp. 1213-1218 ◽  
Author(s):  
Yuri V. Fairuzov ◽  
Hector Arvizu
Keyword(s):  
Heat Transfer ◽  
Numerical Solution ◽  
Heat Generation ◽  
Two Phase ◽  
Convective Boiling ◽  
Wall Superheat ◽  
Boiling Flow ◽  
Rigorous Model ◽  
Two Phase Heat Transfer ◽  
Transient Boiling

A method developed earlier for modeling conjugate two-phase heat transfer in flashing flows was used to obtain a numerical solution for transient boiling flow in heated pipes or channels. Two criteria of applicability of the solution obtained were proposed and numerically tested using a more rigorous model, which accounts for the effects of heat conduction with heat generation in the wall and forced convective boiling. The solution obtained provides a simple and reliable alternative to more rigorous methods for modeling transient two-phase flow in heated channels when the material of the wall bounding the flow has a high thermal conductivity and the wall superheat is small.

Two-Phase Flow Studies in Boiling Single Channel Flow Using Wire Mesh Tomography (WMT) and Ultrasound Velocity Profile (UVP)

2014 ◽  
Author(s):  
Ari Hamdani ◽  
Thang Tat Nguyen ◽  
Daisuke Ito ◽  
Nobuyoshi Tsuzuki ◽  
Hiroshige Kikura
Keyword(s):  
Velocity Profile ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Single Channel ◽  
Swirling Flow ◽  
Flow Behavior ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Boiling Flow

The objective of this work is to investigate characteristics of co-current boiling flow in a circular pipe with an inner diameter of 52 mm by using wire mesh tomography (WMT) and ultrasonic velocity profile (UVP). The inner wall of pipe is modified by adding fins on the inner pipe’s wall. This modification is intended to change the flow behavior into swirling flow in boiling flow. Firstly, the effect of wall modification on flow behavior is investigated by numerical calculation. Secondly, two-phase flow is investigated experimentally using UVP and WMT. In experiments, local time-average void fraction is measured using WMT and velocity profile is measured using UVP. Furthermore, these measured data, both void fraction and velocity profile, will give information about changing in flow pattern caused by modified inner pipe’s wall.

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