Experimental investigation of forced convective boiling flow instabilities in horizontal helically coiled tubes

1996 ◽  
Vol 5 (3) ◽  
pp. 210-216 ◽  
Author(s):  
L. J. Guo ◽  
Z. P. Feng ◽  
X. J. Chen ◽  
N. H. Thomas
Keyword(s):  
Experimental Investigation ◽  
Flow Instabilities ◽  
Convective Boiling ◽  
Boiling Flow

Bubble Lift-Off Diameter in Forced Convective Boiling Flow

2010 ◽  
Author(s):  
In-Cheol Chu ◽  
Chul-Hwa Song
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Bubble Nucleation ◽  
Present Observation ◽  
Convective Boiling ◽  
Digital Video Camera ◽  
Nucleation Frequency ◽  
Boiling Flow ◽  
Lift Off ◽  
Basic Features

A series of experiments were carried out to investigate the bubble nucleation to lift-off phenomena for a subcooled boiling flow in a vertical annulus channel. A high speed digital video camera was used to capture the dynamics of the bubble nucleation to lift-off process. A total of 148 recordings were made, and the bubble lift-off diameter and the bubble nucleation frequency were evaluated for 118 recordings up to now. The basic features of the lift-off diameter and nucleation frequency were addressed based on the present observation. A database for the bubble lift-off diameter was built by gathering and summarizing the data of Prodanovic et al., Situ et al., and the present work. The prediction capability of Unal’s model, Situ et al.’s model, and Prodanovic et al.’s correlation was evaluated against the database. The best prediction results were obtained by modifying the wall superheat correlation in Unal’s model.

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.

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