Effect of Cross-Sectional Perturbation on Critical Heat Flux Criteria in Microchannels

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Mark J. Miner ◽  
Patrick E. Phelan
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Phase Velocity ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Channel Diameter ◽  
Cross Sectional ◽  
Growing Body ◽  
Circular Microchannel ◽  
Expanding Channel

A variety of predictive correlations for critical heat flux (CHF) are examined in light of the growing body of work exploring enhanced flow boiling CHF via cross-sectional expansion. The analysis considers the effect of a small perturbation of the diameter of a circular microchannel on the predictions made by the selected criteria, and seeks to demonstrate an optimum rate of expansion. It is demonstrated that a nonzero diameter expansion necessarily improves performance under several criteria for critical heat flux, and an optimum expansion rate exists for many of these criteria. CHF relations are seen to follow a few distinct types, and those relations which contemplate effects which may directly influence CHF, such as pressure and phase velocity, tend to better reflect the experimentally demonstrated effect of the expanding channel diameter on CHF. Experimental data are examined from several investigators, including the authors' group, and the validity of both the criteria and the analysis is compared to the data.

Critical Heat Flux Measurement and Model for Refrigerant-123 Under Stabilized Flow Conditions in Microchannels

2006 ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Flux Measurement ◽  
Absolute Error ◽  
Cross Sectional ◽  
Boiling Process ◽  
Parallel Microchannels

The present work is aimed toward understanding the effect of flow boiling stability on critical heat flux (CHF) with Refrigerant-123 (R-123) in microchannel passages. Experimental data and theoretical model to predict the CHF are the focus of this work. The experimental test section has six parallel microchannels with each having a cross sectional area of 1054 × 157 μm2. The effect of flow instabilities in microchannels is investigated using flow restrictors at the inlet of each microchannel to stabilize the flow boiling process and avoid the backflow phenomena. This technique resulted in successfully stabilizing the flow boiling process as seen through a high-speed camera. The present CHF result is found to correlate to mean absolute error (MAE) of 24.1% with a macroscale empirical equation by Katto [13]. A theoretical analysis of flow boiling phenomena revealed that the ratio of evaporation momentum to surface tension forces is an important parameter. For the first time, a theoretical CHF model is proposed using these underlying forces to represent CHF mechanism in microchannels, and its correlation agrees with the experimental data with MAE of 2.5%.

Experimental Study and Model on Critical Heat Flux of Refrigerant-123 and Water in Microchannels

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Flow Instabilities ◽  
Cross Sectional ◽  
Rectangular Channels ◽  
Boiling Process ◽  
Parallel Microchannels ◽  
Surface Tension Forces

The present work is aimed toward understanding the effect of flow boiling stability on critical heat flux (CHF) with Refrigerant 123 (R-123) and water in microchannel passages. Experimental data and theoretical model to predict the CHF are the focus of this work. The experimental test section has six parallel microchannels, with each having a cross-sectional area of 1054×157μm2. The effect of flow instabilities in microchannels is investigated using flow restrictors at the inlet of each microchannel to stabilize the flow boiling process and avoid the backflow phenomena. This technique resulted in successfully stabilizing the flow boiling process. The present experimental CHF results are found to correlate best with existing correlations to overall mean absolute errors (MAEs) of 33.9% and 14.3% with R-123 and water, respectively, when using a macroscale rectangular equation by Katto (1981, “General Features of CHF of Forced Convection Boiling in Uniformly Heated Rectangular Channels,” Int. J. Heat Mass Transfer, 24, pp. 1413–1419). A theoretical analysis of flow boiling phenomena revealed that the ratio of evaporation momentum to surface tension forces is an important parameter. A theoretical CHF model is proposed using these underlying forces to represent CHF mechanism in microchannels, and its correlation agrees with the experimental data with MAE of 2.5%.

Flow boiling in microgravity: Part 2 – Critical heat flux interfacial behavior, experimental data, and model

2015 ◽  
Vol 81 ◽  
pp. 721-736 ◽  
Author(s):  
Christopher Konishi ◽  
Hyoungsoon Lee ◽  
Issam Mudawar ◽  
Mohammad M. Hasan ◽  
Henry K. Nahra ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Interfacial Behavior

Optimized Expanding Microchannel Geometry for Flow Boiling

2011 ◽  
Author(s):  
Mark J. Miner ◽  
Patrick E. Phelan ◽  
Brent A. Odom ◽  
Carlos A. Ortiz ◽  
Jonathan A. Sherbeck ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Cross Section ◽  
Flow Boiling ◽  
Flow Direction ◽  
Experimental Studies ◽  
Separated Flow ◽  
Channel Geometry ◽  
Heated Channel ◽  
Expanding Channel

This study discusses the simulation of flow boiling in a microchannel and the predicted effects of channel geometry variation along the flow direction. Recent experimental studies have generated interest in expanding the cross-section of a microchannel to improve boiling heat transfer. The motivation for this geometry change is discussed, constraints and model selection are reviewed, and Revellin and Thome’s critical heat flux criterion is used to bound the simulation of separated flow in a heated channel, via MATLAB. Expanding channel geometry permits higher heat rates before reaching critical heat flux.

Flow Boiling of R134a in Circular Microtubes—Part II: Study of Critical Heat Flux Condition

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Saptarshi Basu ◽  
Sidy Ndao ◽  
Gregory J. Michna ◽  
Yoav Peles ◽  
Michael K. Jensen
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Heat Flux ◽  
Flow Pattern ◽  
Flow Regime ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Absolute Error ◽  
Two Phase

A detailed experimental study was carried out on the critical heat flux (CHF) condition for flow boiling of R134a in single circular microtubes. The test sections had inner diameters (ID) of 0.50 mm, 0.96 mm, and 1.60 mm. Experiments were conducted over a large range of mass flux, inlet subcooling, saturation pressure, and vapor quality. CHF occurred under saturated conditions at high qualities and increased with increasing mass fluxes, tube diameters, and inlet subcoolings. CHF generally, but not always, decreases with increasing saturation pressures and vapor qualities. The experimental data were mapped to the flow pattern maps developed by Hasan [2005, “Two-Phase Flow Regime Transitions in Microchannels: A Comparative Experimental Study,” Nanoscale Microscale Thermophys. Eng., 9, pp. 165–182] and Revellin and Thome [2007, “A New Type of Diabatic Flow Pattern Map for Boiling Heat Transfer in Microchannels,” J. Micromech. Microeng., 17, pp. 788–796]. Based on these maps, CHF mainly occurred in the annular flow regime in the larger tubes. The flow pattern for the 0.50 mm ID tube was not conclusively identified. Four correlations—the Bowring correlation, the Katto-Ohno correlation, the Thome correlation, and the Zhang correlation—were used to predict the experimental data. The correlations predicted the correct experimental trend, but the mean absolute error (MAE) was high (>15%) A new correlation was developed to fit the experimental data with a MAE of 10%.

Experimental Study on Saturated Flow Boiling Critical Heat Flux in Microchannels

2006 ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Quantitative Information ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Saturated Flow ◽  
Cross Sectional ◽  
Parallel Microchannels ◽  
Cartridge Heater

The saturated flow boiling critical heat flux in microchannels is investigated using water as the working fluid. The experimental test section has six parallel microchannels with each having a cross sectional area of 1054 × 157 micrometers. The mass flow rate, inlet temperature of the working fluids, and the electric current supplied to the resistive cartridge heater are controlled to provide quantitative information near the CHF condition in microchannels. The trends in present CHF with mass flux and quality are similar to those obtained by Qu and Mudawar [1] and earlier investigators.

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