Theoretical study on the characteristics of critical heat flux in vertical narrow rectangular channels

2012 ◽  
Vol 36 ◽  
pp. 21-31 ◽  
Author(s):  
D.X. Du ◽  
W.X. Tian ◽  
G.H. Su ◽  
S.Z. Qiu ◽  
Y.P. Huang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Theoretical Study ◽  
Rectangular Channels

Correlation for Flow Boiling Critical Heat Flux in Thin Rectangular Channels

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Futoshi Tanaka ◽  
Takashi Hibiki ◽  
Kaichiro Mishima
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Rectangular Channels ◽  
Hydraulic Design ◽  
Wide Range ◽  
Outlet Flow ◽  
Triggering Mechanisms ◽  
Small Channels ◽  
Heated Length

The effect of heated length on critical heat flux (CHF) in thin rectangular channels under atmospheric pressure has been studied. CHF in small channels has been widely studied in the last decades but most of the studies are based on flow in round tubes and number of studies focused on rectangular channels is relatively small. Although basic triggering mechanisms, which lead to CHF in thin rectangular channels, are similar to that of tubes, applicability of thermal hydraulic correlations developed for tubes to rectangular channels are questionable since heat transfer in rectangular channels are affected by the existence of nonheated walls and the noncircular geometry of channel circumference. Several studies of CHF in thin rectangular channels have been reported in relation to thermal hydraulic design of research reactors and neutron source targets and correlations have been proposed, but the studies mostly focus on geometrical conditions of the application of interest and therefore effect of channel parameters exceeding their interest is not fully understood. In his study, CHF data for thin rectangular channels have been collected from previous studies and the effect of heated length on CHF was examined. Existing correlations were verified with data with positive quality outlet flow but none of the correlations successfully reproduced the data for a wide range of heated lengths. A new CHF correlation for quality region applicable to a wide range of heated lengths has been developed based on the collected data.

Theoretical study on critical heat flux with non-uniform axial power distribution

2017 ◽  
Author(s):  
Wenxing Liu ◽  
Dawei Zhao ◽  
Yuanfeng Zan ◽  
Wanyu Xiong ◽  
Jun Huang
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Power Distribution ◽  
Theoretical Study

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%.

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