scholarly journals Thermal Analysis on Mono-Block Type Divertor Based on Subcooled Flow Boiling Critical Heat Flux Data against Inlet Subcooling in Short Vertical Tube

2006 ◽  
Vol 1 ◽  
pp. 017-017 ◽  
Author(s):  
Koichi HATA ◽  
Masahiro SHIOTSU ◽  
Nobuaki NODA
Keyword(s):  
Thermal Analysis ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Block Type ◽  
Subcooled Flow Boiling ◽  
Flux Data ◽  
Subcooled Flow

Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube

2006 ◽  
Author(s):  
Koichi Hata ◽  
Masahiro Shiotsu ◽  
Nobuaki Noda
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Test Tube ◽  
304 Stainless Steel ◽  
Tube Material ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow

The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u = 4.0 to 13.3 m/s), the inlet subcoolings (ΔTsub,in = 48.6 to 154.7 K), the inlet pressure (Pin = 735.2 to 969.0 kPa) and the increasing heat input (Q0exp(t/τ), τ = 10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tubes of inner diameters (d = 6 mm), heated lengths (L = 66 mm) and L/d = 11 with the inner surface of rough finished (Surface roughness, Ra = 3.18 μm), the Cupro Nickel (Cu-Ni 30%) test tubes of d = 6 mm, L = 60 mm and L/d = 10 with Ra = 0.18 μm and the Platinum (Pt) test tubes of d = 3 and 6 mm, L = 66.5 and 69.6 mm, and L/d = 22.2 and 11.6 respectively with Ra = 0.45 μm are used in this work. The CHF data for the SUS304, Cu-Ni 30% and Pt test tubes were compared with SUS304 ones for the wide ranges of d and L/d previously obtained and the values calculated by the authors’ published steady state CHF correlations against outlet and inlet subcoolings. The influence of the test tube material on CHF is investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux is discussed.

Numerical investigation of the effect of bump and indent inside a vertical tube on the subcooled flow boiling and critical heat flux

2020 ◽  
Vol 14 (2) ◽  
pp. 6690-6708
Author(s):  
Kianoush DolatiAsl ◽  
Ehsan Abedini ◽  
Younes Bakhshan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Volume Fraction ◽  
Flow Boiling ◽  
Vapour Phase ◽  
Vertical Tube ◽  
Ansys Fluent ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Euler Model

One of the essential industry problems is the critical heat flux (CHF) phenomenon in the flow boiling regime which leads to the temperature jumping and damaging to the systems. Increasing the vapour volume fraction decreases the heat transfer coefficient, and finally, temperature jump will occur. Also, the existence of the bumps and indent in the flow domain changes the flow pattern. In this study, by considering bumps and indent in the tube, the boiling of fluid flow in the vertical tube is discussed. For modelling and simulating the problems, the Euler-Euler model for studying the interaction of the liquid-vapour phases was used. Some models and material specifications are declared using the user-defined function (UDF) codes to the ANSYS Fluent program. The results show that the existence of bumps and indent inside the tube causes the flow of liquid phase to be less redirected in comparison to vapour phase flow due to having more momentum; therefore, at the end of the bumps in the tube, the amount of vapour volume fraction near the wall rises sharply. By increasing the flow mass flux, the vapour volume fraction at the end of bumps increases which lead to decreasing CHF value. It has also observed that if there are bumps and indents inside the tube, there will be no significant change in the liquid flow and vapour volume fraction in the other parts of the tube, as compared to the regular tube.    

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