Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in a SUS304-Circular Tube With Various Twisted-Tape Inserts (Influence of Twist Ratio)

2013 ◽  
Author(s):  
Koichi Hata ◽  
Yasuyuki Shirai ◽  
Suguru Masuzaki
Keyword(s):  
Circular Tube ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Circular Tubes ◽  
Twisted Tapes ◽  
Swirl Velocity ◽  
Twist Ratio ◽  
Inner Diameter

The transient critical heat fluxes in SUS304-circular tubes with various twisted-tape inserts are systematically measured for mass velocities (G = 3988 to 13620 kg/m2s), inlet liquid temperatures (Tin = 287.55 to 313.14 K), outlet pressures (Pout = 805.11 to 870.23 kPa) and exponentially increasing heat inputs (Q = Q0exp(t/τ), τ = 28.39 ms to 8.43 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-circular tube of inner diameter (d = 6 mm), heated length (L = 59.4 mm), effective length (Leff = 49.4 mm), L/d (= 9.9), Leff/d (= 8.23) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted tapes with twist ratios, y [= H/d = (pitch of 180° rotation)/d], of 2.40 and 4.45 are used. The transient critical heat fluxes for SUS304-circular tubes with various twisted-tape inserts are compared with authors’ transient CHF data for the empty SUS304-circular tube and a SUS304-circular tube with twisted-tape of y = 3.37, and the values calculated by authors’ transient CHF correlations for the empty circular tube and the circular tube with twisted-tape insert. The influences of heating rate, twist ratio and swirl velocity on the transient CHF are investigated into details and the widely and precisely predictable correlations of the transient CHF against inlet and outlet subcoolings for the circular tubes with various twisted-tape inserts are given based on the experimental data. The correlations can describe the transient CHFs for SUS304-tubes with various twisted-tape inserts obtained in this work within −27 to 7.9% difference.

Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in SUS304-Circular Tubes With Various Twisted-Tape Inserts (Influence of Twist Ratio)

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Suguru Masuzaki
Keyword(s):  
Circular Tube ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Flow Boiling ◽  
Circular Tubes ◽  
Twisted Tapes ◽  
Subcooled Flow ◽  
Twist Ratio

The transient critical heat fluxes (transient CHFs) in SUS304-circular tubes with various twisted-tape inserts are systematically measured for mass velocities (G = 3988–13,620 kg/m2s), inlet liquid temperatures (Tin = 287.55–313.14 K), outlet pressures (Pout = 805.11–870.23 kPa) and exponentially increasing heat inputs (Q = Q0 exp(t/τ), exponential periods, τ, of 28.39 ms to 8.43 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-circular tube of inner diameter (d = 6 mm), heated length (L = 59.4 mm), effective length (Leff = 49.4 mm), L/d (=9.9), Leff/d (=8.23), and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted-tapes with twist ratios, y [H/d = (pitch of 180 deg rotation)/d], of 2.40 and 4.45 are used. The transient critical heat fluxes for SUS304-circular tubes with the twisted-tapes of y = 2.40 and 4.45 are compared with authors' transient CHF data for the empty SUS304-circular tube and a SUS304-circular tube with the twisted-tape of y = 3.37, and the values calculated by authors' transient CHF correlations for the empty circular tube and the circular tube with twisted-tape insert. The influences of heating rate, twist ratio and swirl velocity on the transient CHF are investigated into details and the widely and precisely predictable correlations of the transient CHF against inlet and outlet subcoolings for the circular tubes with various twisted-tape inserts are given based on the experimental data. The correlations can describe the transient CHFs for SUS304-circular tubes with various twisted-tapes of twist ratios (y = 2.40, 3.37, and 4.45) in the wide experimental ranges of exponential periods (τ = 28.39 ms to 8.43 s) and swirl velocities (usw = 5.04–20.72 m/s) obtained in this work within −26.19% to 14.03% difference. The mechanism of the subcooled flow boiling critical heat flux in a circular tube with twisted-tape insert is discussed.

Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in a Short SUS304-Tube With Twisted-Tape Insert

2012 ◽  
Author(s):  
Koichi Hata ◽  
Yasuyuki Shirai ◽  
Suguru Masuzaki
Keyword(s):  
Steady State ◽  
Flow Boiling ◽  
Test Tube ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Swirl Velocity ◽  
Twist Ratio ◽  
Inner Diameter ◽  
Heated Length

The transient critical heat fluxes (transient CHFs) in a short SUS304-tube with twisted-tape insert are systematically measured for mass velocities (G = 3997.79 to 13419.8 kg/m2s), inlet liquid temperatures (Tin = 293.55 to 300.85 K), outlet pressures (Pout = 825.19 to 860.95 kPa) and exponentially increasing heat inputs (Q = Q0exp(t/τ), τ = 26.85 ms to 8.42 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304 test tube of inner diameter (d = 6 mm), heated length (L = 59.4 mm), effective length (Leff = 49.4 mm), L/d (= 9.9), Leff/d (= 8.23) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted-tape with width (w = 5.6 mm), thickness (δT = 0.6 mm), total length (l = 372 mm) and twist ratio, y [= H/d = (pitch of 180° rotation)/d], of 3.37 is used. The transient CHFs for a short SUS304-tube with twisted-tape insert are compared with authors’ steady-state CHF data for a short SUS304-tube with various twisted-tape inserts, their transient CHF data for the empty SUS304-tube and the values calculated by authors’ steady-state CHF correlations for the test tubes with various twisted-tape inserts and their transient CHF correlations for the empty test tubes. The influences of twisted-tape insert, heating rate and swirl velocity on the transient CHF are investigated into details and the widely and precisely predictable correlations of the transient CHF for the test tube with twisted-tape insert are given based on the experimental data. The correlations can describe the transient CHFs for a short SUS304-tube with twisted-tape of y = 3.37 obtained in this work within −27 to 7.9 % difference.

Subcooled Swirl-Flow Boiling and Burnout With Electrically Heated Twisted Tapes and Zero Wall Flux

1965 ◽  
Vol 87 (3) ◽  
pp. 342-348 ◽  
Author(s):  
W. R. Gambill
Keyword(s):  
Tube Wall ◽  
Flow Boiling ◽  
Heated Surface ◽  
Swirl Flow ◽  
Heat Fluxes ◽  
Twisted Tape ◽  
Centripetal Acceleration ◽  
Head Tank ◽  
Twisted Tapes ◽  
Twist Ratio

A series of swirl-flow tests was conducted in which all of the heat was generated in twisted-tape swirl generators. This is in contrast to past ORNL swirl-flow tests with twisted tapes, in which ∼99 percent of the heat was generated in the metallic tube wall. In the present study, water from a constant-head tank flowed by gravity at 5 to 8 fps through a vertical 0.27-in.-ID glass tube ∼13 in. long, in which was located a resistance-heated, 16-mil-thick A-nickel tape. Tape-twist ratios were varied from 2.7 to ∞ inside tube diameters/180-deg twist, inlet water temperatures from 63 to 173 F, and heat fluxes from 0.21 × 106 to 1.20 × 106 Btu/hr·ft2. The water head above the top of the tube was held at 30.7 in. In all cases, the critical wall superheat increased with decrease of tape-twist ratio, whereas the critical heat fluxes for the twisted tapes fell between 93 percent and 122 percent of those for flat tapes, maximizing in all cases at a tape-twist ratio of 7 to 10. It is postulated that the deleterious effect of centripetal acceleration with this geometry, which tends to hold the vapor on the heated surface, is compensated in the swirl-flow entrance region by inertial impingement of the liquid onto the tape surface, and along the remainder of the length by a double-vortex secondary flow pattern in the plane normal to the tube wall. The power density of a swirl-flow tube assembly may therefore be significantly increased by generating heat in the twisted tape as well as in the tube wall.

Subcooled Water Flow Boiling Heat Transfer in a Short SUS304-Tube With Twisted-Tape Insert

2010 ◽  
Author(s):  
Koichi Hata ◽  
Suguru Masuzaki
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Test Tube ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The subcooled boiling heat transfer (HT) and the steady-state critical heat fluxes (CHFs) in a short SUS304-tube with twisted-tape insert are systematically measured for mass velocities (G = 4016 to 13850 kg/m2s), inlet liquid temperatures (Tin = 285.82 to 363.96 K), outlet pressures (Pout = 764.76 to 889.02 kPa) and exponentially increasing heat input (Q = Q0exp(t/τ), τ = 8.5 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304 test tube of inner diameter (d = 6 mm), heated length (L = 59.5 mm), effective length (Leff = 49.1 mm), L/d (= 9.92), Leff/d (= 8.18) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.18 μm) is used in this work. The SUS304 twisted tape with twist ratio, y [= H/d = (pitch of 180° rotation)/d], of 3.39 is used. The relation between inner surface temperature and heat flux for the SUS304-tube with the twisted-tape insert are clarified from non-boiling to CHF. The subcooled boiling heat transfer for SUS304-tube with the twisted-tape insert is compared with our empty SUS304-tube data and the values calculated by our and other workers’ correlations for the subcooled boiling heat transfer. The influences of the twisted-tape insert and the swirl velocity on the subcooled boiling heat transfer and the CHFs are investigated into details and the widely and precisely predictable correlations of the subcooled boiling heat transfer and the CHFs for turbulent flow of water in the SUS304-tube with twisted-tape insert are given based on the experimental data. The correlations can describe the subcooled boiling heat transfer coefficients and the CHFs obtained in this work within −25 to +15% difference.

Heat Transfer and Critical Heat Flux of Subcooled Water Flow Boiling in a SUS304-Tube With Twisted-Tape Insert

2010 ◽  
Author(s):  
Koichi Hata ◽  
Suguru Masuzaki
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Test Tube ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Boiling ◽  
Transfer Coefficients ◽  
Heat Transfers

The subcooled boiling heat transfer (HT) and the steady-state critical heat fluxes (CHFs) in a short SUS304-tube with twisted-tape insert are systematically measured for mass velocities (G = 4016 to 13950 kg/m2s), inlet liquid temperatures (Tin = 285.82 to 363.96 K), outlet pressures (Pout = 764.76 to 889.02 kPa) and exponentially increasing heat input (Q = Q0 exp(t/τ), τ = 8.5 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304 test tube of inner diameter (d = 6 mm), heated length (L = 59.5 mm), effective length (Leff = 49.1 mm), L/d (= 9.92), Leff/d (= 8.18) and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted tape with twist ratios, y [= H/d = (pitch of 180° rotation)/d], of 2.39, 3.39 and 4.45 are used. The relations between inner surface temperatures and heat fluxes for the SUS304-tubes with various twisted-tape inserts are clarified from non-boiling to CHF. The subcooled boiling heat transfers for SUS304-tubes with various twisted-tape inserts are compared with our empty SUS304-tube data and the values calculated by our and other workers’ correlations for the subcooled boiling heat transfer. The influences of the twisted-tape insert, the twist ratio and the swirl velocity on the subcooled boiling heat transfer and the CHFs are investigated into details and the widely and precisely predictable correlations of the subcooled boiling heat transfer and the CHFs for turbulent flow of water in the SUS304-tubes with twisted-tape inserts are given based on the experimental data. The correlations can describe the subcooled boiling heat transfer coefficients and the CHFs obtained in this work within −25 to +15% difference.

Heat Transfer and Critical Heat Flux of Subcooled Water Flow Boiling in a SUS304-Tube With Twisted-Tape Insert

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Koichi Hata ◽  
Suguru Masuzaki
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Test Tube ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Boiling ◽  
Transfer Coefficients ◽  
Heat Transfers

The subcooled boiling heat transfer and the steady state critical heat fluxes (CHFs) in a short SUS304-tube with twisted-tape insert are systematically measured for mass velocities (G=4016–13,950 kg/m2 s), inlet liquid temperatures (Tin=285.8–364.0 K), outlet pressures (Pout=764.8–889.0 kPa), and exponentially increasing heat input (Q=Q0 exp(t/τ) and τ=8.5 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304 test tube of inner diameter (d=6 mm), heated length (L=59.5 mm), effective length (Leff=49.1 mm), L/d(=9.92), Leff/d(=8.18), and wall thickness (δ=0.5 mm) with average surface roughness (Ra=3.89 μm) is used in this work. The SUS304 twisted-tape with twist ratios y[=H/d=(pitch of 180 deg rotation)/d] of 2.39, 3.39, and 4.45 are used. The relations between inner surface temperatures and heat fluxes for the SUS304-tubes with various twisted-tape inserts are explored for different flow regimes ranging from single-phase flows to CHF. The subcooled boiling heat transfers for SUS304-tubes with various twisted-tape inserts are compared with authors’ empty SUS304-tube data and the values calculated by authors’ and other workers’ correlations for the subcooled boiling heat transfer. The influences of the twisted-tape insert, the twist ratio, and the swirl velocity on the subcooled boiling heat transfer and the CHFs are investigated into details, and the correlations of the subcooled boiling heat transfer and the CHFs for turbulent flow of water in the SUS304-tubes with twisted-tape inserts are given based on the experimental data. The precision or accuracy of a more widely set of correlations in predicting the present set of data is evaluated. The correlations can describe the subcooled boiling heat transfer coefficients and the CHFs obtained in this work from −25% to +15% difference.

Subcooled Water Flow Boiling Heat Transfer in a Short SUS304-Tube With Twisted-Tape Insert

2010 ◽  
Vol 133 (5) ◽  
Author(s):  
Koichi Hata ◽  
Suguru Masuzaki
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Test Tube ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The subcooled boiling heat transfer and the steady-state critical heat fluxes (CHFs) in a short SUS304-tube with twisted-tape insert are systematically measured for mass velocities (G=4016–13,850 kg/m2 s), inlet liquid temperatures (Tin=285.82–363.96 K), outlet pressures (Pout=764.76–889.02 kPa), and exponentially increasing heat input (Q=Q0 exp(t/τ), τ=8.5 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304 test tube of inner diameter (d=6 mm), heated length (L=59.5 mm), effective length (Leff=49.1 mm), L/d(=9.92), Leff/d(=8.18), and wall thickness (δ=0.5 mm) with average surface roughness (Ra=3.18 μm) is used in this work. The SUS304 twisted tape with twist ratio, y(=H/d=(pitch of 180 deg rotation)/d), of 3.39 is used. The relation between inner surface temperature and heat flux for the SUS304-tube with the twisted-tape insert are clarified from nonboiling to CHF. The subcooled boiling heat transfer for SUS304-tube with the twisted-tape insert is compared with our empty SUS304-tube data and the values calculated by our and other workers’ correlations for the subcooled boiling heat transfer. The influences of the twisted-tape insert and the swirl velocity on the subcooled boiling heat transfer and the CHFs are investigated into details and the widely and precisely predictable correlations of the subcooled boiling heat transfer and the CHFs for turbulent flow of water in the SUS304-tube with twisted-tape insert are given based on the experimental data. The correlations can describe the subcooled boiling heat transfer coefficients and the CHFs obtained in this work within −25 to +15% difference.

scholarly journals Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in a SUS304-Circular Tube Caused by a Rapid Decrease in Velocity From Non-Boiling Regime

2014 ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Suguru Masuzaki
Keyword(s):  
Steady State ◽  
Flow Velocity ◽  
Circular Tube ◽  
Rapid Decrease ◽  
Heat Fluxes ◽  
Effective Length ◽  
Initial Flow ◽  
Circular Tubes ◽  
Boiling Regime ◽  
Initial Heat

The flow transient critical heat fluxes (FT-CHFs, qcr,sub) in a SUS304-circular tube caused by a rapid decrease in velocity from non-boiling regime are systematically measured for initial flow velocities (u0=7.057 to 13.635 m/s for conditions of u0=6.9, 9.9 and 13.3 m/s), initial heat fluxes (q0=15.59 to 17.34 MW/m2), inlet liquid temperatures (Tin=290.12 to 308.51 K), outlet pressures (Pout=698.38 to 1288.97 kPa) and decelerations caused by a rapid decrease in velocity (u(t)=u0+αt, α=−7.357 to −0.326 m/s2) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-circular tubes of inner diameter (d=6 mm), heated length (L=59.5 to 59.7 mm), effective length (Leff=48.7 to 50.2 mm), L/d (=9.92 to 9.95), Leff/d (=8.12 to 8.37) and wall thickness (δ=0.5 mm) with average surface roughness (Ra=3.89 μm) are used in this work. The flow transient CHFs for SUS304-circular tube are compared with authors’ steady-state CHF data for the empty VERTICAL and HORIZONTAL SUS304-circular tubes and the values calculated by authors’ steady-state CHF correlations against outlet and inlet subcoolings for the empty circular tube. The influences of initial flow velocity (u0), initial heat flux (q0) and deceleration caused by a rapid decrease in velocity (α) on the flow transient CHF are investigated into details and the widely and precisely predictable correlations of CHF and flow velocity at the flow transient CHF for the circular tube is given based on the experimental data. The correlations can describe the flow velocity and the CHFs at the flow transient CHFs for SUS304-circular tube obtained in this work within ±20 % difference.

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