scholarly journals Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in a SUS304-CIRCULAR Tube with Twisted-Tape Insert

2013 ◽  
Vol 7 (2) ◽  
pp. 122-137 ◽  
Author(s):  
Koichi HATA ◽  
Yasuyuki SHIRAI ◽  
Suguru MASUZAKI
Keyword(s):  
Water Flow ◽  
Circular Tube ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Twisted Tape ◽  
Subcooled Water

Non-Linear Characteristics of Subcooled Water Flow Boiling CHFS Versus Outlet Subcoolings for Flow Velocities at Pressures in Various Tubes

2008 ◽  
Author(s):  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Flow Velocity ◽  
Water Flow ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Twisted Tape ◽  
Outlet Pressure ◽  
Subcooled Water ◽  
Twisted Tapes ◽  
Non Linear ◽  
Bare Tube

Non-linear characteristics of the subcooled water flow boiling CHF versus outlet subcooling for a flow velocity with outlet pressure as a parameter in a horizontal or vertical tube with a twisted tape having flowing subcooled water was clarified using the existing databases expanding quite recently derived the CHF correlations based on two CHF mechanisms for the bare tubes with various inside diameters and length-to-diameter ratios for a flow velocity with outlet pressure as a parameter. The databases were applied measured using, the horizontal tubes with inside diameters of 8 and 12 mm, having length-to-diameter ratios of 6.25 and 4.17 respectively with twisted-tapes having a twist ratio of 2.0, for flow velocities of 7 and 10 m/s, at pressures ranging from 0.2 to 1.1 MPa. The nonlinear characteristics of subcooled water flow boiling CHFs for outlet subcoolings in the tubes having helically coiled 1 mm diameter wires of the coil pitches of 12, 24 and 36 mm, with flowing subcooled water of a flow velocity of 7 m/s at outlet pressures of 0.2, 0.3 and 1.1 MPa were investigated based on the subcooled water flow boiling CHF correlations for bare tubes previously derived. The following results were derived that (1) the non-linear characteristic of CHF versus outlet subcooling, for a horizontal or vertical tube having a twisted tape, divided into three regions for middle, transition, and high outlet subcooling was clarified. The characteristics were similar to that for a identical bare tube, with higher CHF values for middle and high outlet subcooling values respectively, and (2) the enhanced CHF values for middle and high outlet subcooling values being dependent on outlet pressuret and being independent of one respectively, were described by the same CHF correlations derived for a identical bare tube, with higher coefficients of the correlations depending on the tubes with twisted tapes of twist ratios.

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.

scholarly journals Critical Heat Fluxes of Subcooled Water Flow Boiling against Inlet Subcooling in Short Vertical Tube

2004 ◽  
Vol 47 (2) ◽  
pp. 306-315 ◽  
Author(s):  
Koichi HATA ◽  
Hirokazu KOMORI ◽  
Masahiro SHIOTSU ◽  
Nobuaki NODA
Keyword(s):  
Water Flow ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Heat Fluxes ◽  
Subcooled Water

Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in a Short Vertical Tube Caused by Exponentially Increasing Heat Inputs

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Koichi Hata ◽  
Nobuaki Noda
Keyword(s):  
Water Flow ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Heat Fluxes ◽  
High Heating Rate ◽  
Subcooled Flow Boiling ◽  
Subcooled Water ◽  
Subcooled Flow ◽  
Inner Surface ◽  
High Heating

The transient critical heat fluxes (CHFs) of the subcooled water flow boiling for the flow velocities (u=4.0–13.3m∕s), the inlet subcoolings (ΔTsub,in=68.08–161.12K), the inlet pressures (Pin=718.31–1314.62kPa), the dissolved oxygen concentrations (O2=2.94ppm to the saturated one), and the exponentially increasing heat inputs (Q0exp(t∕τ), τ=16.82msto15.52s) are systematically measured with an experimental water loop comprised of a pressurizer. The SUS304 tubes of the inner diameters (d=3mm, 6mm, 9mm, and 12mm), heated lengths (L=33.15–132.9mm), L∕d=5.48–11.08, and wall thickness (δ=0.3mm and 0.5mm) with the rough finished inner surface (surface roughness, Ra=3.18μm) are used in this work. The transient CHF data (qcr,sub=6.91–60MW∕m2) are compared with the values calculated by the steady state CHF correlations against inlet and outlet subcoolings. The transient CHF correlations against inlet and outlet subcoolings are derived based on the experimental data. The dominant mechanisms of the subcooled flow boiling CHF for a high heating rate are discussed.

ICONE11-36116 CRITICAL HEAT FLUXES OF SUBCOOLED WATER FLOW BOILING AGAINST INLET SUBCOOLING IN SHORT VERTICAL TUBE

2003 ◽  
Vol 2003 (0) ◽  
pp. 239 ◽  
Author(s):  
Koichi Hata ◽  
Takeya Tanimoto ◽  
Hirokazu Komori ◽  
Masahiro Shiotsu ◽  
Nobuaki Noda
Keyword(s):  
Water Flow ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Heat Fluxes ◽  
Subcooled Water

Critical Heat Fluxes of Subcooled Water Flow Boiling Against Outlet Subcooling in Short Vertical Tube

2002 ◽  
Author(s):  
Koichi Hata ◽  
Toshiyuki Sato ◽  
Takeya Tanimoto ◽  
Masahiro Shiotsu ◽  
Nobuaki Noda
Keyword(s):  
Experimental Data ◽  
Water Flow ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Heat Fluxes ◽  
Outlet Pressure ◽  
Subcooled Water ◽  
Wide Range ◽  
Inner Diameter ◽  
Flow Velocities

The critical heat fluxes (CHFs) of subcooled water flow boiling are systematically measured for the flow velocities (u = 4.0 to 13.3 m/s), the outlet subcoolings (ΔTsub,out = 3 to 129 K) and the outlet pressure (Pout = 800 kPa). The SUS304 test tubes of 3, 6, 9 and 12 mm in inner-diameter, d, and 33, 66, 99 and 133 mm in length, L, respectively for L/d = 11 are used. The CHFs first become lower and then become higher with the increase in subcooling. The CHFs for four different inner-diameters with L/d = 11 measured here become higher with the decrease in the diameter. CHF correlation for the latter increasing regime was given in non-dimensional form against average outlet subcoolings based on the experimental data. The correlation can describe not only the CHFs obtained in this work at the outlet pressure of 800 kPa but also the authors’ published CHFs (1284 points) for the wide range of Pout = 159 kPa to 1 MPa, d = 6, 9 and 12 mm, L = 49, 99 and 149 mm, ΔTsub,out = −4 to 130 K and u = 4.0 to 13.3 m/s within 15% difference for 50 K≤ΔTsub,out≤130 K and within +30 to −10% for 30 K<ΔTsub,out<50 K.

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