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.

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

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.

Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube: Influence of Inner Surface Roughness

2004 ◽  
Author(s):  
Koichi Hata ◽  
Masahiro Shiotsu ◽  
Nobuaki Noda
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Flow Boiling ◽  
Vertical Tube ◽  
Heat Transfer Characteristics ◽  
Subcooled Flow Boiling ◽  
Transfer Characteristics ◽  
Subcooled Flow ◽  
Wide Range ◽  
Inner Surface

The subcooled flow boiling CHF and the heat transfer characteristics for the flow velocities (u=4.0 to 13.3 m/s), the inlet subcoolings (ΔTsub,in=137.49 to 153.87 K), the inlet pressure (Pin=740.67 to 975.78 kPa) and the dissolved oxygen concentration (O=8.63 to 0.0288 ppm) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tubes of d=3 mm and L=66.5 mm (L/d=22.17) with the inner surfaces of smooth and mirror finished are mainly used in this work. Heat transfer characteristics and CHF data are compared with those for the rough finished inner surface (RF) previously obtained and the CHFs are compared with the values calculated by the CHF correlations against outlet and inlet subcoolings based on the experimental data for the rough finished inner surface under the N2 gas pressure. The influence of inner surface roughness on the heat transfer characteristics and the CHFs for wide range of dissolved gas concentration are investigated in detail.

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

2004 ◽  
Vol 126 (3) ◽  
pp. 312-320 ◽  
Author(s):  
Koichi Hata ◽  
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=800kPa. 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=159kPa to 1 MPa, d=6, 9 and 12 mm, L=49, 99 and 149 mm, ΔTsub,out=−4 to 140 K and u=4.0 to 13.3 m/s within 15% difference for 50K⩽ΔTsub,out⩽140K and within −10 to +30% for 30K<ΔTsub,out<50K.

An Experimental Study of Bubble Nucleation Frequency in Subcooled Flow Boiling

2010 ◽  
Author(s):  
Guodong Wang
Keyword(s):  
Flow Boiling ◽  
Rectangular Cross Section ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Dimensionless Frequency ◽  
Micro Channel ◽  
Subcooled Flow Boiling ◽  
Nucleation Frequency ◽  
Mass Fluxes ◽  
Subcooled Flow

In this paper, a simultaneous visualization and measurement study have been carried out to investigate bubble nucleation frequency of water in micro-channel at various heat fluxes and mass fluxes. A single micro-channel with an identical rectangular cross-section having a hydraulic of 137 μm and a heating length of 30 mm was used in this experiment. It is shown that the frequency of bubble nucleation increased drastically with the increase of heat flux and was also strongly dependent on the mass flux. A dimensionless frequency of bubble nucleation was correlated in terms of the Boiling number. The predictions of bubble nucleation frequency in the microchannel are found in good agreement with experimental data with a MAE of 10.4%.

High Heat Flux Subcooled Flow Boiling of Methanol in Microtubes

2015 ◽  
Author(s):  
Farzad Houshmand ◽  
Hyoungsoon Lee ◽  
Mehdi Asheghi ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Two Phase ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Inner Diameter ◽  
Phase Pressure

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm2 is investigated. Methanol was propelled into microtubes (ID = 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (1/ID), while for a given inner diameter, it decreases with increasing heated length.

Sign in / Sign up

Export Citation Format

Share Document