CHF IN HIGH-PRESSURE REGIME FOR FORCED CONVECTION BOILING IN UNIFORMLY HEATED VERTICAL TUBES OF LOW LENGTH-TO-DIAMETER RATIO

1982 ◽  
Author(s):  
Yoshiro Katto ◽  
S. Ashida
Keyword(s):  
High Pressure ◽  
Forced Convection ◽  
Diameter Ratio ◽  
Pressure Regime ◽  
Vertical Tubes ◽  
Length To Diameter Ratio

scholarly journals Design and Optimization of High-Pressure Water Jet for Coal Breaking and Punching Nozzle Considering Structural Parameter Interaction

Machines ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 60
Author(s):  
Lihuan Chen ◽  
Muzheng Cheng ◽  
Yi Cai ◽  
Liwen Guo ◽  
Dianrong Gao
Keyword(s):  
High Pressure ◽  
Coal Seam ◽  
Structural Parameters ◽  
Water Jet ◽  
Diameter Ratio ◽  
Divergence Angle ◽  
Pressure Water ◽  
High Pressure Water Jet ◽  
Contraction Angle ◽  
Length To Diameter Ratio

The technology of increasing coal seam permeability by high-pressure water jet has significant advantages in preventing and controlling gas disasters in low-permeability coal seam. The structural parameters of a nozzle are the key to its jet performance. The majority of the current studies take strike velocity as the evaluation index, and the influence of the interaction between the nozzle’s structural parameters on its jet performance is not fully considered. In practice, strike velocity and strike area will affect gas release in the process of coal breaking and punching. To further optimize the structural parameters of coal breaking and punching nozzle, and improve water jet performance, some crucial parameters such as the contraction angle, outlet divergence angle, and length-to-diameter ratio are selected. Meanwhile, the maximum X-axis velocity and effective Y-axis extension distance are used as evaluation indexes. The effect of each key factor on the water jet performance is analyzed by numerical simulation using the single factor method. The significance and importance effect of each factor and their interaction on the water jet performance are quantitatively analyzed using the orthogonal experiment method. Moreover, three optimal combinations are selected for experimental verification. Results show that with an increase in contraction angle, outlet divergence angle, and length-to-diameter ratio, the maximum X-axis velocity increases initially and decreases thereafter. The Y-direction expansion distance of the jet will be improved significantly with an increase in the outlet divergence angle. Through field experiments, the jet performance of the improved nozzle 3 is the best. After optimization, the coal breaking and punching diameter of the nozzle is increased by 118%, and the punching depth is increased by 17.46%.

Mechanisms of Subcooled Water Flow Boiling CHFS for Outlet Subcooling at a Flow Velocity With Pressures for Test Sections With Various Shapes

2001 ◽  
Author(s):  
Akira Sakurai ◽  
Katsuya Fukuda
Keyword(s):  
Flow Velocity ◽  
Water Flow ◽  
Flow Boiling ◽  
Hydrodynamic Instability ◽  
Diameter Ratio ◽  
Metal Strip ◽  
Spontaneous Nucleation ◽  
Subcooled Water ◽  
Vertical Tubes ◽  
Length To Diameter Ratio

Abstract The mechanisms and the correlations for the subcooled water flow boiling CHF, qct,sub, for outlet subcooling at fixed flow velocities with the pressure as a parameter measured were investigated using the existing database measured for the test sections such as a vertical metal strip in the channel with a wide cross section, and the vertical tubes having the inside diameters ranging from 0.4 to 12 mm and the length-to-diameter ratio ranging from 2.4 and 96.6 with water flowing upward based on the unified subcooled pool and flow boiling CHF correlations previously presented: the unified CHF correlations based on the two different mechanisms due to the hydrodynamic instability (HI) and the heterogeneous spontaneous nucleation (HSN). The qct,sub versus outlet subcooling, ΔTsub,out, for the test tubes at a flow velocity with the pressure were clearly divided into four regions for the ΔTsub,out in general: namely, first, the qct,sub decrease down to minimum one for low ΔTsub,out (1st Region), secondly, the qct,sub increase up to maximum one for middle ΔTsub,out (2nd Region), thirdly, the qct,sub considerably decrease down to minimum one for transition ΔTsub,out (3rd Region), and finally, the qct,sub again increase monotonously for high ΔTsub,out (4th Region) with an increase in ΔTsub,out. The trend of the qct,sub versus the ΔTsub,out, in the third region for the transition ΔTsub,out became significant with a decrease in tube inside diameter though the trend of the qct,sub for the tubes having large inside diameters of 9 and 12 mm became insignificant. It was clarified that the qct,sub data for middle ΔTsub,out (2nd Region) and those for high ΔTsub,out (4th Region) for the test sections with various shapes of the metal strip and the tubes having the inside diameters ranging from 0.4 to 12 mm and length-to-diameter ratio ranging from 2.4 to 96.6 were well expressed by the unified subcooled water flow boiling CHF correlations derived based on the existing database.

Optimized growth of high length-to-diameter ratio Lu2O3 single crystal fibers by the LHPG method

CrystEngComm ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 1657-1662
Author(s):  
Na Zhang ◽  
Yuqing Yin ◽  
Jian Zhang ◽  
Tao Wang ◽  
Siyuan Wang ◽  
...  
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
High Power ◽  
Diameter Ratio ◽  
Solid State Lasers ◽  
Crystal Fibers ◽  
High Length ◽  
Length To Diameter Ratio

Lu2O3 crystals have attracted intense attention due to their great potential in the field of high power solid-state lasers.

EXPERIMENTAL STUDY ON FLAME PROPAGATION IN A STRAIGHT PIPE

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Siti Zubaidah Sulaiman ◽  
Rafiziana Md Kasmani ◽  
A. Mustafa
Keyword(s):  
Experimental Study ◽  
Flame Propagation ◽  
Experimental Work ◽  
Diameter Ratio ◽  
Straight Pipe ◽  
Pipe Length ◽  
Operating Condition ◽  
Consistent Trend ◽  
Length To Diameter Ratio

Flame propagation in a closed pipe with diameter 0.1 m and 5.1 m long, as well as length to diameter ratio (L/D) of 51, was studied experimentally. Hydrogen/air, acetylene/air and methane/air with stoichiometric concentration were used to observe the trend of flame propagation throughout the pipe. Experimental work was carried out at operating condition: pressure 1 atm and temperature 273 K. Results showed that all fuels are having a consistent trend of flame propagation in one-half of the total pipe length in which the acceleration is due to the piston-like effect. Beyond the point, fuel reactivity and tulip phenomenon were considered to lead the flame being quenched and decrease the overpressures drastically. The maximum overpressure for all fuels are approximately 1.5, 7, 8.5 barg for methane, hydrogen, and acetylene indicating that acetylene explosion is more severe. 

Roller Skewing Behavior in Roller Bearings

1982 ◽  
Vol 104 (3) ◽  
pp. 311-320
Author(s):  
L. J. Nypan
Keyword(s):  
Diameter Ratio ◽  
Radial Load ◽  
Outer Race ◽  
Roller Bearings ◽  
Length To Diameter Ratio

Measurements of roller skewing of a 1.15 length to diameter ratio roller in 118 mm bore roller bearings of 0.18 and 0.21 mm (0.0073 and 0.0083 in.) clearance operating with a 4450 N (1000 lb) radial load at shaft speeds of 4000, 8000, and 12,000 rpm with outer race misalignment of 0, 0.5, and −0.5 deg are reported.

The supersonic and low-speed flows past circular cylinders of finite length supported at one end

1962 ◽  
Vol 12 (3) ◽  
pp. 367-387 ◽  
Author(s):  
D. M. Sykes
Keyword(s):  
Mach Number ◽  
Finite Length ◽  
Central Region ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Form Drag ◽  
Drag Coefficients ◽  
Low Speed ◽  
Flow Past ◽  
Length To Diameter Ratio

The flow past circular cylinders of finite length, supported at one end and lying with their axes perpendicular to a uniform stream, has been investigated in a supersonic stream at Mach number 1.96 and also in a low-speed stream. In both stream it was found that the flow past the cylinders could be divided into three regions: (a) a central region, (b) that near the free end of the cylinder, and (c) that near the supported end. The locations of the second and third regions were found to be almost independent of the cylinder length-to-diameter ratio, provided that this exceeded 4, while the flow within and the extent of the first region were dependent on this ratio. Form-drag coefficients determined in the central region in the supersonic flow were in close agreement with the values determined at the same Mach number by other workers. In the low-speed flow the local form-drag coefficients were dependent on length-to-diameter ratio and were always less than that of an infinite-length cylinder at the same Reynolds number.

Numerical Analysis on the Electrical Performance of Microstructured Environmentally-Friendly Electrical Contact Material Ag/SnO2

2013 ◽  
Vol 419 ◽  
pp. 355-359
Author(s):  
Lei Wang ◽  
Wei Li Liu ◽  
Le Sheng Chen
Keyword(s):  
Numerical Simulation ◽  
Electrical Contact ◽  
Environmentally Friendly ◽  
Weight Percent ◽  
Diameter Ratio ◽  
Electrical Performance ◽  
Structural Parameter ◽  
Contact Material ◽  
Electrical Contact Material ◽  
Length To Diameter Ratio

The paper analyzes the influence of structural parameters on the electrical performance of the microstructured environmentally-friendly electrical contact material Ag/SnO2 by using numerical simulation method.The numerical results show that the reisitivity of fiber-like electrical contact material Ag/SnO2 is significantly reduced compared with the resistivity of Ag/SnO2 adding reinforcing nanoparticles in the traditional way.So the fiber-like electrical contact material Ag/SnO2 exhibits higher conductivity in macro. On further analysis, we learn that the resistivity of fibrous electrical contact materials is related to weight percent of reinforced phase, and micro-structural parameter of length to diameter ratio. The resistivity increases as weight percent of reinforced phase increases,and decreases non-linearly with micro-structural parameter of length to diameter ratio increasing.This demonstrates that numerical simulation is one of effective methods for analysis of the electrical performance of the microstructured electrical contact material.

scholarly journals A new method for calculating the sonic conductance of airflow through a short-tube orifice

2017 ◽  
Vol 9 (2) ◽  
pp. 168781401668726 ◽  
Author(s):  
Fan Yang ◽  
Gangyan Li ◽  
Dawei Hu ◽  
Toshiharu Kagawa
Keyword(s):  
Flow Rate ◽  
Critical Pressure ◽  
Pressure Ratio ◽  
Momentum Equation ◽  
Diameter Ratio ◽  
Test Method ◽  
Theoretical Formula ◽  
Engineering Applications ◽  
Short Tube ◽  
Length To Diameter Ratio

In this study, we proposed a method for calculating the sonic conductance of a short-tube orifice. First, we derived a formula for calculating the sonic conductance based on a continuity equation, a momentum equation and the definition of flow-rate characteristics. The flow-rate characteristics of different orifices were then measured using the upstream constant-pressure test method in ISO 6358. Based on these test data, the theoretical formula was simplified using the least squares fitting method, the accuracy of which was verified experimentally. Finally, the effects of the diameter ratio, the length-to-diameter ratio and the critical pressure ratio were analysed with reference to engineering applications, and a simplified formula was derived. We conclude that the influence of the diameter ratio is greater than that of the length-to-diameter ratio. When the length-to-diameter ratio is <5, its effect can be neglected. The critical pressure ratio has little effect on the sonic conductance of a short-tube orifice, and it can be set to 0.5 when calculating the sonic conductance in engineering applications. The formula proposed in this study is highly accurate with a mean error of <3%.

Erratum: Low‐frequency instabilities in the high‐pressure regime of Penning discharges

1979 ◽  
Vol 50 (9) ◽  
pp. 6032-6032
Author(s):  
S. K. Guharay ◽  
S. N. SenGupta ◽  
M. R. Gupta
Keyword(s):  
High Pressure ◽  
Low Frequency ◽  
Pressure Regime
Sign in / Sign up

Export Citation Format

Share Document