Analysis of heat transfer of spilling fire spread over steady flow of n-butanol fuel

2020 ◽  
Vol 116 ◽  
pp. 104685
Author(s):  
Yang Pan ◽  
Manhou Li ◽  
Xinjiao Luo ◽  
Changjian Wang ◽  
Qiuting Luo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Steady Flow ◽  
Fire Spread

Experimental Study on Horizontal Fire Spread Characteristics of Transformer Oil

2021 ◽  
pp. 1-11
Author(s):  
Liyang Li ◽  
Xincheng GUO ◽  
Rongsheng Lu ◽  
Peng Chen ◽  
Congling Shi
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Convective Heat Transfer ◽  
Flame Propagation ◽  
Convective Heat ◽  
Fire Spread ◽  
Surface Flow ◽  
Transformer Oil ◽  
Total Heat Flow ◽  
Flame Radiation

Abstract In order to study the horizontal fire spread characteristics of transformer oil, a series of experiments were carried out on the experimental platform developed, the influence of the initial temperature and the width of the oil pool on the flame propagation, including the propagation speed, flame morphology and the temperature field distribution of the gas-liquid two-phase, was analyzed to reveal the flame propagation characteristics and the oil surface temperature rise law in the process of transformer oil fire propagation, and a theoretical model of coupled liquid-phase convective heat transfer and flame radiation heat transfer was established by combining thermodynamic theory to quantitatively calculate the heat transfer process of surface flow in flame propagation process. Through the theoretical analysis and quantitative calculation of gas-liquid heat transfer, it is proved that the surface flow is mainly driven by surface tension and the flame spreads in the form of pulsation. Combined with the experimental data for verification, it is found that the proportion of liquid-phase convective heat transfer to the total heat flow is much larger than that of flame radiation to the total heat flow, which proves that liquid-phase convective heat transfer is the main mode of surface flow heat transfer.

Subcooled Flow Boiling Inception and Heat Transfer of Water in a Circular Tube Under Pulsatile Flow

2018 ◽  
Author(s):  
Hongsheng Yuan ◽  
Sichao Tan ◽  
Kun Cheng ◽  
Xiaoli Wu ◽  
Chao Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady Flow ◽  
Flow Rate ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
Subcooled Flow Boiling ◽  
Average Heat ◽  
Subcooled Flow

The flow rate can fluctuate in offshore nuclear power systems which are exposed to wind and waves, as well as in loops where flow instabilities occur, resulting in different thermal-hydraulic characteristics compared with that under steady flow. Among the thermal-hydraulic characteristics, onset of nucleate boiling (ONB) model determines whether the fluid is boiling, and boiling heat transfer is crucial to equipment performance and safety, both being key issues in subcooled flow boiling. Therefore, an experimental study was conducted to investigate how an imposed periodic flow oscillation affects the boiling inception and heat transfer of subcooled flow boiling of water in a vertical tube. The experiments were conducted under atmospheric pressure with the average flow rate ranging from 96kg/m2s to 287kg/m2s and heat flux ranging from 10kW/m2 to 197kW/m2. The relative pulsatile amplitude range is 0.1–0.3 and pulsatile period range is 10s-30s. Photographic images and thermal parameters such as temperatures and flow rate were recorded. The lack of nucleation site on the heated surface of the test section results in high wall superheat at ONB. The effects of pulsatile amplitude and period on superheat at boiling onset and average heat transfer were analyzed. The results show that the superheat at boiling inception is decreased when the average heat flux is lower than the heat flux at boiling inception of the corresponding steady flow, and the superheat at boiling onset is increased when the average heat flux is higher than the heat flux at boiling onset of the corresponding steady flow. The above effect of flow rate pulsation on superheat increases with increasing amplitude and decreasing period, and the mechanism can be explained by boiling nucleation theory. The lack of large active nucleation site also affects the boiling heat transfer. By comparing the contribution of nucleate boiling to heat transfer with the widely used Cooper’s pool boiling correlation, the subcooled flow boiling was found suppressed by convection. The average heat transfer of both the intermittent flow boiling and the single phase flow is influenced by flow oscillation.

Heat Transfer With Thermoacoustic Self-Circulating Heat Exchangers

2005 ◽  
Author(s):  
S. Backhaus ◽  
G. W. Swift
Keyword(s):  
Heat Transfer ◽  
Steady Flow ◽  
Heat Exchangers ◽  
Mutual Influence ◽  
Simple Calculation ◽  
The Other ◽  
Steady Flows ◽  
Acoustic Oscillations ◽  
Flow And Heat Transfer ◽  
Stirling Engines

An asymmetrical constriction in a pipe functions as an imperfect gas diode for acoustic oscillations of gas in the pipe. One or more gas diodes in a loop of pipe create substantial steady flow, which can carry substantial heat between a remote heat exchanger and a thermoacoustic or Stirling engine or refrigerator; the loop’s flow is driven directly by the oscillations in the engine or refrigerator itself. This invention gives Stirling and thermoacoustic devices unprecedented flexibility, and may lead to Stirling engines of unprecedented power. We have built two of these self-circulating heat exchangers, one for fundamental tests and the other as a demonstration of practical levels of heat transfer. Measurements of flow and heat transfer are in factor-of-two agreement with either of two simple calculation methods. One calculation method treats the oscillating and steady flows as independent and simply superimposed, except in the gas diodes. The other method accounts for the interaction between the oscillating and steady flow with the quasi-steady approximation. The mutual influence of superimposed turbulent oscillating and steady flows is a theoretical challenge.

CFD Simulations of Flow and Heat Transfer in a Zigzag Channel With Flow Pulsation

2010 ◽  
Author(s):  
Bolaji O. Olayiwola ◽  
Gerhard Schaldach ◽  
Peter Walzel
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Steady Flow ◽  
Inclination Angle ◽  
Oscillation Amplitude ◽  
Fluid Mixing ◽  
Transfer Enhancement ◽  
Flow And Heat Transfer ◽  
Flow Through

Heat transfer enhancement by pulsating flow in a zigzag channel has been numerically studied using a commercial CFD software for the ranges of laminar flow 0 < Re < 550. The influence of inclination angle α of the zigzag channel and oscillation parameters is investigated. The amplitude of the pulsatile flow was varied between 0.5 mm and 4 mm. The frequency f ranges between 0.5 Hz and 5.5 Hz. For steady flow, fluid mixing is promoted by self induced fluctuation due to the instability of the flow. The Reynolds number Re for the occurrence of significant eddy decreases with increase of the inclination angle of the channel. Superposition of oscillation additionally promotes further fluid mixing by the propagation of different scales of vortices. In comparison to straight channels, significant heat transfer in the laminar regime is possible using a zigzag channel with inclination angle greater than 15°. Further intensification of the heat transfer is possible with superposition of oscillation on the main flow through the channel. However, the heat transfer enhancement due to imposed oscillation is found to increase with decreasing Reynolds number. The effect of the imposed oscillation yields heat transfer enhancement E of up to 1.41 when compared with steady flow in zigzag channel at Reynolds number Re = 107, frequency f = 2.17 Hz and oscillation amplitude A = 1mm using a zigzag channel with an inclination angle α = 15°. Further heat transfer enhancement E of up to 1.80 at the same flow and oscillation conditions is possible with a zigzag channel having inclination angle α = 45°. The influence of oscillation frequency on the heat transfer enhancement E becomes significant as soon as the Womersley number W > 41.32. The effect of superposition of oscillation is not significant using a zigzag channel with inclination angle α = 60°. When the oscillation amplitude is increased up to 4 mm at Reynolds number Re = 107, frequency f = 2.17 Hz and inclination angle α = 45°, the heat transfer enhancement E of about 3.3 is obtained.

On the Effectiveness of Ion Slip on Steady MHD Flow and Heat Transfer Above a Rotating Disk With Ohmic Heating

2006 ◽  
Vol 128 (6) ◽  
pp. 1236-1239 ◽  
Author(s):  
Hazem Ali Attia
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Steady Flow ◽  
Finite Differences ◽  
Ohmic Heating ◽  
Mhd Flow ◽  
Rotating Disk ◽  
Flow And Heat Transfer ◽  
Ion Slip ◽  
Steady Magnetic Field

The steady flow and heat transfer of a conducting fluid due to the rotation of an infinite, nonconducting disk in the presence of an axial uniform steady magnetic field are studied considering the ion slip and the Ohmic heating. The relevant equations are solved numerically using finite differences and the solution shows that the inclusion of the ion slip gives some interesting results.

scholarly journals Steady Flow over a Rotating Disk in Porous Medium with Heat Transfer

2009 ◽  
Vol 14 (1) ◽  
pp. 21-26 ◽  
Author(s):  
H. A. Attia
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Energy Transfer ◽  
Viscous Fluid ◽  
Steady Flow ◽  
Numerical Solutions ◽  
Rotating Disk ◽  
Incompressible Viscous Fluid ◽  
Governing Equations ◽  
Temperature Distributions

The steady flow of an incompressible viscous fluid above an infinite rotating disk in a porous medium is studied with heat transfer. Numerical solutions of the nonlinear governing equations which govern the hydrodynamics and energy transfer are obtained. The effect of the porosity of the medium on the velocity and temperature distributions is considered.

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