scholarly journals The Critical Capture Velocity of Coal Ash Particles Oblique Impact on a Stainless Steel Surface

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5231
Author(s):  
Jun Xie ◽  
Haodong Ma ◽  
Chenxi Li ◽  
Shaobai Li ◽  
Zhengren Zhu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Steel Surface ◽  
Incident Angle ◽  
Coal Ash ◽  
Stainless Steel Surface ◽  
Normal Velocity ◽  
Restitution Coefficient ◽  
Static Contact ◽  
Capture Velocity ◽  
The Impact

In this paper, the rebound characteristics of coal ash particles impacting on a stainless steel surface are studied experimentally with the background of ash deposition on the heating surface of the boiler. The impact processes of coal ash particles with different incident angles were recorded by high-speed digital camera technology. The evolution of the normal restitution coefficient with incident normal velocity was obtained. Three different static contact theories are used to establish the equations of motion to predict the critical capture velocity of particles. The results show that the normal restitution coefficient first increases and then decreases with the increase of incident normal velocity. The critical capture velocity of particles under the three models was predicted. It is found that the prediction results of the Brach and Dunn (BD) model for the critical capture velocity are close to the experimental results. Taking the particle of size 23 μm as an example, the maximum critical capture velocity predicted by BD model is 1.0611 m/s at 0° incident angle. The minimum value is 0.7940 m/s when the incident angle is 45°.The critical capture velocity of particles decreases with the increase of incident angle and with the increase of particle diameter.

Splat Solidification of Tin Droplets

1996 ◽  
Author(s):  
R. Bhola ◽  
S. Chandra
Keyword(s):  
Experimental Study ◽  
Stainless Steel ◽  
Simple Model ◽  
Surface Temperature ◽  
Steel Surface ◽  
Liquid Droplet ◽  
Contact Angles ◽  
Stainless Steel Surface ◽  
Splat Solidification ◽  
The Impact

Abstract An experimental study was done of the impact and solidification of tin droplets falling on a stainless steel surface. The surface temperature was varied from 25°C to 240°C. Measurements were made of droplet diameters and contact angles during droplet spread. At a surface temperature of 240°C there was no solidification, and a simple model of liquid droplet impact successfully predicted the extent of droplet spread. Droplets impacting on surfaces at 25°C and 150°C solidified before spreading was complete.

Boiling during high-velocity impact of water droplets on a hot stainless steel surface

2006 ◽  
Vol 462 (2074) ◽  
pp. 3115-3131 ◽  
Author(s):  
Navid Z Mehdizadeh ◽  
Sanjeev Chandra
Keyword(s):  
Stainless Steel ◽  
Substrate Temperature ◽  
Impact Velocity ◽  
High Velocity ◽  
Steel Surface ◽  
Stainless Steel Surface ◽  
High Velocity Impact ◽  
Water Droplets ◽  
Velocity Impact ◽  
The Impact

High-velocity impact of water droplets (0.55 mm diameter) on a heated stainless steel surface was photographed. To achieve high impact velocities, the test surface was mounted on the rim of a rotating flywheel, giving linear velocities of up to 50 m s −1 . Two cartridge heaters were inserted in the substrate and used to vary substrate temperature. A charge coupled device (CCD) video camera was used to photograph droplets impinging on the substrate. To photograph different stages of droplet impact, the ejection of a single droplet was synchronized with the position of the rotating flywheel and triggering of the camera. Substrate temperature was varied from 100 to 240 °C and the impact velocity from 10 to 30 m s −1 . High-resolution photographs were taken of vapour bubbles nucleating sites inside the thin liquid films produced by spreading droplets. An analytical expression was derived for the amount of superheat required for vapour bubble nucleation as a function of the impact velocity. For a given surface roughness, the amount of superheat needed decreased with impact velocity, which agreed with experimental results. For a fixed impact velocity, the maximum extent of droplet spread increased with substrate temperature.

Effect of Impact Velocity and Substrate Temperature on Boiling of Water Droplets Impinging on a Hot Stainless Steel Surface

Volume 3 ◽  
2004 ◽  
Author(s):  
N. Z. Mehdizadeh ◽  
S. Chandra
Keyword(s):  
Stainless Steel ◽  
Substrate Temperature ◽  
Impact Velocity ◽  
Steel Surface ◽  
Bubble Nucleation ◽  
Test Surface ◽  
Stainless Steel Surface ◽  
Water Droplets ◽  
Droplet Spreading ◽  
The Impact

We photographed high velocity impact of small water droplets (0.55 mm) on a heated stainless steel surface. To achieve high impact velocities the test surface was mounted on the rim of a rotating flywheel, giving linear velocities of up to 50 m/s. Two cartridge heaters were inserted in the substrate and used to vary substrate temperature. A CCD video camera was used to photograph droplets impinging on the substrate. By synchronizing the ejection of a single droplet with the position of the rotating flywheel and triggering of the camera, different stages of droplet impact were photographed. Substrate temperature was varied from 100–240°C and the impact velocity from 10–30 m/s. High-resolution photographs were taken of vapor bubbles nucleating sites inside the thin films produced by spreading droplets. For a given impact velocity, the extent of droplet spreading increased with substrate temperature. The superheat needed to initiate bubble nucleation decreased with impact velocity. We derived an analytical expression for the amount of superheat required for vapor bubble nucleation as a function of impact velocity.

On the collision of a droplet with a solid surface

1991 ◽  
Vol 432 (1884) ◽  
pp. 13-41 ◽  
Keyword(s):  
Stainless Steel ◽  
Surface Temperature ◽  
Liquid Film ◽  
Steel Surface ◽  
Ambient Pressure ◽  
Early Period ◽  
Metallic Surface ◽  
Stainless Steel Surface ◽  
Droplet Shape ◽  
The Impact

The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The primary parameter was the surface temperature, which ranged from 24°C to above the Leidenfrost temperature of the liquid. Experiments were also performed on a droplet impacting a surface on which there existed a liquid film created by deposition of a prior droplet. The evolution of wetted area and spreading rate, both of a droplet on a stainless steel surface and of a droplet spreading over a thin liquid film, were found to be independent of surface temperature during the early period of impact. This result was attributed to negligible surface tension and viscous effects, and in consequence the measurements made during the early period of the impact process were in good agreement with previously published analyses which neglected these effects. A single bubble was observed to form within the droplet during impact at low temperatures. As surface temperature was increased the population of bubbles within the droplet also increased because of progressive activation of nucleation sites on the stainless steel surface. At surface temperatures near to the boiling point of heptane, a spoke-like cellular structure in the liquid was created during the spreading process by coalescence of a ring of bubbles that had formed within the droplet. At higher temperatures, but below the Leidenfrost point, numerous bubbles appeared within the droplet, yet the overall droplet shape, particularly in the early stages of impact (< 0.8 ms), was unaffected by the presence of these bubbles. The maximum value of the diameter of liquid which spreads on the surface is shown to agree with predictions from a simplified model.

scholarly journals Study on the effect of Weber Number to heat transfer of multiple droplets on hot stainless steel surface

2018 ◽  
Vol 154 ◽  
pp. 01114 ◽  
Author(s):  
Aria Riswanda ◽  
Indro Pranoto ◽  
Deendarlianto ◽  
Indarto ◽  
Teguh Wibowo
Keyword(s):  
Stainless Steel ◽  
Surface Temperature ◽  
Weber Number ◽  
Steel Surface ◽  
Cooling System ◽  
Spray Cooling ◽  
Stainless Steel Surface ◽  
Temperature Decrease ◽  
Evaporation Time ◽  
Decrease Rate

Multiple droplets are drops of water that continuously dropped onto a surface. Spray cooling is an application of the use of droplet on a cooling system. Spray cooling is usually used in a cooling system of electronic devices, and material quenching. In this study, correlations between Weber number and surface temperature decrease rate during multiple droplets impingement are investigated and analyzed. Visualization process is used to help determine the evaporation time of droplets impingement by using high speed camera. Induction stove is used to maintain a stainless steel surface temperature at 120°C, 140°C, and 160°C. The Weber number was varied at 15, and 52.5 to simulate low and medium Weber number. The result of this study shows that increase in Weber number does not increase the temperature decrease rate noticeably. Whereas the Weber number decrease the time required for surface temperature to reach its lowest surface temperature. It was also found that for low and medium Weber number, Weber number affect the evaporation time of multiple droplets after impingement.

Sign in / Sign up

Export Citation Format

Share Document