scholarly journals Critical Heat Flux of Ice Accretion along a Fine Wire Immersed in Cold Air Stream with Water Spray. Effects of Ration of Droplet Diameter and Wire Diameter and Air Stream Velocity and Temperature.

2001 ◽  
Vol 67 (660) ◽  
pp. 2062-2067
Author(s):  
Koji FUMOTO ◽  
Hideaki YAMAGISHI ◽  
Shoichiro FUKUSAKO
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Droplet Diameter ◽  
Wire Diameter ◽  
Stream Velocity ◽  
Water Spray ◽  
Ice Accretion ◽  
Cold Air ◽  
Fine Wire ◽  
Air Stream

Experimental Researches on Micro-Droplet Freezing on a Solid Surface Under Atmospheric Conditions: Part I

2008 ◽  
Author(s):  
Heyun Liu ◽  
Xiaohui Ma
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Electrostatic Force ◽  
Droplet Diameter ◽  
Ccd Camera ◽  
Freezing Process ◽  
Ice Accretion ◽  
Power Transmission Lines ◽  
Atmospheric Conditions ◽  
Air Stream

Atmospheric ice accretion on structures is a problem of fundamental importance to a number of industries. Examples of engineering problems caused by ice accretion involving aircraft, power transmission lines, telecommunication towers, electrical railway contact-wires, and other structures. Under atmospheric icing conditions two basic types of ice may form; rime or glaze. The supercooled micro-droplets in clouds are an important factor in icing. The objective of this study was to develop a new experimental method to investigate a single supercooled micro-droplet freezing process, in order to better understand the mechanism of rime or glaze ice accretion. The experimental device and principles are described in this paper. The experimental set has two small cold rooms, which is separated by a board with a central hole. A droplet with diameter of 15∼40 μm, temperature of 0∼−5°C was levitated in the cold air stream by electrostatic force. A CCD camera tracked its trace. The air temperature is from 0∼−10°C, the micro-droplet diameter is from 15∼40μm, and its temperature is from 0∼−5°C in the experimental study. This article focused on the experimental set and the experimental principles, and the next article will focus on the experimental data analysis.

Boiling Heat Transfer Rates for Small Precisely Placed Water Droplets on a Heated Horizontal Plate

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Sally M. Sellers ◽  
W. Z. Black
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Weber Number ◽  
Droplet Diameter ◽  
The Other ◽  
Droplet Generator ◽  
Water Droplets ◽  
Transfer Rates ◽  
The Impact

Two small horizontal surfaces, heated to temperatures up to 220°C, were cooled by small (50–300 mm diameter) room-temperature droplets at 1 atmosphere pressure. One surface was a 10×10 mm thin-film nichrome heater that was used to measure heat fluxes below 100 W/cm2. The other surface, used for fluxes in excess of 100 W/cm2, was a solid copper heater with an 8×8 mm exposed surface. A continuous jet droplet generator coupled with two mutually perpendicular deflection plates was used to manipulate the path of constant diameter water droplets so that the impact of the drops could be precisely located on the heated surfaces. The droplet generator and the deflection plates were employed so that the effect of the impact frequency, droplet diameter, droplet velocity and spacing on the resulting heat transfer rates could be studied under controlled conditions. Optimal droplet spacing between 0.75 and 1.5 times the droplet diameter increased the critical heat flux approximately 30 percent above the value that was achieved when the drops were deposited in one location. For area-averaged mass flow rates less than about 0.08 g/(cm2s), there was no trend in the critical heat flux with the Weber number. However, for larger mass flux rates, the critical heat flux increased with an increasing Weber number. The measured critical heat flux values were roughly twice the heat flux of traditional pool boiling for identical superheat temperatures. Two droplet cooling dimensionless critical heat flux correlations are proposed as a function of Weber and Strouhal numbers; one for a single stream of drops and the other for drops that are spaced across the heated surface. The correlation for the spaced droplets is a function of a dimensionless droplet spacing on the heater.

Sign in / Sign up

Export Citation Format

Share Document