typical value free air convection heat transfer coefficientby Askara Tags: coefficient, convection, free, heat, transfer, typical 

#1
Apr2713, 05:32 AM

P: 21

whats would be typical value for free air convection heat transfer coefficient at high temperature of 1000 degree c?
let say i have a vertical cylinder of diameter 5 cm and 3 cm high. and i heat it to 1000 degree c. the room temperature is 20c . what would the convection heat transfer coefficient be? 



#2
Apr2713, 07:36 AM

Engineering
Sci Advisor
HW Helper
Thanks
P: 6,347

Pick whatever formula you like best from http://en.wikipedia.org/wiki/Heat_transfer_coefficient
Or guess a number between 5 and 25 W/m^2.K, according to http://www.engineeringtoolbox.com/co...ferd_430.html If you want an "accurate" value, you need to find a correlation based on measurements similar to your actual situation. For eaxmple your very short cylinder might be better approximated as a sphere than as a long cylinder ignoring end effects. 



#3
Apr2713, 07:58 AM

Mentor
P: 21,999

Note that at that temperature, radiation is probably a much bigger factor than convection, so you're going to want to calculate that.




#4
Apr2813, 02:36 AM

P: 21

typical value free air convection heat transfer coefficient
the thing is engineering box say 5 and 25 W/m^2.K, i have seen some website say 5 and 50 W/m^2.K, and wikipedia 10100 W/m^2.K so i dont really know what to chooese.
plus onvection heat transfer coefficient increase with temperature, it may be 25 W/m^2.K at 20200 degree c but it will be higher at 1000 degree c. 



#5
Apr2813, 05:44 PM

Mentor
P: 21,999

It's a very difficult thing to estimate. I'd pick something conservative inside all three ranges. Like, 20.
What exactly the purpose of this question? Ie, how much accuracy is required? Can you measure instead of calculating? Use a controller? 



#6
Apr2913, 02:28 AM

P: 21

russ_watters thanks, i alway just assumed radiation doesnt matter much but actually as you said, is it much bigger factor than convection. thats why the data i got doesnt match the result from convection



Register to reply 
Related Discussions  
Heat transfer determine heat of chip using convection  Engineering, Comp Sci, & Technology Homework  13  
Free convection heat transfer  Mechanical Engineering  5  
convection heat transfer coefficient  Mechanical Engineering  0  
Heat transfer (convection & radiation)  Engineering, Comp Sci, & Technology Homework  5  
Heat transfer question: Finding the convection coefficient  Engineering, Comp Sci, & Technology Homework  0 