Heat transfer coefficient calculation 3

[poseilus]

Hi to all,

I am trying to calculate the heat transfer coefficient for different fluids on various surfaces.

I would really appreciate if you could give me any information around this subject. Also a program would be more suitable.

Mostly I am interested in calculating heat transfer coefficient of a circular aboveground storage tank storing heavy fuel oil.

Thank you in advance.

 

[athomas236]

ASTM C680-82 gives guidance on calculating surface heat transfer coefficients although the equations have two errors in them.

The heat transfer coefficient for cylinders greater than 24 inches diameter can be calculated as for vertical flat plates and will consist of radiation and convection coefficients.

Radiation coeff = 5.673E-8*Em*((Ts+273)^4-(Ta+273)^40/(Ts-Ta) W/m^2

Convection coeff=C*5.678*Wc/(Dc*1000/25.4)^0.2/(2/(Ts+Ta))^0.181*(Ts-Ta)^0.266

Ts=surface temperature C
Ta=ambient temperature C
Em=emissivity of surface, suyggest 0.2 for bright surfaces
C=factor for geometry, 1.394 for vertical plates
Wc=wind speed correction
= (1+1.277*V)^0.5 where V is wind speed in mph, suggest 0.5mph for design
Dc= diameter for calculation, actual diameter if less than 0.6096m otherwise use 0.6096m

regards,
athomas236

 

[poseilus]

Hi athomas236,

thank you very much for this information.

Could you please tell me where I can find this info?

I searched ASTM I only found ASTM C680 with a title STANDARD PRACTICE FOR ESTIMATE OF THE HEAT GAIN OR LOSS AND THE SURFACE TEMPERATURES OF INSULATED FLAT, CYLINDRICAL, AND SPHERICALSYSTEMS BY USE OF COMPUTER PROGRAMS

Will I find the info I want in there or is it somewhere else.

I basically want to find heat transfer coefficient for a large upright oil storage tank around 10m diameter 10m height 10mm thickness of carbon steel sheets. The fluid stored is fuel oil at 55degrees celcius.

I have found at the moment this formula for vertical flow of air outside a pipe.

(4.65+0.35*Ta/100)*Ua^0.61/d^0.39

Ta temp of air C
Ua speed of air m/s
d diameter m

or for vertical surface flow along its length

0.037*Pr^(1/3)*(Re^0.8-23100) for Re close to 5*10^5

Pr prandtl number

Re reynolds

For my example:
air at 0 degrees and speed 10m/s surf temp of 40degrees and diameter 10

I get for the pipe assumption around 50W/m^2K

and for vertical plate I get 42W/m^2K

For your equation I get 33W/m^2K

I would really appreciate if you could tell me your thought around this matter.

Thanks again for your help.

 

[imok2]

poseiles
Try this site:

http://www.martindalecenter.com/Calculators.html

 

[25362]

To estimate heat losses from hot surfaces there is an article in an old issue of Petroleum Refiner (May 1959) titled Find Heat Losses Graphically by Charles R. Kise, that may solve your problem. I suppose you may find it in any technical library. Good luck.

 

[TD2K]

There was also an article on this in Chemical Engineering Progress, May 1982 titled "Predict storage tank heat transfer efficiently".

Drop me a line at testdog2000@yahoo.com and I'll email you a copy.

No program I'm afraid. You might also want to talk to Brown Fintube. They produce tank heaters and do similar calcs, they might have some information they are willing to provide to you.

 

[TD2K]

One more link

http://www.spiraxsarco.com/learn/

 

[athomas236]

poseilus
That is the correct reference

Glad to help.

athomas236