What is the effective surface area of a half pipe jacket?

[mechprocess]

What is the effective surface area of a half pipe jacket?

The program DeltaT credits the tank surface area between half pipe loops. I am using 3 inch sch 40 180° half pipe, 7 inches on center. This leaves 3.5 inches not covered between the loops. I need some sort of reference that tells me how much of this area I can take credit for. Not that I need to take credit for all of it but I would also like to know what the expected duty will be on the chill water system when I start cooling this 19 ft diameter tank down.

PS

Does anyone have any guidlines for determining inside heat transfer coefficients for tanks agitated by pulse jet mixers? Or how about eductors. Mechanical mixers are not allowed. Don't ask.

 

[Montemayor]

A prior post on this very subject may prove useful or educational: thread391-71471

If you require efficient and responsive heat transfer through the walls of a tank, you couldn't have picked a more inefficient and expensive method than a half-pipe. You're going to require a lot of efficient and thorough convection heat transfer that can only be achieved by efficient mixing - and even then you are limited by the scarce heat transfer area available to you. It's going to be expensive and limited.

Good Luck.

 

[mechprocess]

I read the post you mentioned several times and I learned allot from your comments in that thread.

My tank is 19 ft in diameter.

The ½ inch 304 SS wall external design pressure is dictating a half pipe design not to mention a bunch of other unspecified design limitations. The expense is not an issue.

They just increased the diameter by a foot against my will. We have agitation test data on the mixing (1/3) scale. We are waiting on inside film values. They should be reasonable (I’m hoping for 70 btu/hr-ft^2-°F). Overall I can deal with 40. We are mixing with approx 0.5 hp/Kgal.

I have a bottom zone and two parallel side loops. DP 20 to 30 psi available. Velocity 8 fps using a DP of 30.

My jacket side calculated film is high 500 – 600. The tank is the open item to all this. We shall see.

Bottom half pipe Archimedes spiral is 377 ft long and 7 in on center

Both parallel side helix half pipes are 335 ft each

My main question is the available effective surface area. I calculated 96 and 171 for the coincident to tank portion of the bottom and side 3 in. half pipes. This program DeltaT referenced from thread you mentioned takes credit for area in between coils.

I’m looking for a basis. Reference etc.

Thanks