Seaking the wisdom of the wall

Craig Bergman_2

What would you do?
We need to heat two stainless steel tanks with 5,000
Gal of Soy wax each. Each tank is about 9' tall and 9'
in diamiter. We plan to spray urethane insulation on the tanks, top and sides w/insulated base to keep it off the concrete floor. The wax melts at 120 deg and needs to be maintained at 150 deg.

What would be the best way to do this???
Loops inside or outside the tanks?
What kind of loop? PEX tubing or maybe a copper line-set?
What type of controls to keep each tank at temp with a Munchkin Boiler?
This needs to be done in the simplest way...

Thank you;
Craig R. Bergman
Air Comfort Inc.

Mike T., Swampeast MO

Outside the tank would eliminate concerns regarding mechanical damage to the tubes--particularly when encased in foam--but you have to conduct the heat through the tank walls to the wax. This may well be a problem with PEX as there's not much surface contact. Copper is an exceptional conductor of heat

Inside the tank you have to keep the tubing in place and expect the possibility of mechanical damage. Might be rather difficult...especially when you consider that some form of mechanical agitation may be required to keep that big tank of was somewhat consistent in temperature--not sure if that 30 degree difference between melting point and desired temp will be enough to produce natural convection sufficient to keep the entire tank molten... But, you can be fairly safe in assuming that you will transfer quite a bit of heat from the tube to the product if the product surrounds the tube.

I'm gathering this is an industrial application where product is both used and added. You should check the specific heat of the product and verify that you can produce enough heat to desired temperature at period of maximum use. Even if product isn't immediately added you still have to have ability to raise temp for the next period of use within the proper amount of time.

Isn't this the sort of thing that would typically be done with a double-walled tank and steam?

flange

i just retrofitted some very similar tanks. they were for a wax manufacturer, they use several types of wax, the highest melting point was 140 degrees. their old coils were made of copper, this caused discoloration of the wax. we removed the copper and i had stainless steel coils formed using 304 stainless with .029 wall. the coils were actually just bent tubing which ran in a u shape up the walls, across the bottom then back up. these were shipped bundled, then i cut the bundles once inside the tanks. i spread them out accordingly and used a stainless steel criss cross mesh which was tied to the tubing with stainless wire to strengthen and also to provide additional surface area to radiate heat. the customer absolutely loves them. each coil took about a day to install neatly. if you need assistance, feel free to drop me an email.

Dave Yates (PAH)

plating

I once had a similar situation in a plating process where elevated temperatures were wanted. We ran copper tubing outside of the chemical bath (for obvious reasons), but found it too slow for recovery as the metals being plated would quickly cool the plating solution.

We ended up building a water resevoir outside the SS tanks to immerse them in the heated solution. Our copper tubing ran through the exterior water bath. The heat transfer rate was greatly enhanced by having direct contact for Btu transfer and that solved the problem. Our tubing remained out of harms way.

A water heater provided the energy.

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Bruce_6

didn't

Told Plumbing from Lindon Utah win an award this year for doing the same thing???

you can see his award winning design and system at
http://www.blueskybroadcast.com/Client/RPA/start.swf

click on the Innovative, then IN303 to see this system.

Josh M.

Well no matter what way you do this start with the fundamentals... In other words don't play a guessing game. Find out how many btuh it takes to raise the soy 1 degree per pound just like we do for water and then you will be able to calculate how much heat you have to transfer and how much pex it will take or copper. If you put the tubing on the outside you have to plan for the thermal resistance of the tank. Do the math first and find out which method is possible before you even think about the mechanical advantages.