Determining Heat Loss From an Insulated Tank
Determining Heat Loss From an Insulated Tank
(OP)
I am trying to determine the heat loss from an insulated tank. The insulation is calcium silicate with a 2.5" thickness. The tank construction is cyllindrical 14' ID, 24' ht, carbon steel construction with 0.5" thickness. The product is 50% NaOH, so the idea is to use an electrical heater external to the tank to maintain product temp 80-100F to prevent it from freezing in the winter months. Any help would be greatly appreciated, I have looked everywhere and can't seem to find the help I need





RE: Determining Heat Loss From an Insulated Tank
RE: Determining Heat Loss From an Insulated Tank
<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying " Damn that was fun!" - Unknown>>
RE: Determining Heat Loss From an Insulated Tank
RE: Determining Heat Loss From an Insulated Tank
So, you have 3 temperatures to be concerned about, the interior temperature, assumed to be the same as the interior surface temperature of the steel, the external surface temperature of the steel, and tha ambient air temperature. You can model the steel/insulation as a single layer of insulation, by replacing the steel with a thinner layer of insulation that matches the thermal conductivity of the steel layer.
The heat transfer coefficient, you'll just have to dig around on the web. You can calculate it from first principles, using the Reynolds, Nusselt, and Prandtl numbers.
You'll then have two simultaneous equations, with same heat flow in both. The objective is to get a value of external insulation surface temperature that results in the same heat flow in both the conduction and convection equations.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Determining Heat Loss From an Insulated Tank
http://web.mit.edu/lienhard/www/ahtt.html
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Determining Heat Loss From an Insulated Tank
I found all heat transfer coefficient equations are emphirical or at least semi. could you clarify me on that "You can calculate it(heat transfer coefficient) from first principles"? Thanks.
jarooney:
You can find emphirical equations on cylinder external flow, in the form of Nu=CRe^a*Pr*b, in Fundamentals of Heat and Mass Transfer by Frank P. Incropera.
It boils down to simple math.
RE: Determining Heat Loss From an Insulated Tank
RE: Determining Heat Loss From an Insulated Tank
While you continue to sort through all the good responses, you may wish to take a look at NFPA-22. This is a National Fire Protection Association standard for fire sprinkler tanks. One of the appendices gives excellent info about the heat loss and design of water heaters to prevent freezing of the water. I know you are dealing with caustic soda, but the reference may help you pull this stuff together.
Joe Tank
RE: Determining Heat Loss From an Insulated Tank
rmw