Heat loss

[udpolo15]

I am trying to estimate the the amount of energy required to maintain a fire water tank at a certain temperature. I need to quickly calculate the heat loss through a steel tank.

This can be very rough.

 

[Sschell]

oooh... The only way I would know to approach this is "by the book" which for heat transfer is anything other than quick... as there are many factors involved.

Hopefully someone who has experience specific to your application can chime in with the quick and dirty way to do it...

Sorry I cant offer any real help!

 

[Dleg]

Yeah, I seem to remember learning how to program finite element heat transfer models on this kind of problem in school. But I bet there's a quick method that will give you a ballpark figure.

 

[Guest]

Yeah, I seem to remember learning how to program finite element heat transfer models on this kind of problem in school.

Heat transfer (flow) is based on the Laplace Equation (2nd Order Partial Differential Eqn) as I recall - the same equation that is used to solve movement of groundwater flow. While it has been a long time since I have worked with heat flow - I routinely work with groundwater flow which does have an implicit solution in the form of finite elements.

In terms of rough order approximation, could you use Newton's Law of Cooling based on the material of the tank?

JR

 

[BluSkyy]

I'd figure your q from convection equations. add up the vertical plates and the horizontal plates, assume the plate temperature and air temperature and a convective coefficient. If it can be rough you could probably get reasonably close with educated guessing as to coefficients.

 

[Sschell]

^that would be the correct way to do it... not exactly quick though...

 

[BluSkyy]

yeah, now that I think about it...you can figure up free convection pretty quickly [h =approx 10 w/m^2*K (at Ttank=60ºC Tair=20ºC); q=h*Atank*(Ttank-Tair)]

But am not sure you can assume free convection...if you have airflow across the tank, the heat transfer coefficient is likely to be much higher.

 

[udpolo15]

yeah, now that I think about it...you can figure up free convection pretty quickly [h =approx 10 w/m^2*K (at Ttank=60ºC Tair=20ºC); q=h*Atank*(Ttank-Tair)]
But am not sure you can assume free convection...if you have airflow across the tank, the heat transfer coefficient is likely to be much higher.

Thanks. This is what I came up with. For my purposes, if I underestimate, that is ok.