Heat Load From Piping, Tanks, Equipment

[afmepe]

I've never done heat load calcs before, and am confused on a few things. What's the best (quickest) way to calculate heat load from piping, tanks, and process equipment? The purpose is to size the HVAC units for a large process building. Does the heat capacity of the process fluid matter? Or just the temperature? It seems like alcohol would give up heat faster than water. Does the metal thickness of the equipment matter? The equation I was going to use is Q=k*A*deltaT/L. But then I would have to know the metal thickness L. Thats easy for pipe and tanks but not equipment. Your assistance would be greatly appreciated!

 

[ChrisConley]

Heat loss from a pipe, or tank, or process equipment is dependent on a large number of factors.

First off, it does matter what the material and temperature, and flow rate is on the 'hot' side as this will be used to determine half of the heat transfer equation.
The second half is the pipe material, the inside air temperature and any insulation you might have to determine the heat transfer from the pipe to the room.

Heat transfer textbooks will get you started. I recommend 'Fundamentals of Heat and Mass Transfer' by Incropera and Dewitt.

Another method would be to use 'rule of thumbs' you can get from insulation manufacturers that give you an approximate heat loss for bare un-insulated pipe at various temperatures.

 

[KiwiMace]

If you are ok with tapping into a healthy design margin at the end... The process fluid can mostly be considered a constant (worst case) temp, as a steady state operation (excluding batch processes).

Then all you need to do is work out heat loss per unit area through the insulation on each chunk of plant and multiply by area. I would bin this out into temperature ranges to save number crunching.

Then don't forget the building envelope effects, latent loads etc.

 

[afmepe]

Thanks ChrisConley and CinciMace for your responses. They will definitely help!

 

[marcoh]

Good Luck!

Another way may be to do an energy balance on the plant.

Energy in: (actual gas/electricity demand, not maximum design demand)

Energy out: (dedicated coolers for plant, does the piping system leave the building?)

All energy will be converted to heat at some stage, just need to consider if this will happen in the space you are looking at or will energy go up flues, pumped out of the building, etc?

And don't forget building envelope heat gains.

 

[MintJulep]

Or smaller scale energy balances:

For a pipe or a tank, if you know the flow rates, fluid thermal properties and temperature at two points (in and out) then it is simple to calculate the energy/unit flow at each point. The difference went somewhere, and somewhere is most likely the space.

The same applies for equipment, but you need to consider the power input as well.