When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
(OP)
At what point does ventilation of a boiler room become excessive based on air changes per hour? I have several rooms that I am considering, so I will just give one of the more extreme examples here.
I have a requirement to maintain a boiler room at no more than 10 degrees above outdoor ambient conditions. I have been using the sensible heat formula of Q=(CFM)*1.08*Delta-T to calculate the required CFM at a 10 deg Delta-T. In this one room, I have estimated the boiler heat loss to be 42,000 BTUH, which give me a calculate CFM of approx 3,900 CFM.
My room is very small (only 3,500 cubic feet). When I compare the calculated ventilation rate to the room volume, I get 1.11 air changes every minute, or 67 air changes per hour. That's insane!!! With an air flow rate like that, won't the heat be immediately swept off the boiler and not actually heat up the room very much?
I think the basic sensible heat equation "breaks down" (for lack of a better term) in such a small space. Although it may be true that the air sweeping across the boiler is receiving a 10 degree temp rise, it would seem to me that the room itself will be much closer to ambient since so much air is being ventilated.
Is there a better way to perform this calculation?
I have a requirement to maintain a boiler room at no more than 10 degrees above outdoor ambient conditions. I have been using the sensible heat formula of Q=(CFM)*1.08*Delta-T to calculate the required CFM at a 10 deg Delta-T. In this one room, I have estimated the boiler heat loss to be 42,000 BTUH, which give me a calculate CFM of approx 3,900 CFM.
My room is very small (only 3,500 cubic feet). When I compare the calculated ventilation rate to the room volume, I get 1.11 air changes every minute, or 67 air changes per hour. That's insane!!! With an air flow rate like that, won't the heat be immediately swept off the boiler and not actually heat up the room very much?
I think the basic sensible heat equation "breaks down" (for lack of a better term) in such a small space. Although it may be true that the air sweeping across the boiler is receiving a 10 degree temp rise, it would seem to me that the room itself will be much closer to ambient since so much air is being ventilated.
Is there a better way to perform this calculation?





RE: When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
Trying to stay within 10 degrees of ambient is a tall order. You are going to end up with a room like a wind tunnel.
B.E.
You are judged not by what you know, but by what you can do.
RE: When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
RE: When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
Alternately, you could enclose the boiler in its own air space. We used to have diffusion furnaces dumping about 60 kW into a 6000 cfm room, but the heat from the furnaces were always dumped directly into their own air streams, so little of the heat was actually getting into the inhabited space.
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RE: When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
Can you insulate the boiler jacket more to reduce losses?
RE: When does Boiler room ventilation to cool room become too excessive based on air changes per hour?
RE: When does Boiler room ventilation to cool room become too excessive based on air changes per hour?