HVAC System Selection
HVAC System Selection
(OP)
I am working on a project where I have to put a new HVAC system in a building full of pipe transporting hot bitumen and steam. The building is H5.2m x L15m x W7.2m and is at a temp of 40 deg C. How should I approach this problem? I have been told that there are not many people in this building for a long period of time. Does that mean that I can simply fit it with a make up air unit (no coolant) and exhaust grills? How would I calculate how much CFM the fan should be if I wanted the room temperature to be about 25 deg C? Am I going about this problem incorrectly, I would appreciate any comments.
Thanks !
Thanks !





RE: HVAC System Selection
Once you have a heat loss you then need to look at what the practical maximum temperature you'd like to maintain is, and then look at your summer design condition. If you intend to cool using only make-up air the volume of air can get very high if you are trying to maintain a setpoint too close to your outdoor temperature.
The formula for outdoor air required for cooling is:
cfm = Heat Gain/(1.08 * delta T)
- Where delta T is the difference between summer design temperature and your desired indoor temp.
This is where you have to make the judgment call on how hot is too hot. You might consider making personal cooling equipment available for workers and increasing the maximum allowable temperature.
RE: HVAC System Selection
Dave
RE: HVAC System Selection
You may want to know a lot more about the piping layouts and processes that are going on in the building. The best design would be to place your air delivery/exhaust as close as you can to any heat/fume generation as you can. If it is simply a plant for heat exchange and you only need to cover the losses, the calcs become easier. If there is heat generation or chemical mixing going on, you will most likely need a good ventilation system to deal with excess combustion gases or emergency spills. If there aren't workers in the building doing maintenance for extended periods you should be ok to provide a bare minimum, although codes might dictate you give the space more.
For a difficult layout requiring a lot of coordination from the contractor, I would keep as much of the HVAC units outside of the box by putting them on the roof, if possible.