swainw
Aerospace
- Apr 25, 2003
- 27
Hello,
Im doing some building calcs on a thermal rise of air temperature due to a heat exhanger being installed in a very large whse space for use with a temp chambers refrigeration unit. The equations are pretty straight forward for when the outside conditions are lower that the internal temperatures and revolve around the thermal resistance of the walls and ceiling to calculate the building losses.
On the other end when the temperature is above the inside, the ASHRAE recommendation is to use solar incidence on non-shaded walls as the means to transfer heat into the building. It seams awkward that the conduction equation doesn't work in reverse to get the ambient outside temperature accross the walls as a heatload as a resistive network.
Does anyone know why ASHRAE recommends the Sol-Air approach. Or is this just an additive factor to the conductive heat transfer to the internal walls.
My ultimate goal is to determine the internal temperature rise since it is warehouse space versus offices and we do not want to work with the Delta T principle from a control set point. If the warehouse temp rise due to the heat exchanger is only a few degrees for the large volume space, we want to go to the county to request that due to warehouse type building, that we do not need to have to add additional A/C which the building currently has non. The architects engineer is indicating that a 12 ton A/C unit would need to be installed to keep the warehouse space at 70 degrees. We have no reason to keep the wharehouse space that cool or controlled to a specific temp. The only requirement is that it not fall below a certain temp due to the commodity stored in the whse space. The BTU output of our heat exchanger is sufficient to meet the heating requirements, plus the whse has four overhead electric heaters that would work less hard when we were running the chamber.
Any thoughts would be great.
Regards,
Bill
Bill Swain
Ultra Electronics Precison Air Systems
Technical Coordination Manager-US Programs
swainw@asme.org
Im doing some building calcs on a thermal rise of air temperature due to a heat exhanger being installed in a very large whse space for use with a temp chambers refrigeration unit. The equations are pretty straight forward for when the outside conditions are lower that the internal temperatures and revolve around the thermal resistance of the walls and ceiling to calculate the building losses.
On the other end when the temperature is above the inside, the ASHRAE recommendation is to use solar incidence on non-shaded walls as the means to transfer heat into the building. It seams awkward that the conduction equation doesn't work in reverse to get the ambient outside temperature accross the walls as a heatload as a resistive network.
Does anyone know why ASHRAE recommends the Sol-Air approach. Or is this just an additive factor to the conductive heat transfer to the internal walls.
My ultimate goal is to determine the internal temperature rise since it is warehouse space versus offices and we do not want to work with the Delta T principle from a control set point. If the warehouse temp rise due to the heat exchanger is only a few degrees for the large volume space, we want to go to the county to request that due to warehouse type building, that we do not need to have to add additional A/C which the building currently has non. The architects engineer is indicating that a 12 ton A/C unit would need to be installed to keep the warehouse space at 70 degrees. We have no reason to keep the wharehouse space that cool or controlled to a specific temp. The only requirement is that it not fall below a certain temp due to the commodity stored in the whse space. The BTU output of our heat exchanger is sufficient to meet the heating requirements, plus the whse has four overhead electric heaters that would work less hard when we were running the chamber.
Any thoughts would be great.
Regards,
Bill
Bill Swain
Ultra Electronics Precison Air Systems
Technical Coordination Manager-US Programs
swainw@asme.org
