HVAC系统的空气体积是根据条件空间中明智的热量计算得出的。对于典型的加热和冷却单元，计算是用于冷却的，因为要冷却空间比加热需要更多的空气。如果可以使用给定数量的CFM正确冷却条件空间，则可以使用相同量的CFM正确加热空间。
The sensible cooling load in a conditioned space is the heat that needs to be removed from the space to maintain the desired room temperature (75 °F, for example). The cooling load is calculated from the sensible heat from the people (approximately, 225 Btuh), lights, computers and other equipment, and the heat transfer through the building envelope on the historically warmest day and time of the year (e.g., 90 °F, 3 pm, July 7).
例: The sensible cooling load for conditioned space (Building A) is 113,400 Btuh小号。查找所需的风扇CFM。传热方程是：
btuh小号 = CFM×1.08×TD
cfm = Btuhs ÷ (1.08 × TD)
TD = Btuhs ÷ (1.08 × cfm)
- btuh小号 = BTU每小时明智的热量，
- CFM =气流的体积
- 1.08 =常数，60分钟/小时×0.075 lb/cf×0.24 btu/lb f
- TD = the difference between the supply air temperature (SAT) dry bulb and the room air temperature (RAT) dry bulb.
To find cfm required, use cfm = Btuhs ÷ (1.08 × TD)
cfm = Btuhs ÷ (1.08 × TD)
cfm = 113,400÷ (1.08 × 20 °F) (SAT is 55 °F and RAT is 75 °F)
CFM = 5250
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