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What is the CFM formula?

  1. cfm = [sensible heat btu/h] DIVIDED by [1.08 x RH]

  2. cfm = [sensible heat btu/h] DIVIDED by [1.08 x SD]

  3. cfm = [sensible heat btu/h] DIVIDED by [1.08 x TD]

  4. cfm = [sensible heat btu/h] DIVIDED by [1.08 x WD]

The correct answer is: cfm = [sensible heat btu/h] DIVIDED by [1.08 x TD]

The CFM formula is used to calculate the required air flow for heating and cooling systems. Sensible heat refers to the heat that causes a change in temperature, and btu/h is the unit of measurement for heat flow. The constant 1.08 is the conversion factor for converting sensible heat to standard cubic feet per minute (SCFM). This conversion factor remains the same regardless of the choice of units for heat and air flow. Therefore, options A, B, and D are incorrect because they use incorrect units or conversion factors. Option A uses the incorrect unit of relative humidity (RH), instead of temperature difference (TD). Option B uses the incorrect unit of specific density (SD), instead of TD. And option D uses the incorrect unit of wind direction (WD), instead of TD. The correct formula is cfm = [sensible heat btu/h] DIVIDED by [1.08 x TD], where TD is the temperature difference in Fahrenheit.