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### Temperature Rise Across Fan Calculator

Temperature Rise Across Fan Calculator

In certain applications, it may be desirable to calculate the temperature rise across the fan application. For low pressure rises (< 10 in. of water), the temperature rise may be estimated by the following:

Eq. 1
ΔT = ΔP · Cp / ( ρ · cp · J · η )

Eq. 2
ΔP = Pout - Pin

where

ΔT = temperature rise across fan (°F)
ΔP = pressure rise across fan (inches of water)
Pin = pressure at inlet of fan (inches of water)
Pout = pressure at outlet of fan (inches of water)
Cp = conversion factor = 5.193 lbf / ft2-inches of water
ρ = density (lbm / ft3) air, 0.075 lbm / ft3)
cp = specific heat - 0.24 Btu / lbm-°F
J = mechanical equivalent of heat 778.2 ft-lbf / Btu
η = efficiency, in decimal

1 Atmosphere = 406.7825 (inches of H2O)

If the motor is not in the airstream, the efficiency is the fan total efficiency. If the motor is in the airstream, the efficiency is the combined efficiency of the motor and fan.

References

ASHRAE Fundamentals Handbook, 2021

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