Sizing a Duct heater

[integrator]

Hello

I'm sizing a duct heater and can't remember how to figure out the delta T for my temp drop.

I would like to have a discharge of at least 71 DegF when the outside air temp drops to -40 DegF


Thanks

Clinton

[Carnak]

air be kind of dense at -40

if you got a duct heater with SCR discharge air control then I would try

CFM x 1.12x111/3.413 = watts