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what is the formula for

what is the formula for

what is the formula for

(OP)
how do i get the grains per pound out of tempiture and relative humidity. i need it to create a excell spread sheet. i use it for structural drying.  

RE: what is the formula for

grains of what per pound of what?  I assume that's water, and air?

The RH tells you the percentage of water relative to the saturation level at the temperature stipulated.  There are equations and articles all over the internet about this.

TTFN

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RE: what is the formula for

See ASHRAE Handbook of Fundamentals, Psychrometrics.  There are equations in there to calculate what you need.

RE: what is the formula for

In ASHRAE fundamentals there is an empirical formula for water vapor pressure as a function of temperature only (2009 IP version Chap 1.2 Eqn.6).

Then you need to use the following and be consistent with your units:

W = 0.62198.RH/100.PVsat
    ____________________
    Patm - RH/100.PVsat

Multiply by 7000 for grains.

This appears to rely on the assumption that the RH is the same as degree of saturation, which is a minimal error for most applications.

Should do the trick.
 

RE: what is the formula for

You can get the details from psychrometric chart.

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