## Latent heat calculations

Hey all,

This is my first post. I work for a company called Durable Machinery which works out of the Brooklyn Navy Yard in New York. We are a relatively recent company, and we are trying to figure out how to gauge the power of our units. My understanding is that total heat = latent heat + sensible heat. Sensible heat is simple enough, however latent heat seems to be another story.

So far, I have that latent heat = 0.68 x cfm x change in W. W is presumably moisture content.

Using a psychrometric chart, I have been able to calculate W in grains or moisture/lb of dry air.

The problem is this. Our unit got these test results:
Dry bulb in: 77
Web bulb in: 55
(W in: 29.5)

Dry bulb out: 55
Wet bulb out: 46
(W in: 31.8)

W in - W out = -2.3, which means that the latent heat is going to be negative.

Please let me know if there is something I'm doing wrong or the numbers are just impossible.

If there are any better ways people have out there to calculate latent heat, I'm all ears.