[Stoves] Relative Humidity question

[Kevin]

Dear Frank

"Relative Humidity" is a measure of the actual water content of the air 
compared to the water it would contain when saturated.

For example, if it could hold 100 units of water vapour at 40 C, but it only 
had 48 units, then it would have a "Relative Humidity" of 48%

In the case of your magnesium Nitrate example, if you started with air 
having say 75% RH, or 25% RH, the air and the solution would come into 
equilibrium at 48.42 % RH, +/- .37% RH

You can get information on what moisture content air will hold by consulting 
a "Psychrometric Chart" or table. See:
http://www.engineeringtoolbox.com/air-psychrometrics-properties-t_8.html
You have heard of "User Friendly"... well, Psychrometric Charts are "User 
Hostile" :-( They are complicated, but there is an enormous amount of 
helpful information contained within them.

Best wishes,

Kevin

----- Original Message ----- 
From: "Frank Shields" <frank at compostlab.com>
To: "'Discussion of biomass cooking stoves'" 
<stoves at lists.bioenergylists.org>; <biochar at yahoogroups.com>
Sent: Friday, March 22, 2013 5:51 PM
Subject: [Stoves] Relative Humidity question


> Dear Stovers,
>
> I have a question regarding Relative Humidity.
> A saturated mix of water and magnesium nitrate (for example) at 40c will
> produce a 'percent relative humidity' in the air trapped in the container
> above of 48.42 +/- 0.37.
>
> What does this mean? Is there a value of grams water per cubic meter of 
> gas
> (or some other unit) that we can use to calibrate instrumentation 
> measuring
> water vapor?
>
> Thanks
>
> Frank
>
>
> Frank Shields
> Control Laboratories, Inc.
> 42 Hangar Way
> Watsonville, CA  95076
> (831) 724-5422 tel
> (831) 724-3188 fax
> www.controllabs.com
>
>
>
>
>
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