There is a fundamental problem with both explanations below: When air is
heated or cooled the specific moisture content does not change, only the
relative
ability of the air to hold moisture changes. Warm air can hold more moisture
relative to cool air. But heating air neither drives out moisture nor causes it
to absorb moisture. Heating & cooling air changes the sensible temperature
not a latent heat content of the air.
Gary Hodson
In a message dated 1/6/2006 6:50:00 PM Central Standard Time,
rudedoggg@earthlink.net writes:
Close. When air warms up, the amount of water vapor the air can hold
increases. When the air cools, the amount of water vapor the air can hold
decreases.
The temperature at which the air becomes saturated--i.e., can hold no more
water--is known as the dewpoint. The dewpoint is higher in humid climes and
lower in drier climes.
When ambient temperature dips below the dewpoint, the air can no longer hold
all the water vapor. The vapor condenses in the form of visible liquid.
So, what happens is that the warm air in the gauge absorbs the moisture but
when it comes in contact with the cooler glass, the moisture is released.
Some alternatives might be keeping the instrument warm via some small
heater, or, keeping the instrument dry through the use of a dessicant.
JR
Original Message -----
From: "Alan Schultz" <alan@andysnet.net>
To: <Warthodson@aol.com>
Cc: <jnew@hazelden.ca>; <Alan@nfahc.co.uk>; <sbyers@ec.rr.com>;
<healeys@autox.team.net>
Sent: Friday, January 06, 2006 8:40 AM
Subject: Re: gauges fogging up
> Yes, what you are saying is true. Liquid does not exist inside the gauge.
>
> This is what is happening. The gauge contains moisture just like all air
> contains moisture. When the coil warms up the air surrounding the coil
> warms up driving the moisture out. Warm air becomes drier thus increasing
> the moisture level of the remaining air which condenses on the glass.
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