Hello,
standard sea level air density is often quoted as 1.225 kg/m^3
for air temp 15 deg C
relative humidity 0%

If I wanted to express the above using dew point temp instead of
relative humidity what value of dew point temp would I use ?

Thanks & regards

wrote:
Hello,
standard sea level air density is often quoted as 1.225 kg/m^3
for air temp 15 deg C
relative humidity 0%

If I wanted to express the above using dew point temp instead of
relative humidity what value of dew point temp would I use ?

Thanks & regards


Well, any small value would do. Technically, of course,
RH = 0% means there's no moisture in the air so the
dewpoint would be undefined -- there's no point to which
you can cool the air [at constant pressure] to condensation
if there's nothing to condense. I'd just use -50C, or so,
and ignore the little error.

I guess a good question would be: why do you want to do this?

Scott

Well, part of my application which calculates air density uses air
pressure and humidity. I want to give the user the choice of specifying
humidity as either relative or dew point. The initial defaults
presented to the user are 1.225 kg/m^3, 15 deg C and 0%. So if the user
wishes to select dew point I wanted to start with the equivalent to 0%
at 15 deg C.