Dew Point Calculation in a Gas Mixture
fac
temperature of water in a gas mixture.
In air it is stated in ASHRAE, but what happens with water in different
gases (for example a mixture of H20, Ar, N2 .......)
Thanks
Marc O'Brien
As I understand, as long as the others don't have dew points close to
waters then the dew point of water does not change.
It is a question I have often asked myself but have never properly
investigated, though I have investigated it - if you know what I mean.
The dew point of water is the same for an atmosphere made up purely of
water as it is for our earthly atomosphere. The mixture of air and
water only introduces a wet bulb condition.
Zyp
And I don't want to be the poo pooer, but who the f*** cares? I only care
about the dew point as it relates to the air I live in. And quite frankly
Betty, I don't give a sh** about *your* air. LOL
--
Zyp
fac
not should be the same. I will try to explain with an example familiar to
me:
Natural gas, is a mixture of gases (C1 to C6+). C6+ is the heavier and so is
the first that condensate when you cool down the mixture. However, this
temperature is not always the same, it depends on the exact composition of
the mixture. So I understand it should be similar for water in different
gases that ambient air.
"Marc O'Brien" <m...@fridgetech.com> escribió en el mensaje
news:4b1cac30-51db-48e7...@s37g2000prg.googlegroups.com...
Old & Grumpy
water contents in gases are measured in parts per million
and the dew point temperature varies with temperature
of particulars gas/refrigerant lower the Temp. the lower the dew
point, example while 10 parts per million maybe ok for R-134A
it is not good for R-508B which it needs to be 7 parts per million
or lower, there for dew point will be much lower.
if you are looking for formulas sorry can't help you.
In another process you can dry air what you are breathing
to 100 below zero dew point or lower using chemical reactivation.
which I am sure you are not looking for that.
Tony
"fac" <in...@nospam.com> wrote in message
news:frrhes$nj7$1...@hefestos.uned.es...
.p.jm@see_my_sig_for_address.com
wrote:
>I don't know what are you trying to get or do
>water contents in gases are measured in parts per million
>and the dew point temperature varies with temperature
>of particulars gas/refrigerant lower the Temp. the lower the dew
Bullshit.
>point, example while 10 parts per million maybe ok for R-134A
>it is not good for R-508B which it needs to be 7 parts per million
>or lower, there for dew point will be much lower.
>if you are looking for formulas sorry can't help you.
>In another process you can dry air what you are breathing
>to 100 below zero dew point or lower using chemical reactivation.
>which I am sure you are not looking for that.
>Tony
>
>"fac" <in...@nospam.com> wrote in message
>news:frrhes$nj7$1...@hefestos.uned.es...
>> Does anybody knows where to find information to calculate the Dew Point
>> temperature of water in a gas mixture.
>>
>> In air it is stated in ASHRAE, but what happens with water in different
>> gases (for example a mixture of H20, Ar, N2 .......)
>>
>>
>>
>> Thanks
>>
>>
>
--
Click here every day to feed an animal that needs you today !!!
http://www.theanimalrescuesite.com/
Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'
'With sufficient thrust, pigs fly just fine.'
HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Old & Grumpy
Tony
"fac" <in...@nospam.com> wrote in message
news:frrhes$nj7$1...@hefestos.uned.es...
fac
O2: 12%
H2O: 13%
N2: 70%
CO2: 5%
Temperature: is around 200ºC.
Somebody is asking me about the dew point. I know how to calculate the dew
point if it were H2O in air (using psicometric ASHRAE diagrams) but I am not
able to calculate it in this mixture.
Does anybody knows any standar o procedure to calculate this?
Thanks
"Old & Grumpy" <t.s...@verizon.net> escribió en el mensaje
news:QWwEj.6015$sw3.3357@trnddc06...
.p.jm@see_my_sig_for_address.com
>I have a heated mixture of:
>O2: 12%
>H2O: 13%
>N2: 70%
>CO2: 5%
No, you don't. No way do you have that much water vapor.
What is the compositoin of the gas BEFORE you add water to
it ? It looks similar to air ( not exact ).
--
Zyp
Looks like air to me - just missing some errant gasses. Albeit the O2 is a
bit small. I'm thinking nitros oxide.
--
Zyp
-zero
>I have a heated mixture of:
> O2: 12%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
>
> Temperature: is around 200ºC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew
> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am
> not
> able to calculate it in this mixture.
That would be a flue-gas mixture, not a fuel-gas mixture. It will
condense according to the environment the flue is discharged into.
To keep it from condensing inside the pipe, insulate the pipe
to keep it above 250° Fahrenheit.
-zero
Zyp
Well there ya go... see, I didn't see the writing on the wall :)
--
Zyp
fac
not remain always the same, so the dew point should change
Thanks
"-zero" <sometimes.zer...@gmail.com> escribió en el mensaje
news:47e3e359$0$4940$4c36...@roadrunner.com...
-zero
"Zyp" <nos...@yahoo.com> wrote in message
news:aMqdna08t_13eX7a...@championbroadband.com...
Well,,, sniffing too much flue gas will do that to ya. ;o)
> Zyp
>
-zero
> Do you know if there is any standar to calculate this. The composition
> will
> not remain always the same, so the dew point should change
You may want to start here;
http://www.jehar.com/dewpnt.htm
This will calculate the fuel dewpoint based upon the sulfur content, and
will very according to burner, fuel type and combustion air used.
However, your numbers look more like sampling from a Kiln or Process
Dryer. That involves variable moisture from the process interacting with
burner
firing rate. It can be VERY complicated to calculate in advance.
You can monitor that in real time if you must, but why you would want
to, I have no idea.
Why DO you need this information?
-zero
Noon-Air
"-zero" <sometimes.zer...@gmail.com> wrote in message
news:47e438c6$0$30688$4c36...@roadrunner.com...
He wants you to do his homework for him :-)
.p.jm@see_my_sig_for_address.com
It's a burning question.
Abby Normal
try daltons law of partial pressures, work out the pressure of the
water vapour then go look in a staurated steam table for the
saturation temperature.
I just pulled that out of my ass but would probably work.
Otherwise tell then it is a 140F
On Mar 21, 4:57 am, "fac" <i...@nospam.com> wrote:
> I have a heated mixture of:
> O2: 12%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200ºC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew
> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am not
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
> "Old & Grumpy" <t.se...@verizon.net> escribió en el mensajenews:QWwEj.6015$sw3.3357@trnddc06...
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
> > Tony
>
> > "fac" <i...@nospam.com> wrote in message
> >news:frrhes$nj7$1...@hefestos.uned.es...
> > > Does anybody knows where to find information to calculate the Dew Point
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in different
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
> > > Thanks- Hide quoted text -
>
> - Show quoted text -
Abby Normal
out not so much water condensing out
some acids need water, but some can be a liquid unto themselves
On Mar 21, 5:38 pm, "-zero" <sometimes.zero_removeth...@gmail.com>
wrote:
> "fac" <i...@nospam.com> wrote in message
-zero
"Noon-Air" <Noon...@comcast.net> wrote in message
news:POSdnZoDHKFB3Xna...@comcast.com...
True. That's never ruled out of the realm of possibility on alt.hvac. ;-)
>
Abby Normal
> I have a heated mixture of:
> O2: 12%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200ºC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew
> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am not
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
use a pyschrometric calculator
> > Tony
>
> > "fac" <i...@nospam.com> wrote in message
> >news:frrhes$nj7$1...@hefestos.uned.es...
> > > Does anybody knows where to find information to calculate the Dew Point
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in different
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
-zero
<.p.jm@see_my_sig_for_address.com> wrote in message
news:1cl8u39ibgk1tta8v...@4ax.com...
> On Fri, 21 Mar 2008 18:38:12 -0400, "-zero"
> <sometimes.zer...@gmail.com> wrote:
>
>>
>>"fac" <in...@nospam.com> wrote in message
>>news:fs0u0n$4m7$1...@hefestos.uned.es...
>>> Do you know if there is any standar to calculate this. The composition
>>> will
>>> not remain always the same, so the dew point should change
>>
>>You may want to start here;
>>http://www.jehar.com/dewpnt.htm
>>
>> This will calculate the fuel dewpoint based upon the sulfur content,
>> and
>>will very according to burner, fuel type and combustion air used.
>> However, your numbers look more like sampling from a Kiln or Process
>>Dryer. That involves variable moisture from the process interacting with
>>burner
>>firing rate. It can be VERY complicated to calculate in advance.
>>You can monitor that in real time if you must, but why you would want
>>to, I have no idea.
>>
>>Why DO you need this information?
>
> It's a burning question.
And may ignite a plume of fiery discussion.
-zero
Abby Normal
> O2: 12%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200ºC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew
> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am not
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
> > Tony
>
> >news:frrhes$nj7$1...@hefestos.uned.es...
> > > Does anybody knows where to find information to calculate the Dew Point
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in different
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
>
> - Show quoted text -
if all else fails then the ASHRAE HOF has a chapter on combustion, has
dewpoint charts to use
Zyp
ROFL
--
Zyp
.p.jm@see_my_sig_for_address.com
Well, don't sit around and fume about it !
Tekkie®
I'm all dewy eyed... My gases flue away and condensate dribbles down my pipe
while acid tongued and sulphurous smells ignite the flames that heat my very
being. It's been a gas.
--
Tekkie Don't bother to thank me, I do this as a public service.
Noon-Air
"Tekkie®" <Tek...@comcast.net> wrote in message
news:wJ6dnQ7AUqEcLXTa...@comcast.com...
I guess thats just a fancy way of saying you had lunch at Taco Bell??
Abby Normal
the water vapour pressure will make up 13% of the pressure in the flue
gas. The total pressure in the flue should be close to atmospheric so
the vapour pressure of water, assuming sea level, would be 0.13 x
14.696 = 1.9 psia
So looking in a saturated steam table on hand here at home the
stauration temperature and therefore the dewpoint will be in between
120F (1.69 psia) and 130F (2.22 psia), maybe around 124F. This is low
for natural gas, but you have a lot of excess air which lowers the
'pounds moisture per pounds dry air' if you will.
Usually 140F is an assumed dewpoint for natural gas, I am rusty but it
is for lower excess air amounts maybe around 50%.
I used to work for a custom build OEM, on our modulating gas burners,
we used to ramp up the combustion air blowers on low fire to get the
dewpoint down and reduce the risk of condensation.
Some one mentioned sulfur in fuel oil, sulfuric acid will condenses
out at higher temperatures than water will.
On Mar 21, 4:57 am, "fac" <i...@nospam.com> wrote:
> I have a heated mixture of:
> O2: 12%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200ºC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew
> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am not
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
> "Old & Grumpy" <t.se...@verizon.net> escribió en el mensajenews:QWwEj.6015$sw3.3357@trnddc06...
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
> > Tony
>
> > "fac" <i...@nospam.com> wrote in message
> >news:frrhes$nj7$1...@hefestos.uned.es...
> > > Does anybody knows where to find information to calculate the Dew Point
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in different
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
Marc O'Brien
>
> - Show quoted text -
Hi Abby.
Surely the water vapour will assume its own vapour pressure. The
higher its vapour pressure then just the less of the other gases?
Surely the water vapour pressure is constant, regardless of the rising
total pressure on account of the pressure of each additional gas?
With or without air is the water vapour dew point not the same? This
is why wet air is lighter than dry air - waters atomic mass is less?
Abby Normal
on Daltons Law of partial pressure and the ideal gas law.
Air has the oxygen, nitrogen ,trace gases and water vapour
Daltons law says when you have a mixture of gas, the total pressure is
the sum of the partial pressures exerted by all the gas in the
mixture.
So if you assumed air was 20 percent oxygen andd 80 percent nitrogen,
then 20% of the pressure came from oxygen and 80 percent from the
nitrogen.
So what really limits how much mositure can be held in the air, is how
well the vapour pressure of the water vapour can compete against
atmospheric pressure.
I think if you were in a high altitude place and atmospheric pressure
was lower, water vapour pressure can more easily compete. So you can
get a higher humidity ratio in terms of pounds of moisture per pound
of dry air in high altitudes compared to sea level.
When you heat up water until it starts boiling, its vapour pressure is
equalling atmospheric, there is nothing holding it back and it can
change state 'at will' as long as there is enough heat being added.Go
up in altitude and water boils at a lower pressure.
So anyways that wet flue gas the original poster was talking about was
13% water vapour, so I figure it is making 13% of the pressure in the
flue gas. Outside of the effect of draft, that flue gas is under
atmospheric pressure. 13% of atmospheric is the vapour pressure of the
water vapour, and then you just look in a saturated steam table to get
the corresponding saturation temperature for that pressure as your
dewpoint.
I am half pulling this one out of my ass but it sounds plausible to
me.
> is why wet air is lighter than dry air - waters atomic mass is less?- Hide quoted text -
Old & Grumpy
"Marc O'Brien" <m...@fridgetech.com> wrote in message
news:223d4f56-825c-45f7...@i7g2000prf.googlegroups.com...
Hi Abby.
is why wet air is lighter than dry air - """""WHAT"""""waters atomic mass is
less?
Abby Normal
O2 or N2
On Mar 29, 1:33 pm, "Old & Grumpy" <t.se...@verizon.net> wrote:
"""""WHAT"""""waters atomic mass is
> less?-
Stormin Mormon
N = 14
O = 16
O2 = 32, H20 = 18
--
Christopher A. Young
Learn more about Jesus
www.lds.org
.
"Abby Normal" <a_bee_...@yahoo.com> wrote in message
news:5ec363c8-44a7-4ecd...@u10g2000prn.googlegroups.com...
Abby Normal
I checked in the ASHRAE 20005 HOF, chapter 18 they got figure 2 for
dewpoint of water vapour in flue gas. Looks like the Dalton appraoch
to me, I pulled it corectly out of my ass
figure 3 is for the dewpoint of the acids it loos like
On Mar 28, 5:30 pm, "Marc O'Brien" <m...@fridgetech.com> wrote:
> Hi Abby.
>
> Surely the water vapour will assume its own vapour pressure. The
> higher its vapour pressure then just the less of the other gases?
>
> Surely the water vapour pressure is constant, regardless of the rising
> total pressure on account of the pressure of each additional gas?
>
> With or without air is the water vapour dew point not the same? This
> is why wet air is lighter than dry air - waters atomic mass is less?- Hide quoted text -
.p.jm@see_my_sig_for_address.com
<a_bee_...@yahoo.com> wrote:
>Marc
>
>I checked in the ASHRAE 20005 HOF, chapter 18 they got figure 2 for
>dewpoint of water vapour in flue gas. Looks like the Dalton appraoch
>to me, I pulled it corectly out of my ass
What the hell was it doing up there in the first place ?
>
>figure 3 is for the dewpoint of the acids it loos like
>
>
>On Mar 28, 5:30 pm, "Marc O'Brien" <m...@fridgetech.com> wrote:
>
>> Hi Abby.
>>
>> Surely the water vapour will assume its own vapour pressure. The
>> higher its vapour pressure then just the less of the other gases?
>>
>> Surely the water vapour pressure is constant, regardless of the rising
>> total pressure on account of the pressure of each additional gas?
>>
>> With or without air is the water vapour dew point not the same? This
>> is why wet air is lighter than dry air - waters atomic mass is less?- Hide quoted text -
>>
>> - Show quoted text -
--
Old & Grumpy
"Abby Normal" <a_bee_...@yahoo.com> wrote in message
news:5ec363c8-44a7-4ecd...@u10g2000prn.googlegroups.com...
carl69
http://www.thestuccocompany.com/hvac/Re-Dew-Point-Calculation-in-a-Gas-Mixture-31367-.htm
:
.p.jm@see_my_sig_for_address.c wrote:
> On Fri, 21 Mar 2008 10:57:33 +0100, "fac"
> <in...@nospam.com> wrote:
>>I have a heated mixture of:
>>O2: 12%
>>H2O: 13%
>>N2: 70%
>>CO2: 5%
> No, you don't. No way do you have that much water vapor.
> What is the compositoin of the gas BEFORE you add water to
> it ? It looks similar to air ( not exact ).
What! Who is this clown! Of course you can get 13% water in a gas. As a
matter of fact I am sitting with a gas stream containing 56% water vapor
at 140degC. The rest consists of CO2 (6%), O2 (3%), N2 the balance.
The dew point temp of your gas stream will be a function of the R-value of
your process gas (dry basis) and the R-value of water, both in J/kg.K. You
can then use the following formula:
Td = B / Ln(A*Rg/(Rw*W*P))
with:
Td: dew point temp in Kelvin
A: 2.53x10E8 kPa
B: 5420 K
W: gas moisture fraction on mass basis
P: Pressure
Rg: R-value for gas on dry basis, J/kg.K
Rw: R-value for water, 462 j/kg.K
For your gas, the R value is 282.1 and water is 8.4%mass. I assumed the
pressure is 100kPa in the line. Your dew point temp comes out as 51 degC.
I hope it helps.
-------------------------------------
Carl
Grunpy
are "NIST" traceable????????????????????
"carl69" <carl69_at_y7...@foo.com> wrote in message
news:7e1c6$4b06319f$45499b77$15...@news.flashnewsgroups.com...
> carl69 had written this in response to
> http://www.thestuccocompany.com/hvac/Re-Dew-Point-Calculation-in-a-Gas-Mixture-31367-.htm
> :
>