Boiling point calculations

[David HK]

As far as I know water boils at 100 C at one atmosphere (14 psi).

If my solar hot water heater is pressurised at between 4 to 6 Bar (56 psi to 84psi) what would the revised boiling point be?

I would be grateful for any ideas in Celsius.

Regards,

Dave HK

[fishfarm]

http://www.engineeringtoolbox.com/boiling-point-water-d_926.html

Temperature converter (F to C) is on the left hand side of the page.

[WXYZCIENCE]

Water under the  pressure that you listed is 55psi = 300 d F  85psi 328 d F.
Your relief valve on hot water tanks is set to 150Psi and 100 degree c. This makes water very dangerous coming from a hot water tank.Joe
100c + 32 = 132 x 8 = 1056 / 5 = 211.2f close cal.
300f x 5 = 1500 / 8 = 187 - 32 = 155c very hot.

[David HK]

Yes It is very hot!

Today my water temperature was up to 76 degrees Celsius and I could not keep my finger on the copper delivery pipe, and this is only April!

But I am not interested in a straight conversion. I was asking what the boiling point would be under pressure. It cannot be the same as one Bar at sea level.

Dave HK

[WXYZCIENCE]

Any water over 100c is boiling. We are now talking about Steam. The more the pressure the higher the boiling point. approx. +1 degree c per 1 psi.

[wphfla]

Try this site:  http://www.chem.purdue.edu/gchelp/liquids/boil.html

Kevin

[Nando]

To clear the "Pressure" Boiling temperature at indicated pressure

1. 4 Bar = 59.6 PSI Boiling point = 292.7 F; 145 Celsius
   
2. 6 Bar = 89.4 PSI Boiling point = 320.3 F; 160 Celsius
   
   

Nando

[dinges]

'any water over 100c is boiling'

Negative.

Water boils at about 80-something deg. C on Mt. Everest.

It boils at temps over 100 deg.C under higher pressure; I don't know from memory the exact relationship between pressure & temp., but others seem to have already answered.

It boils at 100 deg. C ONLY under conditions of the International Standard Atmosphere. (1013,25 hPa, from memory).

And under the right conditions, water can be superheated; which means it stays LIQUID at temperatures over 100 deg. C! (at 1bar)

Please be careful with absolute statements like you made.

[Kwazai]

isn't it just boyle's law  p1*v1/t1=p2*v2/t2 in degK,pascals and m**3? (p/t=constant at constant volume).

Mike

[Shadow]

Not sure if this relevant, but in a vehicle cooling system,plain water can boil at just over 212 degrees at 15 lbs pressure, but water mixed with antifreeze at 15 lbs pressure can go over 232 degrees before boiling.I guess thats why antifreeze is sometimes referred to as coolant.

[David HK]

Well done Nando.

A spot on reply.

Just the answer I was looking for.

My sensors on my solar heater are very useful and are beginning to tell me all sorts of things. So far the water temperature seems to be having difficulty in going beyond 77 or 78 C.

Will keep you all posted as time goes by.

Davd HK

[WXYZCIENCE]

I agree and I apologize for my ignorance of elementary scientific understanding. And my blood will boil in space. Your relief valve is set to around 100 degrees c yet the pressure is set to around 150 psi. How is this possible? Simple there is also a temperature release built into the relief valve. What I was trying to say is that in a hot water tank any temperature over 100 degrees c is boiling, this will set off the relief regardless of the pressure. You can live anywhere in the county and that valve will go off if the temperature exceeds 100c. Safety was my only concern. Joe

[Daggs]

Boyle's Law only applies to gasses, IIRC.

[Kwazai]

but isn't it the vapor pressure that determines the boiling point?

[dinges]

Yup. And only to ideal gasses, for that matter.

Water is not a gas. Steam isn't a gas, it's a vapour.

BTW, this is one of the most common mistakes that's made with Boyle's gas law, so I've been told.

Peter.

[Spelljammer]

Actually, steam is a gas and is invisible.  The stuff everyone calls steam is really wet vapor.  Like when you are boiling water..the hottest part and the first to reach boiling is the bottom of the pot.  Those bubbles coming up are not air but they are a gas...water in the gaseous state.  Then you will see a space above the water for a few inches then you see what you call steam.  Well, that invisible area is steam and the stuff you call steam is wet vapor because it is starting to cool and condense.