[IamIan]

Originally Posted by t vago

If you're talking about saturated steam, then yes, it does.

It does what?
That's very vague.

Are you claiming that temperature alone is the only information needed to determine what the expansion ratio will be for saturated steam? ... that no other factors of the context will have any influence at all???

Originally Posted by t vago

Are there flaws with the example? Sure there are!

I agree.

Originally Posted by t vago

Could an example model be rigged up such that it uses integration to arrive at a more accurate final state? Sure, but I'm not going to do it.

I'm not asking you to ... I think there are diminishing returns ... to increasing efforts to make the model closer and closer to reality... I'm not asking for that.

Originally Posted by t vago

In the end, the example tries to mix together an ideal process using the ideal gas law, with real-world properties of water. Something's gotta give.

agree... there are no ideal gasses ... as such , reality will always be a bit different ... but that doesn't change the basic concepts and interconnected ratios shown in the ideal gas law.

Originally Posted by t vago

And you're missing the point here. In the real world, there wouldn't be superheated steam in the same vessel as liquid water, at least not at the given example.

I never claimed there would be superheated steam... there doesn't need to be ... the steam can be at the same temperature as the still liquid water in the container for the point I have been trying to making... Restricting the expansion as we have in this example will result in higher pressures.

Originally Posted by t vago

You're trying to, by going by the 1700:1 thumbrule, which has already been shown to be incorrect.

Incorrect ... I am not adding more steam... I've already said this directly.

I have also already directly told you I am not trying to reach the 1700:1 point as a fixed point.

Your claim here is false.

Even if under a given set of conditions the unimpeded expansion were 1600:1 or 1500:1 ... the point I was trying to make doesn't change ... if the volume restricts the expansion to less than it otherwise would have gone to ... it will result in , increased pressure ... will there also be temperature effects ... of course ... the Ideal Gas Law shows that connection ... but that still doesn't change or effect the point I was making.

Originally Posted by t vago

And you're neglecting the real-world properties of the water.

Your reply does not address the point made in what I wrote in the quote of mine you reference.

And you are also yourself neglecting some of the real-world properties of the water ... The phase change temperature will not be the 100C you claimed at these pressures.

So ... While I do not know what specific property of water you are referring to here , in regards to me ... at this time I don't see it as being any more significant than the aspects you are also neglecting yourself... and as said above ... there are diminishing returns to ever increasing complexity of a closer to real world model ... so as said above , I understand that limitation for the sake of simplicity.

But none of that changes the reality of the point I've been trying to make and you've been fighting so hard against ... is correct ... by having a restricted volume for the steam to expand into , below that which it would otherwise expand into , will result in higher pressures.

Originally Posted by t vago

You are correct, but not for the reason you think.

Hint ... your not a powerful enough psychic to know what I think.


The fact that it is correct ... is in itself the point I have been trying to make ... about the limitations of the volume in this case will increase the pressure above the 14.7psi you listed.

So as much as you have been fighting against this ... thank you.

Originally Posted by t vago

Did you consider that in each of your 600 cc and 100 cc and 10 cc cases, the water and steam will adjust to fit the volume dictated by the temperature of the system?

Yes ... but not temperature alone ... and the point I was making is that the pressures will be different for the same 0.96g of Liquid Water + 0.04g of steam in each of those examples... as long as the pressure is different than that is the point I was making.

In the 40cc example the increased pressure will change the phase transition point of the liquid water to higher than the 100C you listed ... this will happen before all the thermal energy from the initial gasses has been transferred to the liquid water ... as the temperature for the phase transition of the water to steam goes up ... it means that some of the heat energy transfer from the initial hot gasses must instead be spent raising the liquid water above 100C to the new higher phase transition temperature ... the higher the temperature of the liquid water the less of the temperature gap between it and the initial hot gasses ... which means less total Joules of thermal energy will transfer to the liquid water from the initial hot gasses...

etc .... etc ... as you said we can keep taking it further and further ... with diminishing returns for doing so.

So yes there will be a temperature effect ... I never said their wouldn't be ... I was claiming their would be a pressure effect due to the limited volume restriction on the expansion of the steam.

Originally Posted by t vago

In the 100 cc and 600 cc cases, the liquid will boil off to admit more steam into the vapor part of the system. The boiling off will absorb heat from the liquid water, causing the liquid to cool. The steam will also cool so as to maintain equilibrium temperature with the water. This will cool off the system as it goes to equilibrium, which will be at a lower final temperature. This follows the properties of saturated steam. The ideal gas law does not apply here.

Doesn't Apply?

That is a rather interesting claim ... especially sense it includes the effects of volume, pressure, and temperature... ie it allows for the temperature changes you are so fixated on.

What initial requirements of the ideal gas law do you think are not being met? ... I don't recall a specific water+steam exception ever being listed.

Originally Posted by t vago

Similarly, the steam, now at a much higher pressure in a 10 cc vessel than in the original 40 cc vessel, will condense out into the liquid. This releases latent energy of vaporization into the system, causing the temperature of the system to rise until the system again goes into equilibrium. Again, this reflects the properties of saturated steam, not the ideal gas law.

Incorrect.
It reflects both.
The Ideal gas law requires the change in pressure to cause a change in Temperature ... remember PV=nRT ... T=Temperature.

Originally Posted by t vago

Sure, for an initial condition gas that we're treating as an ideal gas for purposes of an example.

Originally Posted by t vago

Because, like I just said, water and saturated steam do not follow the ideal gas law. There are saturated steam tables for this.

Technically no gas 100% follows the ideal gas law ... because no gas is actually 100% ideal... but the basic principle of the relationships shown in the ideal gas law do still apply ... even to saturated steam.

And the point I was trying to make ... that you have been fighting so hard against ... is still correct ... the partial pressure of the steam will be higher than the 14.7 psi you listed ... which would be the partial pressure if there was no restriction to the volume for it to expand into... that just isn't the case in this 40cc example.

I am also getting the impression you seem to hold that the existence of steam tables somehow nullifies or contradicts the relationships shown in the Ideal Gas Law ... I disagree with this ... No gas is actually ideal ... steam tables are just the measured results of carrying out experiments under the listed conditions ... it in no way changes or nullifies the relationships shown in the Ideal Gas Law ... the most it might do is tweak the resolution of some of the results... but one must keep in mind the context of those tables, to keep their shown values properly applied.