CM, from the content I see in your most recent big thermo post, I suspect you have been subjecting yourself to a quick refresher in what thermo really says. But alas, like many cram study sessions, that just isn’t a good way to firm up your understanding of a subject.
And I have to offer caveat for my absence over a few days. Crossing lotsa time zones, - trains, planes, and automobiles - are not conducive to my being promptly responsive to TOL threads. But at least I suspect the Laws of Thermo are the same here as they are far away where I was a few days ago.
So now back to the subject at hand. You posted:
[MENTION=5148]redfern[/MENTION] is talking about water coming to a boil and changing phases. Basically, he is discussing this graph:
This is the typical graph for phase changes of water at one atmosphere. Everything he said about this is correct. Even his comment regarding a closed system wherein you heat the water past the boiling point by 10° to 30° and the releasing the pressure are correct.
I appreciate the graph and the accompanying comments. You are right when you say “This is the typical graph for phase changes of water at one atmosphere”, and that means this graph is very relevant to your claim about water flashing to steam that spawned my jumping into this thread.
But … I can’t resist putting this in here – Look near the bottom of the graph. In blue it says “heat of vaporization”. Now look directly above that to where the dark horizontal line is that depicts the vaporization (and condensation). How to label that line – no problem – since we are depicting the heat of vaporization, we’ll label this line as “e + vaporization = evaporization” line. Uhhh – no, like it said in blue near the bottom, that is called just “vaporization”, with no “e” on the front. Maybe whoever made up that term was thinking of “evaporation”, which is almost the same as vaporization, but at lower temperature. Where did you find this graph anyway, at “Uncle Clem’s School of Thermodynamics for Moonshiners?”
The very next thing I see in your post says:
This is not the system that is being discussed in the rest of this thread.
Speak for yourself. In spite of your strenuous efforts to try to keep the focus on perceived faults in Walt’s ideas, until you convince me that you get this regime of thermo right, I am not inclined to trust your judgment in Walt’s far more esoteric regimes of temperature and pressure.
I have pleaded with you to go the math route on the water flashing to steam question, only to have you say that I should do the math, and then you again assure us that you took classes in this stuff, and that this stuff applies in systems like the Rankine Cycle. But oodles of engineers and others who fundamentally rely on physics have to take classes in which thermo is taught. A whole lotta them think that thermo is not gonna be something they will be dealing with after graduating, and so they just muddle through it, and most of the time they are right. But occasionally one of them finds himself involved in a TOL discussion. Not a good time to confidently assert you know thermo, when you’re one of the masses that just muddled thru it in college.
I hope to soon move past this thermo issue with you, but first still some residual red flags I have on what you have said.
… Finally, you are attempting to deal with gradual ling heating water to boiling.
I don’t think I specified with how fast I heated the water. Can you show me in the thermo equations where that is gonna be a factor? All I am concerned with is the water at the conditions you originally mentioned – 212 F (and I was willing to go above that temp just to be sure). If you want me to heat it in a hurry with using a bank of welder’s blowtorches, fine.
I am talking about a closed system that is already well above 212 degrees.
Do you think ignoring the heating process up to the 212 temp, and only looking at the thermo involved above 212 is gonna change how much of water flashes to steam?
There is enough energy in the water to more than account for the latent heat of vaporization needed to convert liquid water to steam.
And that pretty well states our point of divergence. More later on that.
Tell you what – I will move on from this thermos business if you go with me through a specific mathematical example. If you want, I will do the math, and you will either concur or show where I am in error, OK? Here is what I am proposing, based on your recent comments. You said:
Go get a pressure cooker and fill it with water and put the lid on and seal the pressure release valves. Heat the water to 300 degrees and remove the lid
Gotcha. I’m going to put a beautiful fluorescent label on the lid that says “New Soccer & Rugby Equipment Inside – Free”, so Stripe will be the one taking the lid off. We will start with say, 10 pounds of water (I pick pounds instead of kg or liters or whatever just because it simplifies some of the calculations). The water will initially be at just above freezing – 32 F. (Starting with cold water also simplifies some of the math.) I’m gonna measure the heat in BTUs, again for mathematical simplicity. If you object to any of these units, let me know and I will use units you prefer, and will toss in the necessary conversion factors. For the comfort of the readership who don’t deal much with units of heat, a moderate sized home water heater will need to use about 35,000 BTUs each day for showers, baths, laundry, etc.
We will use a heat source that can supply enough heat to raise the temperature of the entire 10 lbs of water by 10 degrees F each minute. Gonna keep cooking that water right up till the water it is at the 300 F you mentioned (water will be under pressure, of course). Since you earlier said you were “talking about a closed system that is already well above 212 degrees”, I propose we keep this thing at that 300 F level for 16 solid weeks, 24 hours a day, 7 days a week, long enough to really see if “there is enough energy in the water to more than account for the latent heat of vaporization need to convert liquid water to steam.”
Now my first question to you is, since “some portion of that water will flash to steam”, roughly how much do you say will flash to steam when we have Stripe take the lid off that pressure cooker? An answer that is within 10% will be fine, in pounds or kg or whatever of water that flashes. What say ye? Give us your guess and let’s then do the math.
