Why a temperature differential?

[Tom Booth]

Jack I would recommend you do some research on Wikipedia, don't let Tom confuse you over these basic issues. Having alternative views and theories is great but you should first (try to) understand the established theories of thermo.

And what exactly is your problem with me lately Vincent?

I said nothing to "confuse" anyone. Just factual, straightforward information.

You were at one time a valuable contributor to the forum through your rapid 3D prototyping and frequent experiments, lately however you seem to have joined the bash and dump on Tom club.

Have I done something to offend you personally?

[Jack]

Jack if you heat 1 liter of 300k air to 600k and expand it adiabatically, it will reach 1 bar well before it lowers to 300k.

I'll try to find the real values fir you but maybe Matt will beat me to it.

Just curious, but how do you heat air and have it expand adiabatically?

First do one, then the other.
This is just to get an understanding of what air or a fluid goes under these conditions.

Well, how?

You indicated "Without engines in mind".

To first "heat 1 liter of 300k air to 600k" without the gas expanding would require confinement of some kind.

Following that with adiabatic expansion would require some circumstance or mechanism for removing such confinement. That could be accomplished in various ways.

If not in an engine cylinder than you will, I think, need to clarify what circumstances you have in mind.

What do you mean by "these conditions?"

Under purely hypothetical conditions where I can heat up a gas a given amount and measure the data without any losses to anything. No friction, no conduction.
It's not something that can be done in the real world I guess. But it's the basis of it all.
From there, I think, you can start imagining what that fluid can do in an engine.

[VincentG]

Not to discard or talk over what you just explained, but I'm trying to get to the bottom first. Without engines in mind yet.

What happens to a fluid when heated up and how does manipulating either temperature, volume or pressure change that.

So if you heat a liter of air, expand it until it's back to starting temperature, what do you end up with? Bigger volume, lower density, same pressure?

Tom I've been very patient with you, more than most, but there are limits.

I'm not trying to bash anyone but geez the guy is just looking for a simple answer to get his thoughts inline. Start with the basics and work out from there.

Any standard model of an adiabatic expansion is shown within a perfectly insulated piston and cylinder with STP as a buffer pressure, like the Carnot engine.

[Tom Booth]

Just as you have been doing to me and others on this forum since your arrival.

It is not I that discourages you. The Carnot theorem is reflecting nature.

You would have to prove that assertion. The Carnot limit equation and how it's being applied in academia, is a completely arbitrary theoretical imposition, 100% the product of the human imagination without reference to "nature" actual observation of reality or empirical experiment.

Nature will discourage anyone by failure. The Carnot rule protects a very long drawn out process of building leading up to what has already learned to be a failure.

I've asked for ANY evidence of any such "failure". But there have been no such experiments. Under such circumstances there can be no repetition of failure for something that has never been tried.

Just for example, on the old thermodynamics thread I was told several times if the sink of a Stirling engine was insulated the engine would stall.

Nobody had done the experiment, that was a logical assumption based on the Carnot limitations theory. A false assumption.

There are posts on old threads stating a Stirling engine could never run without a flywheel, at all. Again, based on the Carnot limit assumption. Again this turned out to be false.

Instead it can be used to help. Oh my! My engine is only getting an efficiency of 1.5%! Wow! That's good! What do you mean? Well Carnot says the maximum you will get is 2%. You are getting an incredible 75% of the Carnot limit. That is way better than most engines. Keep up the good work.

That is not encouragement. It's stopping progress in its tracks, saying little if any additional progress or improvement is possible so don't waste any more time trying, and conveys the same message to everyone else, in perpetuity.

A very damaging consequence immediately as well as for future generations.

[Tom Booth]

Just curious, but how do you heat air and have it expand adiabatically?

First do one, then the other.
This is just to get an understanding of what air or a fluid goes under these conditions.

What do you mean by "these conditions?"

Under purely hypothetical conditions where I can heat up a gas a given amount and measure the data without any losses to anything. No friction, no conduction.
It's not something that can be done in the real world I guess. But it's the basis of it all.
From there, I think, you can start imagining what that fluid can do in an engine.

What "hypothetical conditions" then?

If it can't be done in the real world, then it cannot be verified by experiment so would be pure speculation or theory without real evidence. In other words mere opinions.

[Tom Booth]

Not to discard or talk over what you just explained, but I'm trying to get to the bottom first. Without engines in mind yet.

What happens to a fluid when heated up and how does manipulating either temperature, volume or pressure change that.

So if you heat a liter of air, expand it until it's back to starting temperature, what do you end up with? Bigger volume, lower density, same pressure?

Tom I've been very patient with you, more than most, but there are limits.

I'm not trying to bash anyone but geez the guy is just looking for a simple answer to get his thoughts inline. Start with the basics and work out from there.

Any standard model of an adiabatic expansion is shown within a perfectly insulated piston and cylinder with STP as a buffer pressure, like the Carnot engine.

It seems you and "Jack" answer for each other rather often.

So not a real engine, but a Carnot engine?

Not reality but a fiction?

The hypothetical behavior of a hypothetical gas in a hypothetical engine. No actual conditions or parameters.

Seems to me that could lead to confusion as well as very misleading conclusions when and if transposed into the real world.

Why not just start with real conditions in the real world. That is the only way to get real, verifiable answers to anything.

[Jack]

I don't think you'd need any more info or conditions for the question I asked.

I merely want to know the behaviour of a fluid. Not exact volumes or densities.

My question in short was what happens to the pressure, volume and density ratio when I heat up a fluid and then expand it to reach its starting temperature.
I'm interested in finding out what happens on a molecular level.

[Jack]

The answer seemed to be, bigger volume, lower pressure and density.

[Tom Booth]

The answer seemed to be, bigger volume, lower pressure and density.

And temperature?

And how exactly do you arrive at any conclusions, on a molecular level or otherwise.

You get different results under different circumstances, even on a molecular level.

It's like asking, what happens when you cook a meal.

Well, what's the menu, the recipe, the ingredients, the method, gas stove, microwave.

No, you don't want a menu, no ingredients, no recipe, no heat appliance, just what happens when you cook a meal?

That's not a question that can be answered without some additional information.

Which BTW, leads me to believe "Jack" is simply a "sock puppets" set up by someone to try to prove a point, not someone actually interested in a real answer or solution to a question or problem.

[Jack]

Temperature is the constant in my question.

[Tom Booth]

Temperature is the constant in my question.

Since when?

[Jack]

Which BTW, leads me to believe "Jack" is simply a "sock puppets" set up by someone to try to prove a point, not someone actually interested in a real answer or solution to a question or problem.

Everyone is entitled to their belief. And everyone believes what they want to believe. But be careful with fitting every little piece of "evidence" to your belief. It blinds one to other possibilities.

[Jack]

Temperature is the constant in my question.

Since when?

I guess you didn't read my question thoroughly.

I'm asking about the behaviour of a fluid when it's heated up and, afterwards, expanded to its starting temperature.

So while the temperature doesn't stay the same through the whole idea, the goal is to bring the fluid back to original temperature and give info about the other variables.

[Tom Booth]

Temperature is the constant in my question.

Since when?

I guess you didn't read my question thoroughly.

I'm asking about the behaviour of a fluid when it's heated up and, afterwards, expanded to its starting temperature.

So while the temperature doesn't stay the same through the whole idea, the goal is to bring the fluid back to original temperature and give info about the other variables.

Then you are imposing conditions to arrive at a specific result or "goal" which seems contrary to your earlier statements.

You would need some means of preventing further expansion and cooling.

[Jack]

No, I think I was asking this from the beginning. Maybe poorly worded, as English isn't my first language.