Merged DDWFTTW in a “Real” Wind

[EHocking]

An internal combustion engine is a heat engine. The transfer of heat of combustion to mechanical work, is done at the piston, rather than externally as with a hot air balloon. My, you don't know much.

As I said. Precious moments like these.

Heat is a by-product.

The mechanical work is achieved by expansion of gases in a piston after combustion. Heat is a by-product - it is not transferred to the drive-shaft.

 

[humber]

Most, if not all of the "opinions" I state are obvious to anybody with a rudimentary knowledge of physics. I learned it in high school and college courses, and independent reading. I became a "cart supporter" because it was clear to me that though the design was non-obvious (to me anyway) there was absolutely no reason it couldn't work.


Also, Spork and JB were clearly not hiding anything. They gave detailed instructions on how to replicate their treadmill tests, and others confirmed their results.

OTOH, you, while trying to pass yourself off as some kind of expert, made an incredible string of laughable, fundamental errors that made it clear that you were either deliberately spouting nonsense to yank our chains, or that you had no idea what you were talking about, starting with your dismissal of the validity of the treadmill test.

I doubt that. All you have done is repeated Spork verbatim.
One error is not to see that the TM works by means that you may not have learned in junior high school, but have limited yourself to even less than that.
I like the way you want what I write to be errors or something to jerk your chains. You need to keep both options open, because you can't tell fact from fiction, and so fall for Spork's fiction, because that appeals to your self-satisfaction.

 

[EHocking]

An internal combustion engine is a heat engine. The transfer of heat of combustion to mechanical work, is done at the piston, rather than externally as with a hot air balloon. My, you don't know much.

A Chinese Sky Lantern^WPis "powered" by a candle.

Are you saying that a candle is an engine?

 

[humber]

As I said. Precious moments like these.

Heat is a by-product.

The mechanical work is achieved by expansion of gases in a piston after combustion. Heat is a by-product - it is not transferred to the drive-shaft.

Oh dear. What do you think "heat" is? The property of "hotiness"?
Heat is the molecular velocity. When hot, the combusted gases gain a great deal of momentum. The mass does not change, the molecular velocity does.
That gas hits the piston, and transfers momentum to it, producing mechanical work. The heat dissipated to the atmosphere and the exhaust is the result of inefficiency.
And yes, the candle is an engine. The heat directly increases the momentum of the air.
p = m*v.

 

[zooterkin]

It gains PE by rising.

Oh, dear, I don't know what to believe now, humber is agreeing with me.

 

[humber]

Oh, dear, I don't know what to believe now, humber is agreeing with me.

And that means you disagree with Spork. Go on, you can say it.

 

[sol invictus]

I would claim that a positively buoyant hot air balloon LOSES potential energy as it ascends - just as a rock loses P.E. as it falls.

Balloons rise because the force due to the vertical gradient in atmospheric pressure is larger than the force of gravity acting on them. As they rise, they of course gain gravitational PE (m*g*h).

You could define a "pressure potential energy" - a sensible thing to do, since the pressure force is the gradient of the pressure - and a buoyant, rising balloon would be losing pressure potential faster than it is gaining gravitational potential. In this language, that's why it rises.

"Pressure potential" isn't a term I've heard used much, but I wouldn't be surprised if it's common in some fields - and it's a sensible notion.

 

[humber]

Balloons rise because the force due to the vertical gradient in atmospheric pressure is larger than the force of gravity acting on them. As they rise, they of course gain gravitational PE (m*g*h).

You could define a "pressure potential energy" - a sensible thing to do, since the pressure force is the gradient of the pressure - and a buoyant, rising balloon would be losing pressure potential faster than it is gaining gravitational potential. In this language, that's why it rises.

"Pressure potential" isn't a term I've heard used much, but I wouldn't be surprised if it's common in some fields - and it's a sensible notion.

Double post

 

[humber]

Balloons rise because the force due to the vertical gradient in atmospheric pressure is larger than the force of gravity acting on them. As they rise, they of course gain gravitational PE (m*g*h).

You could define a "pressure potential energy" - a sensible thing to do, since the pressure force is the gradient of the pressure - and a buoyant, rising balloon would be losing pressure potential faster than it is gaining gravitational potential. In this language, that's why it rises.

"Pressure potential" isn't a term I've heard used much, but I wouldn't be surprised if it's common in some fields - and it's a sensible notion.

Air pressure is the result of gravity. So the "differential pressure" is the result of the difference in gravitational force on the balloon and air, due to their differing densities. As such, it is possible to make NB balloons, with a wide range of gas density and overall volume, while also allowing for the mass of the envelope.

 

[sol invictus]

Air pressure is the result of gravity.

Nonsense, of course. The air in the international space station has pressure.

It is true that the pressure gradient in the earth's atmosphere wouldn't exist without gravity. But neither would the sun or petroleum, and we don't regard cars as powered by gravity.

 

[humber]

Nonsense, of course. The air in the international space station has pressure.

Yes, I know, and you have left out some details concerning the gravity of the ISS, which is known to upset delicate micro-gravity experiments.

That air pressure the result of applied force contained by the rigid walls of the ISS. That force increases the pressure, by limiting the mean free path of the molecules. On the Earth, the force of gravity increases the pressure.

It is true that the pressure gradient in the earth's atmosphere wouldn't exist without gravity.

Without gravity, the gas molecules are largely free. Interaction is limited to Van der Waals forces, momentum, and the mean free path of the molecules.

But neither would the sun or petroleum, and we don't regard cars as powered by gravity.

The Sun would not operate as a fusion reactor, if not for the force of gravity creating enormous pressure and temperature at the core. There would be nothing for the Earth to orbit, should that exist without gravity.
Cars fueled by hydrocarbons, are indirectly powered by the energy accumulated from the Sun, by the plants that long ago absorbed it.
The wind is the result of the Sun heating the Earth and atmosphere.

 

[spork]

Or, since we're talking about a hot-air balloon, just turn off the burner and wait.

You mean wait until it's not a "hot air" balloon?

I'm willing to be convinced by figures, but I don't think it's as simple as because it is rising, it is losing potential energy.

Energy = force x distance
Hooke's law: Energy = 1/2 K * X^2 (again, energy = force x distance).
Gravitational potential energy = mgh (otherwise stated: energy = force x distance).

I could put some numbers to it, but I imagine you get my drift.

It's also gaining PE due to its height, and also losing the potential energy from the fuel being burnt.

In my scenario there is no fuel being burned as it rises. And the gravitational PE gained is clearly less than the buoyancy PE lost - thus it rises.

I think it depends which parts you're going to include whether a rising balloon is gaining or losing potential energy.

Yup - exactly my point.

It gains PE by rising.

Sorry zoots - you know what this means.

Oh, dear, I don't know what to believe now, humber is agreeing with me.

You know what to believe.

Balloons rise because the force due to the vertical gradient in atmospheric pressure is larger than the force of gravity acting on them. As they rise, they of course gain gravitational PE (m*g*h).

You could define a "pressure potential energy" - a sensible thing to do, since the pressure force is the gradient of the pressure - and a buoyant, rising balloon would be losing pressure potential faster than it is gaining gravitational potential. In this language, that's why it rises.

"Pressure potential" isn't a term I've heard used much, but I wouldn't be surprised if it's common in some fields - and it's a sensible notion.

We're on exactly the same page.

 

[humber]

You mean wait until it's not a "hot air" balloon?

Energy = force x distance

work = force*distance.
Power = work/time ---> Energy/time

Hooke's law: Energy = 1/2 K * X^2 (again, energy = force x distance).
Gravitational potential energy = mgh (otherwise stated: energy = force x distance).
I could put some numbers to it, but I imagine you get my drift.

Hooke's law applies to springs, where K is a function of strain, and that is down to the molecular forces that bind the material comprising the spring.
F= k*x.
The potential energy in the spring is the integral of F(x) wrt x.

Substitute F =k*x
PE = 1/2(k*x)*x
= 1/2k*x^2.

That differs for gravity, because near the surface, the force 'g' is nearly constant.

 

[Subduction Zone]

Oh, dear, I don't know what to believe now, humber is agreeing with me.

Yup, that is a sure sign that you are in error.

 

[phunk]

Why the derail about hot air balloons? What does that have to do with ddwfttw?

 

[Llyricist]

Hot air balloons was a red herring thrown out by someone to distract from their faux pas about a neutrally buoyant balloon's behavior in the wind. Tenuous connection, but a connection nonetheless.

 

[CORed]

yes, it's difficult to remain lurking with this stuff flying about.

I hope you didn't miss the posts where the heat source on a hot-air balloon is an engine and the other howler that an internal-combustion engine is a heat engine.

Amazingly enough, I think humber is correct in asserting that an IC engine is a heat engine. Calling the burner of a hot air balloon a heat engine requires stretching the definition of a heat engine almost to the breaking point, so I would say it's kind of silly, but not necessarily wrong.

 

[EHocking]

Amazingly enough, I think humber is correct in asserting that an IC engine is a heat engine. Calling the burner of a hot air balloon a heat engine requires stretching the definition of a heat engine almost to the breaking point, so I would say it's kind of silly, but not necessarily wrong.

Yeah, I gotta concede that in the broad sense of the term it is. I was think more in the terms of engines that generate power through thermal energy exchange from one state to another, i.e., from a heat source to a cold sink.

 

[phunk]

Seems like a silly distraction considering neither heat nor engines are required for neutral buoyancy.

 

[Modified]

Seems like a silly distraction considering neither heat nor engines are required for neutral buoyancy.

The initial question was settled long ago; all we have left are distractions, and humber's twisting of reality and physics has provided plenty of them.