Sidenote.....I have to make ice cubes in trays with hot water. Somehow it freezes different than making them with cold water.

quote:

Originally posted by EmpireState:
Sidenote.....I have to make ice cubes in trays with hot water. Somehow it freezes different than making them with cold water.

Indeed. And they are also smaller, which is why they can end up freezing faster.
Smaller because of evaporation.

quote:

Originally posted by sigmonkey:


I did not say the rapid expansion caused the freezing. I said the rapid expansion of heated gases and the contained water resulted in the contrails, vs none expanding water.

Clearly you've never seen inflight icing trials or done inflight ice experimentation. I have.

All this mental masturbation does not address warm water freezing faster in a freezer...which does not happen.

As for contrails, were your suggestions to be true, and they're not, contrails would form in ambient temperatures above freezing and this is not the case.

Contrails would also form far more consistently than they do, and we wouldn't have distrails in which the inverse of a contrail forms. In distrails, or dissipation trails, rather than forming a contrail behind the aircraft, the exhaust stream "cuts" through cloud or ice crystals and leaves no visible trail. Ambient conditions determine what forms.

Other than icing experimentation, we don't stream water from aircraft at altitude.

Have you ever watched contrails form in flight from your own aircraft or from another aircraft?

quote:

Originally posted by sigmonkey:

If you streamed quantity of water in a non-compressed liquid phase from an orifice and the same amount in gaseous phase that exits from the engine the contrail is going to be the faster freezing, from the expansion and liberation of heat to the colder air, than the stream.

No, it won't.

Again, we don't stream cold water from aircraft, but were we to do so, cold water streamed directly into the atmosphere vs. jet effluence will give a clear visual demonstration that the cold water freezes first, excepting supercooled water droplets which will require either time or loss of surface tension prior to freezing.

You've never dispensed water and other chemicals from an aircraft in freezing conditions?

quote:

Originally posted by sigmonkey:

The gases of jet exhaust do this as well, (and to a greater degree than tossing boiling water), and pressure change upon exit of the nozzle has the effect of cooling the water in the gases rapidly.

You're talking in circles with tossing boiling water into the air and your guesswork regarding contrails.

While your focus on contrails still is irrelevant to the original topic and is incorrect, it's worth noting that given the significantly elevated temperature of effluence behind a turbojet engine, any potential reduction in temperature from expansion does not offset the exhaust temperature adequately to cause freezing, and certainly not to compete with cold water injected into the same parcel of air.

When you figure out how to capture your jet exhaust and apply it to a freezer sample of water, it will be a bit more relevant to the conversation.
As for water samples in a freezer, given two identical volumes, hot water will have a lower mass than cold water due to differences in density; this difference in mass must be accounted when considering the thermal change. It's inadequate to simply note volume, and one should not discount the container or medium by which the water is contained, both container material and temperature.

Most of my observations of flying were either in a circle between 8-11 AGL looking at where we had been, and that was 40 years ago. The other part is from work on turbojet engines, and all that goes with that, as well as some physics crap I had to study almost as many years ago.


That said, masturbation, mental or otherwise is the best I expect to get at this stage in life, so I am not going to miss out on it if I can stay awake long enough.

The original point I was making, and still have not conceded as being incorrect, is that the rapid expansion of hot gases from an aircraft, are the reason contrails occur when contacting colder air (conducive to contrail formation) and the same thing will not produce similar contrail if the same volume of unheated and liquid water (phase) are released.

And that is related to the "tossing of boiling water" that freezes in extreme cold weather, vs tossing "cold" water and not experience any freezing, that is the point of the discussion.

And I never even brought into the discussion the water in a freezer bit.

My point was and still is, water vapor/gas phase under pressure when expanded will result in a wider surface area in contact with colder air mass, or the result of expansion and the resulting lower pressure (and change of energy state) will result in a rapid cooling, and that is directly related to the formation of ice of the water.

quote:

Originally posted by sigmonkey:


I did not say the rapid expansion caused the freezing. I said the rapid expansion of heated gases and the contained water resulted in the contrails, vs none expanding water.

I know exactly what you said. You're still wrong, of course.

quote:

Originally posted by sigmonkey:


Both will freeze, but the expanding contributes to this. If you streamed quantity of water in a non-compressed liquid phase from an orifice and the same amount in gaseous phase that exits from the engine the contrail is going to be the faster freezing, from the expansion and liberation of heat to the colder air, than the stream. The stream will also "boil off" but without the heat, it will do so much more slowly.

You're still wrong. You're still maintaining that water in the free airstream will freeze more slowly than water vapor in jet exhaust, and you seem to think that expansion of the exhaust effluence after leaving the engine will accomplish this. It won't. Ever dispensed water and other chemicals in flight in freezing conditions? Ever watched your own contrail form, and that of other aircraft? Ever done inflight icing testing and trials? Ever done atnospheric research involving an aircraft full of sensors with research scientists aboard sampling the freezing water results in real time? If you said yes to all of the above, you might be me, and you'd know how wrong you are.

You'd also understand just how irrelevant your cobtinuing to beat this wrong, dead horse is to the conversation. And yet you persist.

Simply put, the exhaust stream enters the atmosphere at such an elevated temperature that any adiabatic thermal exchange due to expansion will not be remotely adequate to permit freezing of water vapor in the jet exhaust stream before cold water introduced into the same air parcel outside the jet effluence.

Try it some time. I have.

quote:

Originally posted by sigmonkey:

A tub of boiling water will need to transfer all of it's heat to the air in order to be lowered to freezing point.
Boiling water dispersed will be rapidly turned into steam, as it is at boiling point when it expands by the act of throwing it and it is no longer in a total liquid phase, but a partial (small droplet) vapor phase.

The "spreading" is expansion and there is a small transfer of energy, and the surface area of the water and the cold air are increased dramatically, and the water freezes, leaving a cloud of ice crystals.

Nough with the damn bathtub. You ever throw one full of water out the back of the aircraft? Me either. Why would one do so? It's an idiotic point, and doesnt change the fact that water vapor in turbojet effluence will not freeze faster than cold water introduced in the free airstream.

Go give it a try.

This ranks up there with cow tipping and the snipe hunt.

In case who have been to a hockey game wonder why it appears that the ice resurface machine (Zamboni)is laying hot water down, it is to smooth out the surface not conditioned by the blade better. The layer is so thin that it cools quickly enough to freeze into a nice layer bonded to the lower layers as opposed to a thin top layer that would chip off.

quote:

Originally posted by Skins2881:

quote:

Originally posted by LS1 GTO:
Wives tale.

Now what is not - perfectly still water (that where the surface tension is not broken) can be heated above 212 F and once tension is broken (disturbed) will immediately boil over.

Forgot what it's called but seen the experiment.

Super heated water, can get over 212*, but you must use pure water, won't happen with tap water.

Not true. I have had this happen in a microwave. Fortunately, when the water didn't boil in the time expected, I didn't take it out. I just added more time. When the water eventually reached criticality, it explosively flash boiled. It blew open the microwave door. The interior of the microwave was drenched in hot water. Only about a half inch of water remained in the glass.

People have been seriously burned from this.

Ice makers are supposed to be plumbed off the hot water line. Though I believe this is that the water heater cook off any residual chlorine from water treatment, not because it freezes faster.

^^ Hot water freezes clearer than cold, thus the choice of hot water for ice maker supply lines. As if the appearance of the ice in your fifth rum-and-coke is an issue.

When I was twelve years old, my father told me that hot water will freeze before cold water. I didn’t believe him so I filled an ice tray with cold tap water and I filled another one with hot tap water. I placed both ice trays next to each other in the freezer. The hot water froze first. My guess back then as to the reason why this happens is that the water molecules spread when freezing and since hot water molecules are already spread apart, they get to skip that part.