How Fast Does Ice Sublime to Vapor at Extremely Low Pressure and -40°C?

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In summary: The equilibrium vapor pressure of ice at -40 is the partial pressure of water vapor in the bulk of the hydrogen phase (zero). The difference between this partial pressure and the partial pressure of water vapor in the bulk of the hydrogen phase (zero) provides the driving force for evaporation. The mass transfer occurs by water vapor diffusion through the hydrogen in the immediate vicinity of the interface.
  • #1
NSS
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Say we have 2 liter of water ICE in a 2 liter soda bottle.

Assuming sea level air pressure is, 14.7 PSI

We lower the temperature of the atmosphere around the ice to -40C

And we lower the pressure to 0.5 psi (roughly 75,000 feet)

The air around the ice is pure dry no water vapor in it at all. It's container, (probably a 2 liter soda bottle) will be vented via a tube to a balloon, that is filled with Hydrogen.

assuming this environment, at what rate would the ice Sublime to water vapor?

And how many cuft or cubic meters of water vapor would it produce for "X" amount of time?

Thanks
 
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  • #2
Unless you add heat to the ice, I think the rate of sublimation will be very low, if not zero. At the conditions you specify, the ice will be happy to stay solid.
 
  • #3
Low is a relative number.

How much do you think as a low number?
 
  • #4
How about zero?
 
  • #5
Even at -40 degrees, ice has a non-zero vapor pressure. If the air is bone dry, the ice will certainly evaporate into it. The rate at which this happens depends on a number of factors, but obviously will be very low. By the way, it's very unlikely that atmospheric air at 75000 ft will be bone dry.
 
  • #6
Chestermiller said:
Even at -40 degrees, ice has a non-zero vapor pressure. If the air is bone dry, the ice will certainly evaporate into it. The rate at which this happens depends on a number of factors, but obviously will be very low. By the way, it's very unlikely that atmospheric air at 75000 ft will be bone dry.

But what the water is exposed to is bone dry, 100% Hydrogen only.

Well at least 100% Hydrogen only until the water starts to enter it, by the sublimation.
 
  • #7
NSS said:
But what the water is exposed to is bone dry, 100% Hydrogen only.

Well at least 100% Hydrogen only until the water starts to enter it, by the sublimation.

Well, yes. Hydrogen. But that wasn't really relevant to what I was saying. At the interface between the ice and the hydrogen, the partial pressure of the water is the equilibrium vapor pressure of ice at -40. The difference between this partial pressure and the partial pressure of water vapor in the bulk of the hydrogen phase (zero) provides the driving force for evaporation. The mass transfer occurs by water vapor diffusion through the hydrogen in the immediate vicinity of the interface. The more that the hydrogen is mixed/stirred/agitated, the thinner the diffusion boundary layer at the ice interface, and the higher the rate of mass transfer (evaporation).
 
  • #8
True,
 

Related to How Fast Does Ice Sublime to Vapor at Extremely Low Pressure and -40°C?

1. What is water sublimation at low pressures?

Water sublimation is the process by which a solid water (ice) directly transforms into a gas (water vapor) without going through the liquid phase. This process occurs at low pressures, typically below atmospheric pressure.

2. How does water sublimation at low pressures occur?

Water sublimation at low pressures occurs due to the decrease in surrounding pressure, which reduces the boiling point of water. As a result, the energy from the surrounding environment causes the solid water molecules to break apart and transform into a gaseous state.

3. What factors affect the rate of water sublimation at low pressures?

The rate of water sublimation at low pressures is affected by factors such as humidity, temperature, and surface area. Higher humidity levels and lower temperatures can slow down the sublimation process, while a larger surface area of the solid water can increase the rate of sublimation.

4. What are some common applications of water sublimation at low pressures?

Water sublimation at low pressures has various applications, such as freeze-drying food, preserving historical documents and artifacts, and creating artificial snow. It is also used in laboratory settings for sample preparation and purification.

5. Is water sublimation at low pressures reversible?

Yes, water sublimation at low pressures is reversible. When the pressure is increased, the water vapor molecules can recombine and form solid ice again. This process is known as deposition.

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