Post by Andrew on Sept 16, 2013 6:48:48 GMT
How far have we got with this?
If we ignore supercooling.
1. In all cases the latent heat contained in water vapour or water has to go somewhere if we condense or freeze water.
2. If we mechanically extract heat from water we cannot expect the environment around the water to get warmer once we reach the freezing point. All that happens is that upon reaching the freezing point it takes longer to mechanically extract the heat to cool the icy water.
3. If we place an amount of water into a cold environment the water will cool. We cannot expect that nearby objects will become warmer once the freezing point is reached. The nearby objects are getting less heat from the icy water than they were prior to the formation of ice
4. If a cold environment is cooling a large body of water, the cold environment is heated more before the ice freezes than once the freezing point is reached
5. If we operate a dehumidifier to condense water then the latent heat of condensation that no longer exists must have gone somewhere. As a beginning point we can reason the cooling part of the dehumidifier becomes warmer when humidity increases, and becomes cooler as the air becomes drier, where even if the dehumidifier motor consumes more power when the cooling part becomes warmer, the latent heat of condensation still has to go somewhere, and the only place for it to go is into a heating energy via the hot side of the dehumidifier.
If the dehumidifer extracted the latent heat energy, then that energy must be in the room somewhere.
6. Because water vapour exists in another gas that has nothing to do with water the case of water vapour condensing to water is different to the case of water freezing to ice, where ice exists surrounded by water, whereas water can be separated from air.
We can then compare drier cooling air with wetter cooling air when air rises, and see that wetter cooling air, can directly heat drier cooling air, by radiation or conduction at the boundary of the rising air mass.
However if we separate icy water from ice there is no ability of these two masses to heat each other since they are the same temperature, unless the ice has cooled more than the water, where to do that, the ice has to be entirely separated from water, or the water on the ice has to have become frozen and no more water is available to cover the ice - even as a thin film.
7. Water placed on ice will always warm ice towards the freezing point or higher, and in turn very cold ice will always cool water towards the freezing point or higher. Therefore if we provide sufficient water, even if the water is ice cold, we will always warm a colder amount of ice towards the freezing point or higher. Therefore given sufficient water, in the right conditions, we can protect plants from becoming colder than the freezing point of water.
8. Because of the latent heat of fusion of water, water requires a huge amount of work to cool it to be frozen. In other words, water freezes with difficulty and enables icy water to remain at 0C for far longer than we might have imagined had we not known about the latent heat of fusion of water.
9. Without supercooling, ice formation has no greater ability to heat the environment when it freezes, that is greater than the ability that water had to heat the environment. Heat spikes in an environment or an atmosphere when ice freezes are impossible by anything to do with the latent heat of fusion of water as a heating energy that is somehow more useful to heat the environment than water was before it began freezing.
10. If the air is near freezing and humid and the sky is clear, then the radiating surface of plants will be colder than the air and water will condense on the plants. Because water will always coexist with ice at the freezing point, even if momentarily the plants have only ice upon them without a water film, then an ice layer can build on plants if the water is sufficiently humid to keep the ice layer mainly coated with a film of water. However if the drying action of the colder surface exhausts the amount of near surface water vapour the plants will get colder than the freezing point of water and can continue to cool once the film of water on the ice can no longer periodically return to warm the ice. In a nutshell for the farmer, wet ice is potentially ok and dry ice is likely to be bad.
If we ignore supercooling.
1. In all cases the latent heat contained in water vapour or water has to go somewhere if we condense or freeze water.
2. If we mechanically extract heat from water we cannot expect the environment around the water to get warmer once we reach the freezing point. All that happens is that upon reaching the freezing point it takes longer to mechanically extract the heat to cool the icy water.
3. If we place an amount of water into a cold environment the water will cool. We cannot expect that nearby objects will become warmer once the freezing point is reached. The nearby objects are getting less heat from the icy water than they were prior to the formation of ice
4. If a cold environment is cooling a large body of water, the cold environment is heated more before the ice freezes than once the freezing point is reached
5. If we operate a dehumidifier to condense water then the latent heat of condensation that no longer exists must have gone somewhere. As a beginning point we can reason the cooling part of the dehumidifier becomes warmer when humidity increases, and becomes cooler as the air becomes drier, where even if the dehumidifier motor consumes more power when the cooling part becomes warmer, the latent heat of condensation still has to go somewhere, and the only place for it to go is into a heating energy via the hot side of the dehumidifier.
If the dehumidifer extracted the latent heat energy, then that energy must be in the room somewhere.
6. Because water vapour exists in another gas that has nothing to do with water the case of water vapour condensing to water is different to the case of water freezing to ice, where ice exists surrounded by water, whereas water can be separated from air.
We can then compare drier cooling air with wetter cooling air when air rises, and see that wetter cooling air, can directly heat drier cooling air, by radiation or conduction at the boundary of the rising air mass.
However if we separate icy water from ice there is no ability of these two masses to heat each other since they are the same temperature, unless the ice has cooled more than the water, where to do that, the ice has to be entirely separated from water, or the water on the ice has to have become frozen and no more water is available to cover the ice - even as a thin film.
7. Water placed on ice will always warm ice towards the freezing point or higher, and in turn very cold ice will always cool water towards the freezing point or higher. Therefore if we provide sufficient water, even if the water is ice cold, we will always warm a colder amount of ice towards the freezing point or higher. Therefore given sufficient water, in the right conditions, we can protect plants from becoming colder than the freezing point of water.
8. Because of the latent heat of fusion of water, water requires a huge amount of work to cool it to be frozen. In other words, water freezes with difficulty and enables icy water to remain at 0C for far longer than we might have imagined had we not known about the latent heat of fusion of water.
9. Without supercooling, ice formation has no greater ability to heat the environment when it freezes, that is greater than the ability that water had to heat the environment. Heat spikes in an environment or an atmosphere when ice freezes are impossible by anything to do with the latent heat of fusion of water as a heating energy that is somehow more useful to heat the environment than water was before it began freezing.
10. If the air is near freezing and humid and the sky is clear, then the radiating surface of plants will be colder than the air and water will condense on the plants. Because water will always coexist with ice at the freezing point, even if momentarily the plants have only ice upon them without a water film, then an ice layer can build on plants if the water is sufficiently humid to keep the ice layer mainly coated with a film of water. However if the drying action of the colder surface exhausts the amount of near surface water vapour the plants will get colder than the freezing point of water and can continue to cool once the film of water on the ice can no longer periodically return to warm the ice. In a nutshell for the farmer, wet ice is potentially ok and dry ice is likely to be bad.
