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Post by Andrew on Aug 24, 2013 8:36:58 GMT
 Hot dry air is blown thru a porous screen to produce cold humid air. How does it work? If you add liquid water to a totally dry container then the water will quickly evaporate until the dry chamber becomes humid according to the expected humidity for that particular temperature. However the water and the air inside the container will have been cooled because when water vapour forms the water molecules contain a hidden heat that must be extracted from somewhere. The heat can only be extracted from the container, the water added or the air in the container so all will be cooled. So if you operate the humidifier and water vapour can continually leave the chamber, then the chamber will continually be cooler and more humid than the air that arrives into the chamber. So the question then is can you create heating using water? The humidifier creates cooling by increasing the humidity of dryer air. So what happens if we can create a process that will lower humidity? Nature can do this by transporting cooler wetter air over a mountain range and condensing the water as rain on the windward side then forcing the air containing the latent heat of water back down the mountain on the leewards side as a warm dry fohn wind. For the same altitude the air is now warmer due to the heat added to the air as it was rising and water was forming during which time the temperature of the air did not fall as much as would be expected, where the wet lapse rate is smaller than the dry one. One way to create warming with water and ice would be to supercool the water to say -10C and then add a small amount of ice to the water. The ice created would then be warmer than -10C and if there was a -10C atmosphere above the previously unfrozen super cooled -10C water that atmosphere will now be heated by the warmer ice |
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zaphod
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Post by zaphod on Aug 24, 2013 13:18:29 GMT
I have a process that lowers humidity. It is a dehumidifier. I run it a lot during the winter because of
a condensation problem on windows.
It works, and the lowered humidity can be seen from the state of the windows and reducing figure on an humidity meter.
The dehumidification process creates warming (opposite, as you may expect, from iceskater's humidifier above). However,
the process is caused to function by a motor/compressor which themselves create heat. The energy for the operation comes
from mains electricity, which itself is created by processes which gererate heat and probably moisture as well - say a
carbon fuels power station. So my little dehumidifier "creates" a drier atmosphere and heat, but the electricity production
process also creates heat and humidity.
Iceskater - this dimension seems missing from your analysis; perhaps you could include it?
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Post by sigurdur on Aug 24, 2013 13:48:02 GMT
The humidicell is so efficient that industry used the concept for flash freezing.
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Post by Andrew on Aug 24, 2013 17:15:32 GMT
I have a process that lowers humidity. It is a dehumidifier. I run it a lot during the winter because of a condensation problem on windows. It works, and the lowered humidity can be seen from the state of the windows and reducing figure on an humidity meter. The dehumidification process creates warming (opposite, as you may expect, from iceskater's humidifier above). However, the process is caused to function by a motor/compressor which themselves create heat. The energy for the operation comes from mains electricity, which itself is created by processes which gererate heat and probably moisture as well - say a carbon fuels power station. So my little dehumidifier "creates" a drier atmosphere and heat, but the electricity production process also creates heat and humidity. Iceskater - this dimension seems missing from your analysis; perhaps you could include it? A dehumidifier first cools the air by passing it thru the evaporator part of the chiller to remove the water and then the cold air passes thru the warm refriderant condenser to cool the refridgerant and this warms the air. So the dehumidifier works like the fohn wind. Ie they both do work to enable the latent heat to become a sensed or felt heat. |
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zaphod
Level 3 Rank
Posts: 210
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Post by zaphod on Aug 25, 2013 1:37:38 GMT
Point on the Foehn wind taken, and the two stage dehumidifier process.
What I was attempting to introduce though, was the energy input to the system from mains electricity
and the environmental effects of that (heat and humidity elsewhere). This would need to be included
in your model.
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Post by Andrew on Aug 25, 2013 4:23:27 GMT
Point on the Foehn wind taken, and the two stage dehumidifier process. What I was attempting to introduce though, was the energy input to the system from mains electricity and the environmental effects of that (heat and humidity elsewhere). This would need to be included in your model. I am not sure what you mean by my model. The point about latent heat energies is they are not directly observable as temperature changes or heat generating events. If they were directly observable then by definition they would not be latent heat energies. For example contrary to what the internet says we dont get burnt more by steam than boiling water because steam releases a warming heat upon our skin, but rather when our skin is cooling the steam, our skin is required to provide more cooling for the hot steam than water of the same temperature, before the steam is reduced to a none damaging temperature. |
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Post by icefisher on Aug 25, 2013 4:57:50 GMT
For example contrary to what the internet says we dont get burnt more by steam than boiling water because steam releases a warming heat upon our skin, but rather when our skin is cooling the steam, our skin is required to provide more cooling for the hot steam than water of the same temperature, before the steam is reduced to a none damaging temperature. Provide more cooling? What kind of distinction is this? Our skin has to absorb more heat because the steam carries more heat and its going to release about 600 more warming calories per gram onto our skin than boiling water! Or is it in your view our skin is going to spray a high pressure stream of frozen spitballs at the steam and the burn is going to come from the friction generated by the hard spitballs firing out of pores so that our skin is going to overheat like a machine gun? |
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Post by Andrew on Aug 25, 2013 5:34:23 GMT
For example contrary to what the internet says we dont get burnt more by steam than boiling water because steam releases a warming heat upon our skin, but rather when our skin is cooling the steam, our skin is required to provide more cooling for the hot steam than water of the same temperature, before the steam is reduced to a none damaging temperature. Provide more cooling? What kind of distinction is this? Our skin has to absorb more heat because the steam carries more heat and its going to release about 600 more warming calories per gram onto our skin than boiling water! Or is it in your view our skin is going to spray a high pressure stream of frozen spitballs at the steam and the burn is going to come from the friction generated by the hard spitballs firing out of pores so that our skin is going to overheat like a machine gun? Heat is either sensible or feelable heat or it is latent heat. The latent heat of condensation can only be experienced as a delay in cooling where the temperature does not fall as much as expected You cannot get condensation without cooling. Steam has hidden BTU's that mean when the steam cools on our body those BTU's keep the steam hotter for longer while our skin is cooling the steam. So you have a choice. You can be an abusive or you can learn something. |
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Post by icefisher on Aug 25, 2013 5:53:32 GMT
Provide more cooling? What kind of distinction is this? Our skin has to absorb more heat because the steam carries more heat and its going to release about 600 more warming calories per gram onto our skin than boiling water! Or is it in your view our skin is going to spray a high pressure stream of frozen spitballs at the steam and the burn is going to come from the friction generated by the hard spitballs firing out of pores so that our skin is going to overheat like a machine gun? Heat is either sensible or feelable heat or it is latent heat. The latent heat of condensation can only be experienced as a delay in cooling where the temperature does not fall as much as expected You cannot get condensation without cooling. Steam has hidden BTU's that mean when the steam cools on our body those BTU's keep the steam hotter for longer while our skin is cooling the steam. So you have a choice. You can be an abusive or you can learn something. Ah! I think I finally got it! (hear snapping of fingers) You were right all along! If burnt by steam worse than boiling water I won't feel it because its latent heat BTUs not sensible heat BTUs! Dang why didn't I think of that in the first place! How dumb I must be! Your my hero Iceskater! Thank you so much! |
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Post by Andrew on Aug 25, 2013 6:09:29 GMT
Heat is either sensible or feelable heat or it is latent heat. The latent heat of condensation can only be experienced as a delay in cooling where the temperature does not fall as much as expected You cannot get condensation without cooling. Steam has hidden BTU's that mean when the steam cools on our body those BTU's keep the steam hotter for longer while our skin is cooling the steam. So you have a choice. You can be an abusive or you can learn something. Ah! I think I finally got it! (hear snapping of fingers) You were right all along! If burnt by steam worse than boiling water I won't feel it because its latent heat BTUs not sensible heat BTUs! Dang why didn't I think of that in the first place! How dumb I must be! Your my hero Iceskater! Thank you so much! Why is it that you are continually abusive towards me? Hot steam has sensible heat that can burn you. Obviously. Latent heat means the hot steam burns you for a longer period of time than the same weight of hot water. |
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Post by sigurdur on Aug 25, 2013 6:57:03 GMT
You are correct Iceskater.
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Post by Andrew on Aug 25, 2013 7:07:34 GMT
You are correct Iceskater. I very much doubt you are saying i am correct. Instead I suspect at the moment it will be the sarcasm that is typical of you where sarcasm is anger disguised as humour and is not something a person who is polite or mature will use. Perhaps therefore you can be clear about what you mean in the context that you have been telling me i am wrong for the last god knows how long. |
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Post by sigurdur on Aug 25, 2013 21:10:28 GMT
Iceskater:
Ok.....in relation to your hot steam comments you are correct. That work?
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Post by Andrew on Aug 26, 2013 2:02:43 GMT
Iceskater: Ok.....in relation to your hot steam comments you are correct. That work? OK. Thank you for confirming that no heat is released in an observable manner when steam cools to go from a less complex phase to a more complex phase. Now why do you think heat is released in an observable manner when water cools to go from a less complex phase to a more complex phase as ice forms? |
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Post by sigurdur on Aug 26, 2013 2:07:23 GMT
Because plants don't freeze.
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