Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 9 replies
  • Subscribers 32 subscribers
  • Views 895 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Evaporative Air Cooling Conundrum

Sparkymania
Hi


This is going off topic on this forum, I know, but as I am registered with this one and not an A/C forum I thought I might give this a try.

Something different.

I understand the workings of refrigeration and A/C units.

However, there is a "cooler unit" (not described as an A/C unit ) that uses water rather than refrigerant.

Now the principle of A/C units is to move the heat, via the refrigerant, from inside to outside.

The air inside gets recirculated and cooled and dehumidified.

The one that uses water is called an evaporative cooler. There are large commercial and industrial units in hot and dry environments like south west USA where they are used extensively. The reason is they draw in air from outside, which is already cooler that the inside air, cools it and pushes the inside air out through vents. It also humidifies the air with the evaporated water. This is good in environments where the humidity is too low.

However, they are also found as small portable room units in this country. 

They work by water soaking a filter. The warm air is drawn in and as it goes through the wet filter the water evaporates transferring the heat from the air to the water thereby cooling the air. In these units the air is recirculated. The expelled air feels cooler than if you run it without water as it will then just act as a fan.

So it works.

Now here's the thing I don't understand. I've watched loads of YouTube videos and none of them explain this, only what I have explained above.

This goes for both types, industrial and small portable.

If the heat transfers from the air to the evaporated water and the evaporate is expelled with the cooled air, the heat being expelled should end up being the same. Why can you feel the cooler air and not the warmed up evaporate? In the case of an industrial unit why does the cooled air cool the area and the warm air not heat the area at the same time canceling each other out?


Hope this has sparked someones interest as a departure from the usual electrical topics.
Parents
  • 0
    I hope I understand the question, and that what follows makes sense in that context.

    This has quite a lot in  common with sweating and standing in a breeze - when you are in equilibrium at temperature T you the molecules on your surface have a mixture of energies that represent that temperature on average.  That means that some of the more energetic molecules have boiled off, but will return - rather as the steam above your coffee will to a degree rain back into it if undisturbed.  Others molecules in the group are less energetic than the average, so move more slowly and are more tightly bound,  but these do not interest us yet, but as they bump into other hotter molecules they may acquire energy and become more mobile..

    However in both the coffee and the sweaty body if there is a breeze, then the friskier molecules that have borrowed some energy 'from the bank of averages' to briefly break slightly free, are taken away on the breeze before they can give it back.

    The population of water molecules that remain, is now missing its most energetic members, now has a lower energy - so energy flows in to compensate, from the body or the coffee, leaving it cooler. (so you can catch a chill while sweaty if you stand in a breeze, and you can cool your drink by blowing on it.  - except for dragons  who according to some children's book blow on their food if it is too cold.)


    The work  that is done is in breaking the weak Van der Waals and hydrogen bonds between water molecules that by rights should have stayed a bit more together at that temperature, and the energy to do this is removed from the environment.
Reply
  • 0
    I hope I understand the question, and that what follows makes sense in that context.

    This has quite a lot in  common with sweating and standing in a breeze - when you are in equilibrium at temperature T you the molecules on your surface have a mixture of energies that represent that temperature on average.  That means that some of the more energetic molecules have boiled off, but will return - rather as the steam above your coffee will to a degree rain back into it if undisturbed.  Others molecules in the group are less energetic than the average, so move more slowly and are more tightly bound,  but these do not interest us yet, but as they bump into other hotter molecules they may acquire energy and become more mobile..

    However in both the coffee and the sweaty body if there is a breeze, then the friskier molecules that have borrowed some energy 'from the bank of averages' to briefly break slightly free, are taken away on the breeze before they can give it back.

    The population of water molecules that remain, is now missing its most energetic members, now has a lower energy - so energy flows in to compensate, from the body or the coffee, leaving it cooler. (so you can catch a chill while sweaty if you stand in a breeze, and you can cool your drink by blowing on it.  - except for dragons  who according to some children's book blow on their food if it is too cold.)


    The work  that is done is in breaking the weak Van der Waals and hydrogen bonds between water molecules that by rights should have stayed a bit more together at that temperature, and the energy to do this is removed from the environment.
Children
No Data

Community Rules & Guidelines