How to explain evaporative cooling to idiots?

The local Grainger has a big swamp cooler running as a demo just outside their building. They have sold a bunch of them just so the boss can get his MRO guys back to the shop after a parts run. :-) Here in South Georgia the humidity is close to 80% but that thing still drops the temperature a good

Considering that a gallon of water absorbs almost 6,000 BTUs of heat as it evaporates a swamp cooler is cheap air conditioning as long as the shop humidity doesn't get to high.

If you change the discussion to dew point temp, it's a LOT easier. Of course you have to define dew point and get folks to ignore humidity, a tall order. Since the DP doesn't cahnge with temp (like humidity), you can see what's going on.

Goes like this:

Your normal dewpoint in desert Pheonix runs in the 40's F in the hot dry summer. Your body is at 98.6F, puts out some sweat, sweat evaporates nicely due to the 50 degree difference, you get cool. A swamp cooler does the same thing, evaporates some water which drops the temp and raises the dewpoint.

The trouble comes when you get higher dewpoints. Most people think DP in the 40's as 'dry', 50's as 'comfortable', 60's as 'humid', 70's as 'sultry (soggy?), and 80's as unbearable. I hust looked at Pheonix stats: 95F and 61F dewpoint at 7:00AM If you run a swamp cooler, it bring the temp down 15 degrees or so but will add another 10 degrees to the dewpoint. Moves the body reaction into the really soggy feeling.

John: I can't be any help on the subject of explaining evaporation. However I can offer solid advice on working with idiots. Don't fall into the trap of caring about something more than they do. If you do, then you become the idiot.

-Mike

JohnF wrote:

Well if it's hot and you're moving around and sweaty, do you feel cooler with a rainproof jacket on, or with a thin cotton T-shirt?

Best regards, Spehro Pefhany

I know but it's hard to let go.

JohnF

Put a drop of rubbing alcohol on their forearm. Ask them if if got cold. That's how evap cooling works except with water.

Well, "I'm cool because evaporating the water cools the air, let me know if you want help; buy me beer and I'll get you set up."

HI,

First point out that the swamp cooler has a fan, which can only move air if there is somewhere for the air to go. Suggest a two stage experiment, and promise to shut up if your are wrong. First a very quick test, feel the air flow with the shop buttoned up and with the it open. Next suggest a real test, that is two see if the shop is cooler with it opened up

Trying to keep the cool air in sounds like a good idea, but this "cool" air quickly heats up because of the hot walls, roof, and floor. The air is just a fluid coolant, once it has absorbed some heat it is time to move it out. In a car one does not pump cool coolant into the engine without an outlet for the fluid, instead it is recycled back to the radiator. In the shop, the now hot moist air cannot be recycled through the swamp cooler because it is moist to evaporate much more water.

S> We're in Phoenix, it's been up to 118 degrees in the last week but the

Stick them in a hot closet with a fan and close the door. Ask them if they feel cooler in there or outdoors when there's a breeze.

Stan

They are bright compared to the idiots I ran into one time. I was in an antique shop on a hot summer day. They had just purchased a new window refer. type unit and had not had time to install it in the window. So they had it sitting on a table with the window closed running. They couldn't understand that all they had was 1600 to 2000 watt heater going.

Chuck P.

My tin roof over the factory in Tijuana provided an insufferable heat during the summer when I took over as plant manager. I quickly changed intolerable to very comfortable by putting some sprinklers on top of the roof and turning them on during hottest periods of the day. Also at night ran exhaust fans full blast until mid morning then shut them down to low speed while adding some swamp coolers. One hundred and eighty people wanted to hug me and I got a lot of free tacos! (not to mention a boost in productivity that quickly paid for the changes).

Wayne

Tell him to blow on his arm and see how cold it gets. Now pour water on his arm and repeat the blowing.

Easy ! (perhaps then you can talk about laten heat of vaporisation of water)

AWEM

We had a weld shop doing smaller parts that was air conditioned. By 4:00 PM on a 95 degree day the AC just wasn't keeping up, the temp had crept up to 78 degrees. One new guy was complaining. A couple of the older guys took him aside and explained that most weld shops have NO A/C and they didn't want to hear any more about it.

We did notice that sec> My tin roof over the factory in Tijuana provided an insufferable heat during

The swamp box is blowing cool air into the building. This air is cooler than the air already in the building. Have the idiot(s) measure the temp the incoming air and the shop air away from the incoming air stream. Now if no air is allowed to escape from the shop then no air can enter either. Even the dumbest asshole should be able to figure it out from here.

Art

They 'might' have the right idea, but only if they (you) shut down the swamp coolers and provide an alternate method of circulating the internal air when they close the windows. Of course, if the inside ambient temperature rises above the outdoor temp, then it's definitely time to open some windows. The moving air is what evaporates the moisture from one's skin and gives a feeling of comfort. Personally, I think swamp coolers suck once humidity is over about 20 %.

For example, even at 116 degrees F., it's reasonably comfortable outside (in shade) if a good breeze is going. Isn't it amazing how much 10-15 mph breeze will cool you down? I guess outside, it actually envelopes your whole body?????

But good luck in your quandary, Ace

"Wood Butcher" wrote in news:J6ydnROgG7Qs8FvZnZ2dnUVZ snipped-for-privacy@comcast.com:

Art, There are 6.5 billion people on the planet, by my personal estimate at least 6.0 billion of those are stupid with 0% common sense. And as Ron White so aptly put it, 'You can't fix stupid'.

You are greatly underestimating the magnitude of the problem. I think it was George Carlin(?) who put so aptly. "People are stupid. Individuals, however, *may* be intelligent."

Art

Have the DS put a coat on and stand in the sun. Sun won't touch them, but will cook them inside their coat.

Now take a wet towel and wet hair - walk outside where air moves and their head will get cold from rapid evap.

Swap coolers in a closed house will melt the glue in the wood - all dressers, all couches....... as most glue is water types. When open to the outside and allowing air flow - the moisture dissipates (thus cooling).

The act of water evaporating off the body - that started somewhere like a swamp cooler is what chills.

Think - mist drip lines - the misters chill out those under them - outdoors!

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

JohnF wrote:

Don't explain if you can demonstrate. If you have multiple rooms in the building, open the window(s) in one room. After that room is appreciably cooler than the room/area with closed windows, bring moron from sauna into cool room, and ask if he notices a difference.