Air Conditioning

[Sgt Badass]

So, we're sweating more than a glass blowers arse and we put on the air conditioning. The local office security/engineer/odd-job man says the aircon doesn't work unless the windows and doors are shut, which means we have to sweat some more while it kicks in.

So, is this true? Do aircons only blow cold air in a closed environment?

[tkingdoll]

My understanding is that it will work (as in, function) but that it won't be as effective. At least, that's what I was told by an irate Boston taxi driver when I dared to open the passenger window ;D

[Admin]

Yes it works best in an enclosed space otherwise the cool air just escapes.

[Sgt Badass]

My understanding is that it will work (as in, function) but that it won't be as effective. At least, that's what I was told by an irate Boston taxi driver when I dared to open the passenger window ;D


LOL! I was shouted at by a Greek bus driver for the same reason.

Turns out our Aircon is just crap. For some reason it just stops kicking out cold air and circulates the room air.

[vbloke]

I saw a fan today that had two plastic inserts that sat behind the fan.

You put them in the freezer overnight and then replace them back into the fan - the theory is that they provide cold air.

I wasn't convinced by it though, any cold benefit would surely vanish after a few inches, or am I wrong?

[brodski]

I saw a fan today that had two plastic inserts that sat behind the fan.

You put them in the freezer overnight and then replace them back into the fan - the theory is that they provide cold air.

I wasn't convinced by it though, any cold benefit would surely vanish after a few inches, or am I wrong?
I often put a bag of ice cubes in a dish front of a fan, and that works wonders, I suspect that this would work in the same manner.

[Aardvark]

Air con is basically an inside out fridge. Air is drawn across a refrigeration coil, this not only cools the air but also removes moisture as this condenses out on the coil and has to drain away either to a tank or to a drain hose.

A dehumidifier works the same way except there is normally a heat exchanger which then re warms the air before discharge back tinto the room.

My son has a cheaper unit which is filled with iced water and this is drawn through evaporation pores in the unit. This actually adds moisture into the air but takes away heat in causing the evaporation. Called an evaporation cooler they only draw about 90watt as opposed to around 500 watts plus for a basic portable air con unit

[doubting thomas]

I don't know, you office types want to have cake and eat it.

You should think yourselves lucky, the only air-con we have is a great big open roller shutter door, which in these temperatures is about as much use as a chocolate fire guard.

Seriously, I'm in the air-con business though more on the electrical side of things.

Its true you have to keep windows closed because the the design of the system is carefully worked out for the internal area.

The actual cooling is achieved by using chillers. In large office buildings these use huge amounts of electricity so they are sized accordingly.

[median]

My son has a cheaper unit which is filled with iced water and this is drawn through evaporation pores in the unit. This actually adds moisture into the air but takes away heat in causing the evaporation. Called an evaporation cooler they only draw about 90watt as opposed to around 500 watts plus for a basic portable air con unit

Aardvark, I believe that these have limited application in our climate and are mostly effective in dry environments.

Most air cons are of the DX (direct expansion) coil type which as you say, remove heat by evaporation and discharge it to atmosphere by condensation and because moisture collects on the cold inner coil there is a certain amount of dehumidification.

Going slightly off on a tangent, whilst talking about cooling strategies, I was chatting to someone the other day who was extolling the virtues of drinking hot drinks to 'cool themselves down'

I think the idea behind this was that it would provoke a general physiological cooling reponse (vasodilation etc), however I don't think it was taking into account the net increase due to the hot drink itself. ???

On days like these, given a choice of a cup of hot choccy and a glass of cold lager, I know which one my money's on ;)

[vbloke]

In that case, I now have 4 bottles of water in the freezer ready for later on in the day to put in front of my fan to see if they help keep me cool.

[Mongrel]

Going slightly off on a tangent, whilst talking about cooling strategies, I was chatting to someone the other day who was extolling the virtues of drinking hot drinks to 'cool themselves down'

I think the idea behind this was that it would provoke a general physiological cooling reponse (vasodilation etc), however I don't think it was taking into account the net increase due to the hot drink itself. ???

On days like these, given a choice of a cup of hot choccy and a glass of cold lager, I know which one my money's on ;)


I believe your friend is a little muddled, drinking hot drinks doesn't "cool you down faster" but it does hydrate you better (whether it's enough to make a difference in this sort of weather is a different matter). When you drink that chilled water it absorbs heat from the surrounding tissue until it equalises with your internal temperature that you body wants to stay at. The parts that were cooled down need to be re-heated, which requires the use of stored energy, which is the part of the process that uses water - therefore you get less useable water out of 1 pint of cold water then you would from a pint of Tea.

Given how easy it is for us to get fresh, clean water it's really a non-issue

[wollery]

...snip...
therefore you get less useable water out of 1 pint of cold water then you would from a pint of Tea.


Of course, tea, being a diuretic, makes your body use up that available water faster.

[Ginger Rogers]

I would just like to add that for anyone who keeps animals who's ability to sweat is very limited, plain old fans do diddly squat and you need to either put iced water in front of the fan (although i've not tried this myself) or buy an air conditioning unit. I think air coolers work the same way as the ice in front of the fan thing.

it's amazing how many people think fans actually cool the air ::)

[Admin]

Good point about fans Kristie.

They help humans by circulating the air and so aiding the evaporation of sweat from the skin. That won't do much for animals though.

Also, I once had an argument with someone who said that hot tea was better at cooling you down than a cold drink. It didn't make sense to me but his explanation was that as it's hot it would make you sweat more and so cool you down. I said that if it made you sweat more it must be heating you up. I don't think the argument got resolved..... ;D

I wonder if there's an answer. :ponder:

[median]

John

See the above few entries O0

[median]

The parts that were cooled down need to be re-heated, which requires the use of stored energy, which is the part of the process that uses water - therefore you get less useable water out of 1 pint of cold water then you would from a pint of Tea

Mmm Mongrel

Not sure about this one and in the case of the hot tea wouldn't the net heat gain offset the proposed water loss?
I would have thought that the amount of hydration would be negligible and there would be a time delay in its perceived effects. ???

[Ginger Rogers]

someone recommended a hot shower or bath to cool you down as then you feel much cooler when you come out :o er no. a cool shower cools you down.
can you imagine having a hot bath in this heat :'( you'd die!

[Mongrel]

Of course, tea, being a diuretic, makes your body use up that available water faster.


Ok - maybe Tea was a bad example :P

Mmm Mongrel

Not sure about this one and in the case of the hot tea wouldn't the net heat gain offset the proposed water loss?
I would have thought that the amount of hydration would be negligible and there would be a time delay in its perceived effects. ???


Well the difference in temperature is a lot smaller from a drinkable hot drink (not the masochisticly tongue searing coffee temperatures that some people think is appropriate) than something that's served at 4C. And yes, I agree, the actual, real life gain for most people is not worth bothering about :)
The only time I could see it making a difference is during\after heavy exercise but since it's too damn hot to do that..... ;)

[Admin]

If you're too hot then drink something else hot to cure it - sounds like a familiar concept. ??? ;D

So, if you're bloody freezing would a bowl of ice cream warm you up? :ponder:

[median]

If you're too hot then drink something else hot to cure it - sounds like a familiar concept.



Ah but only if the temperature has been diluted a billion times ;D ;D

[Aardvark]

I would just like to add that for anyone who keeps animals who's ability to sweat is very limited, plain old fans do diddly squat and you need to either put iced water in front of the fan (although i've not tried this myself) or buy an air conditioning unit. I think air coolers work the same way as the ice in front of the fan thing.

it's amazing how many people think fans actually cool the air ::)


The local farmers are using fans plus water sprayers when the cattle are in for milking. Basically spray the cow until the hair is all wet, switch of the spray, switch on a high volume fan, latent heat of evaporation cools the cows. This cycle is repeated every 10 minutes whilst they are inside.

[vbloke]

do they get ice cream from this?

[Admin]

do they get ice cream from this?


;D ;D ;D ;D ;D ;D