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Weather - or not!

General socialising and light-hearted discussions take place in here.
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Dave B
Posts: 17809
Joined: May 17th, 2010, 9:15 pm

Re: Weather - or not!

#1121 Post by Dave B » November 12th, 2015, 7:52 pm

Latest post of the previous page:

On reflection Alan is probably busy tying things doan!
"Look forward; yesterday was a lesson, if you did not learn from it you wasted it."
Me, 2015

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Dave B
Posts: 17809
Joined: May 17th, 2010, 9:15 pm

Re: Weather - or not!

#1122 Post by Dave B » November 16th, 2015, 5:57 pm

Alan H wrote:
Dave B wrote:
Alan H wrote:30.8°C at my desk, industrial fan running full blast, windows open as far as they can be with inquisitive cats...
Fans don't do much for dry objects, they rely on evaporation to cool. Had trouble convincing a qualified engineer at work that leaving his fan on all night was a waste of energy and money. Had to do the actual experiments with wet and dry thermometer bulbs in draught to prove it to him!
Ha! Not seen one of those old-fashioned one for years - not since electronic hygrometers took over.
Meant to reply to this yonks ag!

Had to prove that the sensation of cooling in a draught was due to evaporation - thus the wet bulb reads lowest in the draught and the readings are much closer in still air. Thus fans do not actually cool the air, only the skin.
"Look forward; yesterday was a lesson, if you did not learn from it you wasted it."
Me, 2015

Nick
Posts: 11027
Joined: July 4th, 2007, 10:10 am

Re: Weather - or not!

#1123 Post by Nick » November 17th, 2015, 12:04 am

In fact, leaving the fan on all night would create more heat, as (some of?) the energy used to turn the blades is converted to heat.

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Dave B
Posts: 17809
Joined: May 17th, 2010, 9:15 pm

Re: Weather - or not!

#1124 Post by Dave B » November 17th, 2015, 8:03 am

Nick wrote:In fact, leaving the fan on all night would create more heat, as (some of?) the energy used to turn the blades is converted to heat.
You are correct, Nick. Merely moving air is doing work that ends up as friction and heat, putting energy into the system.
"Look forward; yesterday was a lesson, if you did not learn from it you wasted it."
Me, 2015

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