Weather - or not!

[Dave B]

Latest post of the previous page:

On reflection Alan is probably busy tying things doan!

[Dave B]

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.

[Nick]

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.

[Dave B]

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.