Messages from a thread in UK.d-i-y:
My university physics is quite up to date, I don't recall the rules changing over the past 50 yrs.
Just do a few calculations and then take the trouble to measure the actual practical results. The theory of heat reflection is not particularly effective over a distance of two inches from another surface with substantially the same emissivity. Radiators on outside walls placed under windows simply increase the heat loss from the room and contribute little or nothing to the cross room temperature gradient.
*********************So you think but that only goes to show you are losing your marbles and
may soon join Dribble in never-never land where reality is whatever you
want it to be.
Well there my have been one or two changes along the way particularly with units. Even ISO metric is different in some ways to the cgs and mks we were taught at school.
Right total emissivity of aluminium at 100C 0.09, oil paint 0.92 -
0.96. Whoops stupid reference book must be wrong. Capitol has decreed that they should be much the same.In the real world there is a temperature gradient from the heat source to the environment at large (unless the heat source is largely radiant).
In the simplest example where the interior walls of a room are heated to the same temperature on both sides there would be no heat loss through the internal walls and little or no temperature gradient across the room if there was a full width radiator across the outside wall.
Reverse the situation with the radiator across the opposite wall and you will get a significant temperature drop across the room. The more poorly insulated the outside wall, the bigger the drop and the larger the convection currents within the room.
*********************Sort it out will you chaps?
(Not you Uncle Schwartz. You can ****-off!)