Russell,

On Fri, 24 Dec 2004 18:40:23 +1300, Russell McMahon wrote:

> > Convectors have extra fins (just a thin corrugated sheet spot welded to
> > the back of the panel rad. This creates a series of chimneys that gives 
> > 50% more output per size
> 
> The "output" is entirely linked to the energy input unless there is a 
> thermostat which measures the temperature of the heater (not the air). 

Yes, but the "input" for a water-filled radiator is related to the flow rate of the water (probably constant 
unless there are radiator thermostats) and the temperature difference between the incoming and outgoing water 
(flow and return as plumbers call it).  The heat given to the room by the radiator cools the water, and the 
more efficiently it does this, the more heat is emitted and the cooler the return water for given flow and 
room temperatures.

> A finned heater will run cooler for the same energy input and give far better 
> convection, but two eg 1 kW heaters, one with fins and one without, will 
> both deliver the same energy to a room one way or the other if left to their 
> own devices. With heaters "what goes in must come out" applies.

Yes, but you're talking about "1kW" by which presumably you mean an electric heater (which must be almost 100% 
efficient, since almost all of its energy turns to heat, which is what you want!) whereas we're talking about 
central heating using water as the heat-carrying medium.  Water-filled radiators don't emit all the heat 
they're given since the return water isn't at 0K :-) 

Merry Christmas!


Howard Winter
St.Albans, England


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist