DIYbanter - View Single Post - High Efficiency gas furnace

Dave Martindale

writes:

"Plate thickness ranges from .024" for high efficiency to a heavy-duty
and durable .050" thick plate"

Cearly they agree cutting the thickness in half makes a significant
difference in efficiency.

That's an interesting definition of "efficiency". In this context, they
must mean that the heat transfer is higher *per unit area* or *per unit
volume* of heat exchanger.

That's unrelated to the efficiency of a furnace, which is a measure of
how much of the theoretical heat energy in the fuel gets transferred to
the house.

You can have two furnaces, one with a thin-wall heat exchanger and the
other with a thick-wall heat exchanger that is somewhat larger, such
that both furnaces have the same amount of heat transferred with the
same air and flue gas inlet and exhaust temperatures. Both *furnaces*
will have the same efficiency at heating the house, but the thin-walled
heat exchanger is more "efficient" because it's smaller.

Dave