Fire box design

[metalspinner]

Our fireplace has a very large firebox.  I remember seeing a program on television a while back discussing the shape of the firebox.  Some shapes are more efficient heat reflector's than other shapes.  We don't have any smoke problems from the fireplace.  I was just wondering where my box is on the efficiency spectrum.  I'll take a pic tonight.

Edit:
Just came across this to study...


http://www.bia.org/html/frmset_thnt.htm

[mike_van]

Here's a good link on Rumford fireplaces http://www.rumford.com/