for the Conduction equation k*A* [(Th-Tc)/L] where are you getting the value for A? Is it the area of the side being heated or cooled?
Example, if you take a cone and chop off the "point" side a little. Then, you'd have two different size sides. A smaller circle with radius of say "2" and the other end with radius of say "5"
If the r=2 side of the cone is being heated and the r = 5 side is the cooler side, which side do you use as the value for A (Area)?