Heat Loss Calculator Surface Area Error

[pmstory]

The heat loss calculator appears to have a bug in calculating surface area of a cycliner when adding layers to the cylinder. Refer to the example for Hot water tank. The outside surface is off by 2%. If you change the thickness or make the diamter larger the error increasese rapidly.

Any comments? or am I doing something wrong?

[Peter B]

In the Hot water tank example, the outside area is:

outside diameter outside height
Asides= PI*(3+2*0.005+2*0.05)*(4+0.005+0.05+0.005+0.05)=40.156m2

outside diameter
Atop=PI*(3+0.005*2+0.05*2)^2/4=7.596m2

outside diameter
Abottom=PI*(3+0.005*2+0.05*2)^2/4=7.596m2

The thickness of the walls, roof and bottom are added on to the inner dimensions according to the simple picture shown by pressing the "Draw" button.

Best Regards,
Peter