Thermal conductivity through a cylinder?

[nelson_gslc]

Homework Statement

A copper tube, of internal radius 6.959mm, overall radius 7.975mm, thickness 1.016mm, contains water at 68 deg Celsius, and is present in a room with an ambient temp of 26.65 deg Celsius. If the tube is 1000mm long, what will be the rate of heat transferred from the copper tube?
k copper = 401 W/mK, A of tube = 0.050m, change in T=42.35 deg C, thickness =0.001016m.

Homework Equations

Q/t=kAΔT/d... or Heat transfer across length of cylindrical tubing equation (not specifically known)

The Attempt at a Solution

I have entered into the Q/t=kAΔT/d equation and received an answer of about 850 000 W, or 850kW, which seems entirely unrealistic. what am I doing wrong?

 

[Astronuc]

One needs to use the appropriate formula for heat conduction in the radial direction for a cylinder. One is using the formula for heat conduction normal to a plane in Cartesian coordinates.

See - http://www.engineersedge.com/heat_transfer/conduction_cylidrical_coor.htm