Temperature profile around heat source

[Haye]

Homework Statement

A point source in water provides 10 W of heat for 10 seconds, and is then shut off. The surrounding water has a temperature of 20 °C. Provide the temperature profile as a function of distance r and time t.

Homework Equations

The Attempt at a Solution

If it were steady-state, I could use Gauss theorem to solve this problem. But since the point source is turned on and off again, I have no idea how to approach this problem.
If someone could hint me in the right direction, it would be very much appreciated.

 

[dauto]

You have to use the inhomogeneous heat transfer partial differential equation.