1. The problem statement, all variables and given/known data A pipe of internal radius r1=0.03 m is built to have conductivity variable with radius: k=ar2, where a=250 Wm/K. 1) Find the critical radius r2 for the maximum heat transfer by convection from its external surface if the heat transfer coefficient is h2=30 W/m2K. 2. Relevant equations 3. The attempt at a solution I am just wondering do i start differenticate the rate of heat transfer Q equation ? if not can anyone guide me.