The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti – T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?

• A. q = [2π k (Ti + T0)/2]/ln (ri/r0)
• B. q = 2π ri k (Ti – T0)/(r0/ri)
• C. q = 2π k (Ti – T0)/(r0/ri)
• D. q = 2π k (Ti – T0)/[(r0 + ri)/2]