Heat Transfer L16 p1 - Example - Sphere - Transient Convection - Approximate Equations 

Thank u so lot. U have a fan in Brazil.

do biot number characteristiic length is equal to diameter/6 or radius/3 then why you took radius it should be

I have a question. I have steam flow inside a cylinder with 3 different kind of layer, like aluminium and two thermal insulation material. All of these materials with different r and coefficient(k,p,cp...etc). How could i calculate the temperature at some point, for example, temperature when r = 1.2, 2.4, 3.0 and so it goes. Because after some point of the r coordinate we aren't not talking about the same material anymore. Ex: material 1 is between 0.6