heat diffusion throughout a sphere

[NEWO]

Hey there I was wondering if someone maybe be able to help me with a couple of questions I have.

I attach a set of equations the help define the heat diffusion throughout a sphere could you please tell me;

in V=rT What is V when r is the radius of the sphere and T is the temperature ?

and also What is the symbol V with the bar above it??

and in the last equation on the attachement, is s the entropy??

If you can help me I would be very greatful

Thanks for any help possible

Newo