Dear Shaylin Rm ,

Choose the related boundary and use the bellow command:

d(T,r)=0

-k*d(T,r)=h*(T-T0)

d(T,r) shows the first order differentiation of T respect to r. note that, if T is temperature, it is no problem, because Comsol knows that by default. T0 is the fluid temperature, which you write its value.

Hi Shaylin Rm ,

you can try to use pointwise constrains, it should work.

Best,

Antoni

Dear Shaylin Rm ,

Choose the related boundary and use the bellow command:

d(T,r)=0

-k*d(T,r)=h*(T-T0)

d(T,r) shows the first order differentiation of T respect to r. note that, if T is temperature, it is no problem, because Comsol knows that by default. T0 is the fluid temperature, which you write its value.