Undefined value found in the equation residual vector

hi. i met some problems during simulating a conjugate heat transfer problem. I tried to finer the mesh but it could not help. The detailed description is as following:
Undefined value found.
- Detail: Undefined value found in the equation residual vector.
There are 283 degrees of freedom giving NaN/Inf in the vector for the variable comp1.T.
at coordinates: (1.17089,3.35878), (1.16589,3.35878), (1.16839,3.35605), (1.17089,3.35333), (1.16589,3.35329), ...
- Feature: Stationary Solver 1 (sol1/s1)

thank you for your help