I have a assembly in which there is heat transfer ( conduction, convection and radiation) between two parts inside a assembly. Initially when I have selected SS 321 for two parts which is default material in engineering database for rough estimation purpose it was showing accurate results but when I changed the material to actual material of part which is (SS 316L) by defining its properties in user defined dialog box using same boundary conditions it is showing some error. (Iteration is starting from 0 K rather than starting from 40C) Please someone help.

Note: It is time dependent analysis where one part is at 70 C and other part whose initial temperature is 40 C. I want to calculate at what flow rate of air do the temperature of other part (40C) becomes stabilized at 40 C. I have attached images of error and one  of (Pressure velocity convergence) by selecting default SS 321.