Thank you very much！
Let me confirm once again that the User-Defined Function (UDF) needs to provide the actual volumetric heat transfer coefficient in units of W/m²*K. This coefficient should be calculated using the properties of the gas to define the Prandtl number.
This information is mentioned in both the theoretical manual and the UDF manual. However, I've noticed a discrepancy between this information and the heat transfer coefficient UDF example provided in the UDF manual. So, I would like to verify this once again for clarity.
In the example 22.214.171.124 provided in the UDF manual, the returned heat transfer coefficient is multiplied by the interface area density. However, according to the definitions and descriptions given earlier, the expected return value should be the true, unmodified heat transfer coefficient. Does this mean that there is an error in the provided example? Below is a screenshot of the code from the example.