Rotary cooler and water bath
 

I am modelling a rotary cooler and a water bath system to acheive the overall temperature profile.
At present, I have two domains i.e domain 1 = cooler & domain 2 = water bath.
I have defined the boundary conditions for each domains. However, I want to investigate the heat transfer
between the two domains. The inlet temperature for domain is 700 degrees celsius and the inlet water bath temperature is 25 degrees celsisus.
How can define an interphase between the domains as they are both independent in the industry? The outlet temperature from the domain 1 is 250 degrees celsisus. It should be noted that domain 1 is rotating.

I look forward to any suggestion.