# Applying different periodic conditions to system (two fluid domains)

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August 17, 2020, 13:24
Applying different periodic conditions to system (two fluid domains)
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I have a cross-flow heat exchanger with a complex tube design.The crossflow arrangement with circular tubes is taken as an example for simplification.Here,the hot flow will flow through the tubes and outer fluid will be cold fluid. I am considering to apply periodic conditions to this heat exchanger in order to reduce computation cost and do parametric study.
Hence,I have created a unit cell of the cross-flow HX which will be periodically be repeated in the X, Y and Z direction.The outer fluid will be flow in the X-direction.The direction of the tubes is in Z-direction.Hence, the inner fluid will be in the Z-direction.I have created multiple periodic boundaries for outer fluid and inner fluid.The basic idea is to apply different upstream bulk temperature and mass flow rate to periodic planes(inlet and outlet) of the two fluid domains(hot and cold).Due to different bulk temperatures, the conjugate heat transfer is expected to take place between two fluids.
The problem I am facing is that the periodic boundary conditions are common to every set of periodic planes.I cannot apply different periodic conditions such as different mass flow rates, upstream bulk temperatures, and flow directions to periodic pairs of planes of each fluid.Any idea of how to apply different periodic conditions in Fluent?Furthermore,Is it possible to do a periodic calculation with conjugate heat transfer?
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 November 26, 2020, 21:40 #2 New Member   Wei Xiong Join Date: Oct 2020 Posts: 2 Rep Power: 0 Hi, I'm thinking about the same problem as you. I will continue to focus on this topic.

 Tags conjugate heat transfer, periodic conditions