## Fluids

#### Setting the energy source term for porous zones

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• ESL
Subscriber

I am a university student in Japan who uses ANSYS for research.

I am doing a research on heat transfer when a fluid flows through a packed layer.

In my simulation, the temperature of the solid in the packed layer increases when the fluid flows in the positive direction and decreases when it flows in the negative direction.　This temperature rise and fall is set by the energy of the source term in the porous zone.

However, the simulation does not work well with the following message

• Message: Error at Node 0: Invalid expression : energy_profile/1[s].

The expression I set for the energy term is as follows

• IF(u_profile/1[m/s]>0,energy,-energy)

where u_profile is the flow velocity and energy is the temperature rise and fall.

The equations for u_profile and energy are as follows

• u_profile = 0.9*sin(omega*Time)
• energy = entoropy_change*mass(['porous_zone'])*T(['porous_zone'])/(3.0[m^3]*10^-6)
• entoropy_change = 5.3[J/(kg*K)]*exp(-(T/1[K]-110)^2/5.0^2)

A simple model diagram is shown below.

• Rob
Ansys Employee
If you don't hook up the expression what value does each part return after you initialise the model but before you start iterating?
• ESL
Subscriber

• ESL
Subscriber
Are you sure you are asking what the initial conditions are?
I'm sorry, I'm not familiar with ANSYS, so I can't see a list of what the initial values are.
Just in case you are wondering, the temperature conditions and pressures I have set are 110K (=-160┬░C) and atmospheric pressure as the initial values for all zones.
• DrAmine
Ansys Employee
If you compute the expression does it work and return proper values? Your velocity expression is missing dimension.
• ESL
Subscriber