 ## General Mechanical

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#### Some suggestions for setting up thermal constraints for oil cooling simulation

• Nikai Ryosuke
Subscriber

Hello everyone, I am doing a steady-state thermal simulation which involves a linear motor that drives grinding machine and the motor has a cooling pipe installed inside a coil slider (=heat source). The flow is laminar and heat transfer via forced convection occurs in internal flows of grinding oil. It is assumed that there is constant heat flux which is transferred to the grinding oil per unit area. From there I theoretically derived a linear equation describing the temperature profile across the fluid walls, which I use in Fluent. After that, I import the temperature result from Fluent into steady-state thermal

Figure below shows all thermal load and constraints that I have defined so far. The only load is in this case the internal heat generation from the coil slider. The last two constraints are applied on the fluid.

So my question is, have I already over-constrained or put too much redundant thermal constraints on the fluid? If yes, which one should choose? I was thinking about to suppress the heat flux option since the imported temperature profile has the heat flux quantity included based on the equation below, where T_m is the bulk fluid temperature and q_s is the constant heat flux.

Also if you looked in the model a solid cooling pipe is also included and it is also in contact with the grinding oil fluid. So should I extra define something like fluid-solid interface region in the steady-state thermal? Any explanations and suggestions are highly appreciated.

Nikai

• Adriano Zaffora
Ansys Employee

Hello Nikai,

at the boundary of your fluids domain, always think of the type of information you would need to transfer:

• if temperatures, you are getting the "solution" of the thermal problem, hence in a parallel to structures calculation it is worth as a displacement boundary condition
• if Heat Flux, you're setting a Newmann problem, hence the boundary is free to change the Temperature to chace for an equilibrium.

So to spot overconstraints in a steady-state thermal simulation you just need to check if there is any change in the flux of hear in your model: e.g. the CFD simulation is not forcing the model to a state that is obviouse at the beginning of the simulation itself.

Applications of Steady-State Conduction | Ansys Courses

Regards 