[ZEUS]

I'm analyzing the operation of a pump, when the fluid changes.

Can you tell me if the following fluids are Newtonians?

The fluids are:
R245fa
R134a
R152a
R141b
R142b
Benzene (C6H6)
Toluene (C7H8)
Acetone (C3H6O)

Thank you

[ghorrocks]

All fluids are non-Newtonian if measured with sufficient accuracy and to extreme enough conditions. The question you should be asking is whether in my application the non-Newtonian properties are significant or not. We cannot answer that as that depends on what you are trying to do and what you wish to learn from the simulation.

[ZEUS]

I'm analyzing the performance of a centrifugal pump that has a rotation speed of 2900 [rev min ^ -1].
the pump is designed to work with water, which at the inlet is in the condition of saturated liquid with a temperature of 30 ° C.

I want to know the trend of the hydraulic head according to the flow rate, varying the fluid.

In the simulations with water and other fluids, I considered the properties of each fluid (viscosity, specific heat, etc ...) constant and associated with the saturated liquid condition at a temperature of 30 ° C.

For each simulation I have set as input condition the pressure associated with the saturated liquid condition at the temperature of 30 ° C, while I set the flow rate as an output condition.

My doubt is if these settings are correct, especially if it is correct to consider the constant viscosity as if the fluid is Newtonian.

Thank you.

[ghorrocks]

You really should go to the literature and determine for yourself whether these fluids are non-Newtonian in the application you have.

But in my experience I think you will find that most pure substances (ie liquids of a single molecule) are Newtonian for most applications. You will find viscosity and density variations due to temperature and pressure are likely to be much bigger than any non-Newtonian properties for these fluids.

The big exception is if any of these fluids cavitate, boil, freeze or other multiphase effects occur then this will be seen as strong non-Newtonian properties - but it would be better described as multiphase properties (eg wet steam).