[yanqoue]

Hello, I couldn't figure this out.


There is no heat transfer in the system. I've just used temperature dependent variables for fluid (n-heptane). Things like density, viscosity, evaporation pressure are changing with respect to temperature.


I have two case with excatly the same dimensions. With higher temperature case (75 Celcius) mass flow is lower in the same cross section inside the domain compared to lower temperature case (25 Celcius).


There isn't any separation or evaporation that can limit the hydraulic diameter in that section. So what can cause this mass flow deviation? Is it due to lower density? But how about lower viscosity? Due to lower resistance, flow will have higher velocity. Since the cross section area is fixed, shouldn't mass flow rate increase in this case?

[ghorrocks]

If you have variable density, viscosity and evaporation pressure with temperature then anything could happen. With the vague details you have provided we can't help you. You are just going to have to look at your results and figure it out - compare the velocities, densities and everything else so you know the complete picture.