The problem is about a very simple heat exchanger.
One pipe with cold water at the inlet and at some points heat is applied uniformly. Assumed no buoyancy. Wall is smooth and with no slip.
I simulate different a matrix of volume flow rates and inlet water temps. For 5 l/min, water inlet temp varies from 50°C to 150°C; same for 10 l/min and 20 l/min.
My questions are:
1.- If the water properties (density, viscosity, heat capacity, thermal conductivity) are constant, should the pressure drop be constant for a given volume flow rate?
2.- If I simulate water accordingly with variable density and viscosity, should the pressure drop increase with the increase of density or decrease?
I dont know if I explained correctly. Dont hesitate to ask if needed.
Thank you very much in advance!