# Heat exchanger question

by rideway
Tags: exchanger, heat
 P: 6 Hello everybody 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! Regards
 P: 6 Anyone can help me? Im still stucked with it. Thanks!!
HW Helper
PF Gold
P: 2,907
 Quote by rideway Hello everybody 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! Regards
Hi rideway. Fluid flow and pressure drop through pipes and networks of pipes including through pipes making up heat exchangers can be done using the Darcy Weisbach equation. If you're not familiar with that you can look through the Pipe-Flo document I posted here: