How to Find Temperature Field of Two Phase Flow?

Shomaz ul Haq · October 15, 2017, 09:32

Dear all,

Hello. Hope all are well. I am new at two phase flow so forgive me if I ask. Can anyone tell me how to find the temperature of a two phase nanofluid in an Eulerian Eulerian homogeneous model in CFD-Post?The flow field doesn't change compared to two phase flow as its single coupled that I understand. I know there is a variable for the base fluid i.e. Basefluid.Temperature and there is a variable for particle i.e. particle.Temperature but how can I find and plot contour of the two phase fluid itself i.e. both fluids combined? I have tried adding temperatures of the two fluids as an expression and that using it as a variable and then plotting its contour but that gives me a wrong value i.e. just the addition of individual values of the two fluids. Also, the base fluid temperature field in the longitudinal direction is less than that of single phase nanofluid. Why is that? I was expecting it to be higher in two phase flow. Would be extremely grateful if somebody could shed some light on this. Thanks.

ghorrocks · October 15, 2017, 18:46

First of all - and I think we have talked about this before - the concept of "phase" does not really exist at the nanofluid level. You are talking molecular level stuff here, so all sorts of different considerations come into play. Are you sure a CFD solver is suitable for this work?

Putting those misgivings aside..... If you want to work out some average temperature of the two phases then you are going to have to write an expression to evaluate it. It will probably rely on the mass of each volume fraction in a unit volume to give a mass weighted average temperature. But you are going to have to define a variable to do this as nothing is built in.

Shomaz ul Haq · October 16, 2017, 01:27

Yes. You're right Glenn. Thanks. I am just comparing and experimenting with nanofluid two phase simulation. I think CFD Solver may solve it. You said something about "mass of each volume fraction in a unit volume to give a mass weighted average temperature". What should be the expression? I know this isn't built in and I'll have to make a variable after creating expression. Hope to hear from you. Thanks again!

ghorrocks · October 16, 2017, 01:32

The function would be very simple, something like

(Phase1.vf*Phase1.Density*Phase1.Temperature+Phase 2.vf*Phase2.Density*Phase2.Temperature)/(Phase1.vf*Phase1.Density+Phase2.vf*Phase2.Density )

Shomaz ul Haq · October 16, 2017, 03:05

Thanks again Glenn. One more question through. Does the same principle apply for calculating other variables as well, e.g. my interest lies in calculating heat transfer coefficient field? Like (Phase1.vf*Phase1.Density*Phase1.Wall Heat Transfer Coefficient+Phase 2.vf*Phase2.Density*Phase2. Wall Heat Transfer Coefficient)/(Phase1.vf*Phase1.Density+Phase2.vf*Phase2.Density ). Thanks.

ghorrocks · October 16, 2017, 06:25

The equation was just a general mass weighted average. You can average anything you like using it.

October 15, 2017, 09:32	How to Find Temperature Field of Two Phase Flow?	#1
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 12	Dear all, Hello. Hope all are well. I am new at two phase flow so forgive me if I ask. Can anyone tell me how to find the temperature of a two phase nanofluid in an Eulerian Eulerian homogeneous model in CFD-Post?The flow field doesn't change compared to two phase flow as its single coupled that I understand. I know there is a variable for the base fluid i.e. Basefluid.Temperature and there is a variable for particle i.e. particle.Temperature but how can I find and plot contour of the two phase fluid itself i.e. both fluids combined? I have tried adding temperatures of the two fluids as an expression and that using it as a variable and then plotting its contour but that gives me a wrong value i.e. just the addition of individual values of the two fluids. Also, the base fluid temperature field in the longitudinal direction is less than that of single phase nanofluid. Why is that? I was expecting it to be higher in two phase flow. Would be extremely grateful if somebody could shed some light on this. Thanks.

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October 15, 2017, 18:46		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	First of all - and I think we have talked about this before - the concept of "phase" does not really exist at the nanofluid level. You are talking molecular level stuff here, so all sorts of different considerations come into play. Are you sure a CFD solver is suitable for this work? Putting those misgivings aside..... If you want to work out some average temperature of the two phases then you are going to have to write an expression to evaluate it. It will probably rely on the mass of each volume fraction in a unit volume to give a mass weighted average temperature. But you are going to have to define a variable to do this as nothing is built in.

October 16, 2017, 01:27		#3
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 12	Yes. You're right Glenn. Thanks. I am just comparing and experimenting with nanofluid two phase simulation. I think CFD Solver may solve it. You said something about "mass of each volume fraction in a unit volume to give a mass weighted average temperature". What should be the expression? I know this isn't built in and I'll have to make a variable after creating expression. Hope to hear from you. Thanks again!

October 16, 2017, 01:32		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	The function would be very simple, something like (Phase1.vfPhase1.DensityPhase1.Temperature+Phase 2.vfPhase2.DensityPhase2.Temperature)/(Phase1.vfPhase1.Density+Phase2.vfPhase2.Density )

October 16, 2017, 03:05		#5
Shomaz ul Haq Senior Member Shomaz ul Haq Join Date: Aug 2015 Location: Islamabad, Pakistan Posts: 205 Rep Power: 12	Thanks again Glenn. One more question through. Does the same principle apply for calculating other variables as well, e.g. my interest lies in calculating heat transfer coefficient field? Like (Phase1.vfPhase1.DensityPhase1.Wall Heat Transfer Coefficient+Phase 2.vfPhase2.DensityPhase2. Wall Heat Transfer Coefficient)/(Phase1.vfPhase1.Density+Phase2.vfPhase2.Density ). Thanks.

October 16, 2017, 06:25		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	The equation was just a general mass weighted average. You can average anything you like using it.