[engrmansoor2534]

Nanofluid simulation using ansys fluent

Hi everyone
I m simulating nanofluids as single phase. I have updated the entire properties of fluid with that of nanofluid. But I don't know how to enter nanoparticle size as I want to simulate the offect of nano particle size on heat transfer capability and pressure drop characteristics.kindly help me in this regard

[CeesH]

Hi,

If you are running a single-phase simulation, you cannot set particle size, since there are no particles. You will need to alter the heat transfer parameters based on empirical correlations in that case; similar to altering the viscosity when you are considering a particulate flow as single phase. Or am I not understanding you correctly?

Best,
Cees

[LuckyTran]

Keep in mind that many assumptions are made with respect to fluid particles in the fluid model.

Simulating nanoparticles dispersed in a fluid (which is multi-phase problem) is different from simulating a fluid with nanoparticles with effective properties (the single-phase problem). Example, in the fluid flow of air or water, we never talk about the size of the air/water molecules).

[engrmansoor2534]

thanks to both of you.
so does it mean that we can not study the effect of particles size on heat transfer enhancement if we are considering nanofluid as a single phase flow??
I have read in a research paper that if we consider the effect of brownian motion, then effective thermal conductivity is composed of static part (maxwell theory) and dynamic part (brownian motion), In the dynamic part we have nanoparticle diameter.see picture for detail:
thanks again for your time

[LuckyTran]

Originally Posted by engrmansoor2534

thanks to both of you.
so does it mean that we can not study the effect of particles size on heat transfer enhancement if we are considering nanofluid as a single phase flow??
I have read in a research paper that if we consider the effect of brownian motion, then effective thermal conductivity is composed of static part (maxwell theory) and dynamic part (brownian motion), In the dynamic part we have nanoparticle diameter.see picture for detail:
thanks again for your time

The work proposes an equation for calculating an effective thermal conductivity which has contributions from nanoparticle diameter. Ok. But that means once you put in the effective thermal conductivity in Fluent you are done. It's now a single phase flow with an effective thermal conductivity. The fluid doesn't know that there are nanoparticles.

Once you put in effective bulk properties that "account" for the nano particle behavior, you don't talk about nano particles sizes anymore, in the same sense that we stop talking about molecular sizes of individual molecules when we talk about density, thermal conductivity, viscosity, etc.

So I am confused. If you were able to enter the effective properties of the nanofluid, what exactly is the problem here? Did you perhaps put the incorrect property? The statement of your question also states that you have already solved the problem.

[engrmansoor2534]

thanks LuckyTran
I got your point. I am now going to simulate the flow with the effective properties I calculated and will consult you in case of any problem.

[farah]

engrmansoor2534 Can i get this paper please?

[farah]

Originally Posted by engrmansoor2534

thanks to both of you.
so does it mean that we can not study the effect of particles size on heat transfer enhancement if we are considering nanofluid as a single phase flow??
I have read in a research paper that if we consider the effect of brownian motion, then effective thermal conductivity is composed of static part (maxwell theory) and dynamic part (brownian motion), In the dynamic part we have nanoparticle diameter.see picture for detail:
thanks again for your time

Can i get this paper please?

[engrmansoor2534]

Originally Posted by farah

Can i get this paper please?

Farah I could not find that specific paper, but this one also describes the same behavior of nanofluids. part 1 and part 2 respectively.
www.scielo.br/pdf/bjce/v25n4/a01v25n4.pdf
www.scielo.br/pdf/bjce/v25n4/a02v25n4.pdf

[farah]

Originally Posted by engrmansoor2534

Farah I could not find that specific paper, but this one also describes the same behavior of nanofluids. part 1 and part 2 respectively.
www.scielo.br/pdf/bjce/v25n4/a01v25n4.pdf
www.scielo.br/pdf/bjce/v25n4/a02v25n4.pdf

Thanks alot, I want to simulate phase change material and nanoparticle in Fluent but depending on many published papers they used VOF model the big question is how can i define the different properties because i have 3 phases: 1.solid phase, 2.liquid phase 3.nanoparticle effect?
Any help please

[engrmansoor2534]

Farah I don't have knowledge about phase change simulations. I am working on nanofluids. you can model nanofluids as a two phase fluid. nanoparticles + base fluid. multiphase models such as mixture model and eulerian models are a good option for nanofluids. If you are interested in particle tracking you can use discrete phase model. it would be better if you downlaod ansys user's guide and ansys fluent theory guide in order to get a proper idea about your case study.

[VAIBHAV WALI]

Originally Posted by engrmansoor2534

Farah I don't have knowledge about phase change simulations. I am working on nanofluids. you can model nanofluids as a two phase fluid. nanoparticles + base fluid. multiphase models such as mixture model and eulerian models are a good option for nanofluids. If you are interested in particle tracking you can use discrete phase model. it would be better if you downlaod ansys user's guide and ansys fluent theory guide in order to get a proper idea about your case study.

Hi
i am using nano fluids in a pipe which has no inlet and no outlet. the fluid is completely inside the pipe and cant move.

on top of this pipe,in the middle of pipe.i am applying the heat flux. this pipe is embedded in an aluminum block below and convection is happening around the block.
so the heat flux travel down through top of pipe to fluid then to bottom of the pipe then to aluminum block.

i am using single phase for the nanofluids.
my problem is ,the temperature drop on the aluminum is remaining the same ,even if am changing the liquid in the pipe

please help me out.

[engrmansoor2534]

Originally Posted by VAIBHAV WALI

Hi
i am using nano fluids in a pipe which has no inlet and no outlet. the fluid is completely inside the pipe and cant move.

on top of this pipe,in the middle of pipe.i am applying the heat flux. this pipe is embedded in an aluminum block below and convection is happening around the block.
so the heat flux travel down through top of pipe to fluid then to bottom of the pipe then to aluminum block.

i am using single phase for the nanofluids.
my problem is ,the temperature drop on the aluminum is remaining the same ,even if am changing the liquid in the pipe

please help me out.

can you kindly attach an image of your flow domain, so it will be easier to understand your case.
Anyways, according to your statement you are modeling natural convection or buoyancy driven flows?
If yes, then if the temperature difference in your domain is large you need to perform a transient calculation in which the initial density of the fluid is computed from the initial pressure and temperature.
On the other hand if your domain temperature difference is small you can perform a steady state calculation using boussinesq model.
In short you should refer to ansys user's guide " modeling heat transfer (natural convection or buoyancy driven flows)" in order to fully understand the setup required for your domain.
thanks

[VAIBHAV WALI]

Originally Posted by engrmansoor2534

can you kindly attach an image of your flow domain, so it will be easier to understand your case.
Anyways, according to your statement you are modeling natural convection or buoyancy driven flows?
If yes, then if the temperature difference in your domain is large you need to perform a transient calculation in which the initial density of the fluid is computed from the initial pressure and temperature.
On the other hand if your domain temperature difference is small you can perform a steady state calculation using boussinesq model.
In short you should refer to ansys user's guide " modeling heat transfer (natural convection or buoyancy driven flows)" in order to fully understand the setup required for your domain.
thanks

thanks for the information

[VAIBHAV WALI]

air domain.PNG

aluminum heat sink.PNG

copper heat pipe.PNG

cross section of the copper heat pipe.PNG

heat applied on the surface shown in red and light red.PNG

these are the images of the model
Can you please give some insight on this

[kattulanitin]

Hi every one,
I am doing the same thing in star CCM+ using multiphase lagrangian model with two way coupling between the fluid and the solid particles (Dia=4e-5m, Concentration of nanoparticles= 0.01%) and the gave heat flux boundary condition on the wall but while simulating with and without particles the outlet temperature of the pipe is same.
Does this infer that we cannot study the concentration of nanoparticles in the base fluid??
regards
Nitin