[Manu Poolakkal]

I am an M.tech student. To complete my project I have to evaluate a double pipe counter flow ammonia liquid vapor heat exchanger using ANSYS Fluent. I have done the modeling. I am not a pro in Fluent. In my try, I got result which showed no heat transfer (something went wrong and I don't know what it was). Somebody please give the instructions to solve it in Fluent.
Thank You.

[amin.z]

Originally Posted by Manu Poolakkal

I am an M.tech student. To complete my project I have to evaluate a double pipe counter flow ammonia liquid vapor heat exchanger using ANSYS Fluent. I have done the modeling. I am not a pro in Fluent. In my try, I got result which showed no heat transfer (something went wrong and I don't know what it was). Somebody please give the instructions to solve it in Fluent.
Thank You.

hey
are you sure the boundary condition between fluids is correct?
Can you attach a pic and explain your boundary condition?

[Manu Poolakkal]

Thank you for your response

I have given all these values and still the problem persist.
the heat transfer is occurring only at the inlet and outlet manifolds and not in the heat exchanger (concentric tube) region.

BCs are
vapor inlet (inner pipe)
velocity= 101.48 m/s (1,0,0)
temp=263.7056 k
pressure= 137890 pa

liquid inlet (outer pipe)
velocity=0.4511 m/s (0,-1,0)
temp=306.2055 k
pressure= 1275530 pa

Material Properties are
ammonia vapor (inner fluid)
density=1.1182 kg/m3
u=.0000089206 pa-s
Cp=4642.4 j/kgk
k=1.5781 w/mk

ammonia liquid (outer fluid)
density=591.4082 kg/m3
u=.0003112017 pa-s
Cp=4790.2 j/kgk
k=1.432 w/mk

Pipe material steel
k=45 w/mk

[amin.z]

Originally Posted by Manu Poolakkal

Thank you for your response

I have given all these values and still the problem persist.
the heat transfer is occurring only at the inlet and outlet manifolds and not in the heat exchanger (concentric tube) region.

BCs are
vapor inlet (inner pipe)
velocity= 101.48 m/s (1,0,0)
temp=263.7056 k
pressure= 137890 pa

liquid inlet (outer pipe)
velocity=0.4511 m/s (0,-1,0)
temp=306.2055 k
pressure= 1275530 pa

Material Properties are
ammonia vapor (inner fluid)
density=1.1182 kg/m3
u=.0000089206 pa-s
Cp=4642.4 j/kgk
k=1.5781 w/mk

ammonia liquid (outer fluid)
density=591.4082 kg/m3
u=.0003112017 pa-s
Cp=4790.2 j/kgk
k=1.432 w/mk

Pipe material steel
k=45 w/mk

what is the BC between 2 fluid zones? Do you have a wall between them? have the walls between zones "shadow" ?

[Manu Poolakkal]

Yes, there is a steel wall (inner pipe) between the two fluid zones and the walls between zones have shadows.I have attached a pic showing my boundary zones. At present I have the boundary conditions only at the inlet and outlets of the liquid and vapor zone (actually I have to find the outlet temperatures of fluids generated by fluent and compare them with my theoretical values). What do you mean by "boundary conditions between the fluid zones". Can we take the average of inlet and outlet temperatures of each fluid zone to get the fluid zone boundary condition?.

[m7566]

sir can u give me a tutorial how to design double pipe heat exchanger in gambit please help me sir i am final year student i have desing project on cfd analysis of double pipe heat exchanger using gambit and fluent

[Manu Poolakkal]

Originally Posted by m7566

sir can u give me a tutorial how to design double pipe heat exchanger in gambit please help me sir i am final year student i have desing project on cfd analysis of double pipe heat exchanger using gambit and fluent

i am not an expert in gambit. why don't you model the object in design modeler?. It doesn't matter which modeler you are using. if you use design modeler, i will help you.

[Manu Poolakkal]

Originally Posted by amin.z

what is the BC between 2 fluid zones? Do you have a wall between them? have the walls between zones "shadow" ?

sir
i found the error which was in my model. there was an error in creating a hole in the pipe. now everything is cleared. hope u ll help me to rectify my further errors. thank you.

[amin.z]

Oh! Sorry friend! I forgot this post!
I'm Happy that your problem solved!

[Manu Poolakkal]

Originally Posted by amin.z

Oh! Sorry friend! I forgot this post!
I'm Happy that your problem solved!

its fine sir.
but i am in another trouble. in my heat exchanger, there is phase change occurring at the vapor side. i don't know how to achieve the same in fluent. how to select the appropriate phase change model? is there any good tutorial about phase change?

[amin.z]

Hey
Good!
My main skill is in aerodynamics! Not multiphase!
But if you refer to ANSYS fluent tutorial guide ( specially chapters 19,20,21,22,23), maybe helps you!

[Manu Poolakkal]

Originally Posted by amin.z

Hey
Good!
My main skill is in aerodynamics! Not multiphase!
But if you refer to ANSYS fluent tutorial guide ( specially chapters 19,20,21,22,23), maybe helps you!

i have completed fluent procedure. when i give a small number of iterations the temperature range is fine and almost correct(say 250 to 350 k). but for solution convergence when i give a large number of iteration the temperature widens to an abnormal range(say 250 to 5000k).can u id the reason?