[aminhgn]

Hi,

I am modeling water and air evaporation. I read that I can use standard state enthalpy to model latent heat. Water vapor and water SSE should be defined somehow the difference between them become latent heat. So, if we consider that the SSE is 43999434 J/Kmol, how should i define this for both of them? and what is the sign of them (negative, positive)?

Thanks,

Amin

[vivek162]

Material: water-vapor (fluid)

Property Units Method Value(s)
---------------------------------------------------------------
Density kg/m3 constant 0.02307
Cp (Specific Heat) j/kg-k constant 1911.8
Thermal Conductivity w/m-k constant 0.018433
Viscosity kg/m-s constant 9.7009e-06
Molecular Weight kg/kmol constant 18.01534
Standard State Enthalpy j/kgmol constant 43987714
Reference Temperature k constant 298.15
Thermal Expansion Coefficient 1/k constant 0

Material: water-liquid (fluid)

Property Units Method Value(s)
--------------------------------------------------------------------------------------
Density kg/m3 polynomial 717.85 2.3932 -0.00572 2.794e-06
Cp (Specific Heat) j/kg-k constant 4182 Thermal Conductivity w/m-k constant 0.60646
Viscosity kg/m-s constant 0.00089004
Molecular Weight kg/kmol constant 18.0152
Standard State Enthalpy j/kgmol constant 0
Reference Temperature k constant 298
Thermal Expansion Coefficient 1/k constant 0


Define SSE 0 for water, and 43987714 j/kgmol for vapor. if there is no chemical recation in your simulation case the you can simply define the differece as shown above.

[aminhgn]

Originally Posted by vivek162

Material: water-vapor (fluid)

Property Units Method Value(s)
---------------------------------------------------------------
Density kg/m3 constant 0.02307
Cp (Specific Heat) j/kg-k constant 1911.8
Thermal Conductivity w/m-k constant 0.018433
Viscosity kg/m-s constant 9.7009e-06
Molecular Weight kg/kmol constant 18.01534
Standard State Enthalpy j/kgmol constant 43987714
Reference Temperature k constant 298.15
Thermal Expansion Coefficient 1/k constant 0

Material: water-liquid (fluid)

Property Units Method Value(s)
--------------------------------------------------------------------------------------
Density kg/m3 polynomial 717.85 2.3932 -0.00572 2.794e-06
Cp (Specific Heat) j/kg-k constant 4182 Thermal Conductivity w/m-k constant 0.60646
Viscosity kg/m-s constant 0.00089004
Molecular Weight kg/kmol constant 18.0152
Standard State Enthalpy j/kgmol constant 0
Reference Temperature k constant 298
Thermal Expansion Coefficient 1/k constant 0


Define SSE 0 for water, and 43987714 j/kgmol for vapor. if there is no chemical recation in your simulation case the you can simply define the differece as shown above.

Thank you for your reply. it solved my problem. I have two phases, water, and air, I want to get the heat transfer rate or heat transfer coefficient to calculate the nusselt number. I know we can get for the wall in results but it's not wall right now.

[vivek162]

Please refer chapter 5 & 6. it will help you to find out the HTC at condenser wall.

"Fadhl, B., 2016. Modelling of the thermal behaviour of a two-phase closed thermosyphon (Doctoral dissertation, Brunel University London)."

[aminhgn]

Originally Posted by vivek162

Please refer chapter 5 & 6. it will help you to find out the HTC at condenser wall.

"Fadhl, B., 2016. Modelling of the thermal behaviour of a two-phase closed thermosyphon (Doctoral dissertation, Brunel University London)."

Hi,
That's my problem I am modeling water and air and the walls are adiabatic and the heat transfer is between air and water. I am using VOF for multiphase. Can you help me about it?

[vivek162]

so do you want to calculate the heat transfer inside the heat pipe between water and vapor? could you please clear to me what do you want to calculate heat transfer outside at condenser or heat transfer inside the heat pipe?

[aminhgn]

I have two parallel plates the water and air are in parallel flow. the mass transfer and heat transfer happens between water and air. I want to calculate the nusselt number. the nusselt number is based on the heat transfer rate and width of two plates, the thermal conductivity of air, bulk temperature and interface temperature.

[vivek162]

you can solve it using Fluent.

[aminhgn]

so can you help how can i get a heat transfer rate of airside by fluent?

[vivek162]

sure I will.

[xnou]

Hi,

Can you help me to choose the fluid property for LNG and BOG phase transfer.

Methane phase transfer will also work. so anyone, help me for methane phase transfer.

[NeedHelpPls]

Originally Posted by vivek162

Material: water-vapor (fluid)


Property Units Method Value(s)
---------------------------------------------------------------
Density kg/m3 constant 0.02307
Cp (Specific Heat) j/kg-k constant 1911.8
Thermal Conductivity w/m-k constant 0.018433
Viscosity kg/m-s constant 9.7009e-06
Molecular Weight kg/kmol constant 18.01534
Standard State Enthalpy j/kgmol constant 43987714
Reference Temperature k constant 298.15
Thermal Expansion Coefficient 1/k constant 0

Material: water-liquid (fluid)

Property Units Method Value(s)
--------------------------------------------------------------------------------------
Density kg/m3 polynomial 717.85 2.3932 -0.00572 2.794e-06
Cp (Specific Heat) j/kg-k constant 4182 Thermal Conductivity w/m-k constant 0.60646
Viscosity kg/m-s constant 0.00089004
Molecular Weight kg/kmol constant 18.0152
Standard State Enthalpy j/kgmol constant 0
Reference Temperature k constant 298
Thermal Expansion Coefficient 1/k constant 0


Define SSE 0 for water, and 43987714 j/kgmol for vapor. if there is no chemical recation in your simulation case the you can simply define the differece as shown above.

Hello! I try to simulate evaporation-condensation process in water, but on your SSEs Fluent write: "ERROR: Latent heat cannot be less than zero! Latent Heat: -2.64215e+06"
I dont really understand this behaviour of fluent

[NeedHelpPls]

Originally Posted by NeedHelpPls

Hello! I try to simulate evaporation-condensation process in water, but on your SSEs Fluent write: "ERROR: Latent heat cannot be less than zero! Latent Heat: -2.64215e+06"
I dont really understand this behaviour of fluent

Sorry, it works, but, people, be cafeful! In ANSYS 2021R1 are a lot of bugs. (Problem was solved with duplication of project) The same thing is with editing of polynomial materíal properties in fluent. Use piecewise polynomial with 1 range.

[gaza]

Originally Posted by aminhgn

Hi,

I am modeling water and air evaporation. I read that I can use standard state enthalpy to model latent heat. Water vapor and water SSE should be defined somehow the difference between them become latent heat. So, if we consider that the SSE is 43999434 J/Kmol, how should i define this for both of them? and what is the sign of them (negative, positive)?

Thanks,

Amin

In Fluent tutorial on boiling you can find this explanation:

[sree kumaran]

Originally Posted by NeedHelpPls

Hello! I try to simulate evaporation-condensation process in water, but on your SSEs Fluent write: "ERROR: Latent heat cannot be less than zero! Latent Heat: -2.64215e+06"
I dont really understand this behaviour of fluent

Have u found how to solve that please reply

[Karem]

I have the same exact problem and those numbers of SSE didn't solve it.

[gaza]

Originally Posted by sree kumaran

Have u found how to solve that please reply

you have to change phases (primary and secodnary) - vapour should be primary phase