Learning Forum

[snr1]

I am writing mixture properties and its constituent species properties in a material.scm file.

What will be units of formation-enthalpy and formation-entropy in material.scm file.

 

 

[Rob]

Open the materials panel and it should be listed there. It'll be SI units in Fluent. 

[snr1]

Formation-enthalpy and specific enthalpy both are the same or different? If these two are different, how we can calculate the formation-enthalpy for a particular material?

[Rob]

What is shown in the materials panel? Note, there's a reference temperature there too which may be important. 

[snr1]

For material properties, i am writing a material.scm file. In this file, we need to mention the formation-enthalpy value of that material. Now, my query is whether the specific enthalpy and formation-enthalpy are same or not?

 

If these two are different, how we can calculate the formation-enthalpy of a particular material. For example: see below for ammonia properties.

 

(ammonia-liquid  fluid

  (chemical-formula . nh3
  (density (constant . 610) (compressible-liquid 101325 610 2.1e+09 7 1.1 0.9))
  (specific-heat (constant . 4758))
  (thermal-conductivity (constant . 0.493))
  (viscosity (constant . 0.000152))
; Critical Properties from Polling et al.
  (critical-pressure (constant . 11.3530e6))
  (critical-temperature (constant . 405.40))
  (acentric-factor (constant . 0.257))
  (critical-volume (constant . 0.00426))
  )

 
 
 
 
 

 (ammonia-vapor  fluid
  (chemical-formula . nh3)
  (density (constant . 0.6894))
  (specific-heat (polynomial piecewise-polynomial (300 1000 1076.164 4.9380262 -0.0071534199 7.0653986e-06 -2.601377e-09) (1000 5000 1201.9011 2.9580837 -0.00097882914 1.5309961e-07 -9.4628597e-12)) (constant . 2158))
  (thermal-conductivity (constant . 0.0247))
  (viscosity (constant . 1.015e-05))
  (molecular-weight (constant . 17.03061))
  (absorption-coefficient (constant . 0.5) (polynomial piecewise-linear (550 . 3.14) (890 . 1.93) (1220 . 0.95) (1550 . 0.5)))
  (formation-enthalpy (constant . -45915740))
  (reference-temperature (constant . 298.15))
  (thermal-accom-coefficient (constant . 0.9137))
  (velocity-accom-coefficient (constant . 0.9137))
  (formation-entropy (constant . 192612.34))
  ; Critical Properties from Polling et al.
  (critical-pressure (constant . 11.3530e6))
  (critical-temperature (constant . 405.40))
  (acentric-factor (constant . 0.257))
  (critical-volume (constant . 0.00426))

  )

[Rob]

If you open the materials panel up & turn on both species and anything with a phase change you'll see most of the above. If you're poking around in the materials files you'll note that some values are missing: not all materials have all data available. You'll also find a more useful description of both the name & units in the Materials panel. Assuming you've not altered any units these should be what's needed in the file you're writing.