# How to define a specific heat function using usr_properties?

Hi
I want to use the usr_properties to difine a Cp of solid particle:
i.e.

I copied the source code of usr_properties.f to my directory, and I found this line:
` C_PS(IJK,M) =`
But how to represent the Temperature in the formula?

The variable, which I only know, to represent solid temperature is des_T_s(NP), however there is no NP(the particle index).

Thank you

USR_PROP_CPs(ijk,M) is used to define the CPs for each solid phase. If you want to include the temperature effect in CPs, just:

USE fldvar, only: T_S
USE physprop, only: C_PS

! sand
IF(M=1) C_PS(ijk,M)= …
! wood
IF(M=2) C_PS(ijk,M)=1112.0+4.85(T_S-273)

If you want to simulate the chemical reaction of wood particles using DEM model (wood–>char+ash+unreacted wood+gas), the CPs of a particle is also a function of species, thus I suggest you try an easier way as follows:

1. select a solid (e.g. C) from the BURCAT database to mimic wood, ash, char, respectively.
2. Modify the Cp (eg. wood: 1112.0+4.85(T_S-273)) in the following format.
Cp/R=a1+a2T+a3T^2+a4T^3+a5T^4
2 Likes

Hi @chunlei @gaoxi
I am also meeting this problem. What does `R` in format `Cp/R=a1+a2T+a3T^2+a4*T^3+a5* T^4` refer to? Gas constant, 8314 J/kmol/k？

R is the gas constant, 8.3145J