Considering the average temperature in a UDF

[eng_m_m.abd89]

Hello, this is my UDF for heat source; it worked well, but now I want to consider the average temperature instead of the cell temperature. My domain is three bodies [the battery, battery wall, and fluid around them]. I want to consider only the average temperature of the battery. Any help with performing this?

/*my_battery_heat_source_trial.c*/
#include "udf.h"
#include "stdio.h"
#include "math.h"
#include "mem.h"
#include "time.h"

// Inputs
#define V_bat 0.0000165 // Battery volume (m^3)
#define H_chem 11740 // Total heat release of chemical reaction (J)
#define H_sc 17560 // Total heat release of short circuit (J)
#define rho 2600 // Density of battery (kg/m^3)
#define Cp 1720 // Specific heat capacity (J/kg.K)
#define A 0.92 // Pre-exponential factor (unitless)
#define b 28.5 // Reaction rate constant (unitless)
#define T_ref 533.15 // Normalized temperature coefficient (K)
#define T_chem 413.15 // Start temperature of chemical reactions (K)
#define T_tr 533.15 // Triggering temperature of thermal runaway (K)
#define C_chem_max 12
#define C_elec_max 12


// UDF to define heat generation source term
DEFINE_SOURCE(my_battery_heat_source_trial,c,t,ds, eqn)
{
// Declaring Local variable for chemical and electrical energy concentration
real C_chem = 1.0;
real C_chem_old = 1.0;
real C_elec = 1.0;
real C_elec_old = 1.0;
real dC_chem_dt = 0.0;
real dC_elec_dt = 0.0;
real q_chem;
real q_elec;
real qv;
real T = C_T(c,t); // Get the temperature from the cell
real dt = CURRENT_TIMESTEP; // Get the simulation time step
// Function to compute the rate of change of C_chem (dC_chem/dt)
if (T>T_chem && T<=T_tr && C_chem>=0 && C_chem<=1)
dC_chem_dt =(Cp / H_chem) * A * rho * V_bat * pow((T / T_ref), b);
else if (T>T_tr && C_chem>=0 && C_chem<=1)
dC_chem_dt = C_chem_max;
else
dC_chem_dt = 0.0;
// Update the chemical energy concentration
C_chem = C_chem_old - (dC_chem_dt * dt);
// Function to compute volumetric chemical heat generation rate (q_chem)
q_chem = (1.0/V_bat) * H_chem * dC_chem_dt;
// Function to compute short-circuit reaction rate (dC_elec/dt)
if (T>T_tr && C_chem>=0 && C_chem<=1)
dC_elec_dt = C_elec_max;
else
dC_elec_dt = 0.0;
// Update the electrical energy concentration
C_elec = C_elec_old - (dC_elec_dt * dt);
// Function to compute volumetric electric heat generation rate (q_elec)
q_elec = (1.0/V_bat) * H_sc * dC_elec_dt;
// Compute heat generation rates
qv = q_chem + q_elec; // Total heat generation rate (W/m³)
ds[eqn]=0;
return qv; // Return total heat source term for Fluent
}

[Rob]

You'll need to loop over the cell zone cells and remember to account for NODE/HOST issues. 

[eng_m_m.abd89]

Any advice on where/how to start writing it, as I am new to the UDF and don't know how to make the loop over the battery cells? 

[Rob]

Look for examples using begin_c_loop and end_c_loop for some ideas.