inline double waterheater::new_temp_1node(double T0, double delta_t)
{
// old because this happens in presync and needs previously used demand
const double mdot_Cp = Cp * water_demand_old * 60 * RHOWATER / GALPCF;
// Btu / degF.lb * gal/hr * lb/cf * cf/gal = Btu / degF.hr
if (Cw <= ROUNDOFF || (tank_UA+mdot_Cp) <= ROUNDOFF)
return T0;
const double c1 = (tank_UA + mdot_Cp) / Cw;
const double c2 = (actual_kW()*BTUPHPKW + mdot_Cp*Tinlet + tank_UA*get_Tambient(location)) / (tank_UA + mdot_Cp);
// return c2 - (c2 + T0) * exp(c1 * delta_t); // [F]
return c2 - (c2 - T0) * exp(-c1 * delta_t); // [F]
}
inline double range::new_temp_1node(double T0, double delta_t)
{
// old because this happens in presync and needs previously used demand
const double mdot_Cp = specificheat_food * oven_demand_old * 60 * food_density / GALPCF;
// Btu / degF.lb * gal/hr * lb/cf * cf/gal = Btu / degF.hr
if (Cw <= ROUNDOFF || (oven_UA+mdot_Cp) <= ROUNDOFF)
return T0;
const double c1 = (oven_UA + mdot_Cp) / Cw;
const double c2 = (actual_kW()*BTUPHPKW + mdot_Cp*Tinlet + oven_UA*get_Tambient(location)) / (oven_UA + mdot_Cp);
// return c2 - (c2 + T0) * exp(c1 * delta_t); // [F]
return c2 - (c2 - T0) * exp(-c1 * delta_t); // [F]
}
inline double waterheater::new_time_1node(double T0, double T1)
{
const double mdot_Cp = Cp * water_demand * 60 * RHOWATER / GALPCF;
if (Cw <= ROUNDOFF)
return -1.0;
const double c1 = ((actual_kW()*BTUPHPKW + tank_UA * get_Tambient(location)) + mdot_Cp*Tinlet) / Cw;
const double c2 = -(tank_UA + mdot_Cp) / Cw;
if (fabs(c1 + c2*T1) <= ROUNDOFF || fabs(c1 + c2*T0) <= ROUNDOFF || fabs(c2) <= ROUNDOFF)
return -1.0;
const double new_time = (log(fabs(c1 + c2 * T1)) - log(fabs(c1 + c2 * T0))) / c2; // [hr]
return new_time;
}
inline double range::new_time_1node(double T0, double T1)
{
const double mdot_Cp = specificheat_food * oven_demand * 60 * food_density / GALPCF;
if (Cw <= ROUNDOFF)
return -1.0;
const double c1 = ((actual_kW()*BTUPHPKW + oven_UA * get_Tambient(location)) + mdot_Cp*Tinlet) / Cw;
const double c2 = -(oven_UA + mdot_Cp) / Cw;
if (fabs(c1 + c2*T1) <= ROUNDOFF || fabs(c1 + c2*T0) <= ROUNDOFF || fabs(c2) <= ROUNDOFF)
return -1.0;
const double new_time = (log(fabs(c1 + c2 * T1)) - log(fabs(c1 + c2 * T0))) / c2; // [hr]
return new_time;
}
/* the key to picking the equations apart is that the goal is to calculate the temperature differences relative to the
* temperature of the lower node (or inlet temp, if 1node).
* cA is the volume change from water draw, heating element, and thermal jacket given a uniformly cold tank
* cB is the volume change from the extra energy within the hot water node
*/
double waterheater::dhdt(double h)
{
if (/*Tupper*/ Tw - Tlower < ROUNDOFF)
return 0.0; // if /*Tupper*/ Tw and Tlower are same then dh/dt = 0.0;
// Pre-set some algebra just for efficiency...
const double mdot = water_demand * 60 * RHOWATER / GALPCF; // lbm/hr...
const double c1 = RHOWATER * Cp * area * (/*Tupper*/ Tw - Tlower); // Btu/ft...
// check c1 before dividing by it
if (c1 <= ROUNDOFF)
return 0.0; //Possible only when /*Tupper*/ Tw and Tlower are very close, and the difference is negligible
const double cA = -mdot / (RHOWATER * area) + (actual_kW() * BTUPHPKW + tank_UA * (get_Tambient(location) - Tlower)) / c1;
const double cb = (tank_UA / height) * (/*Tupper*/ Tw - Tlower) / c1;
// Returns the rate of change of 'h'
return cA - cb*h;
}
/* the key to picking the equations apart is that the goal is to calculate the temperature differences relative to the
* temperature of the lower node (or inlet temp, if 1node).
*/
double range::dhdt(double h)
{
if (/*Tupper*/ Tw - Tlower < ROUNDOFF)
return 0.0; // if /*Tupper*/ Tw and Tlower are same then dh/dt = 0.0;
// Pre-set some algebra just for efficiency...
const double mdot = oven_demand * 60 * food_density / GALPCF; // lbm/hr...
const double c1 = food_density * specificheat_food * area * (/*Tupper*/ Tw - Tlower); // Btu/ft...
if (oven_demand > 0.0)
double aaa=1;
// check c1 before dividing by it
if (c1 <= ROUNDOFF)
return 0.0; //Possible only when /*Tupper*/ Tw and Tlower are very close, and the difference is negligible
const double cA = -mdot / (food_density * area) + (actual_kW() * BTUPHPKW + oven_UA * (get_Tambient(location) - Tlower)) / c1;
const double cb = (oven_UA / height) * (/*Tupper*/ Tw - Tlower) / c1;
// Returns the rate of change of 'h'
return cA - cb*h;
}
inline double waterheater::new_h_2zone(double h0, double delta_t)
{
if (delta_t <= ROUNDOFF)
return h0;
// old because this happens in presync and needs previously used demand
const double mdot = water_demand_old * 60 * RHOWATER / GALPCF; // lbm/hr...
const double c1 = RHOWATER * Cp * area * (/*Tupper*/ Tw - Tlower); // lb/ft^3 * ft^2 * degF * Btu/lb.degF = lb/lb * ft^2/ft^3 * degF/degF * Btu = Btu/ft
// check c1 before division
if (fabs(c1) <= ROUNDOFF)
return height; // if /*Tupper*/ Tw and Tlower are real close, then the new height is the same as tank height
// throw MODEL_NOT_2ZONE;
// #define CWATER (0.9994) // BTU/lb/F
const double cA = -mdot / (RHOWATER * area) + (actual_kW()*BTUPHPKW + tank_UA * (get_Tambient(location) - Tlower)) / c1;
// lbm/hr / lb/ft + kW * Btu.h/kW +
const double cb = (tank_UA / height) * (/*Tupper*/ Tw - Tlower) / c1;
if (fabs(cb) <= ROUNDOFF)
return height;
return ((exp(cb * delta_t) * (cA + cb * h0)) - cA) / cb; // [ft]
}
