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Minor updates to falling particle receiver flow and temperature itera…
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@jannamartinek
jannamartinek committed Sep 23, 2023
1 parent 4f5584b commit 7d2cb08
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Showing 2 changed files with 22 additions and 12 deletions.
2 changes: 1 addition & 1 deletion ssc/cmod_csp_tower_particle.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,7 @@ static var_info _cm_vtab_csp_tower_particle[] = {
{ SSC_INPUT, SSC_NUMBER, "rec_hadv_fixed", "User-provided fixed receiver advective loss coefficient", "W/m2/K", "", "Tower and Receiver", "rec_adv_model_type=0", "", "" },
{ SSC_INPUT, SSC_NUMBER, "rec_rad_ny", "Number of curtain element groups in vertical dimension for radiative exchange", "", "", "Tower and Receiver", "?=5", "", "" },
{ SSC_INPUT, SSC_NUMBER, "rec_rad_nx", "Number of curtain element groups in width dimension for radiative exchange", "", "", "Tower and Receiver", "?=3", "", "" },
{ SSC_INPUT, SSC_NUMBER, "particle_dp", "Particle diameter", "", "", "Tower and Receiver", "?=350e-6", "", "" },
{ SSC_INPUT, SSC_NUMBER, "particle_dp", "Particle diameter", "m", "", "Tower and Receiver", "?=350e-6", "", "" },
{ SSC_INPUT, SSC_NUMBER, "particle_abs", "Particle absorptivity", "", "", "Tower and Receiver", "?=0.9", "", "" },
{ SSC_INPUT, SSC_NUMBER, "curtain_emis", "Curtain emissivity", "", "", "Tower and Receiver", "?=0.9", "", "" },
{ SSC_INPUT, SSC_NUMBER, "curtain_dthdy", "Rate of curtain thickness increase with respect to fall distance", "", "", "Tower and Receiver", "?=0.0087", "", "" },
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32 changes: 21 additions & 11 deletions tcs/csp_solver_falling_particle_receiver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1056,19 +1056,19 @@ void C_falling_particle_receiver::calculate_steady_state_soln(s_steady_state_sol
qabs_approx = (1.0 - soln.rhoc.at(j, i) - soln.tauc.at(j, i) + rhow * soln.tauc.at(j, i) + rhow * (1.0 - vf_to_ap) * soln.rhoc.at(j, i)) * soln.q_dot_inc.at(j, i); // Approximate solar energy absorbed by the particle curtain (W/m2)
qnet_approx = qabs_approx - hadv * fwind * (Tp.at(j, i) - soln.T_amb) - m_curtain_emis * CSP::sigma * pow(Tp.at(j, i), 4); //Approximate net heat transfer rate using curtain temperature at prior element
dh_approx = qnet_approx * (dy / (soln.phip.at(j + 1, i) * soln.thc.at(j + 1, i) * soln.vel.at(j + 1, i) * particle_density));
Tp.at(j + 1, i) = Tp.at(j, i) + dh_approx / cp;
Tp.at(j + 1, i) = max(T_cold_in_rec, Tp.at(j, i) + dh_approx / cp);
}

qnet_approx = (1.0 - rhow)*(1.0 + rhow*soln.rhoc.at(j,i)) * (m_curtain_emis * CSP::sigma * pow(Tp.at(j, i), 4) + soln.tauc.at(j, i) * soln.q_dot_inc.at(j, i)); // Approximate radiative heat transfer incoming to the back wall (W/m2)
Tw.at(j, i) = pow(qnet_approx / (m_cav_emis * CSP::sigma), 0.25);
Tw.at(j, i) = max(T_cold_in_rec, pow(qnet_approx / (m_cav_emis * CSP::sigma), 0.25));

flux_avg += soln.q_dot_inc.at(j, i) / (m_n_x*m_n_y);
rhoc_avg += soln.rhoc.at(j, i) / (m_n_x * m_n_y);
Ec_avg += (m_curtain_emis * CSP::sigma * pow(Tp.at(j, i), 4)) / (m_n_x * m_n_y);
}
}
qnet_approx = (1.0 - vf_to_ap) * m_cav_emis * (rhoc_avg * flux_avg + Ec_avg);
Twf = max(T_cold_in, pow(qnet_approx / (m_cav_emis * CSP::sigma), 0.25)); // Initial guess for front wall temperature
Twf = max(T_cold_in_rec, pow(qnet_approx / (m_cav_emis * CSP::sigma), 0.25)); // Initial guess for front wall temperature
}


Expand Down Expand Up @@ -1288,6 +1288,14 @@ void C_falling_particle_receiver::calculate_steady_state_soln(s_steady_state_sol
Tp = Tpnew;
Tw = Twnew;
Twf = Twfnew;

// Stop iterations for very low outlet temperature, or if the solution in the previous iteration failed
if (Q_thermal != Q_thermal)
break;

Tp_out = calculate_mass_wtd_avg_exit(mdot_per_elem, Tp); // Mass-weighted average particle exit temperature from receiver [K]
if (Tp_out < 0.0)
break;
}

if (!converged)
Expand All @@ -1299,10 +1307,9 @@ void C_falling_particle_receiver::calculate_steady_state_soln(s_steady_state_sol
double Tp_out_after_transport = Tp_out - m_Q_dot_transport_loss_hot / cp / soln.m_dot_tot; // Outlet temperature accounting from loss from hot particle transport


if (Tp_out <= T_cold_in)
if (Tp_out <= T_cold_in || Q_thermal != Q_thermal)
{
rec_is_off = true;
converged = false;
}


Expand All @@ -1320,11 +1327,8 @@ void C_falling_particle_receiver::calculate_steady_state_soln(s_steady_state_sol
soln.converged = converged;
soln.rec_is_off = rec_is_off;

if (!soln.rec_is_off)
{
soln.T_particle_hot = Tp_out_after_transport;
soln.T_particle_hot_rec = Tp_out;
}
soln.T_particle_hot = Tp_out_after_transport;
soln.T_particle_hot_rec = Tp_out;

return;

Expand Down Expand Up @@ -1441,7 +1445,7 @@ void C_falling_particle_receiver::solve_for_mass_flow(s_steady_state_soln &soln)
}

// If outlet temperature is below the target, compare current solution with previously stored solutions to identify bounds
else
else if (soln.converged)
{
for (int i = 0; i < qq; i++)
{
Expand Down Expand Up @@ -1493,6 +1497,12 @@ void C_falling_particle_receiver::solve_for_mass_flow(s_steady_state_soln &soln)
break;
}

if (soln.Q_thermal < 0.0 || soln.Q_thermal != soln.Q_thermal)
{
soln.rec_is_off = true;
break;
}

// Stop solution if outlet temperature was not achieved and mass flow bounds are within tolerance
if (is_upper_bound && (upper_bound - lower_bound) <= bound_tol * lower_bound)
{
Expand Down

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