Components.Partial.HEXCrossflow ​
Moist-air cross-flow heat exchanger element with condensation.
A single air stream crossing a finned-tube bank, used inside TubeFinHEX. port_a is the upstream air port and port_b the downstream air port; m_flow > 0 means air enters port_a. The wall couples through heatPorts (one per control volume). Currently restricted to N = 1 (single control volume) — set N = 1 when instantiating. The medium must be a moist-air medium (water vapor + dry air).
This component extends from PartialHEXCrossflow
Usage ​
HVACComponents.Components.Partial.HEXCrossflow(htc_nominal, CF_MassTransfer, CF_HeatTransfer, htc=missing, p_in_start, p_out_start, p_loss_start, m_air_flow_start, T_in_start, T_out_start, Xi_in_start, Xi_out_start, Q_start, eta_fin_start, h_in_start, h_out_start, mcond_flow_start, d_mean_start, Q_water_start, cp_mean_start, medium_data, A, d0, delta, S_t, S_l, At_tube, Af_tube, kfin, Ka, k_mair, Qdot_lat_start, Qdot_sens_start, xsat_w_start, eta_start, psat_w_start, psat_w_1K_start, xsat_w_1K_start, der_xsat_w_dT_start, mtc_start, dgradient_start, heff_start, rho_constant)
Parameters: ​
| Name | Description | Units | Default value |
|---|---|---|---|
N | Number of air-side control volumes | – | 1 |
N_Plus_1 | Number of cell faces (= N + 1) | – | N + 1 |
htc_nominal | Nominal air-side heat-transfer coefficient [W/(m^2.K)] | – | |
CF_MassTransfer | Correction factor on the Lewis-analogy mass-transfer coefficient [-] | – | |
CF_HeatTransfer | Correction factor on the air-side heat-transfer coefficient [-] | – | |
p_in_start | Initial air inlet pressure [Pa] | Pa | |
p_out_start | Initial air outlet pressure [Pa] | Pa | |
p_loss_start | Initial air-side pressure drop [Pa] | Pa | |
m_air_flow_start | Initial air mass flow rate [kg/s] | kg/s | |
T_in_start | Initial air inlet temperature [K] | K | |
T_out_start | Initial air outlet temperature [K] | K | |
Xi_in_start | Initial air inlet water-vapor mass fraction [-] | – | |
Xi_out_start | Initial air outlet water-vapor mass fraction [-] | – | |
Q_start | Initial air-side heat flow per element [W] | W | |
eta_fin_start | Initial fin efficiency [-] | – | |
h_in_start | Initial air inlet specific enthalpy [J/kg] | J/kg | |
h_out_start | Initial air outlet specific enthalpy [J/kg] | J/kg | |
mcond_flow_start | Initial condensate mass flow [kg/s] | kg/s | |
d_mean_start | Initial mean air density [kg/m^3] | – | |
Q_water_start | Initial heat flow carried by condensate [W] | W | |
cp_mean_start | Initial mean specific heat capacity of moist air [J/(kg.K)] | – | |
medium_data | Moist-air medium properties | – | |
A | Air-side free-flow cross-sectional area [m^2] | – | |
d0 | Tube outer diameter [m] | – | |
delta | Fin thickness [m] | – | |
S_t | Transverse tube spacing [m] | – | |
S_l | Longitudinal tube spacing [m] | – | |
At_tube | Bare-tube surface area per tube [m^2] | – | |
Af_tube | Fin surface area per tube [m^2] | – | |
kfin | Fin thermal conductivity [W/(m.K)] | – | |
Ka | Air-side pressure-drop constant [Pa/(kg/s)] used as p_loss = m_flow / A * Ka | – | |
k_mair | Ratio of steam to dry-air molar mass used in the humidity-ratio conversion [-] | – | |
Qdot_lat_start | Initial latent heat flow [W] (solver guess) | – | |
Qdot_sens_start | Initial sensible heat flow [W] (solver guess; should track total Q_start for consistency) | – | |
xsat_w_start | Initial wall-side saturation humidity ratio [-] (solver guess) | – | |
eta_start | Initial air dynamic viscosity [Pa.s] (solver guess) | – | |
psat_w_start | Initial wall-side saturation pressure [Pa] (solver guess) | – | |
psat_w_1K_start | Initial wall-side saturation pressure 1 K below the wall temperature [Pa] (solver guess) | – | |
xsat_w_1K_start | Initial wall-side saturation humidity ratio 1 K below the wall temperature [-] (solver guess) | – | |
der_xsat_w_dT_start | Initial derivative of saturation humidity ratio with respect to temperature [1/K] (solver guess) | – | |
mtc_start | Initial mass-transfer coefficient [kg/(m^2.s)] (solver guess) | – | |
dgradient_start | Initial humidity-ratio gradient driving condensation [-] (solver guess) | – | |
heff_start | Initial effective heat-transfer coefficient including fin efficiency [W/(m^2.K)] (solver guess) | – | |
rho_constant | Constant air density used in the Lewis-analogy mass-transfer calculation [kg/m^3] | – |
Connectors ​
port_a- (MoistAirFluidPort)port_b- (MoistAirFluidPort)heatPorts- This connector represents a thermal port with temperature and heat flow as the potential and flow variables, respectively. (HeatPort)
Variables ​
| Name | Description | Units |
|---|---|---|
p | Air-side pressure used internally (= medium_inflow.p = port_a.p) [Pa] | Pa |
T | Air temperature at each face [K] (length N+1) | K |
H_flow | Enthalpy flow at each face [W] (length N+1) | – |
mdot | Dry-and-vapor mass flow at each face [kg/s] (length N+1) | kg/s |
mXi_flow | Water-vapor mass flow at each face [kg/s] (length N+1) | – |
Q_flow | Sensible-plus-latent heat flow into each cell [W] (length N) | W |
mcond_flow | Condensate mass flow leaving each cell [kg/s] (length N) | – |
p_loss | Air-side pressure drop port_a - port_b [Pa] | Pa |
d_mean | Mean air density used in mass-transfer scaling [kg/m^3] | – |
Q_water | Heat flow carried out with the condensate [W] | W |
cp_mean | Mean specific heat capacity of moist air [J/(kg.K)] | – |
T_in | Air inlet temperature [K] (alias for medium_inflow.T at port_a) | K |
T_out | Air outlet temperature [K] (alias for medium_outflow.T at port_b) | K |
eta_fin | Fin efficiency per cell [-] (length N); extender supplies | – |
Qdot_lat | Latent heat flow per control volume [W] (length N) | – |
Qdot_sens | Sensible heat flow per control volume [W] (length N) | – |
xsat_w | Saturation humidity ratio at wall temperature [-] (length N) | – |
eta | Air dynamic viscosity [Pa.s] (length N) | – |
psat_w | Saturation pressure at wall temperature [Pa] (length N) | – |
psat_w_1K | Saturation pressure 1 K below wall temperature [Pa] (length N) | – |
xsat_w_1K | Saturation humidity ratio 1 K below wall temperature [-] (length N) | – |
der_xsat_w_dT | Numerical derivative of saturation humidity ratio with respect to temperature [1/K] (length N) | – |
mtc | Mass-transfer coefficient [kg/(m^2.s)] (length N) | – |
dgradient | Humidity-ratio gradient driving condensation [-] (length N; negative means condensation) | – |
heff | Effective heat-transfer coefficient blending sensible and latent contributions [W/(m^2.K)] (length N) | – |