Model of a discretized coil without water vapor condensation.
The coil consists of two flow paths which are, at the design flow direction,
in opposite direction to model a counterflow heat exchanger.
The flow paths are discretized into nEle
elements.
Each element is modeled by an instance of
Buildings.Fluid.HeatExchangers.BaseClasses.HexElementSensible.
Each element has a state variable for the metal.
The convective heat transfer coefficients can, for each fluid individually, be computed as a function of the flow rate and/or the temperature, or assigned to a constant. This computation is done using an instance of Buildings.Fluid.HeatExchangers.BaseClasses.HADryCoil.
To model humidity condensation, use the model Buildings.Fluid.HeatExchangers.WetCoilCounterFlow instead of this model, as this model computes only sensible heat transfer.
At very small flow rates, which may be caused when the fan is off but there is wind pressure
on the building that entrains outside air through the HVAC system, large temperature differences
could occur if diffusion were neglected.
This model therefore approximates a small diffusion between the elements to have more uniform
medium temperatures if the flow is near zero.
The approximation is done using the heat conductors heaCon1
and heaCon2
.
As this is a rough approximation, neighboring elements are connected through these heat conduction
elements, ignoring the actual geometrical configuration.
Also, radiation between the coil surfaces on the air side is not modelled explicitly, but
rather may be considered as approximated by these heat conductors.
T_m
to avoid using the conditionally
enabled model ele[:].mas.T
, which is only
valid in a connect statement.
Moved assignments of
Q1_flow
, Q2_flow
, T1
,
T2
and T_m
outside of equation section
to avoid mixing graphical and textual modeling within the same model.
initialize_p1
and initialize_p2
.
This is required to enable the coil models to initialize the pressure in the
first volume, but not in the downstream volumes. Otherwise,
the initial equations will be overdetermined, but consistent.
This change was done to avoid a long information message that appears
when translating models.
energyDynamics1
and energyDynamics2
,
and used instead of these two parameters the new parameter energyDynamics
.
This was done as this complexity is not required.
dp2_nominal
.
The previous assignment caused a pressure drop in all except one element,
instead of the opposite. This caused too high a flow resistance
of the heat exchanger.
show_T=false
to avoid state events near zero flow.