.Buildings.Fluid.HeatExchangers.DryCoilDiscretized

Information

Model of a discretized coil with no water vapor condensation. The coil consists of nReg registers that are perpendicular to the air flow path. Each register consists of nPipPar parallel pipes, and each pipe can be divided into nPipSeg pipe segments along the pipe length. Thus, the smallest element of the coil consists of a pipe segment. Each pipe segment is modeled by an instance of Buildings.Fluid.HeatExchangers.BaseClasses.HexElementSensible. Each element has a state variable for the metal.

If the parameter energyDynamics is different from Modelica.Fluid.Types.Dynamics.SteadyState, then a mixing volume of length dl is added to the duct connection. This can help reducing the dimension of the nonlinear system of equations.

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.

In this model, the water (or liquid) flow path needs to be connected to port_a1 and port_b1, and the air flow path need to be connected to the other two ports.

To model humidity condensation, use the model Buildings.Fluid.HeatExchangers.WetCoilDiscretized instead of this model, as this model computes only sensible heat transfer.

Implementation

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.

Revisions


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