.BuildingSystems.Fluid.HeatExchangers.BaseClasses.WetCoilDryWetRegime

Information

This model implements the switching algorithm for the dry and wet regime.

The switching criteria for (counter-flow) cooling coil modes are as follows.

R1: If the coil surface temperature at the air inlet is lower than the dew-point temperature at the inlet to the coil, then the cooling coil surface is fully-wet.

R2: If the surface temperature at the air outlet section is higher than the dew-point temperature of the air at the inlet, then the cooling coil surface is fully-dry.

At each point of a simulation time step, the fuzzy-modeling approach determines the weights for R1 and R2 respectively (namely μ_FW and μ_FD) from the dew-point and coil surface temperatures.

It calculates total and sensible heat transfer rates according to the weights as follows.

Q̇_tot=μ_FD Q̇_tot,FD+μ_FW Q_tot,FW

Q̇_sen=μ_FD Q̇_sen,FD+μ_FW Q_sen,FW

The fuzzy-modeling ensures μ_FW + μ_FD = 1, μ_FW >=0 and μ_FD >=0, which means the fuzzy model outcomes of Q̇_sen and Q̇_tot are always convex combinations of heat transfer rates for fully-dry and fully-wet modes and therefore are always bounded by them.

The modeling approach also results in n-th order differentiable model depending on the selection of the underlying membership functions. This cooling coil model is once continuously differentiable at the mode switches.

Revisions

• Jan 21, 2021, by Donghun Kim:
  First implementation.