This block computes the predicted heat exchanger leaving water temperature as used in Buildings.DHC.ETS.Combined.Controls.WatersideEconomizer.
The predicted heat exchanger approach is computed as
dTApp = dTApp_nominal * m2_flow / m2_flow_nominal.
Which gives the predicted heat exchanger leaving water temperature as
T2WatLvg = T1WatEnt + dTApp.