.Buildings.DHC.Plants.Combined.Subsystems.ChillerGroup .Buildings.DHC.Plants.Combined.Subsystems.ChillerGroupThis model represents a set of identical water-cooled compression chillers that are piped in parallel. Modulating isolation valves are included on condenser and evaporator side.
The following input and output points are available.
y1:
DO signal dedicated to each unit, with a dimensionality of one
TSet:
AO signal common to all units, with a dimensionality of zero
yVal(Con|Eva):
AO signal dedicated to each unit, with a dimensionality of one
T(Con|Eva)Lvg:
AI signal dedicated to each unit, with a dimensionality of one
m(Con|Eva)_flow:
AI signal dedicated to each unit, with a dimensionality of one
In a parallel arrangement, all operating units have the same operating point, provided that the isolation valves are commanded to the same position. This allows modeling the heat transfer through the condenser and evaporator barrel with a single instance of Buildings.Fluid.Chillers.ElectricReformulatedEIR. Hydronics are resolved with mass flow rate multiplier components in conjunction with instances of Buildings.DHC.Plants.Combined.Subsystems.BaseClasses.MultipleValves which represent the parallel network of valves and fixed resistances.
By default, linear valve models are used. Those are configured with a pressure drop varying linearly with the flow rate, as opposed to the quadratic dependency usually considered for a turbulent flow regime. This is because the whole plant model contains large nonlinear systems of equations and this configuration limits the risk of solver failure while reducing the time to solution. This has no significant impact on the operating point of the circulation pumps when a control loop is used to modulate the valve opening and maintain the flow rate or the leaving temperature at setpoint. Then, whatever the modeling assumptions for the valve, the control loop ensures that the valve creates the adequate pressure drop and flow, which will simply be reached at a different valve opening with the above simplification.