ThreeWayValve¶
Mixing valve: the share y of the outlet flow comes from port_1 (supply), 1 - y from port_3 (set flows), or Buildings.Fluid.Actuators.Valves.ThreeWayEqualPercentageLinear, linearized: port_1 equal-percentage on y, port_3 linear on 1 - y (pressure-driven flows)
FastSmoothBuildings.Hydronics.ThreeWayValve, model (source)
Purpose
Mixing valve: the outlet port_2 takes water from the supply inlet port_1 and from the
bypass inlet port_3, in the share set by y. The connections of each inlet mix first, at
T1 and T3, as the inlets of
PartialFlow do (weighted by the positive parts
of their flows with pressure-driven flows).
Set flows and pressure-driven flows
With set flows, y is the share of the supply in the outlet flow ṁ:
ṁ1 = y ṁ, ṁ3 = (1 − y) ṁ, T2 = y T1 + (1 − y) T3,
the outlet flow being set downstream, and the pressures p1, p3 are 0.
With pressure-driven flows, y is the opening of the supply path, limited to [0, 1] by smoothLimit (ys). Each path has the conductance of valveConductance with its fixed resistance in series:
| Path | Characteristic | Pressure drop of the open path | Fixed resistance |
|---|---|---|---|
supply, port_1 |
equalPercentage(ys,
R, l[1], delta0) |
dpValve_nominal | dpFixed_nominal[1] |
bypass, port_3 |
l[2] + (1 − ys) (1 − l[2]) |
dpValve_nominal/fraK2 | dpFixed_nominal[2] |
Each inlet is a pressure node of small compliance, the outlet takes the mean pressure p2 of the nodes downstream:
ṁ1 = G1 (p1 − p2), ṁ3 = G3 (p3 − p2),
τhyd G1,nom dp1/dt =
∑ port_1.m_flow − ṁ1,
τhyd G3,nom dp3/dt =
∑ port_3.m_flow − ṁ3,
with G1Nom and G3Nom the conductances of the open paths. The outlets share
ṁ1 + ṁ3 evenly and leave at the temperature mixed with the
positive parts of the two path flows (positivePart with 10−5 kg/s).
Parameters
fraK: Kv of the bypass path relative to the supply path; the open bypass dropsdpValve_nominal/fraK2 at the nominal flow.l: leakages of the supply and bypass paths.
Relation to Buildings
Buildings.Fluid.Actuators.Valves.ThreeWayEqualPercentageLinear, its flow laws linearized: the supply
path equal-percentage in y, the bypass path linear in 1 − y.
Parameters¶
| Parameter | Type | Unit | Default | Description |
|---|---|---|---|---|
| nPorts_1 | Integer | 1 | Number of connections of the supply inlet | |
| nPorts_2 | Integer | 1 | Number of connections of the outlet | |
| nPorts_3 | Integer | 1 | Number of connections of the bypass inlet | |
| m_flow_nominal | Real | kg/s | 1 | Nominal flow |
| m_flow_small | Real | kg/s | 1e-6 | |
| pressureDriven | Boolean | false | true: flows from the pressures of the circuit | |
| tauHyd | Real | s | 5 | Time constant of the pressure of the inlet nodes |
| dpValve_nominal | Real | Pa | 6000 | Pressure drop of the open path at the nominal flow |
| dpFixed_nominal | Real | Pa | {0, 0} | Pressure drops in series with port_1 and port_3 |
| fraK | Real | 0.7 | Kv of the bypass path relative to the supply path | |
| R | Real | 50 | Rangeability | |
| l | Real | {0.01, 0.01} | Leakages of the supply and bypass paths | |
| delta0 | Real | 0.01 | Linear range of the characteristic near closure | |
| G1Nom | Real | kg/(s.Pa) | m_flow_nominal/(dpValve_nominal + dpFixed_nominal[1]) | Conductance of the open supply path |
| G3Nom | Real | kg/(s.Pa) | m_flow_nominal/(dpValve_nominal/fraK^2 + dpFixed_nominal[2]) | Conductance of the open bypass path |
Revisions¶
- October 2026: moved from trano's
FastModel.Hydronics.