Component 208: Flow Merge by HVACSIM+
General Description
This component models the merging of two flow streams. It calculates
the mass flow rate and temperature of the single outlet flow stream, and the
pressures at the two inlets. The model assumes that the flow resistance
parameter is the same for all three branches.
Nomenclature
K - flow resistance coefficient
P - pressure
T - temperature
w - mass flow rate of fluid
Subscripts
1 - first inlet
2 - second inlet
3 - outlet
Mathematical Description
The outlet mass flow rate is simply the sum of the inlet flow rates:
w3 = w1 + w2
The outlet temperature is a weighted average of the inlet temperatures:
T3 = (w1*T1 + w2*T2)/w3
Inlet pressures are calculated from the outlet pressure, the flow rates, and
the flow resistance coefficient:
P1 = P3 + (K/2)*[sign(w1)*w1^2 + sign(w3)*w3^2]
P2 = P3 + (K/2)*[sign(w2)*w2^2 + sign(w3)*w3^2]
Component 508 Configuration
Inputs Description
1 w1 - flow rate at first inlet
2 w2 - flow rate at second inlet
3 P3 - pressure at outlet
4 T1 - temperature at first inlet
5 T2 - temperature at second inlet
Outputs Description
1 w3 - flow rate at outlet
2 P1 - pressure at first inlet
3 P2 - pressure at second inlet
4 T3 - temperature at outlet
Parameters Description
1 K - flow resistance coefficient
Reference:
1. HVACSIM+ Building Systems and Equipment Simulation Program Reference
Manual (NBSIR 84-2996)
Daniel R. Clark
United States Department of Commerce
National Institute of Standards and Technology
Gaithersburg, Maryland 20899-0001