Component 209:  Flow Split by HVACSIM+

General Description
	This component models the division of a flow stream into two flow 
streams.  It calculates the mass flow rates at the two outlets, and the 
pressure at the single inlet.  The model assumes that the flow resistance 
parameter is the same for all three branches.  Care has been taken to ensure 
that correct results are obtained even when the flow direction of one or more 
flow streams is reversed.

Nomenclature
	K - flow resistance coefficient
	P - pressure
	w - mass flow rate

Subscripts
	0 - center of component
	1 - inlet
	2 - first outlet
	3 - second outlet

Mathematical Description
	The model is derived from the following set of equations:
	P1 - P0 = 0.5*K*sign(w1)*w1^2
	P0 - P2 = 0.5*K*sign(w2)*w2^2
	P0 - P3 = 0.5*K*sign(w3)*w3^2
	w1 = w2 + w3
where P0 is the pressure at the center of the component and 0.5*K is the flow 
resistance between the center and an inlet or outlet.  The set of equations is
solved for w2 and w3, and the solution is expressed in the following form:
	w2 = (w1 / 2) + [sign(w1)]*DeltaP / (K*w1)		     if S >= 0.
	w2 = (w1 / 2) + [sign(DeltaP)]*[abs(DeltaP)/K - w1^2/4]^0.5  if S < 0.
where
	DeltaP = P3 - P2
and
	S = w1^2 - 2*abs(DeltaP)/K
	w3 = w1 - w2
When S is positive, all three flow rates have the same sign, and w1 represents
the single inlet (positive) or outlet (negative) flow rate of a split or merge.
When S is negative, w2 and w3 do not have the same sign, and w1 represents one
of two inlets (w1 positive) or outlets (w1 negative).  The pressure at the 
nominal inlet, P1, is then calculated:
	P1 = P3 + (K/2)*[sign(w1)*w1^2 + sign(w3)*w3^2]

Component 509 Configuration
	Inputs		Description
	1	w1	- flow rate at inlet
	2	P2	- pressure at first outlet
	3	P3	- pressure at second outlet
	Outputs		Description
	1	w2	- flow rate at first outlet
	2	w3	- flow rate at second outlet
	3	P1	- pressure at inlet
	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