Detailed Two-Way Valve - Calculates Flow Rate
By S. Gabel
Revised for TRNSYS by N. Blair and R. Schwarz

      	This model was adapted strictly for use with the TRNSYS Program by
the Solar Energy Laboratory.

	This subroutine determines the flow rate through a valve or damper as a 
function of the pressures and the valve or damper position for given physical 
characteristics.  The algorithm calculates the mass flow rate from the entering
and leaving fluid pressures and valve position given the nominal flow resistance
through the open valve, a parameter that describes the valve characteristics and
a leakage parameter.  Component 1212 calculates pressure given the flow rate
for a 2-way valve or damper.  Component 1214 calculates the entering fluid 
pressures for a 3-way mixing valve or damper given the leaving pressure and the 
flow rates through the two ports.  Component 1215 calculates the flow rates for
a 3-way mixing valve or damper given the entering and leaving pressures.
Sample inputs and outputs are included with the source code.

REF: A Toolkit for Secondary HVAC System Energy Calculations  May 25, 1992
     Joint Center for Energy Management  University of Colorado at Boulder