Detailed Two-Way Valve-Calculates Pressure
by M. Brandemuehl
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 calculates the pressure drop through a two-way valve
or damper as a function of the mass flow rate and the valve or damper position
for given physical characteristics.  The algorithm calculates the outlet 
pressure from the inlet pressure, flow rate and valve position given the 
nominal flow resistance through the open valve, a parameter that describes the
valve characteristic and a leakage parameter.  The algorithm nominally 
calculates outlet pressure from inlet pressure and flow by using a negative 
value for the flow and substituting the leaving pressure as the subroutine 
input pressure.  The resulting subroutine output pressure will be the pressure
entering the valve.  Component 1213 calculates the flow rate given entering 
and leaving pressure for a two-way valve or damper.  Component 1214 calculates
the entering fluid pressures for a 3-way mixing valve or damper.  Component 
1215 calculates flow rates for a 3-way mixing valve or damper given the entering
and leaving pressures.  Sample input and output 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