Detailed Three-Way Mixing Valve - Calculates Flow Rates
By M. Brandemuehl
Revised for TRNSYS by N. Blair and R. Schwarz

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

	This subroutine determines the flow rates for a three-way mixing valve
or damper as a function of fluid pressures and the valve or damper position for
given physical characteristics.  The algorithm calculates the flow rate at each
port 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 characteristic, and a leakage parameter for each port.  The algorithm 
nominally calculates entering fluid flow rates at each port for a mixing valve
assuming that the two entering pressures are greater than the leaving pressure.
In addition, it may also be employed to model a diverting valve with a single
fluid input and two fluid outputs, calculating the flow rate at each port.  If
the "leaving" pressure is greater that the "entering" pressures, the flow rates
will be negative and the valve will behave as a diverting valve.  Component
1212 calculates the pressure for a two way valve.  Component 1213 calculates the
flow rate for a two-way valve.  Component 1214 calculates the pressure for a 
three-way mixing valve or damper.  Sample input and output values are located
in 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