Component 206:  Steam Spray Humidifier by HVACSIM+

General Description
	The steam spray humidifier model calculates an outlet air temperature, 
flow rate, and humidity ratio for a constant pressure process in which steam is
injected into an air flow stream to increase the humidity of the air.  The 
outlet air humidity ratio is limited either by the steam flow rate or by the 
saturation humidity ratio (at atmospheric pressure) times a saturation 
efficiency.  The mass flow rate of the air increases slightly due to the 
addition of moisture.

Nomenclature
	Cpa - specific heat of dry air (kJ / kg-K)
	Cpai - specific heat of moist inlet air (kJ / kg-K)
	Cps - specific heat of steam or water vapor (kJ / kg-K)
	Patm - atmospheric pressure (101.325 kPa)
	Tai - temperature of inlet air (C)
	Tao - temperature of outlet air (C)
	Ts - temperature of inlet steam (C)
	wai - mass flow rate of moist inlet air (kg/s)
	wao - mass flow rate of moist outlet air (kg/s)
	ws - mass flow rate of inlet steam (kg/s)
	n - saturation efficiency ( - )
	Hai - inlet air humidity ratio (kg water / kg dry air)
	Hao - outlet air humidity ratio (kg water / kg dry air)
	Haos - saturation humidity ratio (kg water / kg dry air)

Mathematical Description
	The inlet air specific heat depends on the inlet air humidity ratio:
	Cpai = (Cpa + Hai*Cps) / (1 + Hai)
where Cpa is the specific heat of dry air and Cps is the specific heat of steam
or water vapor.  The air outlet temperature is a weighted average of the inlet 
air and steam temperatures:
	Tao = (ws*Cps*Ts + wai*Cpai*Tai) / (ws*Cps + wai*Cpai)
Assuming that all of the entering steam is absorbed by the air, the outlet 
humidity ratio is
	Hao = Hai + ws*(1 + Hai) / wai
The saturation humidity ratio at the outlet temperature is calculated next, 
using the subprogram PSATS described in Chapter 3 to find the saturation 
pressure at the outlet temperature.  The constant in the following equation is 
the ratio of water to air molecular weights.
	Haos = (0.62198*PSATS(Tao)) / (Patm - PSATS(Tao))
where Patm is 101.325 kPa.  The outlet humidity ratio, Hao, cannot exceed the 
saturation efficiency times the outlet humidity ratio at saturation, n*Haos:
	Hao = min(Hao, n*Haos)

Component 206 Configuration
	Inputs		Description
	1	Ts	- steam temperature (C)
	2	Tai	- inlet air temperature (C)
	3	Hai	- inlet air humidity ratio ( - )
	4	wai	- inlet air mass flow rate (kg/s)
	5	ws	- steam mass flow rate (kg/s)
	Outputs		Description
	1	Tao	- outlet air temperature (C)
	2	wao	- outlet air mass flow rate (kg/s)
	3	Hao	- outlet air humidity ratio ( - )
	Parameters	Description
	1	n	- saturation efficiency

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