Honeywell MS4103 manual When sizing steam jet humidifier valves, Simplifying, Fices use, 259

Appendix A: Valve Selection and Sizing

NOTE: The scaling constant 1.08 is derived as follows:

1.08 =	0.24-----------BTU---------------⋅ 60---min--------- ⋅		---1---lbair--------------
Where:	lbairF	1hr	13.35ft3
1lbair	= the specific volume of air at standard
13.35--------------ft----3--
	conditions of temperature and

atmospheric pressure.

Simplifying the equation:

14.40Btumin

1.08= ---------------------------------

3

Fhr13.35ft

To find the scaling constant for air conditions other than standard, divide 14.40 Btu by specific volume of air at those conditions.

3.For sizing steam to hot water converter valves: Q = gpm ⋅ TDw ⋅ 0.49

Where:

gpm = Gallons per minute of water flow through converter.

TDw = Temperature difference of water entering and leaving the converter.

0.49= A scaling constant. This value is derived as follows:

0.49 =	8.33-----------lbwater-------------------- ----⋅ 60---min--------- ---⋅ 1-lbsteam---------------------- ⋅			-----------------------1Btu
	1gal	1hr	1000Btu	lb water F

Simplifying the equation:

0.49minlbsteam

0.49= --------------------------------------------

galhrF

4.When sizing steam jet humidifier valves:

(W1 – W2)lbmoisture			⋅	1	⋅	ft3	⋅	60min
Q = ----------------------------------------------------------		lbair		--------------------13.35ft3		min---------		----------------hr
				--------------------
				lbair
Where:
W1	=	Humidity ratio entering humidifier, pounds
		of moisture per pound of dry air.
W2	=	Humidity ratio leaving humidifier, pounds
		of moisture per pound of dry air.
13.35ft3		= The specific volume of air at standard
--------------------lbair
		conditions of temperature and
		atmospheric pressure.
ft3	=	Cubic feet per minute (cfm) of air from the
min---------
		fan.
60----------------min=		A conversion factor.
hr

Simplifying:

Q = 4.49	(W1 – W2)lbmoisture
	----------------------------------------------------------hr

5. When Equivalent Direct Radiation (EDR) is known: Q = EDR(Total) ⋅ 0.24

Where:

EDR (Total)=Radiators are sized according to Equivalent Direct Radiation (EDR). If controlling several pieces of radiation equipment with one valve, add the EDR values for all pieces to obtain the total EDR for the formula.

0.24= A scaling constant, lb steam/unit EDR. See Table 4.

Table 4. Output of Radiators and Convectors.

Average Radiator of	Cast Iron Radiator	Convector, Btu/
Convector
Temperature, Deg F	Btu/Hr/EDRa	Hr/EDRb
215	240	240
200	209	205
190	187	183
180	167	162
170	148	140
160	129	120
150	111	102
140	93	85
130	76	69
120	60	53
110	45	39
100	31	27
90	18	16

a At Room Termperature

b At 65 F Inlet Air Temperature

STEAM VALVE PRESSURE DROP

Proportional Applications

When specified, use that pressure drop (h) across the valve.

When not specified:

1.Calculate the pressure drop (h) across the valve for good modulating control:

		h = 80% x (Pm-Pr)
NOTE:	For a zone valve in a system using radiator ori-
	fices use:
		h = (50 - 75)% x (Pm-Pr)
Where
Pm	=	Pressure in supply main in psig or psia
		(gage or absolute pressure).
Pr	=	Pressure in return in psig or psia. A

APPENDIX

259