Honeywell AUTOMATIC CONTROL SI Edition User Manual

ENGINEERING MANUAL OF AUTOMATIC CONTROL
VALVE SELECTION AND SIZING
438
REPRINTED BY PERMISSION FROM ASHRAE HANDBOOK—
1996 HVAC SYSTEMS AND EQUIPMENT
Fig. 15. Pressure Drop Correction for
Propylene Glycol Solutions.
QUANTITY OF WATER
To find the quantity of water (Q) in cubic meters per hour
use one of the following formulas:
1. When heat flow rate is known:
Where:
watts = Heat flow rate.
∆T
w
= Temperature difference of water entering
and leaving the coil.
S = Value from Table 3; based on temperature of
water entering the coil.
Table 3. Water Flow Formula Table.
2. For hot water coil valves:
Where:
m
3
/s = Airflow through the coil.
1202.4 = A scaling constant.
∆Ta = Temperature difference of air entering and
leaving the coil.
S = Value from Table 3; based on temperature of
water entering the coil.
∆T
w
= Temperature difference of water entering
and leaving the coil.
3. For fan system chilled water coil valves:
Q=
watts
S • ∆T
w
Where:
m
3
/s = Airflow through the coil.
Heat removed =Heat per kilogram of dry air removed in kJ/
kg. Includes both sensible and latent heat.
1.02 = A scaling constant.
∆T
w
= Temperature difference of water entering
and leaving the coil.
WATER VALVE PRESSURE DROP
To determine valve pressure drop:
1. For two-way valves consider the following guidelines for
valve pressure drop:
a. Include the pressure drop in the design of the
water circulating system.
— In systems with two-way valves only, it is often
necessary to provide a pump relief bypass or
some other means of differential pressure
control to limit valve pressure drops to the
valve capabilities. For control stability at light
loads, pressure drop across the fully closed
valve should not exceed triple the pressure drop
used for sizing the valve.
— To avoid high pressure drops near the pump,
reverse returns are recommended in large
systems.
Q=
1202.4
S
•
m
3
s
•
∆Ta
∆Tw
-20 -10 0 10 20 30 40 50 60 70
PRESSURE DROP CORRECTION FACTOR
TEMPERATURE, °C
M15320
0.8
0.9
1.1
1.3
1.5
1.0
1.2
1.4
1.6
PROPYLENE GLYCOL SOLUTION
WATER
10%
20%
30%
40%
50% BY MASS
Water
Temp °CS
Water
Temp °CS
20
30
40
50
60
75
90
1158
1154
1150
1145
1141
1134
1128
105
120
135
150
165
180
200
1121
1114
1108
1101
1094
1088
1080
Q = 1.02
m
3
s
•
Heat removed
∆Tw

Honeywell AUTOMATIC CONTROL SI Edition Specifications

General

Brand	Honeywell
Model	AUTOMATIC CONTROL SI Edition
Category	Control Systems
Language	English