Johnson Controls York YCRL0064, Installation Operation & Maintenance

Page: 49 / 162

JOHNSON CONTROLS
49
SECTION 5 – TECHNICAL DATA
FORM 150.27-NM1
ISSUE DATE: 09/30/2015
55
ETHYLENE AND PROPOLYNE GLYCOL
CORRECTION FACTORS
Evaporator Pressure Drop
When using evaporator pressure drop to determine flow,
error may result due to actual pressure drops that are be-
low the published data. In all cases, the published values
are worst case values. Errors of 10 to 25% below pub-
lished values are not uncommon due to manufacturing
differences. When attempting to operate with flow near
the high end of the pressure drop curve, always use a
flowmeter to avoid excessive flow through the evapora-
tor, which will cause damage and premature failure.
Table 8 on page 49 lists glycol correction factors
that should be used in conjunction with pressure drops.
Pressure drop will increase at a given flow rate as the
glycol concentration is increased.
TABLE 8 - ETHYLENE AND PROPOLYNE GLYCOL
CORRECTION FACTORS
ETHYLENE GLYCOL
%
WEIGHT TONS
COMPR
KW
GPM
PRESS
DROP
FREEZE
PT
10 0.993 1.002 1.029 1.095 26
20 0.98 1.004 1.04 1.191 18
30 0.964 1.007 1.055 1.302 7
40 0.945 1.009 1.071 1.435 -8
50 0.922 1.013 1.091 1.599 -29
PROPYLENE GLYCOL
%
WEIGHT TONS
COMPR
KW
GPM
PRESS
DROP
FREEZE
PT
10 0.985 1.002 1.003 1.078 26
20 0.968 1.005 1.000 1.157 19
30 0.937 1.008 0.992 1.266 9
40 0.898 1.012 0.982 1.414 -6
50 0.862 1.019 0.985 1.605 -28
TABLE 9 -
RECOMMENDED GLYCOL SOLUTION
STRENGTHS
ETHYLENE
GLYCOL
LCHLT °C
PROPYLENE
GLYCOL
CONCENTRATION
% W/W
CONCENTRATION
% W/W
6 5 5
4 12 13
2 18 20
0 23 25
-2 28 30
-4 32 34
-6 35 38
Pressure drop across the evaporator should only be
used as a guide for setting up flow. When very accu-
rate flows need to be measured, use a flowmeter. When
gauges are used to measure pressure drop and calculate
flow, always use a single gauge to measure the pressure
drop at both inlet and outlet of the evaporator to avoid
introducing more error into the measurement resulting
from the use of two gauges.
The cooler design allows for an increase
in pressure drop of up to 15% above the
design value given. Debris in the water
may also cause additional pressure drop.
When using glycol solutions, pressure
drops are higher than with water. Spe-
cial care must be taken not to exceed the
maximum allowed.
LD06934
ETHYLENE GLYCOL
PROPYLENE GLYCOL
B
A
C
B
A
C
A = Correction Factor B = Temperature
C = Concentration % Through Cooler
FIGURE 15 - GLYCOL SOLUTION STRENGTHS