ASHRAE Journal - February 2024 - 58

TECHNICAL FEATURE
FIGURE 6 Plot showing trend lines of pressure difference across a cold plate for
all test liquids at accelerated degradation.
Pressure Difference vs. Time
4
3.5
3
2.5
2
1.5
1
0.5
Time (h)
liquids, respectively. PG-25 had the least reduction of
4.2% and 3.8% in both sets, while PG-55 had the highest
reduction of 54.8% and 13.5%. EG-25 showed a reduction
of 12.47% and 2.7%, while EG-55 had reductions of 12.9%
and 8.2% in Set I and Set II, respectively.
ORP values indicate a liquid's potential to oxidize
Linear (PG-25)
Linear (PG-55)
Linear (EG-55)
Linear (EG-25)
FIGURE 7 Variation of pH values for test liquids kept at stagnation condition.
pH vs. Time
12
11.5
11
10.5
10
9.5
0 25 50 75 100 125 150 175 200 225 250 275
Time (h)
PG-55
PG-25
EG-25
EG-55
metal surfaces; higher ORP values indicate increased
oxidation reactions. Online Figure 8 shows ORP changes
for Set I test liquids (those under stagnated conditions),
and Online Figure 9 shows ORP changes for Set II liquids
with immersed wetted materials. PG-55 had the least
ORP increase, while PG-25 had the highest. EG-55 and
EG-25 had 50 mV to 51 mV increases. In the presence of
wetted materials, PG-25 had the highest ORP increase
(120 mV), and EG-25 had the least change (23 mV).
PG-55 and EG-55 had ORP increases of 93.8 mV and
83 mV, respectively.
Variation II
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In this set of experiments, the liquids were kept inside
an airtight jar for the same amount of time as in Set I,
and only the initial and final readings were measured
to avoid exposure of the liquid to the surrounding
atmosphere. This can give us the comparison of liquid
chemistry that was never in contact with air and that
was exposed to the outside air.
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58
ASHRAE JOURNAL ashrae.org F E B R U A RY 2 0 2 4
In stagnated conditions, liquids concealed from
outside air have better noncorrosive properties. In Set I,
the pH values of liquids increased by their base value
when compared to those immersed in wetted materials.
Without wetted materials, EG-25 and PG-25 showed
2.17% and 1.62% increases in pH value, respectively.
PG-55 had the least increase of 0.39%, and EG-55 had a
1.35% increase in pH value (Figure 8).
Online Figure 10 shows the pH values for wetted
materials immersed. Only EG-25 had an increase in pH
value, of 0.087%. The other liquids had a decrease, with
EG-55 showing the highest decrease at 2.57%, followed
by PG-55 at 2.07% and PG-25 at 0.77%.
Online Figure 11 shows that for Set I, the highest change
was in EG-55 with a 2.62% increase in conductivity value
and PG-55 with a 2.23% increase in conductivity value.
The other two liquids, EG-25 and PG-25, had the same
Pressure Differrence (KPa)
1
8
15
22
29
36
43
50
57
64
71
78
85
92
99
106
113
120
127
134
141
148
155
162
169
176
183
190
197
pH
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ASHRAE Journal - February 2024

Table of Contents for the Digital Edition of ASHRAE Journal - February 2024
