Brochure

11
Better Performance with PICV
Off Coil Air Temperature
Relative Flow Control Relative Power Output from Coils
The impact of replacing a traditional pressure dependent globe valve with a PICV on the AHU in the South portion of
the building is apparent again. The graphs below show the chilled water differential temperature. Shown in the right
chart, while operating the system with a globe valve, the chilled water differential temperature is much lower, roughly
around 5˚C or 10˚F.
The same system when outfitted with a PICV, shows a gain in water differential temperature at about 8˚C or 14˚F,
giving a 4˚F difference in differential temperature. Naturally, this also impacts the overall flow capacity needed to deliver
the same relative cooling in this study, conducted over a 4 week period.
0%
20%
40%
60%
80%
100%
120%
140%
160%
% Cooling Output
0
10 20 40 60
Time (Minutes)
12.4
12.3
12.2
12.1
12.0
11.9
11.8
11.7
11.6
Temperature °C
0
10 20 40 60
Time (Minutes)
160%
140%
120%
100%
80%
60%
40%
20%
0%
% Flow
0
10 20 40 60
Time (Minutes)
Naturally, all three charts are interdependent of one another so the measured performance, whichever you choose to
look at, shows that the PICV does provide better stability and heat transfer performance within the system during
operation. This also leads to a predicted outcome regarding delta-T.
These three charts below capture the significant difference
in performance between the pressure dependent globe
valve and the PICV.
While monitoring the off coil air temperature (supply air
temperature), the globe valves show overshooting and
undershooting during the time period where data was
captured. Peaks and valleys of the over/undershoot were
50% greater than those of the PICV in the same timeframe.
In this middle chart, the impact PICV will have on the
relative flow control of the circuit compared to globe valves is
apparent. There is a much tighter spread in flow percentages
right around the desired levels compared to the globe valve.
Over/undershoots are also much smaller in comparison with
smaller times of adjustment between periods
The chart on the right shows the power output from
the coils when using the two different valves. The coil
performance is much more consistent when using the
PICV compared to the globe valve.
Impacts to Delta-T
South Globe Valve Delta-T
South PICV Delta-T
Chilled water differential temperature
10.0
5.0
6:00 am 7:00 am 8:00 am 9:00 am
10:00 am
11:00 am
12:00 pm
1:00 pm 2:00 pm 3:00 pm 4:00 pm 5:00 pm 6:00 pm 7:00 pm 8:00 pm
Delta-T (°C)
Time
10.0
5.0
Chilled water differential temperature
6:00 am 7:00 am 8:00 am 9:00 am
10:00 am
11:00 am
12:00 pm
1:00 pm 2:00 pm 3:00 pm 4:00 pm 5:00 pm 6:00 pm 7:00 pm 8:00 pm
Delta-T (°C)
Time
Setpoint PICV Globe PICV Globe PICV Globe