ASHRAE Journal - September 2019 - 25

TECHNICAL FEATURE

FIGURE 1 Texas A&M main campus CHW (blues lines) and LTHW (red lines) map.

FIGURE 2 Schematic of plant and Building A with PSV.

Bldg. Side
548 ft.
Current Plant Static Pressure

50 psig
465 ft.

5 AHU
8

6

9
AHU

AHU
Plant Side
Plant Pumps
2

Bldg. Pump
3 4
PSV
10
7

Boiler
Chiller
Exp. Tank

1

Pressure (psig)

Pressure (psig)

Pressure (psig)

the Darcy-Weisbach equations.3 Building
FIGURE 3 Simplified pressure distribution profiles (points correspond to Figure 2 Points) (a) raising
pump requirements vary with primary loop
whole loop PSP; (b) pre-PSV operation; (c) new operation with PSV.
pressure, building friction pressure loss,
2
110
4
and the difference between PSP (in ft w.c.)
106
7
3
and top coil height. Figure 2 is a simplified
100
schematic of TAMU's large hydronic loop
1
90
Plant Static Pressure
that includes the CUP and Building A. It dia5
grams the current PSP at 50 psig (344 kPag)
18
6
at an elevation above sea level of 465 ft (142
16
(a)
m), and the top coil elevation above sea level
4
102
of 548 ft (167 m). The building top coils are
2
70
198 ft (60 m) above the plant elevation. The
3
7
PSP only yields 115 ft (35 m) of head, which
60
8
1
causes the negative pressures in the top coils
51
50
Plant Static Pressure
since Building A was built in 1974. Pressure
5
9
14
11
distribution profiles for three scenarios
0
were generated to evaluate pump require-24
6
(b)
ment and further identify whether the PSV
4
96
7
option is the best solution. These pressure
90
10
distribution profiles are displayed in Figure
2
70
3: (a) is raising PSP to remove negative top
3
60
coil pressure; (b) is pre-PSV operation; and
1
(c) is with PSV and positive top coil pressure.
50
5
Plant Static Pressure
8
The purpose for listing scenario (a) here is
6
6
just for reference even though this scenario
(c)
has already been invalidated in the previous
study.1 These pressure distribution profiles
are drawn based on trend pressure values on the plant
(Figure 2). In the Figure 3, the vertical axis indicates presand building as shown in the simplified schematic
sure value and the horizontal axis shows approximate
S E P T E M B E R 2 0 19

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ASHRAE Journal - September 2019

Table of Contents for the Digital Edition of ASHRAE Journal - September 2019

Contents
ASHRAE Journal - September 2019 - Intro
ASHRAE Journal - September 2019 - Cover1
ASHRAE Journal - September 2019 - Cover2
ASHRAE Journal - September 2019 - 1
ASHRAE Journal - September 2019 - Contents
ASHRAE Journal - September 2019 - 3
ASHRAE Journal - September 2019 - 4
ASHRAE Journal - September 2019 - 5
ASHRAE Journal - September 2019 - 6
ASHRAE Journal - September 2019 - 7
ASHRAE Journal - September 2019 - 8
ASHRAE Journal - September 2019 - 9
ASHRAE Journal - September 2019 - 10
ASHRAE Journal - September 2019 - 11
ASHRAE Journal - September 2019 - 12
ASHRAE Journal - September 2019 - 13
ASHRAE Journal - September 2019 - 14
ASHRAE Journal - September 2019 - 15
ASHRAE Journal - September 2019 - 16
ASHRAE Journal - September 2019 - 17
ASHRAE Journal - September 2019 - 18
ASHRAE Journal - September 2019 - 19
ASHRAE Journal - September 2019 - 20
ASHRAE Journal - September 2019 - 21
ASHRAE Journal - September 2019 - 22
ASHRAE Journal - September 2019 - 23
ASHRAE Journal - September 2019 - 24
ASHRAE Journal - September 2019 - 25
ASHRAE Journal - September 2019 - 26
ASHRAE Journal - September 2019 - 27
ASHRAE Journal - September 2019 - 28
ASHRAE Journal - September 2019 - 29
ASHRAE Journal - September 2019 - 30
ASHRAE Journal - September 2019 - 31
ASHRAE Journal - September 2019 - 32
ASHRAE Journal - September 2019 - 33
ASHRAE Journal - September 2019 - 34
ASHRAE Journal - September 2019 - 35
ASHRAE Journal - September 2019 - 36
ASHRAE Journal - September 2019 - 37
ASHRAE Journal - September 2019 - 38
ASHRAE Journal - September 2019 - 39
ASHRAE Journal - September 2019 - 40
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ASHRAE Journal - September 2019 - 42
ASHRAE Journal - September 2019 - 43
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ASHRAE Journal - September 2019 - 48
ASHRAE Journal - September 2019 - 49
ASHRAE Journal - September 2019 - 50
ASHRAE Journal - September 2019 - 51
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ASHRAE Journal - September 2019 - 88
ASHRAE Journal - September 2019 - Cover3
ASHRAE Journal - September 2019 - Cover4
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