ASHRAE Journal - September 2019 - 26

TECHNICAL FEATURE

location. Each of pressure distribution diagrams in
Figure 3 clearly shows primary plant pump head (Points
1-2), building pump head (Points 3-4), top coil inlet
and outlet pressures (Points 5-6), and building return
pressure at Point 7. The pre-PSV scenario (b) results in
negative top coil outlet pressure, which is detrimental
to the hydronic loop. Raising PSP (a) and installing PSVs
(c) both eliminate negative top coil pressure, but raising
PSP affects the entire hydronic loop and might lead to
other issues, while the PSV option just affects individual
buildings with insufficient PSP.
Table 1 summarizes the building pump head requirement for the three pressure distribution diagrams shown
in Figure 3. The pumping head required varies as a result
of building friction loss and other factors such as lifting
water head. The Raising PSP option shown in Table 1 has
the lowest building pump head requirement at 6 psig
(41 kPag), which is only the friction head loss shown for
comparison here. The PSV option requires a significantly
lower required building pump head of 36 psig ( 248 kPag),
compared to pre-PSV operation, which requires 42 psig

26

ASHRAE JOURNAL

ashrae.org

S E P T E M B E R 2 0 19

TABLE 1 Pump head requirement for three options.
ITEMS

OPTIONS RAISING PSP

W/O PSV

PSV

PSP in Height > Top Coil in Height?

Yes

No

No

Top Coil Outlet Pressure ± psig

+16

-24

+8

Bldg. Friction Loss, psig

6

6

6

Lift Head, psig

0

36

30

Bldg. Pump Requirement, psig

6

42

36

(289 kPag) of pumping head. The building pressure profile analysis confirms the building pump head and power
for the PSV option is much lower than the pre-PSV operation. When PSP is lower than top coil pressure in height,
the PSV is able to gain hydraulic pressure to meet the
top coil's requirement. Options 1 and 3 belong to closed
hydronic system operation while Option 2 is a "half" open
hydronic system because air infiltration from leaks and
water will coexist in the top coil outlet just above PSP.

Simulation Model and Scenarios
Generally, large hydronic systems are too complicated
to manually test, so valid simulation software is becoming more widely accepted as a reliable source of information for understanding a hydronic system's characteristics and deciding on the best solution for complicated problems. A commercially available hydraulic
simulation software has been used for the analysis of the
hydronic loop while varying primary pressure scenarios.
The software assumes incompressible, one-dimensional flow and uses principles of heat transfer and
system energy balance to model pressures, flows, temperatures, and power consumption in the loop. The
model was developed based on as constructed loop pipe
dimensions, materials, and elevation, and calibrated
using field data to obtain the most reliable results possible. Figure 4 shows a large campus loop simulation model
with two plants (CUP and SUP 3), four tall buildings
with PSVs, and others without PSVs. These two plants are
approximately a mile apart with 90,000 ft (27 432 m) of
underground piping throughout the loop.
The simulation assumes varying pumping speed to
react to primary pressure variation and to keep the
coil flow and design temperature differential constant.
Two scenarios were evaluated: varying primary supply pressure and varying primary return pressure. In
each case, a simulation was performed with the PSV
installed as well as without it, so the effect of the PSV


http://versablock.com/ https://www.ashrae.org

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
ASHRAE Journal - September 2019 - 41
ASHRAE Journal - September 2019 - 42
ASHRAE Journal - September 2019 - 43
ASHRAE Journal - September 2019 - 44
ASHRAE Journal - September 2019 - 45
ASHRAE Journal - September 2019 - 46
ASHRAE Journal - September 2019 - 47
ASHRAE Journal - September 2019 - 48
ASHRAE Journal - September 2019 - 49
ASHRAE Journal - September 2019 - 50
ASHRAE Journal - September 2019 - 51
ASHRAE Journal - September 2019 - 52
ASHRAE Journal - September 2019 - 53
ASHRAE Journal - September 2019 - 54
ASHRAE Journal - September 2019 - 55
ASHRAE Journal - September 2019 - 56
ASHRAE Journal - September 2019 - 57
ASHRAE Journal - September 2019 - 58
ASHRAE Journal - September 2019 - 59
ASHRAE Journal - September 2019 - 60
ASHRAE Journal - September 2019 - 61
ASHRAE Journal - September 2019 - 62
ASHRAE Journal - September 2019 - 63
ASHRAE Journal - September 2019 - 64
ASHRAE Journal - September 2019 - 65
ASHRAE Journal - September 2019 - 66
ASHRAE Journal - September 2019 - 67
ASHRAE Journal - September 2019 - 68
ASHRAE Journal - September 2019 - 69
ASHRAE Journal - September 2019 - 70
ASHRAE Journal - September 2019 - 71
ASHRAE Journal - September 2019 - 72
ASHRAE Journal - September 2019 - 73
ASHRAE Journal - September 2019 - 74
ASHRAE Journal - September 2019 - 75
ASHRAE Journal - September 2019 - 76
ASHRAE Journal - September 2019 - 77
ASHRAE Journal - September 2019 - 78
ASHRAE Journal - September 2019 - 79
ASHRAE Journal - September 2019 - 80
ASHRAE Journal - September 2019 - 81
ASHRAE Journal - September 2019 - 82
ASHRAE Journal - September 2019 - 83
ASHRAE Journal - September 2019 - 84
ASHRAE Journal - September 2019 - 85
ASHRAE Journal - September 2019 - 86
ASHRAE Journal - September 2019 - 87
ASHRAE Journal - September 2019 - 88
ASHRAE Journal - September 2019 - Cover3
ASHRAE Journal - September 2019 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2021
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPDJKD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VJKSRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDHUTC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JPPKRR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDLTTH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CKLLES
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SLDOX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_HJETUK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OLUHGE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ZERDGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QVMNEO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTPOKE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BBATRE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_STUBMW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TPEMPE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JNMKDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FBTTPA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WQMMNE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TVBRYN
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2020
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_KTUZMA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
https://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
https://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
https://www.nxtbook.com/nxtbooks/amca/2014summer2
https://www.nxtbook.com/nxtbooks/amca/2014summer
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
https://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
https://www.nxtbookmedia.com