ASHRAE Journal - September 2011 - 29

tower cells, this can eliminate the need for isolation valves, which cost much more than the weir dams and nozzles. This option is also the most efficient; tower energy use is minimized by operating as many cells as possible, particularly when tower fans are controlled by variable speed drives. This is because fan speed is reduced (reducing fan power by almost the cube of the speed) and cooling is achieved through tower cells even when fans are off. With most manufacturers and tower types, nozzles and dams are available to reduce flow by 50%, and many can go down to 33% or even 25% depending on the selection and design flow rate. Because of low cost and high efficiency, this option should always be the first choice. When a plant has many tower cells and automatic isolation valves are unavoidable, the dams and nozzles should still be selected to allow as many cells to operate as possible. Option B: Install automatic isolation valves on supply lines only. This option uses the equalizer to keep basin levels between overflow and fill lines and will require that equalizers be oversized from that required by normal duty. For example, assume there are three tower cells, and only one is active; supply flow to the others is shut off. But water is drawn out of all three cell basins since the suction lines have no automatic isolation valves. The water level in the basin

of the cell that is supplied will rise while the other two basin levels will fall. The difference in the two elevations must provide enough head for water to transfer from the supplied cell to the others through the equalizer. If the equalizer is undersized, water will overflow in the supplied cell, and the others will be drawn so low that makeup water valves open, wasting water and water treatment chemicals. There are only a few inches of elevation difference between the overflow and fill lines, so it is imperative that the equalizer be properly sized for this option to work. Another approach is to eliminate the basins at each tower and use a common sump, often located indoors in cold climates. This avoids the need for equalizer lines entirely but is much more expensive. Option C: Install automatic isolation valves on both supply and suction lines. This is usually the most expensive option since automatic valves are expensive relative to an incremental increase in equalizer size. This design also increases exposure to a valve failure; an oversized equalizer line has no failure modes. It also increases the risk of freezing (or increases the energy used by basin heaters) in the basins of inactive cells in systems that must operate in cold weather. But this is often the best option when there are many tower cells that are not located close together (long equalizer lines).

www.info.hotims.com/37990-52

September 2011

ASHRAE Journal

29



ASHRAE Journal - September 2011

Table of Contents for the Digital Edition of ASHRAE Journal - September 2011

Contents
Commentary
Industry News
Meetings and Shows
Feature Articles
Adsorption Refrigeration: New Opportunities for Solar
Optimizing Design & Control of Chilled Water Plants—Part 2: Condenser Water System Design
Designing for Comfort: Selecting Air-Distribution Outlets
Technology Award Case Studies
Library Sets Example
Sustainable Campus
Standing Columns
Building Sciences
IAQ Applications
Emerging Technologies
Products
Classified Advertising
Advertisers Index
Special Supplement: AMCA International inmotion Magazine
ASHRAE Journal - September 2011 - Intro
ASHRAE Journal - September 2011 - Cover1
ASHRAE Journal - September 2011 - Cover2
ASHRAE Journal - September 2011 - 1
ASHRAE Journal - September 2011 - 2
ASHRAE Journal - September 2011 - Contents
ASHRAE Journal - September 2011 - Commentary
ASHRAE Journal - September 2011 - 5
ASHRAE Journal - September 2011 - Industry News
ASHRAE Journal - September 2011 - 7
ASHRAE Journal - September 2011 - 8
ASHRAE Journal - September 2011 - 9
ASHRAE Journal - September 2011 - Meetings and Shows
ASHRAE Journal - September 2011 - 11
ASHRAE Journal - September 2011 - 12
ASHRAE Journal - September 2011 - 13
ASHRAE Journal - September 2011 - Adsorption Refrigeration: New Opportunities for Solar
ASHRAE Journal - September 2011 - 15
ASHRAE Journal - September 2011 - 16
ASHRAE Journal - September 2011 - 17
ASHRAE Journal - September 2011 - 18
ASHRAE Journal - September 2011 - 19
ASHRAE Journal - September 2011 - 20
ASHRAE Journal - September 2011 - 21
ASHRAE Journal - September 2011 - 22
ASHRAE Journal - September 2011 - 23
ASHRAE Journal - September 2011 - 24
ASHRAE Journal - September 2011 - 25
ASHRAE Journal - September 2011 - Optimizing Design & Control of Chilled Water Plants—Part 2: Condenser Water System Design
ASHRAE Journal - September 2011 - 27
ASHRAE Journal - September 2011 - 28
ASHRAE Journal - September 2011 - 29
ASHRAE Journal - September 2011 - 30
ASHRAE Journal - September 2011 - 31
ASHRAE Journal - September 2011 - 32
ASHRAE Journal - September 2011 - 32A
ASHRAE Journal - September 2011 - 32B
ASHRAE Journal - September 2011 - 33
ASHRAE Journal - September 2011 - 34
ASHRAE Journal - September 2011 - 35
ASHRAE Journal - September 2011 - 36
ASHRAE Journal - September 2011 - 37
ASHRAE Journal - September 2011 - Designing for Comfort: Selecting Air-Distribution Outlets
ASHRAE Journal - September 2011 - 39
ASHRAE Journal - September 2011 - 40
ASHRAE Journal - September 2011 - 41
ASHRAE Journal - September 2011 - 42
ASHRAE Journal - September 2011 - 43
ASHRAE Journal - September 2011 - 44
ASHRAE Journal - September 2011 - 45
ASHRAE Journal - September 2011 - 46
ASHRAE Journal - September 2011 - 47
ASHRAE Journal - September 2011 - Library Sets Example
ASHRAE Journal - September 2011 - 49
ASHRAE Journal - September 2011 - 50
ASHRAE Journal - September 2011 - 51
ASHRAE Journal - September 2011 - 52
ASHRAE Journal - September 2011 - 53
ASHRAE Journal - September 2011 - Sustainable Campus
ASHRAE Journal - September 2011 - 55
ASHRAE Journal - September 2011 - 56
ASHRAE Journal - September 2011 - 57
ASHRAE Journal - September 2011 - 58
ASHRAE Journal - September 2011 - 59
ASHRAE Journal - September 2011 - 60
ASHRAE Journal - September 2011 - 61
ASHRAE Journal - September 2011 - 62
ASHRAE Journal - September 2011 - 63
ASHRAE Journal - September 2011 - Building Sciences
ASHRAE Journal - September 2011 - 65
ASHRAE Journal - September 2011 - 66
ASHRAE Journal - September 2011 - 67
ASHRAE Journal - September 2011 - 68
ASHRAE Journal - September 2011 - 69
ASHRAE Journal - September 2011 - 70
ASHRAE Journal - September 2011 - 71
ASHRAE Journal - September 2011 - 72
ASHRAE Journal - September 2011 - 73
ASHRAE Journal - September 2011 - 74
ASHRAE Journal - September 2011 - 75
ASHRAE Journal - September 2011 - IAQ Applications
ASHRAE Journal - September 2011 - 77
ASHRAE Journal - September 2011 - 78
ASHRAE Journal - September 2011 - 79
ASHRAE Journal - September 2011 - 80
ASHRAE Journal - September 2011 - Special Supplement: AMCA International inmotion Magazine
ASHRAE Journal - September 2011 - AMCACover2
ASHRAE Journal - September 2011 - AMCA3
ASHRAE Journal - September 2011 - AMCA4
ASHRAE Journal - September 2011 - AMCA5
ASHRAE Journal - September 2011 - AMCA6
ASHRAE Journal - September 2011 - AMCA7
ASHRAE Journal - September 2011 - AMCA8
ASHRAE Journal - September 2011 - AMCA9
ASHRAE Journal - September 2011 - AMCA10
ASHRAE Journal - September 2011 - AMCA11
ASHRAE Journal - September 2011 - AMCA12
ASHRAE Journal - September 2011 - AMCA13
ASHRAE Journal - September 2011 - AMCA14
ASHRAE Journal - September 2011 - AMCA15
ASHRAE Journal - September 2011 - AMCA16
ASHRAE Journal - September 2011 - AMCA17
ASHRAE Journal - September 2011 - AMCA18
ASHRAE Journal - September 2011 - AMCA19
ASHRAE Journal - September 2011 - AMCA20
ASHRAE Journal - September 2011 - AMCA21
ASHRAE Journal - September 2011 - AMCA22
ASHRAE Journal - September 2011 - AMCA23
ASHRAE Journal - September 2011 - AMCA24
ASHRAE Journal - September 2011 - AMCA25
ASHRAE Journal - September 2011 - AMCA26
ASHRAE Journal - September 2011 - AMCACover3
ASHRAE Journal - September 2011 - AMCACover4
ASHRAE Journal - September 2011 - Emerging Technologies
ASHRAE Journal - September 2011 - 82
ASHRAE Journal - September 2011 - 83
ASHRAE Journal - September 2011 - 84
ASHRAE Journal - September 2011 - 85
ASHRAE Journal - September 2011 - 86
ASHRAE Journal - September 2011 - 87
ASHRAE Journal - September 2011 - 88
ASHRAE Journal - September 2011 - Products
ASHRAE Journal - September 2011 - 90
ASHRAE Journal - September 2011 - 91
ASHRAE Journal - September 2011 - 92
ASHRAE Journal - September 2011 - 93
ASHRAE Journal - September 2011 - Classified Advertising
ASHRAE Journal - September 2011 - 95
ASHRAE Journal - September 2011 - Advertisers Index
ASHRAE Journal - September 2011 - Cover3
ASHRAE Journal - September 2011 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_MCDEBX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WNYSQY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XATVOD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FJSHSS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CCBZDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XDEFVG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHGNBL
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WPKBNJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_UUVCDE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTGDEW
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2023
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LKRFXS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AZSOFG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ERCDBH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QWDFRV
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JHGVDF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPUYHG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SREIBM
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LRTGLK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OKRFGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TZSERA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LVRUIX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RPTVYZ
https://www.nxtbook.com/nxtbooks/ashrae/mini_pub_catalog
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XIYTGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2022
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RFGDOB
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PABXNU
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_REMKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PICVBT
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AOYTVW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JQOPLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IOYTBC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SGAJJF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IGHYER
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PDRKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XCODFR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QSLFGO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ILKVNM
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