User Guide for Desiccant Dehumidification Technology
Transcript of User Guide for Desiccant Dehumidification Technology
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FACILITIES ENGINEERING
APPLICATIONS PROGRAM
User Guide for DesiccantDehumidification Technology
byThomas E. Durbin and Michael A. Caponegro
U.S. Army Construction Engineering Research LaboratoriesChampaign, IL 61826-9005
Approved for Public Release; Distribution Is Unlimited.
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The contents of this report are not to be used for advertising, publication,
or promotional purposes. Citation of trade names does not constitute an
official endorsement or approval of the use of such commercial products.
The findings of this report are not to be construed as an official
Department of the Army position, unless so designated by other authorized
documents.
DESTROY THI S REPORT WHEN IT I S NO LONGER NEEDED
DO NOT RETURN IT TO THE ORIG INATOR
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USACERL FEAP UG-97/107
Foreword
This study w a s done for t he U .S. Army Cent er for public Works (U SACP W) under
the Facilities Engineering Application Program (FEAP); Work Unit F56, FEAP
Desiccant Demonstrat ion at APG. The technical monitor was Dennis Vevang,
CECPW-EM.
The work was performed by the Troop Installation Operation Division (UL-T) of the
Util i t ies and Industrial Operations Laboratory (UL), U.S. Army Construction
Engineering Research Laboratories (USACERL). The USACERL princ ipa l
investigator was Thomas E. Durbin. Chang W. Sohn is Acting Chief, CECER-UL-U;
Mart in J . Sa voie is Act ing Operat ions Chief, CE CE R-U L; a nd G ary W. Schanche is
the associated Technical Director, CECER-UL. The USACERL technical editor was
William J . Wolfe, Technical R esources.
COL J am es T. Scott is Comman der an d Dr . Micha el J . OConnor is D irector of
USACERL.
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2 USACERL FEAP UG-97/107
Contents
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1 Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pre-Acquisition: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Technology Description and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Possible Solutions Offered by Desiccant Dehumidification . . . . . . . . . . . . . . . . . . . . . ...8
Costs and Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Sample Cost Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Life Cycle Cost/Benefit Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Utility and Space Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
3 Acquisition/Procurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Acquisition/Procurement Strategy.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Potential Funding Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Procurement Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Procurement Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Construction Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
4 Post Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Acquisition Scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Operation and Maintenance issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Appendix A: Vendors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Appendix B: Example Scope of Work for Two-Wheel Desiccant Dehumidification
Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Appendix C: Sample Specifications for Two-Wheel Desiccant
Dehumidification/Cooiing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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USACERL FEAP UG-97/107 3
1 Executive Summary
Manufacturing industries have used desiccants in various applications for over 50
years, but have only recently begun to apply desiccant dehumidification systems
(DDSs) to Heating, Ventilation, and Air-Conditioning (HVAC) applications.
Depending on climat e an d fa cility loading, a high percent a ge of a buildings cooling
load can be la tent (moisture) load. C onventional cooling equipment operat es at low
temperat ures to cool the a ir to i ts dew point t empera ture, w here dehumidif ica t ion
via condensat ion on the coils begins. I t ma y t hen be necessary t o reheat the a ir to
a comfortable tempera ture before i t enters t he occupied space. DD Ss, by contr ast ,
remove water from the air by using a desiccant , or chemical drying agent. DDSs
offer several benefits when used in conjunction with air-conditioning systems.
Removing moisture from the air by desiccation decreases the amount of vapor-
compression energy needed to dehumidify the air being supplied to the user, and
increases the comfort level in the conditioned space. Desiccant systems also decrease
moisture accumulation in ducts and around coils, inhibiting the growth of mold and
mildew.
While research in desiccant dehumidification technology development has been
conducted for severa l yea rs, commercial a pplica tions of desiccant dehumidifica tiontechnology have been l imited in th e past by ma terial a nd ma nufacturing consider-
ations. Current desiccant dehumidification systems range in capacity to 30,000 cubic
feet per minute (cfm) and are near the commercialization stage. Since these systems
are heat driven (not electrically driven), conversion to a desiccant system can reduce
site peak electrical demand and levelize utility loads, allowing for more efficient
power plant operation. Energy cost savings result from reduced chiller loads,
reduced electrici ty peak demand, and el imination of air reheating requirements .
Desiccant dehumidification systems can also reduce or eliminate the use of harmful
CFC s in the HVAC system by using na tura l gas or l iquid propane gas (LPG ) as t he
prima ry fuel for dehumidifica tion.
AS yet , very few desiccant systems have been instal led at mil i tary instal la t ions, and
only then in specialized applications. Desiccant dehumidification systems may offer
advantages for military applications over other energy supply options by increasing
force readiness, providing greater system reliability, controlling humidity in areas
with sensit ive mat erial and equipment, a nd by reducing environmental impact a nd
energy costs.
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4 USACERL FEAP UG-97/107
Points of Contact :
Dennis Vevang
U .S. Army C enter for P ublic Works (U SACP W)
ATTN: CE CP W-E M
2701 Telegra ph R oadAlexandria, VA 22312-3862
Comm: (703) 806-6071
FAX: (703) 806-5220
Thomas E. Durbin
U .S. Army C onstruction En gineering Resear ch L aborat ories (U SACERL)
ATTN: CECER-ULU
P O B ox 9005
Champaign, IL 61826-9005tel : 217/352-6511, X5543
F AX: 217/373-7222
U RL : ht t p://w w w .cecer.a rm y.m il
Micha el A Ca ponegro
USACERL
ATTN: CECER-ULU
P O B ox 9005
Champaign, IL 61826-9005tel: 217/352-6511, X5552
F AX: 217/373-7222
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USACERL FEAP UG-97/107 5
2 Pre-Acquisition:
Technology Description and Application
Conventional Air-Conditioning/Ventilation Process
Conventional air-conditioning systems are typically controlled by a thermostat (or
simila r ty pe receiver/cont roller combina tion). They opera te in a ma nn er th a t keeps
the space dry bulb temperature from exceeding the thermostat setpoint. To
maintain that setpoint , condit ioned air is typical ly introduced into the space
approximately 20 F* lower than the setpoint, so that the conditioned air can absorb
the so-called sensible heat entering the space. Having absorbed this heat, air from
the space is drawn back to the air-handling unit , where i ts temperature is again
decreased before being returned to the space. The temperature decrease is
accomplished by the returned air being drawn (or blown) through a cooling coil
within the air handling unit. The coil is typically a specially designed finned-tube
heat exchanger, containing a relatively cold circulating fluid (usually chilled water
or a ref i igerant) into which heat from the air is transferred. Invariably, the
described situation is somewhat more complicated since some amount of outside air
is mixed with the returned air from the space, and then the mixture is cooled by thecoil. The most common reason for introducing outside (fresh) air is to provide
ventila tion for th e occupant s of the spa ce. As the cooling coil reduces t he dry bulb
temperature of the air so that the air, in turn, will provide sensible cooling for the
space, the dry bulb temperature of the air is reduced almost to i ts dew point
temperat ure. In fact , a considera ble portion of the a ir a ctua l ly reaches sat ura tion
due to its contact with, or proximity to, the cooling coil, which has a temperature
considerably lower than the air s dew point temperature. As a result , water
condenses from th e a ir ont o the coil, w here proper selection of a irflow velocities (