The Nautica dehumidifier uses a regenerative heat exchanger to reduce the load on the cooling coil by pre-cooling.. CONVENTIONAL DEHUMIDIFICATION TECHNOLOGY FIGURE 1 CONVENTIONAL DEHUMID
Trang 1MAKEUP AIR DEHUMIDIFICATION
DESIGN MANUAL
Trang 2MAKEUP AIR DEHUMIDIFICATION DESIGN MANUAL
The energy crisis of the mid 1970’s gave birth to a
movement to conserve energy Over the ensuing years
much has been done to reduce the energy consumption
of new and existing buildings Lighting efficiency has
improved so much that today we use ½ the wattage
without sacrificing lumens Improved construction
methods, better insulation and high efficiency windows
have also helped reduce energy consumption
However, all of these measures have resulted in a
reduction of Sensible heat gains while Latent heat gains
have increased This is the reason that humidity related
issues have surfaced since the mid 1970’s
One of the methods for dealing with this issue is to
dehumidify and “neutralize” the moisture level of
outdoor air used for makeup This can be partially done
using Latent energy recovery devices, such as desiccant
enthalpy rotors However, dedicated dehumidification
component is needed to reduce the outdoor air grain
level equal to or lower than indoor grain level It is
important to note that a Latent energy recovery device
alone can never bring the outdoor air humidity below
that of indoors
Conventional makeup air dehumidifiers are and costly
to operate The refrigeration controls are sensitive,
susceptible to failure and difficult for field technicians
to troubleshoot
Nautica has resolved these problems by developing a
more energy efficient and reliable makeup air
dehumidification system Driven by many years of
practical refrigeration experience, the Nautica makeup
air dehumidification system is designed to be simple and less expensive to install, operate, maintain, troubleshoot and service
Makeup air dehumidifiers have been around for several decades and the basic concept, to remove humidity by overcooling pool air, and then compensate with re-heating, has not changed
The Nautica dehumidifier uses a regenerative heat exchanger to reduce the load on the cooling coil by pre-cooling This unique feature reduces energy consumption
by up to 50%
Conventional makeup air dehumidifiers use hot refrigerant gas to reheat the air after cooling This process use automatic solenoid valves, check valves and piping to route the refrigerant hot gas to the appropriate device On paper it looks good However, excessive amounts of costly refrigerant are needed to fill the system and the devices in the refrigerant circuit are subject to malfunction if a slight amount of dirt is present
Designing dehumidification systems for makeup air is a specialized area of HVAC design engineering This design manual provides a simple method for sizing dehumidification equipment for makeup air
Nautica dehumidifiers utilize MSP® heat transfer technology, that is compatible with chilled water, or refrigerant based systems and can be served by a wide range
of conventional chillers and condensing units, using any fuel source
KEY FEATURES AND BENEFITS
OPERATING SAVINGS Energy consumption up to one-half that of conventional dehumidification systems No reheating to compensate for over-cooling
INSTALLATION SAVINGS Lower cooling load Lower power requirements
HIGH RELIABILITY Eliminates complicated and temperamental refrigerant-side controls, reduces breakdowns, and simplifies troubleshooting
LOW MAINTENANCE Simple design results in reduced chance for breakdowns and low maintenance costs
Trang 3NAUTICA vs CONVENTIONAL DEHUMIDIFICATION TECHNOLOGY
FIGURE 1 CONVENTIONAL DEHUMIDIFIER
COOLING COIL HEATING
COIL FAN
With conventional dehumidification technology (Figure 1,
above), warm humid air, flows through a cooling coil
where it is cooled and dehumidified The dehumidified
and cooled air is then reheated through a heating coil prior
to entering the conditioned space
In the regenerative dehumidification technology (Figure
2, above), warm, humid air flows through the first pass of
an air-to-air heat exchanger for pre-cooling and
dehumidification by thermal exchange with the cooler
leaving air The air then passes through a cooling coil for
final cooling and dehumidification The dehumidified
and cooled air is then drawn back through the opposite
side of the air-to-air heat exchanger to be heated, prior to
entering the conditioned space
FIGURE 2 REGENERATIVE DEHUMIDIFIER
EXCHANGER
COOLING COIL
CONDENSED MOISTURE
As in conventional dehumidification, the regenerative technology uses ordinary refrigerants or chilled water However, in the energy-efficient regenerative dehumidifier, a lower temperature air enters the cooling coil as a result of pre-cooling and dehumidification through the air-to-air heat exchanger This innovative combination of an air-to-air heat exchanger with conventional cooling coil results in reduced compressor capacity, requiring half the energy for dehumidification compared with conventional dehumidification systems
Trang 4DH AND DE UNIT CONFIGURATIONS
DH—DEHUMIDIFIER ONLY
EVAPORATOR
SUPPLY FAN MSP TM DEHUMIDIFYING
COIL
DE—WITH ROTARY HEAT EXCHANGER
EVAPORATOR
EXHAUST FAN
SUPPLY FAN HEAT
MSP TM
DEHUMIDIFYING COIL
ENTHALPY ROTOR
Makeup air dehumidifier with rotary heat exchanger for energy recovery
DE—INTEGRAL UNIT
EVAPORATOR
EXHAUST
FAN
SUPPLY FAN
COMPRESSOR
HEAT MSP TM
DEHUMIDIFYING COIL
ENTHALPY ROTOR
CONDENSER
Totally self-contained air-cooled packaged unit for
indoor or outdoor installation
DE—WITH PLATE HEAT EXCHANGER
EXHAUST FAN
SUPPLY FAN HEAT MSP TM
DEHUMIDIFYING COIL
PLATE EXCHANGER
EVAPORATOR
Makeup air dehumidifier with plate heat exchanger for energy recovery
Features
• Split or packaged units
• Indoor & outdoor construction
• Air-cooled, water-cooled or chilled water
• Heat pumps—water and air source
• Double-wall construction
• Stainless steel drain pans
• Internally isolated fans
• Modular designs
• All voltage options
• Cooling option
Options
• Energy recovery ventilators—using plate or rotary
exchangers
• Hot water or steam heating coils
• Direct or indirect gas heating
• Electric heat
• Integral F&B coils
• Single point electrical connections
• Unit mounted disconnect switch
• Self-contained control system
• High efficiency MSP® heat exchangers
• Variable frequency drives
• Roof curbs—isolation and standard
Trang 5MAKEUP AIR DEHUMIDIFICATION DESIGN STRATEGY
Makeup air dehumidifiers should be sized to deliver a
desired dew point to the conditioned space The delivered
dew point should not exceed the space dew point except
under maximum conditions When outdoor conditions are
at “maximum moisture load” the space relative humidity
may be permitted to rise as high as 70% The designer
should be aware that mold growth and other humidity
related problems would occur only under sustained high
humidity conditions Therefore, a good design will allow
increased humidity during maximum load conditions
ASHRAE publishes three design conditions with three
hours of occurrence for each The worst condition for
humidity control is “maximum wet-bulb with mean
coincident dry bulb temperature” (WB/MCDB) Because
these conditions occur infrequently, it is wise to use a
coincident high indoor humidity to avoid
“over-designing” Nautica recommends using design conditions
of WB/MCDB at 0.4% occurrence Supply air dew point
should be equal to that of the room with a relative humidity of 60% to 65% This design strategy will result
in indoor humidity between 50% and 55% during
“normal” conditions
Humidity is expressed in two ways; absolute and relative
Relative humidity is a good measure of comfort in an
indoor environment because the temperature is stable However, outdoor air temperature is constantly changing and relative humidity, by itself, is meaningless without knowing its temperature
Absolute humidity, on the other hand, only changes
when moisture is added or subtracted from air It is a more appropriate condition to work with in humidification and dehumidification design Absolute humidity is expressed as dew point, grains/pound or pounds/pound
DATA ENTRY FORM
INDOOR AIR CONDITIONS
OUTDOOR CONDITIONS
Trang 6TABLE 1 – OUTDOOR AIR REQUIREMENTS FOR VENTILATION
/person
Cfm /sq ft
/person
Cfm /sq ft
Food and Beverage Service Specialty Shops -
Dining rooms 20 - Barber 15 -
Cafeteria, fast food 20 - Beauty 25 -
Bars, cocktail lounges 30 - Reducing salons 15 -
Hotels, Motels, Resorts Dormitories Cfm/room Florists 15 -
Bedrooms - 30 Clothiers, furniture 0.30 Living rooms - 30 Hardware, drugs, fabric 15 -
Baths - 35 Supermarkets 15 -
Lobbies 15 - Pet shops 1.00 Conference rooms 20 - Sports and Amusement -
Assembly rooms 15 - Spectator areas 15 -
Dormitory sleeping areas 15 - Game rooms 25
Gambling Casinos 30 - Ice arenas (playing areas) 0.50 Offices - Swimming pools (pool and deck area) 0.50 Office space 20 - Playing floors(gymnasium) 20 -
Reception areas 15 - Ballrooms and discos 25 -
Telecommunication centers and data entry 20 - Bowling alleys (seating areas) 25 -
Conference rooms 20 - Theaters -
Public Spaces Cfm/sq ft Ticket booths 20 -
Corridors and utilities - 0.05 Lobbies 20 -
Public restrooms, cfm/wc or urinal 50 - Auditorium 15 -
Locker and dressing rooms - 0.50 Stages, studios 15 -
Smoking lounge 60 - Transportation -
Elevators - 1.00 Waiting rooms 15 -
Retail Stores, Sales and Show Room Floors - Platforms 15 -
Basement and street - 0.30 Vehicles 15 -
Upper floors - 0.20 Workrooms -
Storage rooms - 0.15 Meat processing 15 -
Dressing rooms - 0.20
Malls and arcades - 0.20
Shipping and receiving - 0.15
Warehouses - 0.05
Smoking lounge 60 -
Table 1 prescribes supply rates of acceptable outdoor air required for acceptable indoor air quality These values have been chosen to dilute human
bioeffluents and other contaminants with an adequate margin for safety and to account for health variations among people and varied activity levels Source:
ASHRAE Standard 62-2001
Trang 7TABLE 2 – OCCUPANCY ESTIMATES**
Application Persons
/100 sq ft
Application Persons
/100 sq ft Food and Beverage Service Specialty Shops
Cafeteria, fast food 100 Beauty 25
Bars, cocktail lounges 100 Reducing salons 20
Hotels, Motels, Resorts Dormitories Florists 8
Conference rooms 50 Supermarkets 8
Dormitory sleeping areas 20 Sports and Amusement
Gambling Casinos 120 Spectator areas 150
Office space 7 Playing floors (gymnasium) 30
Reception areas 60 Ballrooms and discos 100
Telecommunication centers and data entry 60 Bowling alleys (seating areas) 70
Public Spaces Ticket booths 60
Retail Stores, Sales and Show Room Floors Stages, studios 70 Basement and street 30 Transportation
Shipping and receiving 10 Workrooms
**Estimated Maximum (Net occupiable space), Source: ASHRAE Standard 62-2001
TABLE 3 - TYPICAL ROOM GRAIN CONDITIONS
ROOM TEMPERATURE DB ROOM HUMIDITY RH
70º 75º 80º 50% 56.81 67.42 79.76 55% 62.57 74.28 87.90 60% 68.35 81.16 96.07
Trang 8TABLE 4a - PEAK CLIMATE CONDITIONS FOR MAKEUP AIR DEHUMIDIFICATION DESIGN
STATE/CITY ELEV
Muscle Shoals/Florence 551 16 137 82 Phoenix, Int'I Airport 1,106 34 118 82
Ozark, Fort Rucker 299 28 146 85 Phoenix, Luke AFB 1,089 35 130 85
Anchorage, Elmendorf AFB 213 -13 69 62 Winslow 4,882 10 95 71
Anchorage, Fort Richardson 377 -19 69 64 Yuma 207 40 136 87
Anchorage, lnt'I Airport 131 -14 68 62 ARKANSAS
Big Delta, Ft Greely 1,283 -45 70 65 Texarkana 390 20 143 85
Fairbanks, Eielson AFB 548 -33 74 66 Barstow/Daggett 1,926 28 103 81
Fairbanks, Int'l Airport 453 -47 72 65 Blue Canyon 5,285 21 74 70
Kodiak, State USCG Base 1 12 7 67 61 Marysville, Beale AFB 112 31 86 85
Middleton Island 46 18 57 56 Mountain View, Moffet NAS 39 36 83 74
Saint Paul island 30 -2 55 52 Riverside, March AFB 1,539 34 104 79
Source: ASHRAE Handbook of Fundamentals 1997
Trang 9TABLE 4b - PEAK CLIMATE CONDITIONS FOR MAKEUP AIR DEHUMIDIFICATION DESIGN
STATE/CITY ELEV
Sacramento, McClellan AFB 75 31 85 84 Miami, New Tamiami A 10 45 145 83 Sacramento, Metro 23 31 84 82 Milton, Whiting Field NAS 200 28 148 86
San Bernardino, Norton AFB 1,158 34 107 83 Panama City, Tyndall AFB 16 33 160 86 San Diego, Int'l Airport 30 44 111 77 Pensacola, Sherman AFB 30 28 150 85 San Diego, Miramar NAS 420 39 104 78 Saint Petersburg 10 43 156 86
Santa Barbara 10 34 96 74 Tampa, int'I Airport 10 36 144 85 Santa Maria 240 32 80 70 Valparaiso, Eglin AFB 85 30 149 85
Victorville George AFB 2,874 27 102 78 West Palm Beach 20 43 143 84
Grand Junction 4,839 2 93 70 Columbus, Fort Benning 233 23 142 85
Trinidad 5,761 -2 96 71 Marietta, Dobbins AFB 1,070 21 134 82
Hartford, Brainard Field 20 2 228 71 Valdosta, Moody AFB 233 30 142 85 Windsor Locks Bradley Fld 180 3 119 81 Valdosta, Regional Airport 203 28 144 83
Jacksonville, Cecil Field NAS 82 31 138 84 Burley 4,150 -5 90 75 Jacksonville, Int'I Airport 30 29 142 85 Idaho Falls 4,741 -12 88 71 Jacksonville, Mavport Naval 16 34 147 86 Lewiston 1,437 6 76 72
Source: ASHRAE Handbook of Fundamentals 1997
Trang 10TABLE 4c - PEAK CLIMATE CONDITIONS FOR MAKEUP AIR DEHUMIDIFICATION DESIGN
STATE/CITY ELEV
Pocatello 4,478 -7 83 70 Wichita, McConnell AFB 1,371 2 133 84
Belleville, Scott AFB 453 3 141 87 Bowling Green 548 7 136 84 Chicago, Meigs Field 623 -4 132 84 Covington/Cincinnati Airport 876 1 132 84 Chicago, O'Hare Int'I A 673 -6 130 84 Fort Campbell, AAF 571 9 143 85
West Chicago 758 -7 138 85 Bossier City, Barksdale AFB 167 22 144 84
Lafayette, Purdue Univ 607 -5 139 85 New Orleans, lnt'l Airport 30 30 151 86 Peru, Grissom AFB 810 -3 142 85 New Orleans, Lakefront A 10 35 150 85
Fort Dodge 1,165 -13 133 84 Limestone, Loring AFB 745 -13 107 75
Mason City 1,214 -15 135 84 MARYLAND
Sioux City 1,102 -11 135 86 Baltimore, BWI Airport 154 11 132 83 Spencer 1,339 -16 134 84 Lex Park, Patuxent River NAS 39 16 136 84
Dodge City 2,592 0 120 79 East Falmouth, Otis Angb 131 11 125 78
Ft Riley, Marshall AAF 1,066 -2 136 86 Weymouth, S Weymouth NAS 161 6 129 82
Source: ASHRAE Handbook of Fundamentals 1997
Trang 11TABLE 4d - PEAK CLIMATE CONDITIONS FOR MAKEUP AIR DEHUMIDIFICATION DESIGN
STATE/CITY ELEV
Grand Rapids 804 0 126 81 Warrensburg whiteman AFB 869 1 139 86
Marquette, Sawyer AFB 1,220 -11 113 77 Cut Bank 3,855 -21 77 67 Marquette/Ishpeming, A 1,424 -13 111 77 Glasgow 2,297 -22 91 74 Mount Clemens, Angb 581 3 131 83 Great Falls, lnt'l Airport 3,658 -19 81 69 Muskegon 633 3 122 80 Great Falls, Malmstrom AFB 3,527 -17 84 71
Alexandria 1,424 -20 123 82 Bellevue, Offutt AFB 1,047 -5 141 85 Brainerd, Pequot Lakes 1,280 -24 108 81 Grand Island 1,857 -8 127 82
International Falls 1 184 -29 112 78 North Platte 2,785 -10 118 80 Minneapolis-St Paul 837 -16 124 83 Omaha, Eppley Airfield 981 -7 136 85
Greenwood 154 20 148 86 Las Vegas, Int'I Airport 2,178 27 102 79
McComb 413 23 141 83 North Las Vegas, Nellis AFB 1 870 28 106 79
Cape Girardeau 341 6 141 86 NEW HAMPSHIRE
Spickard/Trenton 886 1 139 83 NEW JERSEY
Source: ASHRAE Handbook of Fundamentals 1997