Note: Descriptions are shown in the official language in which they were submitted.
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TITLE:
INDOOR AIR QUALITY CONTROLLED FOGGERS
s
BACKGROUND OF THE INVENTION
This invention is in the field of conditioning mixed exhaust air and outdoor
air in a heating, ventilation and air conditioning system or a 100% fresh air
conditioner serving a single temperature control zone.
More particularly the invention relates to the use of a fogger assembly
supporting an array of foggers disposed in the air mixing plenum in which exhaust
air and outdoor air are mixed as supply air to a typical heating ventilating airconditioning system. The invention also relates to the use of a fogger assembly
supporting an array of foggers disposed proximate the inlet of 100% fresh air
15 conditioner serving a single temperature control zone. The fogger array is
controlled by a digital controller such as a microprocessor or microcomputer
connected to sensors and controlling the air and water to the fogger array. The
digital controller also controls dampers and valves in the heating, ventilation and
air conditioning system or 100% air conditioner serving a single temperature
20 control zone. A series of wash down permanent air filters are located in the supply
air path adjacent the fogger array. The series of wash down permanent air filters
provide 65% or better filtration specified for compliance with American Society of
Heating, Refrigeration and Air Conditioning Engineers Indoor Air Quality
Standards 62-1989. The invention may be designed to refit existing systems or
25 applied in new systems.
Indoor air quality has become one of the leading occupational and
environmental health issues. Synthetic materials, modern office equipment
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(photocopiers, laser printers, computers), cleaning products and introduction tooutdoor air pollution via supply inlets of heating, ventilating and air conditioning
system all contribute to indoor air cont~min~tion.
Physical symptoms commonly attributed to indoor air quality problems
include headache, fatigue, shortness of breath, sinus congestion, cough, sneezing,
skin irritation, dizziness, nausea and eye, nose and throat irritation. Some
individuals may be particularly susceptible to the effects of indoor air
cont~min~nts, for instance allergic or asthmatic individuals, people with
respiratory disease, people whose immune systems are suppressed due to
chemotherapy, radiation therapy, and other assorted diseases.
(A) Space-Propagated Ozone
Space propagated ozone is a specific indoor air quality pollutant, when in
excess of 0.1 ppm establishes the legal exposure limit. (Occupational Safety andHealth Act, 29 CFR 1910.1000 Table Z-l, C-12). Prolonged exposure to ozone at
l 5 levels in excess of 0.1 ppm is reported to produce permanent respiratory
impairment which is what all government agencies are concerned with in rlefiningatt~inment standards for ambient air quality.
Space propagated ozone originates from desktop electronics, fax m~chines,
copiers etc. Most modern offices depend on electronic equipment systems and these
produce ozone (O3). Even though most of this equipment (domestic origin) is
designed and certified to emit 0.1 ppm under an Air Conditioning and Refrigeration
Institute protocol, the com~7in~tion of dry air and equipment packing allows space-
propagated ozone accumulations to rise, over a period of hours, to reach debilitating
levels.
Me~h~nic~l rooms are designed nowadays with little to no outside air
circulation. Electrical equipment running continuously produces an even greater
amount of ozone (O3) caused by electrical contacts, rotors etc. arcing. Because most
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of the buildings are pressurized, the cont~min~nt air in the mechanical rooms
usually gets drawn out of the me~h~nic~l rooms by doors opening or through cracks
and breaks and is drawn into the return systems.
The American Society of Heating, Refrigerating and Air Conditioning
5 Engineers dictates ozone's concentrations of between 0.02 to 0.2 ppm related to
building relative humidity and quantifies space-propagated ozone formation at 0.08
ppm within 8 air change space occupancy parameters. Ozone (O3) is a heavy gas.
Ozone (O3) molecular weight is 48. The molecular weight of air is only 29. Hence,
space-propagated ozone purges sluggishly until enough cycles-of-concentration
10 build up ozone (O3) level to convey the gas. Even with increased ventilation and
increased outside air rates the space-propagated ozone problem persists.
(B) Sources and Factors Affecting Indoor Air Quality
Indoor environment results from the interactions of the physical layout of the
site, the outdoor climate, the building's heating, ventilating, and air conditioning
15 systems, potential cont~min~nt sources, and the building occupants. Some of the
sources of factors affecting indoor air quality are:
Carbon Monoxide
Carbon Monoxide is a colourless, odourless, toxic gas that is a product is incomplete
combustion. Pollution results when combustion gases are not properly exhausted or
20 are reintroduced into the building. Most parking garages are equipped with carbon
monoxide sensors that switch on the ventilation systems when levels get above a
pre-set point. Symptoms of low-level exposure include headaches, nausea, fatigueand flu like symptoms. These e~ects are not likely to be observed below about 25ppm. In most buildings levels will be below 5 ppm.
25 Formaldehyde
Formaldehyde is a colourless gas with a pungent odour. Building materials,
especially new ones, are the most common source of the gas, carpets, particleboard,
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furniture, and fabrics often contain cleaning fluids or adhesives with formaldehyde
in them. Slow off-gassing from these building materials can result in concentration
of formaldehyde that affect building occupants.
Particulates
5 Particulates can be both solid or liquid matter. Dust, fumes, smoke, and org~ni.qm.q
such as viruses, pollen grains, bacteria and fungal spores are examples of solidparticulate matter. Both synthetic and natural fibers (e.g. glass wool fibers) that
were used in building insulation may cause problems. Insulation that is in poor
condition and located near areas where people work or beside air vents may
10 indicate potential insulation particulate problem. Particles come from both indoor
and outdoor sources and can be drawn into the building through infiltration and air
intakes. The mechanical ventilation system itself may be a source of particulatematter (e.g. scale, rush, disinfectants, biological growth in ducts and pipe
insulation). Particulates can cause allergic reactions, dry eyes, contact lens
15 problems, nose and throat problems, skin irritation, coughing, sneezing and
respiratory difficulties.
Volatile Organic Compounds
There are several thousand chçmic~l.s, synthetic and natural, that can be calledvolatile organic compounds. All buildings contain a large variety of chemical
20 sources such as plastics, cigarette smoke, floor wax, furniture, building materials,
liquid process printers or copiers. The effect that each of these ch~mic~ product
va~es with the particular chemic~l Most ch~mic~ will cause irritation if the
concentrations in the air are high enough.
Typical Mixed Air Heating. Ventilation and Air Conditioning System
25 (A) The mixed air heating, ventilation and air conditioning system shown in
Figure l is designed to supply conditioned air to a single zone or to some othersystem. The quantity and quality of this air has fixed parameters determined by
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the space requirements. Air passing through the equipment gains and loses heat
by contact with the heat transfer sllrf~ce.s and by mixing with air of another
condition. Some of these mixtures are intentional, as at the outdoor air intake.Others are results of the physical characteristics of a particular component as when
5 untreated air passes between the fins of a coil without contact. It is essential that
all me~h~nic~l mixture of treated and untreated air be thorough for maximum
performance of heat transfer sllrf~ces and llniform temperatures in the air stream.
(B) ~rixing of the air is obtained by a mixing box with baffles arranged to direct
the two air streams to impinge on each other in multiple jets at right angles of each
10 other creating the turbulence required to mix them thoroughly. Outside air and
return air dampers are sequenced and arranged to minimi7~e stratification and
achieve proper mixing. The outside air damper and the return air damper are
modulated to ensure proper amount of outdoor air is brought into the building
when the system is rllnning, and that the outside air damper is tightly closed on
15 shutdown to minimi7~e outdoor air leakage.
(C) The overall performance of air filters, regardless of type or size selected, must
meet or exceed American Society of Heating, Refrigerating and Air Conditioning
Engineers standards 52-76 (Re~ 8). A typical construction of the filters consists of
continuous filament glass fibres with a light coating of viscosine adhesive applied to
20 the air entering side.
(D) Heating coil is used whenever the mixed air temperature starts to drop lowerthan a set point temperature usually 55~F to maintain a constant temperature in
the space. The purpose of the central system is to distribute conditioned air with
gradual changes in temperatures and moisture content to satisfy the air-
25 conditioning load.(E) Cooling coil is used to remove the sensible and latent heat from air. In a
comfort installation, with 25% or less of outdoor air a small internal latent load and
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only temperature controls, dew point of the air mixture leaving the coil will readily
satisfy room conditions.
(F) The supply fan blows directly forward or upward, the best arrangement may
be a double width, double inlet fan. When the air is to be delivered at right angles
S to the flow of air through the equipment, a single inlet fan should be used. These
arrangements will permit a direct flow of air from the fan wheel into the supplyduct without abrupt change in direction with ~ccompanying loss in efficiency.
(G) Return fan generally is essential for proper operation. The main function isto provide a positive return and exhaust stream from the work space, particularly
when mixing dampers are used to permit cooling with outdoor air in intermediate
seasons.
(H) For comfort humidifier installations where close control is not essential,
moisture can be added to the air by pan-type humidifiers with a heating coil, bygrid-steam humidifiers, and in some instances, me~h~nic~l atomizers. Location ofthis equipment is important to prevent stratification of moist air in the system.
The inventors, in recognition of all the above, have invented an engineered
method to elimin~te hazardous and noxious volatile organic compounds from the
indoor re-circulated air stream, at the same time reduce operating costs to the
equipment such as
(l) During spring and fall the indoor air quality controlled fogger is able
to reduce the need of starting the mechanical cooling (chiller) by providing
evaporative cooling due to the humidification.
(2) Indoor air quality controlled foggers will allow the elimin~tion of the
building's existing humidifiers. This may result in lower energy demands from the
heating system which could be as high as 10%.
(3) The elimination of any preheat coil which would reduce (l) heating
costs, (2) fan resistance, which in turn lower the electrical load on the fan.
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IN THE DRAWINGS
Figure 1 is a schematic drawing of a typical mixed air heating ventilating, air
conditioning unit currently in use.
Figure 2 is a representation of the fogger dyn~mics of an individual fogger of
the type used in a fogger array.
Figure 3 is a drawing of added chilled water control valves which would be
added to a conventional heating ventilating air conditioning unit when a bank ofhigh efficiency wash down filters is substituted for current filters.
Figure 4 is a representation of a mixed heating ventilating air conditioning
system with indoor air quality controlled foggers, a bank of high efficiency wash
down filters and a digital controller.
Figure 5 is a schematic drawing showing pneumatic controls of the indoor air
quality controlled foggers.
Figure 6 is an end view of installed foggers.
Figure 7 is a schematic drawing of the invention as used with a 100% fresh
air heating ventilating air conditioning unit.
Figure 8 is a schematic drawing showing the indoor air quality controlled
fogger applied to a multizone heating ventilating air conditioning unit.
Figure 9 is a schematic drawing showing the indoor air quality controlled
fogger used in association with a laboratory exhaust unit.
DESCRIPTION OF THE INVENTION
To fully understand the indoor air quality controller fogger invention a step-
by-step procedure has been developed to simplify and identify the method or
process which is as follows:
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STEP 1
A building Energy Analysis has to be performed to determine the building
design parameters. This is accomplished by estimating energy use and operating
cost for an offlce building (the modified bin method) as dictated by American
5 Society of Heating, Refrigerating and Air Conditioning Engineers 1985
Fundamentals SI Edition.
The modified bin method has the advantage of allowing off-design
calculations by use of diversified, rather than peak load values to establish the load
as a function of outdoor dry bulb temperature. The modified bin method also allows
lO the incorporation of a heating, ventilating and air-conditioning secondary system
and plant equipment effects into the energy calculations. This approach permits
the user to predict more accurately effects such as reheat and heat recovery that
can only be assumed with the degree day or conventional bin methods.
In the modified bin method average solar gain profiles, average equipment
15 and lighting use profiles and cooling load temperature difference values are used to
characterize the time-dependent (3ivel~i ried loads. The cooling load temperature
differences approximate the transient effects of building mass. Time dependencies
resulting from scheduling are averaged over a selected period, or multiple
calculation periods are established. The duration of a calculation period determines
20 the number of bin hours included in it. Normally, two calculation periods
representing occupied and unoccupied hours are sufficient, although any number
can be used.
Loads resulting from solar gains through gl~7ing are calculated by
determining a weighted-average solar load for a summer and a winter day (each
25 being of average cloudiness and having average solar conditions), and then
establishing a linear relationship of this solar load as a function of outdoor ambient
temperature. When the outdoor ambient temperature exceeds the room
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temperature the effect of heat transfer through sunlit roofs and walls is included in
the tr~n.qmi.qsion load by averaging the cooling load temperature ~lifferences and
applying corrections for deviations from the cooling load temperature differences -
reference opaque s~ ces is neglected when the outdoor ambient temperature is
S below room temperature.
Once a total load profile is determined as a function of outdoor ambient
temperature for the occupied and unoccupied periods, the performance of the
heating ventilating air conditioning system is computed by calculating the heating
and cooling coil loads. Then the annual energy consumption at the coils is
determined using bin hour weather data. Finally, the annual plant energy
consumption is calculated using boiler and chiller part-load performance model. To
summ~ri7.e the above statement we ask:
(1) What type of building is it?
(Office tower, two storey, one storey warehouse etc.)
1~ (2) Where is the building located?
(Ottawa, Toronto, W~.qhington etc.)
(3) What is the summer design load?
(4) What are the summer outside design conditions?
(Dry bulb temperature, wet bulb temperature and percent possible sunshine).
20 (5) Inside designconditions?
(Occupied hours, unoccupied hours, humidity ratio, setbacks, no cooling coil
used).
(6) What is the winter design load?
(7) What is the winter outside design condition?
(Dry bulb temperature, wet bulb temperature and percent possible slln.qhine).
(8) What is the building physical data?
(Gross floor area, net conditioned area, perimeter depth, interior space area,
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perimeter space area, wall area, glass area, wall type, roof type.)
(9) What is the internal load and schedules?
a,ights, equipment, people and the hours occupied and unoccupied).
(10) What type of ventilation?
(How much outside air filtration, how much air changes.)
(11) What type of air distribution system is it? VVhat is the design supply air
temperature? What is the design power?
(12) Identify primary equipment and energy consumption.
(Such as chiller, chiller pump, boiler, boiler pump, cooling tower, compressor).
STEP 2
Because of the wide-r~nging and constantly ~h~nging internal and external
factors that determines thermal loads on commercial and industrial buildings,
frequent evaluation is needed to obtain reasonably accurate estimates of annual
energy consumption. Detailed simulation methods allow the engineer to account for
the effect of these (~h~ngin~ conditions and system complexities on the estimated
energy usage.
To apply these methods a mathematical model of the building and its energy
systems must be prepared. This model will normally consist of mathematical
representations of:
(1) the thermal behaviour of the building structure;
(2) the thermodynamic behaviour of the air-conditioning delivery system;
(3) a mathematical relationship for load vs. energy requirements of the primary
energy conversion equipment.
Usually, each model is formulated so that certain "input" quantities allow
calculation of"output" quantities.
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STEP 3
The overall mo(lçlling strategy refers to the sequence and procedures needed
to design the indoor air quality controlled fogger into the building system.
The indoor air quality controlled fogger design starts with the psychrometric
5 chart analysis of the winter and spring/fall design conditions. Once the design
parameters are noted we now can determine the fogging array.
A fogger produces a four to five square foot pattern across 500 FPM air
handler flow, using only 5 SCFM of compressed air, entraining about 500 CFM of
return air for each SCFM of compressed primary air injected and intimately mixing
10 these primary and induced secondary air flow components at point of origin, within
the foggers"'gap".
Within a 5 SCFM of primary air are millions of tiny water pressure atomized
droplets which have been sheared and entrained within the jet stream. What
leaves the fogger orifice, jetted at the acoustic velocity are droplets and compressed
15 air shock wave pulses. The warm return air coming from the work space supplies
the heat source for atmospheric pressure and temperature flash-cooling evaporation
of the fog droplets. The foggers turning me(~h~ni.~m shown in Figure 4 provides the
critical pattern control so that ultra fine water droplets mix within the airflow. Fog
patterns must be carefully engineered, and fully controlled. Pattern control is
20 achieved by "tllrning" the foggers with respect to each other and the actual
turbulence encountered in bringing the system on-line.
While the general rule of compressed air consumption obeys the industrial
standard of 1/8 SCFM per atomized water pound, the need for quick-flash and
distribution control requires higher secondary air entrainment and calculable
25 incremental increases in compressed air pressure and consumption for some of the
foggers within a given array.
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A fogger, shown in Figure 2, is a ballistic type compressed air expander
which discharges compressed air at the acoustic velocity from the fogger's orifice.
Foggers of the ballistic type compressed air expander can be obtained from Turbo-
Fog Systems, Inc., 130 Gun Club Road, Stamford, Connecticut 06903 U.S.A. The
5 air expander (l) is an engineered orifice (2) and its long narrow drilled air passage
length is at least six times the orifice diameter through which the compressed air is
forced by a high inlet pressure on one end and atmospheric pressure at the other.
This means at high velocity, pulsating airflow stream is discharged from the
fogger's orifice (3) whenever the inlet pressure is at least 30 psig to create a Mach 1
10 exit velocity. As the inlet pressure increases so does the exit velocity.
The fogger's ballistic type orifice (2) is engineered for insertion into a
universal body (4). When the ballistic type orifice (2) is inserted into the body (4), it
becomes partially water jacketed by the agitator chamber (5) along its length. The
water jacket (8) is maintained at a controlled pressure, less than equal to the
15 compressed air pressure. Front seals (6) and rear seals (7) separate the compressed
air inlet pressure from the water jacket (8) which allows only the water feed holes
(9) to interconnect the water jacket (8) and compressed air pressure path at thecommon pressure point, through an agitation chamber (10) pressurized to
equilibrium when the compressed air has been allowed to expand to the acoustic
20 velocity choke-point. This assures a standing shock wave and resulting pulsating
air ~ow upon which fog propagation is dependent.
The foggers also in a bigger part act as an evaporative cooler which helps
reduce the use of merh~nic~l cooling.
In a hot environment, where ambient heat control is difficult or impractical
25 cooling is accomplished by passing below skin air temperature over the body.
Evaporative coolers are suited to the purpose and the performance of evaporativecooling is directly related to climate conditions. The entering wet bulb temperature
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governs the final dry bulb temperature of the air discharged from an evaporativecooler. The capacity of the evaporative cooler is determined by how much the drybulb temperature exceeds the wet bulb temperature. The m~qximum reduction in
dry bulb temperature is the difference between the entering air dry and wet bulb5 temperatures. If the air is cooled to the wet bulb temperature, it becomes saturated
and the process is 100% effective. System effectiveness is the depression of the dry
bulb temperature of the air leaving the apparatus divided by the difference between
the dry and wet bulb temperatures of the entering air.
Evaporative cooling performs a good air cleaning cycle, removing particulate
10 and gaseous cont~min~nts. Separation is largely a result of the impingement of
particles on a wetted surface such as the fins of a cooling coil or media.
STEP 4
When de~igning a heating, ventilating air conditioning system utili7~ing
digitally controlled foggers and system, a series of wash-down permanent air filters
15 (106) matching those specified for compliance with American Society of Heating,
Refrigerating and Air Conditioning Engineers Indoor Air Quality Standards 62-
1989, 65% efficiency or better filtration are located in the supply air plenum (lOOa)
proximate the fogger array (lOO) as shown in Figure 4. The efficiency of a filter is
measured in accordance with procedures described in American Society of Heating,20 Refrigerating and Air Conditioning Engineers Standards 52-76 or other industry-
accepted standards. American Society of Heating, Refrigerating and Air
Conditioning Engineers Standards 52-76 specifies a challenge agent with a broad
spectrum of particle size, typical of atmospheric dust. When describing high-
efficiency filters industry standards usually refer to a di-octyl-phthalate test, where
25 the challenge agent has a fairly narrow particle size distribution, around 0.3 micron
diameter. In reviewing filter manufacturers' catalogues there are few references to
filters sperific~lly aimed at the health care market. Rather, such applications are
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left to the engineer to address using "American Society of Heating, Refrigerating
and Air Conditioning Engineers çffi(~içncy filters" as appropriate to the required
filtration task. Filtering incoming air permits extended operation between
equipment cleanings, and tends to reduce maintenance costs. A bonus effect is the
5 reduction in dust accumulation within the conditioned space.
STEP 5
After the cooling coil design conditions have been detçrmined (i.e. cooling
load) and fluid flow (gallons per minute), two three-way automatic control valves
(11) and (13) can be incorporated into the existing chilled water piping system, one
10 control valve (11) installed on the chilled water supply line (12), one control valve
(13) installed on the chilled water return line (14) as shown in Figure 3. The
control valves (11) and (13) are installed on the chilled water lines (12) and (14) to
facilitate the use of cold city water pumped through the cooling coil (15) during the
off season periods (fall, winter, spring). The cooling coil (15) will run year round
15 when the system is in the occupied mode to condense the saturated mixed air
produced by the foggers.
STEP 6
The automatic control system modulates stages or sequences of the
equipment capacity to meet load requirements and provides safe operation of the
20 equipment. The heating, ventilation and air conditioning system with indoor air
quality controlled fogger can use pneumatic, merh~nic~l, electrical or electronic
control devices pending on existing building criteria and implies that human
intervention is limited to starting and stopping equipment and adjusting control set
points. The control system performance in an indoor air quality controlled fogger
25 application is evaluated in terms of speed of response and stability. A stable control
loop will keep the controlled v~ri~hle near set point while avoiding long-term
oscillations. A control loop with a fast speed of response quickly responds to process
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disturbances. The requirements of accuracy, speed and stability are often
contradictory (i.e. a change made in one of the component parameters could
adversely affect others). Hence, the performance level of such systems must be
selected to suit the application and must be evaluated in terms of control, comfort
and energy conservation.
Figure 4 shows the state-of-the-art indoor air quality controlled fogger
incorporated into a typical heating, ventil~ting air control system. The components
which constitute the invention in its entirety are numerically identified in thementioned schematic. The array of foggers (100) is positioned in the mixed air
stream and is sized with respect to the cross sectional area to ensure m~ximum
mixture of the fog jet stream to the mixed air stream. A three-way control valve(101) is located on the chilled water supply to switch me~h~nic~l cooling (chiller) to
city water cooling determined by the outside air temperature. A three-way control
valve (102) is located on the chilled water return circuit to switch from mel~h~nic~l
cooling to city water cooling at the same time and intervals as the control valve
(101) on the chilled water supply. A two-way control valve (103) is located in the
chilled water return to autom~tic~lly open to drain when returned city water is not
needed for foggers (100) or others. Piping (104), pumps (104a), an air solonoid
valve (104b) and water solonoid valve (104c) are needed to control both the
compressed air and water going to the foggers. A central processing unit or a
control panel (105) automatically controls the foggers (100), valves (104b),
temperatures and flows. A bank of high effi~i~?ncy wash down filters (106) aids in
capturing any large particulate such as dust. Proper slopes (107) in the cooling coil
drain pan (107b) ensure no water is left in the drain pan (107c) to foul.
Figure 5 illustrates a pneumatic control system as one way to control the
indoor air quality controlled fogger system. As shown in the schematic, a booster
pump (108) is supplied to increase water pressure when needed to supply the fogger
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."
array (100) with the proper water pressure. A differential pressure switch (109) is
installed across the discharge side and the suction side of the booster pump (109A)
to signal the alarm circuit of the control panel when the booster pump (108) fails. A
water filter system (110) is added onto the city water line to add an extra protection
to the foggers (100). A water control valve (111) and a compressed air control valve
(112) are both modulated to deliver the perfect fog ball.
An EMS (energy monitoring system) (113) with controllers, relays and
others inside the panel is supplied with gauges, alarm lights and on/off switches on
the outside panel face (115). The control tubing (114), which in most installations
is 1/4" copper tube, is distributed to the sensors, valves and other control devices.
The energy monitoring systems (113) is in most cases a nema 1 panel housing
regulators, controllers, fail safe interlocks and alarm annunciator. The outsidepanel face (115) or front cover displays the operating status of the indoor air quality
controlled fogger incorporated into an existing heating, ventilation and air
conditioning system.
Control Components
While control components may be classified in several ways, the indoor air
quality controlled fogger groups components by their function within a complete
control system. The first that is considered is the controlled device or final control
element, examples of which are relays, valves, dampers and variable speed drivesfor fans. Actuators, which are used to drive the valve or damper, are also covered.
The next consideration is the sensing element that measures changes in the
controlled variable. F,x~mples of sensing devices include temperature sensors,
humidity sensors, water and air pressure, water and air differential pressure, water
and airflow rates. While many other kinds of special sensors are available, the
above mention represents the majority of those found in the indoor air quality
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controlled fogger control system. The third consideration, various types of
controllers are reviewed. Controllers are ~l~.qsified according to the control action of
the cause to maintain the desired condition (set point) whether they are two
position, floating control, proportional control, proportional plus integral control, or
5 proportional plus integral plus derivative control. In addition, this also describes
the various techniques av~ hle for m~king the control decision in a modulating
control system, such as pneumatic or digital controllers.
The controlled device is most frequently used to regulate or vary the flow of
vapour (steam), liquid (water) or air within a heating, ventilation, air conditioning
10 system. Liquid and vapour flow regulators are known as valves, and airflow control
devices are called damper and variable speed drives. Both types perform
essentially the same function and must be properly sized and selected for every
indoor air quality controlled fogger application. The control system link to thevalve or damper is a component referred to as an operator, or actuator. This device
15 uses electricity, compressed air, or hydraulic fluid to power the motion of the valve
stem or damper linkage, or the frequency wave form of a speed drive through its
operating range.
Valves
Valves or an automatic valve is designed to control the flow of vapour
20 (steam), liquid (water), gas (air) and other fluids and may be considered as a
variable orifice positioned by an electric or pneumatic operator in response to
impulses or si~n~ from this controller. It may be equipped with a throttling plug
or v-port specially designed to provide desired flow characteristics. Various types of
automatic valves include:
25 - double-seated valves
- three-way mixing valves
- three-way diverting valves
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- butterfly valves.
Valve operators are of the following (1) a solenoid consisting of a magnetic
coil operating a movable plunger; (2) an electric motor operating the valve steam
through a gear train and linkage; (3) a pneumatic operator consisting of a spring-
5 opposed, flexible diaphragm or bellows attached to the valve steam; (4) springlesspneumatic operators, using two opposed diaphragms or two sides of a single
diaphragm, are also used, but are generally limited to special applications involving
large valves or high pressures.
Dampers
Automatic dampers are used in air-conditioning and ventilation systems to
control air flow. They may be used for modulating control to maintain a controlled
variable such as mixed air temperature or supply air duct static pressure. Two
types of damper arrangements re used for air-handling system flow control: (1)
parallel blade dampers which are adequate for two-position control and can be used
15 for modulating control when they are the primary source of system drop; (2)
opposed blade dampers are preferable, since they normally provide better control.
Sensors
A sensor is the component in the control system that measures a value of the
controlled variable. A change in the controlled variable produces a change in some
20 physical or electrical property of the primary sensing element, which is thenavailable for translation or amplification by mech~nic~l or electrical ~ignal VVhen
the sensor uses a conversion from one form of energy (me~h~nic~l or thermal) to
another (electrical), the device is known as a transducer. In some cases, the sensing
element is a transducer, such as a t~rmin~tor in which a change in electrical
25 resistance occurs as a direct result of a change in temperature. The sensors for the
indoor air quality controlled fogger must be capable of providing an identical and
.~ignifi-~nt change in its output signal over the expected operating range. This
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sensor must have a compatibility of the controller input, set-point accuracy andconsistency, system response time (or process dyn~mi~.q), control agent properties
and characteristics, and ~mhient environmental characteristics.
Controllers
Controllers take the sensor effect, compare it with the desired control
condition (set point) and regulate an output signal to cause a control action on the
controlled device. The controller and sensor can be combined in a single
instrument, such as a room thermostat, or they may be two separate devices. Whenseparate pneumatic units are used, the pneumatic controller is usually referred to
as a receiver controller.
Pneumatic Receiver Controller
Pneumatic receiver controllers are normally combined with sensing elements
with a force or position output to obtain a variable air pressure output. The control
mode is usually proportional, but other modes such as proportional-integral can be
used. These controllers are generally ~l~q.qified as non relay, relay direct or reverse
acting.
Direct Digital Controllers
A direct digital controller uses a digital computer (such as a microprocessor
or microcomputer) to implement control algorithm on one or multiple controllers in
that the control algorithm is stored as a set program instructions in memory
(software and fiirmware). The controller itself calculates the proper control .qign~l.q
digitally rather than using an analogue circuit or me~h~nic~l change.
A digital controller can be either a single or multi loop controller. Interface
hardware allows the digital computer to process qign~l.q from various input devices
such as electronic temperature, humidity or pressure sensors described earlier.
Based on digitized equivalents of the voltage or current signals product by the
inputs, the control software calculates the required state of the output devices, such
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- 20 -
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as valves, dampers and low limits. The control algorithm stores in the computer's
memory in conjunction with actual input valves enable the control decisions. Thecomputer scans the input devices, executes the control algorithm, then positions the
output device in a time-multiplex scheme. Digital controllers can be ~ sified with
5 regards to the way the control algorithms are stored in memory.
Figure 6 illustrates the fogger assembly on a typical application where the
fogger (120) is mounted on a bracket (121) to assure that the fog stream is cross
flow to the mixed-air stream. Uni-strut (122) is used to build a H frame to support
all the foggers, piping and fittings. Brass fittings (123) are fiitted with compression
10 nuts (125) for air and water tight seal which is tied into copper tubing to serve the
foggers with air and water. Copper tubing (124) is used to transport water in one
line (1/4") and air in the other line (3/8") to the foggers.
Figure 7 illustrates a 100% fresh air heating, ventilation and air conditioning
system with the indoor air quality controlled foggers incorporated within the
15 system design parameters. The simplest form of all air systems is a 100% fresh air
conditioner serving a single temperature control zone. The unit may be installedeither with or without distributing ductwork. Ideally, we can provide a system
which is completely responsive to the needs of the space.
The indoor air quality controlled fogger is easily installed into the existing
20 unit to assist in the removal of outside pollutants as well as dust.
These types of units are usually found on roofs supplying small commercial
of~ices, retail stores and apartments. Since control is directly from space,
temperature and humidity, close regulation of the system conditions may be
achieved. One hundred (100%) fresh air heating, ventilation and air conditioning25 units without reheat offer cooling flexibility but cannot control summer humidity
independent of temperature requirements.
7~ 5~
- 21 -
Figure 8 illustrates a multizone heating, ventilation and air conditioning
system with the indoor air quality controlled fogger installed in the mixing box(126) to çlimin~te volatile organic compounds and dust (particulate). The
multizone system is applicable to service a relatively small number of zones from a
5 single central air handling unit. The requirements of the different zones are met by
mixing cold and warm air (hot deck, cold deck) through zone dampers (127) at thecentral air handler (128) in response to zone thermostats. The mixed treated
conditioned air is distributed throughout the building by a system of single zone
ducts (129). The most common multizone configuration reveals the physical
10 differences between the multizone and dual-duct systems, with the zone mixingdampers (127) generally distributed horizontally along the hot and cold deck
discharge plenums (130) and (131) of the air handler (128).
Multizone packaged equipment using direct expansion cooling coils, hot gas,
electric or direct fuel-fired hot deck ex~h~ngers generally have step-controls for hot
15 and cold deck capacity, which may substantially limit the quality of temperature
and humidity control unless specific control provisions re incorporated into thesystem such as the indoor air quality controlled fogger.
Figure 9 illustrates a typical laboratory exhaust with the indoor air quality
controlled fogger incorporated into the system for the ~limin~tion of various
20 pollutants. Energy considerations lend themselves to the application of run-around
exhaust heat recovery coils (132) because of the need to clean lab exhaust for a very
wide range of industrial cont~min~nts which may be utilized within the lab
modules. The indoor air quality controlled fogger is designed wherein exhaust air
is blown through the heat recovery coil (132), a downstream fogging array or
25 system, and fogs the cont~min~nt exhaust stream to capture the pollutants in the
10 micron diameter water droplets. The saturated air blows through a
cooling/con-lensing coil (133) where the pollutants are condensed in the cooling coil
-- 22~11560
- 22 -
(133) then run to drain (134). The new clean exhaust stream is discharged to theoutside air.
Scrubbing experience for the broad gamma of expected cont~min~nts has led
us to repeat the indoor air quality controlled fogger practice with the same
5 application of wet film condenser coil scrubbing equipment.
