Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02606878 2007-10-15
1 "VENTILATION SYSTEM FOR HIGH-RISE STRUCTURES"
2
3 FIELD OF THE INVENTION
4 Embodiments of the invention relate to ventilation systems for
structures and more particularly to structures having a plurality of zones on
a
6 plurality of separate floors which require ventilation and temperature
control.
7
8 BACKGROUND OF THE INVENTION
9 As shown in Figs. 1A and 1B, conventional ventilation systems
typically comprise a large single main duct which extends from a roof to a
base
11 of a high-rise building. Air at ambient temperature is drawn into the duct,
such as
12 by large fans, at the roof and during cold seasons is heated to about 55 F,
often
13 to prevent condensation forming in the duct. The air is drawn from the main
duct
14 to individual compartment units on each floor. At each floor, the
compartment
unit or air handler delivers the primary air, which comprises a mixture of
outdoor
16 air from the main duct and re-circulated return air from the floor, to one
or more
17 variable air volume (VAV) units which service individual zones on the
floor. The
18 one or more VAV boxes then circulate the primary air into each
thermostatically
19 controlled zone to maintain the desired temperature. Excess air volumes are
exhausted at the roof. The main duct provides fresh air to all the floors. Due
to
21 volumes of air required, the main duct is sized to provide a maximum amount
of
22 fresh air required to meet the minimum fresh air volumes only.
23 The VAV boxes are typically thermostatically or sensor-controlled
24 and regulate the quantity of conditioned air, typically at 55 F, which is
supplied to
each zone.
CA 02606878 2007-10-15
1 Typically, standards require that outdoor air be provided at a
2 minimum of about 20 cfrn/person or 1 cfm/square foot. Typical high-rises
often
3 have about 15,000-20,000 square feet per floor or more and thus, large
volumes
4 of circulating air of about 15,000 - 20,000 cfm/floor or more are required.
Optional monitoring, using other sensors such as CO2 sensors, is known to
6 regulate the amount of outdoor air based on actual loads per zone and
therefore
7 the amounts required may be lower than design loads when the number of
8 people in the building is reduced.
9 At moderate temperature, such as the typical design temperature
of 55 F, theoretically all air provided to the VAV's could be fresh air.
11 Unfortunately, the main duct cannot be sized large enough for this
scenario.
12 Accordingly, energy is typically expended to cool recirculating air.
13 In addition to the large amounts of energy utilized to draw the large
14 volumes of air required into the main duct and to exhaust excess air from
the
building, as well as the energy required to heat the air delivered to the main
duct,
16 particularly during fall and winter seasons, energy is also consumed in
either
17 heating or re-cooling the air at each compartmental unit and/or VAV to mix
with
18 recirculating air therein to provide desired ambient temperatures at the
plurality
19 of zones on each of the floors.
There is interest in the industry in providing a ventilation system
21 which meets the requirements for fresh air supply to all zones in a high-
rise
22 building while minimizing energy consumption.
23
2
CA 02606878 2007-10-15
1 SUMMARY OF THE INVENTION
2 A novel ventilation system utilizes a damper on each ,floor which is
3 fluidly connected through an external wall of each floor to the outdoors for
4 directly admitting fresh outdoor air to the floor to satisfy regulated
outdoor air
requirements and to provide conditioned air at a design temperature of about
6 55 F to conventional thermostatically or sensor-controlled distributors,
such as
7 VAV's or about 65 F through controlled variable diffusers from a floor
plenum,
8 situated in zones on the floor.
9 When ambient temperatures are about the design temperature, no
additional energy is expended to heat and or cool the air circulated to the
11 distributors and the entirety of the air provided can be admitted through
the
12 intake damper which is sized accordingly.
13 When temperatures are very low or very high, only sufficient
14 outdoor air to meet the minimum fresh air requirements is admitted and is
mixed
with recirculating air from the zones in the floor at a compartment unit for
16 providing conditioned air at about 55 F to the VAV's. At extreme
temperatures,
17 the conditioned air may need to be further cooled, using heat exchangers at
the
18 compartment unit or heated, typically at the VAV's, to satisfy zonal
temperature
19 requirements.
Therefore in a broad aspect of the invention a ventilation system
21 for a high rise building having a plurality of conditioned floors,
comprises: a
22 compartment unit at each of the plurality of conditioned floors for mixing
outdoor
23 air and returned air therein for delivering conditioned air to each floor
at a design
24 temperature; an intake damper at each of the plurality of floors for
directly
connecting between the compartment unit and the outdoors, each intake damper
3
CA 02606878 2007-10-15
1 directly admitting outdoor air from the outdoors to the compartment unit and
2 capable of admitting a volume of outdoor air up to a total volume of
conditioned
3 air for the floor; one or more distributors on each conditioned floor for
receiving
4 the conditioned air from the compartment unit at the design temperature and
for
controlling the amount of conditioned air delivered to each of one or more
zones
6 on the conditioned floor so as to achieve a desired zonal temperature in the
one
7 or more zones; and an exhaust damper for each conditioned floor for
exhausting
8 excess air in an amount equal to or less than the admitted outdoor air.
9 In an embodiment of the invention the distributors are conventional
variable air volume boxes, which deliver the conditioned air from the
11 compartment unit to the zones on the floor under the control of a
thermostat for
12 achieving a desired temperature in each of the zones. Re-heat coils may be
13 provided in the VAV's for heating the conditioned air to meet zonal
temperature
14 requirements. Similarly, heat exchangers in the system may be used to cool
the
conditioned air for delivery to the zones on the floor.
16 In an embodiment of the invention wherein the distributors are
17 zonally controlled variable diffusers connecting the zone to a floor
plenum,
18 conditioned air is provided to the floor plenum at about 65 F and the
recirculated
19 air is returned to the compartment unit through a ceiling plenum.
4
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1 BRIEF DESCRIPTION OF THE DRAWINGS
2 Figure 1A is a longitudinal sectional schematic view of a
3 conventional high-rise ventilation system according to the prior art;
4 Figure 1 B is a side sectional view according to Fig. 1A;
Figure 2A is a longitudinal sectional schematic view of a high-rise
6 ventilation system according to an embodiment of the invention;
7 Figure 2B is a partial longitudinal sectional schematic view of a
8 bottom of the high-rise according to Fig. 2A;
9 Figure 3A is a partial longitudinal view of a plurality of conditioned
floors of a high-rise building having a central ventilation system arrangement
11 according to one embodiment of the invention;
12 Figure 3B is a plan view of a conditioned floor according to Fig. 3A;
13 Figure 4 is a plan view of a floor of a high-rise building having a
14 perimeter ventilation system arrangement according to one embodiment of the
invention;
16 Figure 5 is a graphical representation of the approximate amounts
17 of outdoor air required at a variety of ambient temperatures to permit
maintaining
18 both minimum outdoor air requirements and desired temperatures at each
zone;
19 and
Figure 6 is a side sectional schematic view of a raised floor plenum
21 according to one embodiment of the invention.
22
5
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1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
2 Having reference again to Figs. 1 A and 1 B, a conventional prior art
3 ventilation system 1 typically comprises a single large duct 2 which extends
from
4 a roof 3 of a high-rise building to a base 4 of the high-rise building
through which
fresh air FA, at ambient temperature, is drawn, such as by large fans at the
roof
6 3. During cold seasons the fresh air FA in the duct 2 is heated to about 55
F.
7 The 55 F heated fresh air FA is thereafter distributed at each conditioned
floor 5
8 (5a, 5b, 5c... ) from the main duct 2 to a compartment unit 6 which also
receives
9 retumed air RA from the conditioned floor 5 and utilizes the now-heated
fresh air
FA to condition the returned air RA for providing the minimum required amount
11 of fresh air FA therein and to assist with temperature control in each of a
plurality
12 of individual zones located on the conditioned floor 5.
13 Having reference to Figs. 2A and 2B and in one embodiment, a
14 ventilation system 10 for a high-rise building comprises, on each
conditioned
floor 5, a fresh or outdoor air intake damper 11 which extends through an
16 external wall of the conditioned floor 5 for fluidly connecting to the
outdoors
17 adjacent the conditioned floor 5 to a compartment unit 6 for directly
admitting
18 fresh, outdoor air FA to the compartment unit 6. The compartment unit 6
mixes
19 the outdoor air FA with return air RA returned from the conditioned floor 5
for
forming conditioned air CA and then distributes the conditioned air CA to one
or
21 more distributors 12 on the conditioned floor 5 connected to one or more
zones
22 Z,, Z2, Z3... on the conditioned floor 5. In one embodiment, the
distributors 12
23 are VAV's and each conditioned floor 5 has at least one VAV unit 12 per
zone
24 Zi, Z2, Z3...
6
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1 Wit reference also to Fig. 3A, the return air RA is collected in a
2 ceiling plenum 23 for return to the compartment unit 6.
3 The system 10 further comprises an exhaust damper 13 fluidly
4 connected to the outdoors for exhausting at least a portion of excess air EA
from
the floor typically in an amount equal to or less than the admitted outdoor
air FA.
6 Further, the system typically comprises an exhaust duct 14
7 connecting between the floors 5 for venting at least a small amount of
excess air
8 EA to the base 4 of the building, typically the parkade.
9 Outdoor air FA is drawn directly from outdoors into each
conditioned floor 5, at ambient temperature, through the outdoor intake damper
11 11 in amounts sufficient to satisfy at least a minimum requirement for
outdoor air
12 FA, which is typically about 1 cfm per square foot and at a minimum of
about 20
13 cfm per person. The outdoor air FA is drawn into the compartment unit 6,
such
14 as by fans, where the outdoor air FA is mixed with return air RA from the
conditioned floor 5 as required, for delivery as conditioned air CA by the VAV
16 units 12 to each of the zones Zi, Z2, Z3... at a design temperature of 55
F. Each
17 of the zones Z,, Z2, Z3... is independently thermostatically controlled and
18 therefore each zone Z,, Z2, Z3... may require a different amount of
conditioned
19 air CA to be discharged to the air circulating in the zone Zi, Z2, Z3... to
achieve a
desired zonal temperature.
21 Typically at least the minimum 20 cfm/person is exhausted from
22 each conditioned floor 5 to the parkade, such as through the exhaust duct
14,
23 and a small amount of loss from each conditioned floor 5 occurs through
elevator
24 shafts 15 and the like. Any additional excess air EA is exhausted from each
7
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1 conditioned floor 5 through the exhaust damper 13 so as to balance a
pressure
2 on the conditioned floor 5.
3 For example, if a minimum required volume of outdoor air FA of
4 2000 cfm is drawn in through the intake damper 11, about 1500 cfm is
exhausted to the parkade from bathrooms and generally from the conditioned
6 floor 5 typically through the exhaust duct 14 and about 500 cfm is lost in
the
7 elevator shafts 15 and the like. In this case, no excess air would be
exhausted
8 through the exhaust damper 13.
9 Where 15,000 cfm of outdoor air FA is drawn in through the intake
damper 11, the amount vented to the parkade, being about 1500 cfm is
11 maintained as is the about 500 cfm which is lost in the elevator shafts 15
and the
12 like. In this case, about 13,000 cfm of excess air EA remains to be
exhausted
13 through the exhaust damper 13. In embodiments of the invention, the exhaust
14 damper 13 is a barometric damper.
As one of skill would understand, accommodations are made to
16 meet local code regarding smoke evacuation. One such method is to extend
the
17 exhaust duct 14 to the roof 3 and to size the exhaust duct 14 accordingly
so that
18 smoke can be evacuated through the duct 14 when required.
19 As shown in Fig. 3B, and in one embodiment, the compartment unit
6 is centrally located on each conditioned floor 5 and provides conditioned
air
21 CA to the VAV units 12 in the surrounding zones Z,, Z2, Z3....
22 Alternatively, as shown in Figs. 3A and 4, the compartment unit 6 is
23 located peripherally, typically adjacent the intake damper 11, and provides
24 ventilation to the VAV units 12 in the surrounding zones Z,, Z2, Z3....
8
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1 As shown in Fig. 5, and in an example of a conditioned floor 5 of a
2 building having about 15000 square feet, when the ambient temperature of the
3 outdoor air FA is about 55 F, 100% of the total amount of air required for
the
4 conditioned floor 5 can be outdoor air FA. The outdoor air FA is delivered
to the
compartment unit 6 for delivery to the VAV units 12 and to the various zones
Zi,
6 Z2, Z3.... for satisfying the ventilation, fresh air and temperature
requirements.
7 The entirety of the floors' ventilation requirement can be outside air FA
and thus
8 fresh outdoor air FA is drawn through the intake damper to meet the entire
9 requirement. No additional energy is expended through heating or cooling the
outdoor air FA at the compartment unit 6 or the VAV's 12.
11 As the ambient temperature of the outdoor air FA decreases, the
12 amount of outdoor air FA drawn into the intake damper 11 is decreased. Only
13 sufficient outdoor air FA is admitted and combined with re-circulating air
in the
14 compartment unit 6 so as to result in a distribution mixture of conditioned
air CA
at design temperature, being about 55 F, being discharged at the VAV units 12
16 in each zone Zl, Z2, Z3..... and to meet the minimum outdoor air FA
17 requirements. Clearly when the ambient temperatures are very low, such as
18 about -20 F or lower, only the minimum amount of outdoor air FA is drawn
into
19 the intake damper 11 to satisfy air quality requirements.
In order to result in a desired zonal temperature, one may need to
21 heat the delivered 55 F air at the VAV units 12. Typically, re-heating
coils 16 are
22 provided in some or all of the VAV units 12. Re-heating coils 16 may be
provided
23 only in VAV's 16 serving peripherally located zones Z,, Z2, Z3..... and may
be
24 optionally used for heating the building at night. Alternatively, a heating
coil may
9
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1 be provided at the compartment unit 6 for heating the air provided to the
VAV's
2 12.
3 Added benefits and an even greater reduction in very cold outdoor
4 air FA intake is possible by incorporating sensors 17, such as CO2 monitors,
into
the ventilation system 10. The CO2 monitors 17 sense the actual load in the
6 building and can reduce the amount of outdoor air FA admitted below the
7 minimum design amounts when the number of people in the building is reduced,
8 such as on weekends and during the evening. Thus, energy savings are
realized
9 by reducing the amount of conditioning required.
When ambient air temperatures are above 55 F, the amount of
11 outdoor air FA drawn into the intake damper 11 is similarly reduced to
minimum
12 levels to minimize cooling requirements for cooling the air delivered to
the VAV's
13 12. A heat exchanger in the compartment unit 6 conditions the air, such as
by
14 cooling the returned air RA combined with the minimum amount of outdoor
warmer air FA for delivery of conditioned air CA to the VAV units 12 in the
zones
16 Z,, Z2, Z3..... at about 55 F. Typically, a chiller supplies cooling fluid
to the heat
17 exchangers in the compartment units 6, and is sized to accommodate maximum
18 local ambient summer temperatures.
19 In one embodiment, sensors 17, such as CO2 sensors, are
incorporated into the ventilation system 10 for sensing actual occupant loads,
the
21 outdoor air FA intake through the intake damper 11 is controlled based on
the
22 actual load and may be reduced below a typical or design minimum which is
23 calculated based on a hypothetical number of occupants. As previously
stated,
24 incorporating such sensors 17 is particularly advantageous for weekends,
evenings and other times when occupant loads are typically very low. Rather
CA 02606878 2007-10-15
1 than energize an entire ventilation system to satisfy only a few occupants
on one
2 or more of the floors 5 during these off-peak times, such as is done with
many
3 conventional systems, the ventilation system 10 according to embodiments of
4 the invention is controlled by the sensors 17 to intake and potentially
condition
only the required amount of outdoor air FA for a particular conditioned floor
5
6 which is in use.
7 For example, a typical occupant density of 100 people per floor 5
8 may require a minimum of about 2000 cfm of fresh outdoor air FA. In
9 conventional systems, the intake of the 2000 cfm would be maintained
regardless the number of occupants, to meet the minimum design amount.
11 However, in the ventilation system 10 according to this embodiment, if only
10
12 people were present on a floor, the CO2 monitors 17 sense the reduced
13 occupant load and reduce the minimum outdoor air FA intake to about 200 cfm
14 which meets the minimum required amount of fresh outdoor air FA per person
for that floor 5.
16 Having reference to Fig. 6, and in one embodiment, the distributor
17 12 comprises a floor plenum 20, situated at floor level, to which
conditioned air
18 CA from the compartment unit 6 is supplied. Variable flow diffusers 21 are
19 provided in each zone Z,, Z2, Z3..... and which can be adjusted
individually by
the occupants in each zone Z,, Z2, Z3..... to control the flow of conditioned
air
21 CA to be released to the zone Zi, Z2, Z3..... from the floor plenum 20.
Return
22 grilles 22 are mounted at the ceiling and air circulated though the zone
Zi, Z2,
23 Z3..... is returned to a ceiling space 23 through the grilles 22. Retumed
air RA is
24 returned to the compartment unit 6 as required and the excess air EA is
exhausted to the outdoors through the exhaust damper 13 which is fluidly
11
CA 02606878 2007-10-15
1 connected between the ceiling space 23 and the outdoors 24. In this
2 embodiment, conditioned air CA is supplied to the floor plenum 20 at about
65 F.
3 Thus, embodiments of the invention utilizing this embodiment provide even
4 greater savings as cooling of air is not required unless the ambient
temperature
is above 65 F.
6 Optionally, additional embodiments are possible wherein heating
7 and cooling of the air is augmented using geothermal heat sinks and cold
sinks
8 created for the purpose. In one such embodiment, cold outdoor air FA is
9 exchanged in a heat exchanger with glycol circulated in the ground to freeze
a
portion of the ground situated below the building. The cold from the ground is
11 subsequently circulated through the heat exchanger during summer to cool
the
12 air in the building. Similarly, a heat sink may be created by exchanging
heat from
13 the outdoor air FA during the summer with the ground so as to store heat
for use
14 in the winter.
12
