U.S. patent application number 13/135099 was filed with the patent office on 2012-03-15 for heat recovery and demand ventilationsystem.
Invention is credited to Richard S. Kurelowech.
Application Number | 20120064818 13/135099 |
Document ID | / |
Family ID | 45807179 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120064818 |
Kind Code |
A1 |
Kurelowech; Richard S. |
March 15, 2012 |
Heat recovery and demand ventilationsystem
Abstract
A ventilation system for an air conditioning system includes
dampers, a heat exchange unit, and a control unit. One damper
controls the flow of ambient air into the system. The other damper
controls the flow of relief/exhaust air that is cannibalized from
return air from a room or space being cooled (or heated) by the air
conditioning system. The ventilation system utilizes a control
algorithm in the control unit to calculate, at stepped spaced apart
increasing room ventilation rates, increasing CO2 concentrations in
the air in the room that are below a maximum desired CO2
concentration in a room. The control algorithm permits a control
unit in the ventilation system to open and close the dampers to
maintain a CO2 concentration in the room that is below the desired
CO2 concentration level.
Inventors: |
Kurelowech; Richard S.;
(Phoenix, AZ) |
Family ID: |
45807179 |
Appl. No.: |
13/135099 |
Filed: |
June 24, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12807018 |
Aug 26, 2010 |
|
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13135099 |
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Current U.S.
Class: |
454/251 |
Current CPC
Class: |
F24F 12/006 20130101;
F24F 2012/007 20130101; F24F 2011/0006 20130101; Y02B 30/563
20130101; Y02B 30/56 20130101; F24F 2110/70 20180101 |
Class at
Publication: |
454/251 |
International
Class: |
F24F 7/06 20060101
F24F007/06 |
Claims
1. In combination with a building structure including a room with a
maximum occupancy rating of at least twenty people per 1,000 sq. ft
of occupied space, an air conditioning system including a heat
transfer coil, a first section of duct (D40) leading to the heat
transfer coil to direct supply air from the building structure over
the coil, and a second section of duct (D20) leading away from the
heat transfer coil to carry air from the coil back into the
building, the improvements in the building structure comprising (a)
a ventilation control unit attached to the first section of duct
and including (i) a housing (230), (ii) a heat exchange unit (120),
(iii) a third section of duct (D10) connected to said first section
of duct (D40) to direct a first portion of return air from the room
into said first section of duct, (iv) a fourth section of duct
(D30) to direct a second portion of return air from the room over
said heat exchange unit, (v) a fifth section of duct (D50) to
direct ambient air over said heat exchange unit into said third
section of duct (D10), said heat exchange unit maintaining said
second portion of return air separate from said ambient air and
transferring heat between said second portion of return air and
said ambient air, and directly to said third section of duct (D10)
by bypassing said heat exchange unit, (vi) a sixth section of duct
(D60) to direct said second portion of return air from said heat
exchange unit into the outside atmosphere, (vii) an outlet damper
assembly (160) controlling the flow of said second portion of
return air over said heat exchange unit (120) and into the outside
atmosphere, (viii) a generally semi-cylindrical inlet damper
assembly controlling the flow of said ambient air into said
ventilation control unit and including a member (38, 1150)
rotatable between at least three operative positions, a first
operative position directing ambient air only over said heat
exchange unit (120), a second operative position bypassing said
heat exchange unit and directing ambient air only directly to said
third section of duct (D10) to combine with said first portion of
return air, and a third operative position preventing said ambient
air from flowing to said heat exchange unit and to said third
section of duct (D10) to combine with said first portion of return
air, (ix) a control unit operatively associated with said inlet and
outlet damper assemblies to control the rate of flow of said
ambient air and said second portion of said return air,
respectively, through said inlet and outlet damper assemblies, (x)
a first flow sensor operatively associated with said inlet damper
assembly to generate signals to said control unit representing the
rate of flow of ambient air through said inlet damper assembly,
(ix) a second flow sensor operatively associated with said outlet
damper assembly to generate signals to said control unit
representing the rate of flow of said second return air portion
through said outlet damper assembly, (x) a CO2 sensor in the room
to generate signals to said control unit representing the
concentration of CO2 in the air in the room; (b) a first fan to
direct said ambient air into said fifth section of duct, over said
heat exchanger, and into said first section of duct; (c) a second
fan to direct said second portion of return air from said fourth
section of duct, and through said fourth section of duct over said
heat exchanger, and into the atmosphere; (d) a control algorithm in
said control unit to calculate, at stepped spaced apart increasing
room ventilation rates, increasing CO2 concentrations in the air in
the room that are below a maximum desired CO2 concentration in the
room.
Description
[0001] This application is a continuation in part of U.S. patent
application Ser. No. 12/807,018 filed Aug. 26, 2010.
[0002] This invention relates to heating and air conditioning
systems.
[0003] More particularly, the invention relates to a system to
facilitate ventilation air heat recovery and volume management
while maintaining a high indoor air quality for human occupants.
This invention will substantially reduce the energy consumption of
heating and air conditioning systems in commercial and
institutional buildings with high occupant densities (greater than
20 people per 1,000 square feet of occupied space).
[0004] Commercial and institutional buildings have long been
equipped with constant air volume ventilation systems which employ
a means for outside air to enter and leave the building. Recent
technology also employs ventilation air volume control utilizing
CO2 sensors and operable dampers. Such systems are controlled using
a single point CO2 level as the ventilation reference value and the
objective is to prevent objectionable odors and vapors from
accumulating in buildings.
[0005] It has for many years been desirable to provide, when
possible, improvements to such ventilation air systems.
[0006] Therefore, it is a principal objective of this invention to
provide an improved system to ventilate a building in the most cost
effective, energy efficient manner, and meet the requirements of
indoor air quality standards developed by recognized authorities in
the industry, specifically, ASHRAE Standard 62.1-2010.
[0007] This and other further objects will be apparent to those
skilled in the art from the following detailed description thereof,
taken in conjunction with the drawings, in which:
[0008] FIG. 1 is a top view illustrating a retrofit module
constructed in accordance with one embodiment of the invention and
installed in a pre-existing air conditioning or heating system;
[0009] FIG. 2 is a top view further illustrating the retrofit
module of FIG. 1;
[0010] FIG. 3 illustrates an IRV graph prepared in accordance with
the system of the invention;
[0011] FIG. 4 is a block flow diagram illustrating a heat transfer
and ventilation control system constructed in accordance with the
invention;
[0012] FIG. 5 is a block flow diagram illustrating a logic sequence
utilized by a controller in the system of the invention illustrated
in FIG. 4;
[0013] FIG. 6 is a top view illustrating a retrofit module
constructed in accordance with another embodiment of the invention
and installed in a pre-existing air conditioning or heating
system;
[0014] FIG. 7 is a top view further illustrating the retrofit
module of FIG. 6 and the mode of operation thereof;
[0015] FIG. 8A is a top view illustrating a duct-damper assembly in
the module of FIG. 6 with the damper in a first operative
position;
[0016] FIG. 8B is a top view illustrating the duct-damper assembly
of FIG. 7 with the damper in a second operative position;
[0017] FIG. 8C is a top view illustrating the duct-damper assembly
of FIGS. 6 and 7 with the damper in a third operative position;
[0018] FIG. 9 is a top view further illustrating portions of the
duct-damper assembly of FIG. 8A;
[0019] FIG. 10 is a side view illustrating the drum damper
scalloped arc segment configuration;
[0020] FIG. 11 is a perspective view of the assembled duct-damper
assembly of FIG. 9 in conjunction with a control system and
illustrating further construction details thereof;
[0021] FIG. 12 is a segregated perspective view of FIG. 11
illustrating an angled damper blade configuration and damper
construction;
[0022] FIG. 13 is a segregated perspective view of FIG. 11 of the
drum arc segments illustrating the undulating surface extending
between the scalloped edges of the damper;
[0023] FIG. 14 is a segregated perspective view of FIG. 11 of the
solid drum top and bottom of the damper assembly illustrating
additional construction and operational details thereof;
[0024] FIG. 15 is a segregated perspective view of FIG. 11 of the
air diverter panel illustrating additional construction and
operational details thereof;
[0025] FIG. 16 is a top view illustrating a retrofit module
constructed in accordance with another embodiment of the invention
and installed in a pre-existing air conditioning or heating
system;
[0026] FIG. 17 is a top view further illustrating the retrofit
module of FIG. 16 and the mode of operation thereof;
[0027] FIG. 18A is a top view illustrating a duct-damper assembly
in the module of FIG. 16 with the damper in a third operative
position;
[0028] FIG. 18B is a top view illustrating the duct-damper assembly
of FIG. 18A with the damper in a second operative position;
[0029] FIG. 18C is a top view illustrating the duct-damper assembly
of FIG. 18A with the damper in a first operative position;
[0030] FIG. 19 is a perspective view further illustrating portions
of the duct-damper assembly of FIG. 18A;
[0031] FIG. 20 is a perspective view illustrating an alternate
damper construction;
[0032] FIG. 21 is a front elevation view of the duct-damper
assembly of FIG. 18A in conjunction with a control system and
illustrating further construction details thereof;
[0033] FIG. 22 is a side elevation view illustrating an alternate
damper construction;
[0034] FIG. 23 is a front view of the damper of FIG. 19
illustrating the undulating surface extending between the scalloped
edges of the damper; and,
[0035] FIG. 24 is a top view of the damper of FIG. 18A illustrating
additional construction and operational details thereof.
[0036] Briefly, in accordance with the invention provided are heat
recovery and ventilation improvements in combination with a
building structure. The building structure includes a room with a
minimum occupancy density of 20 people per 1,000 square feet, an
air conditioning system including a heat transfer coil, and a first
section of duct D4 leading to the heat transfer coil of the air
conditioning unit 22 to direct return air from the building
structure over the coil. The building structure also includes a
second section of duct D2 leading away from the heat transfer coil
to carry conditioned (heated or cooled) supply air S1 from the coil
back into the building. The ventilation improvements in the
building structure comprise a retrofit heat recovery and
ventilation control unit (DVHR) connected to the first section of
duct D4. The DVHR unit includes a housing; a heat exchange unit 12;
a section of duct D5 operatively associated with an outside ambient
air source fan 13 to direct ambient air over the heat exchange unit
12 and into the first section of duct D1; an inlet damper 15
controlling the flow of ambient air into duct section D5 and over
the heat exchange unit into the first section of duct D1; a section
of duct D3 connected to the first section of duct to direct a
portion R2 of the return air flowing through the first section of
duct over the heat exchange unit and into the duct section D6
directing the air to the outside atmosphere via exhaust/relief fan
14; an outlet damper 16 controlling the flow of the portion of
return/exhaust air R2 from the first section of duct D1 over the
heat exchange unit and into the outside atmosphere; a control unit
30 operatively associated with the inlet and outlet dampers to
control the rates of flow of ambient and exhaust/relief air,
respectively, through the dampers; a first flow sensor 20B
operatively associated with the inlet damper to generate signals to
the control unit representing the rate of flow of ambient air
through the inlet damper 15; a second flow sensor 21 operatively
associated with the outlet damper 16; and a CO2 sensor in the room
to generate signals to the control unit 30 representing the
concentration of CO2 in the air in the room. The DVHR also includes
a first fan 13 to direct ambient air into the section of duct D5,
over the heat exchanger 12, and into the first section of duct D1;
a second fan 14 to direct return/exhaust air R2 through the first
section of duct D1, through the heat exchanger 12, and through duct
section D6 and into the atmosphere. The ventilation control system
also includes an algorithm in the control unit 30 to calculate, at
stepped spaced apart increasing room ventilation rates
corresponding to increases in room occupancy, acceptable CO2
concentrations below a maximum desired CO2 concentration in the
room, and to increase or decrease the outside air ventilation rate
to achieve the acceptable CO2 concentration.
[0037] In another embodiment of the invention, I provide
improvements in combination with a building structure. The building
structure includes a room with a maximum occupancy rating of at
least twenty individuals per 1000 sq. ft. of occupied space, and an
air conditioning system. The air conditioning system includes a
heat transfer coil; a first section of duct (D4) leading to the
heat transfer coil to direct return air from the building structure
over the coil; and, a second section of duct (D2) leading away from
the heat transfer coil to carry air from the coil back into the
building. The improvements in the building structure comprise a
retrofit ventilation control unit. The unit is attached to the
first section of duct and includes a housing (23); a heat exchange
unit (12); a third section of duct (D1) connected to the first
section of duct (D4) to direct a first portion of return air from
the room into the first section of duct; a fourth section of duct
(D3) to direct a second portion of return air from the room over
the heat exchange unit; a fifth section of duct (D5) to direct
ambient air over the heat exchange unit into the third section of
duct (D1). The heat exchange unit maintains the second portion of
return air separate from the ambient air and transfers heat between
the second portion of return air and the ambient air. The
ventilation control unit also includes a sixth section of duct (D6)
to direct the first portion of return air from the heat exchange
unit into the outside atmosphere; an outlet damper (16) controlling
the flow of the second portion of return air over the heat exchange
unit (12) and into the outside atmosphere; an inlet damper (15)
controlling the flow of the ambient air over the heat exchange unit
(12); a control unit operatively associated with the inlet and
outlet dampers to control the rate of flow of the ambient air and
the second portion of the return air, respectively, through the
dampers; a first flow sensor operatively associated with the inlet
damper to generate signals to the control unit representing the
rate of flow of ambient air through the inlet damper; a second flow
sensor operatively associated with the outlet damper to generate
signals to the control unit representing the rate of flow of the
ambient air through the outlet damper; and, a CO2 sensor in the
room to generate signals to the control unit representing the
concentration of CO2 in the air in the room. The improvements also
include a first fan to direct the ambient air into the fifth
section of duct, over the heat exchanger, and into the first
section of duct; a second fan to direct the second portion of
return air from the fourth section of duct, and through the fourth
section of duct over the heat exchanger, and into the atmosphere;
and, an algorithm in the control unit to calculate, at stepped
spaced apart increasing room ventilation rates, increasing CO2
concentrations in the air in the room that are below a maximum
desired CO2 concentration in the room.
[0038] In a further embodiment of the invention, improvements are
provided In combination with a building structure. The building
structure includes a room with a maximum occupancy rating of at
least twenty people per 1,000 sq. ft. of occupied space; and, an
air conditioning system. The air conditioning system includes a
heat transfer coil; a first section of duct (D40) leading to the
heat transfer coil to direct supply air from the building structure
over the coil; and, a second section of duct (D20) leading away
from the heat transfer coil to carry air from the coil back into
the building. The improvements in the building structure comprise a
ventilation control unit attached to the first section of duct. The
ventilation control unit includes a housing (230); a heat exchange
unit (120); a third section of duct (D10) connected to the first
section of duct (D40) to direct a first portion of return air from
the room into the first section of duct; a fourth section of duct
(D30) to direct a second portion of return air from the room over
the heat exchange unit; a fifth section of duct (D50) to direct
ambient air over the heat exchange unit into the third section of
duct (D10), the heat exchange unit maintaining the second portion
of return air separate from the ambient air and transferring heat
between the second portion of return air and the ambient air, and
to direct ambient air directly only to said third section of duct
(D10) by bypassing the heat exchange unit; a sixth section of duct
(D60) to direct the second portion of return air from the heat
exchange unit into the outside atmosphere; an outlet damper
assembly (160) controlling the flow of the second portion of return
air over the heat exchange unit (120) and into the outside
atmosphere; and, a generally semi-cylindrical inlet damper assembly
controlling the flow of the ambient air into the ventilation
control unit. The inlet damper assembly including a member (38,
1150) rotatable between at least three operative positions, a first
operative position directing ambient air only over the heat
exchange unit (120); a second operative position bypassing the heat
exchange unit and directing ambient air only directly to the third
section of duct (D10) to combine with the first portion of return
air; and a third operative position preventing the ambient air from
flowing to the heat exchange unit and to the third section of duct
(D10) to combine with the first portion of return air. The
ventilation control unit also includes a control unit operatively
associated with the inlet and outlet damper assemblies to control
the rate of flow of the ambient air and the second portion of the
return air, respectively, through the damper assemblies; a first
flow sensor operatively associated with the inlet damper assembly
to generate signals to the control unit representing the rate of
flow of ambient air through the inlet damper assembly; a second
flow sensor operatively associated with the outlet damper assembly
to generate signals to the control unit representing the rate of
flow of a second portion of return air through the outlet damper;
and, a CO2 sensor in the room to generate signals to the control
unit representing the concentration of CO2 in the air in the room.
The improvements also include a first fan to direct the ambient air
into the fifth section of duct, over the heat exchanger, and into
the first section of duct; a second fan to direct the second
portion of return air from the fourth section of duct, and through
the fourth section of duct over the heat exchanger, and into the
atmosphere; and, a control algorithm in the control unit to
calculate, at stepped spaced apart regulated room ventilation
rates, in response to increasing and reducing CO2 concentrations in
the air in the room that are above or below an algorithm calculated
desired CO2 concentration in the room.
[0039] Turning now to the drawings, which depict the presently
preferred embodiments of the invention for the purpose of
illustrating the use thereof and not be way of limitation of the
scope of the invention, and in which like reference characters
refer to corresponding elements throughout the several views, in a
preferred embodiment of the invention, the EMS (Energy Management
System) serves primarily as a diagnostic tool to provide graphic
user interface (GUI) capability for the entire campus HVAC and
lighting systems. The GUI comprises a computer screen with graph
interface software and includes (1) on screen representation of
ambient air flow in cfm, (2) on screen representation of
exhaust/relief air flow in cfm, (3) on screen representation of
mode of operation i.e. (i) heat recovery heating mode (changeover
function), (ii) heat recovery cooling mode (changeover function),
and (iii) economizer cooling mode (changeover function), (4) on
screen representation of occupied `active` or `inactive` mode, (5)
on screen representation of which segment CO2 concentration limit
is prevailing, (6) on screen representation of room CO2
concentration level, and (7) alarm functions associated with no air
flow when dampers are expected to be in some open position or
registering air flow, open damper position, when no air is to be
moving. Room ventilation control functions and all algorithm
defining characteristics, formulae and changeover functionality are
embedded in the programmable controller hardware control board and
processor. Ventilation control functions include (1) determining if
the DVHR is to operate in the heat recovery mode or economizer mode
based on outside air temperature (changeover functions), (2)
calculating the IRV based on the algorithm, (3) varying the outside
ambient air damper to maintain the proper CO2 concentration limit,
and (4) varying the exhaust/relief air damper position to maintain
the correct volume of air based on the outside/ambient air
quantity. Changeover functions include (1) heat recovery heating
mode (changeover function), (2) heat recovery cooling mode
(changeover function), and (3) economizer cooling mode (changeover
function). Input variables, i.e. room square footage, room
ventilation rate (Va), people ventilation rate (Vp), (Occmax), are
transmitted to the controller from external sources, i.e. plug-in
interface tools, a keyboard or other data input means. It is the
intent of this embodiment of the invention to maintain a maximum
steady state ventilation to achieve less than the 700 ppm CO2 level
exposure limit defined in ASHRAE 62-200. The maximum steady state
ventilation rate is the calculated IRV based on the two independent
ventilation rates of people and area. The steady state feature
defines that the 700 ppm concentration increase in CO2 above
ambient is accounted for in the algorithm in addition to the area
ventilation requirement. Further, the energy recovery principles
employed in this embodiment of the invention transfer a minimum of
60% of the differential dry bulb temperature energy from the high
air stream temperature to the lower air stream temperature.
[0040] During the summer (cooling) months, the higher outside air
temperature is transferred to the lower room relief air
temperature. During the winter (heating) months, the higher room
relief air temperature will transfer its heat to the lower outside
air temperature. During periods of time when free cooling is
available, the heat recovery (temperature transfer) unit is
by-passed. Heat recovery in the cooling mode should be active at
about 80.degree. F. ambient temperatures and higher. Heat recovery
in the heating mode should be active at about 50.degree. F. ambient
temperatures and lower. Economizer cooling should be the
temperatures in between. These temperatures are usually `field`
adjustable so that when extreme conditions exist, the changeover
temperatures can be reset without completely reprogramming the
controller.
[0041] High occupant spaces historically experience transient and
variable occupant loads. Prior to the 2010 version of ASHRAE
62.1-2010, indoor air quality (IAQ) standards defined constant use
ventilation rates which influenced sizing of heating and cooling
systems based on peak occupant loads. ASHRAE 62.1-2010 explains the
intent of the ventilation standards with respect to volatile
organic compound (VOC) dilution ventilation and CO2/physiological
odor management. Two ventilation rates are independently derived to
meet these separate IAQ comprising conditions and the sum of the
two rates are intended to define the stead state rate CO2+VOC
dilution rates to achieve a maximum CO2 exposure of 700 ppm above
ambient.
[0042] The approach discussed below concerns the proper control of
ventilation (ambient) air which is introduced into a room.
The Approach
[0043] ASHRAE 62.1-2010 requires a minimum cubic foot per minute
(cfm) of outside air (Va) per square foot (sf) of occupied space
(i.e., space in a room) for VOC dilution. Additionally, each person
is assigned a ventilation value (Vp) in cfm per person for CO2/odor
management which is based on occupant occupation or activity. All
CO2 ventilation rates have been developed with the intent that a
change of CO2 concentration in an occupied room will not be
objectionable if the CO2 level is kept below 700 ppm above the
outside ambient CO2 level. Since CO2 sensors measure the total CO2
in air, ambient CO2 levels (OSACO2) need to be measured. Ambient
CO2 levels normally are in the range of 300 to 500 ppm. The maximum
desired total CO2 concentration in a room in parts per million
(ppm) is then equal to (OSACO2+700), or 1000 to 1200 ppm. When a
ventilation system operates during periods when a room is occupied,
and when a low occupant count is in the room, the CO2/odor
management dilution rate can be met with the minimum VOC
ventilation rate. The minimum ventilation rate equals (Va)(x),
although this is a logical expression ASHRAE still requires
separate dilution ventilation rates for CO2, even though it appears
the VOC dilution rate can achieve both criteria.
[0044] If priority is placed on meeting the VOC ventilation
requirements independently of the CO2 ventilation requirements,
then upon start of any initial space ventilation sequence, the VOC
dilution ventilation rate will define any minimum ventilation rate
requirement. If the VOC dilution air quantity remains an
independent ventilation air quantity (variable) in the total
required steady state ventilation rate calculation, the resultant
CO2 ppm concentration will always be substantially lower than the
maximum allowable 700 ppm exposure limit, even at full occupancy of
the room. [0045] 1. The control logic for the ventilation set forth
in the approach discussed above requires an algorithm to define and
respond to the rate of change in the occupancy of a room. A minimum
unreduced VOC dilution ventilation air flow rate, (Va)(x) (where
x=the sq. ft. area of a room), remains a constant to the controller
when the room is occupied. ASHRAE 62.1-2010 defines a quantity of
ambient ventilation air, Vp, per person to insure that the CO2
concentration in a room does not exceed a desired maximum
concentration. Presuming that the Vp is calculated to insure that
the CO2 concentration in a room does not exceed 700 ppm above the
concentration, OSACO2, in the ambient air, then the outside air
flow increases in response to an increase in occupant respiration
(i.e., in response to an increase in the number of occupants in a
room or a change in their activity level), and incremental target
CO2 levels or checkpoints, RV, are defined to simultaneously
achieve a constant VOC dilution ventilation rate and respond to
increasing and decreasing occupancy of a room. The controller
ventilation algorithm described below uses increases or decreases
in room occupancy in incremental selected segments, where n is the
number of segments selected, IRV is the size in cfm of each
segment, and IRVpt is the estimated cumulative number of persons in
a reset segment and any preceding reset segment. The number, and
therefor the size, of each segment is adjusted as desired. The
design airflow of the VOC dilution ventilation (i.e., the base
ventilation rate of Rb=(Va)(x)) plus the CO2 control ventilation
(i.e., the size of each segment, IRV, times the number of segments
S.sub.(1, 2, 3 . . . n)) is the divisor in the algorithm. The
dampers 15, 16 (FIG. 1) which regulate the amount of outside air to
the space have a defining minimum VOC dilution air flow, (Va)(x),
as the initial open position. The occupied mode is determined by
time schedule stored in the control unit 30 or by an occupant
sensing mechanism operatively associated with the control unit 30.
A velocity sensor utilizing a transducer records the inlet air flow
quantity and adjusts the damper position to maintain a minimum set
point. This is a pressure independent control function which is
employed for air quantity and quality management functions of all
air flow regulating devices in the system. When, as room occupancy
increases, a maximum cfm of incoming ambient ventilation air,
IRVcfm, is reached for a segment, the CO2 limit (i.e., the RV) for
that segment is the upper CO2 limit for the prior segment. The
minimum VOC ventilation rate=(Va)(x). This would suggest that the
CO2/odor management rate is a duplicate of the minimum VOC
ventilation rate. ASHRAE does not recognize this comparative
analysis.
[0046] The control unit 30 achieves this upper CO2 by adjusting the
damper that regulates the flow of incoming ambient air. In
contrast, when the occupancy levels in a room decreases and the CO2
concentration in the room drops, the maximum cfm of a segment,
IRVcfm, must be overshot by a selected amount before the target CO2
concentration is altered. For example, if in the system represented
in FIG. 3, the room occupancy and CO2 concentration are decreasing,
when the CO2 level reaches 668 ppm, coinciding with 228 cfm, the
control unit 30 does not adjust the damper to achieve a CO2
concentration of 668 ppm (at 228 cfm) from 738 ppm (above 228 cfm)
until the value drops to below the IRV cfm quantity of 228 by at
least 10% of the difference of the segment air quantity, which in
this case is 60 cfm.times.10%=6 cfm. This will allow the IRV to
change once the outside air quantity reduces to less than 222 cfm.
This percentage is a field adjustable value based on the normal
occupancy of the space and how quickly it can gain or lose
occupants. Its use is for this example.
[0047] When a building starts in the occupied `inactive` mode, the
ventilation rate is at its minimum. If no one enters the room, the
room CO2 concentration will be essentially the ambient CO2 level.
It is the intent of the control function to move to the first
calculated segment RV upon occupant entry into the room. There is
no way the ambient CO2 level of the room can be maintained once
people enter. Therefore, the RV adjustment takes place once the air
quantity exceeds its segment limit. Using FIG. 3, RV2@550 ppm will
be the first occupied `active` value. At 300 ppm (RV1), the
ventilation rate is in the occupied `inactive` mode.
[0048] The various necessary ventilation criteria set forth below
are incorporated in the control unit 30 (FIG. 1). In one embodiment
of the invention, ASHRAE 62.1-2010 VOC and CO2 management air flow
rates are provided via a handheld plug-in. In another embodiment,
this data is programmed into the control unit 30. When ASHRAE
62.1-2010 ventilation data is revised, a plug-in or any other
desired data entry system is utilized to update the control unit
30.
[0049] Prior art ventilation systems typically have either fixed or
on/off flow rates. Outside air introduced into a room or other
space must be relieved from the space. When a space has no operable
windows or doors which communicate with outside (ambient) air, the
intake and relief systems permit equal volumes of air in and air
out. Gravity air relief systems are most common. Exterior relief
hoods or louvers are connected to a building or space via either a
direct duct and grille in the ceiling, or a return/relief air grill
in the ceiling which communicates with a return/relief air
plenum.
[0050] During any ambient climate temperature condition, when the
outside air can provide a lower temperature source to the air
conditioning system than the set point of the temperature sensor
without over cooling the space, the outside air supply source
should not be tempered to a higher temperature in the heat exchange
unit 12 (FIG. 1). This defeats the cooling process. Instead, in one
embodiment of the invention, in the free cooling mode outside air
is introduced to the return air path in the manner indicated by
arrow A2 in FIG. 2, bypassing the heat exchange unit 12. This
lowers the return air temperature to the air conditioning unit 22,
thereby reducing the amount of compressorized cooling energy
required to maintain the set point temperature in a room or other
space. This is called the partial outside air economizer mode.
Excess air generated by introducing air in a room or other space
during the partial outside air economizer mode is relieved from the
space via a gravity relief air system. The gravity relief air
system has a back draft regulating damper to prevent outside air
from entering into the building when the air conditioner if off.
The back draft damper can be fitted with either a counterbalanced
barometric relief damper or an electronically operated motorized
damper. Either kind of damper will open when the air conditioner is
operating during the partial outside air economizer mode.
[0051] When the ambient climate temperature conditions are not
suitable for either free cooling or reduced compressorized cooling,
the gravity relief air system is disabled and the heat exchange
unit 12 is enabled. The heat exchange unit 12 works efficiently
down to about 20% of the maximum air flow rate. In the system
illustrated in FIG. 3, the maximum air flow rate is 408 cfm.
[0052] In the heat recovery mode of the module 10 (FIGS. 1 and 2)
of the invention, as the ventilation air quality increases and
decreases, dampers 15 and 16 are operated by the control unit 30.
The control unit 30 ordinarily comprises a microprocessor. The
control unit 30 utilizes the ventilation algorithm described below,
along with any other desired algorithms. Ambient air that is
introduced through damper 15 as ventilation air is compensated for
by exhaust/relief air R2 (FIG. 1) that is directed over heat
exchanger 12 and into the ambient atmosphere via damper 16. A
minimum desired flow rate for ambient air through damper 15 is
determined by the potential for trapping air borne particulates in
the heat exchange unit 12 when the air velocity drops to below the
manufacturer recommend air flow. Some manufacturers permit an air
flow rate that is less than 20% of the maximum desired air flow
rate over heat exchanger 12. In FIG. 3, the maximum desired air
flow rate of ventilation air is 408 cfm.
[0053] Where occupied spaces communicate with the outside ambient
air via operable windows and doors, a minor positive air pressure
is maintained to minimize migration of air borne particulates into
a room or other space. Such minor positive air pressures are not
set forth in published standards, but up to 20% of the design
maximum air flow rate (408 cfm in FIG. 3) can be diverted to the
pressurization mode with minimal energy recovery impact at the
design maximum desired air flow rate (i.e., air flow at peak
occupancy). In FIG. 3, the maximum air flow rate is 408 cfm. It is
recommended that no more than 10% of the maximum air flow rate
(i.e., in the system of FIG. 3 this would be 40.8 cfm) be relieved
for ventilation air flow up to 50% of the maximum air flow rate,
and that the 20% maximum pressurization air flow quantity should
not be exacted on the system until 80% of the design maximum
desired air flow rate is in use.
[0054] The heat recovery operation mode requires verifiable air
flow measurements for proper application of the ventilation
algorithm. In order to maximize the reduction in energy required to
operate the system, the flow rates of the incoming ambient
ventilation air and of the exhaust/relief air stream should be the
same or nearly the same. Toward this end, each air inlet (or
outlet) is provided with a velocity sensor 20A, 20B, 21. It may be
possible to use a common sensor for dampers 15 and 17 because these
dampers will not open together. Each sensor is preferably
calibrated and can operate to within 2% accuracy at velocity
pressures as low as 250 fpm (0.03'' velocity pressure) at sea
level.
[0055] During low occupant loads in a room or other building space,
only a minimal amount of exhaust air, R2, may be available for heat
recovery. During such periods of low ventilation air flow, however,
the outside air cooling load on the room air conditioning system is
also low, resulting in a minor increase to the cooling load of the
air conditioning equipment above minimum (no outside cooling load).
Algorithm calculated indoor air quality (IAQ) conditions are
continuously maintained regardless of the quantity of exhaust air,
R2, utilized.
[0056] The combination of heat recovery and demand ventilation
control enables a substantial reduction in energy use, enables
increased sustained IAQ, and enables enhancements in sustainable
system performance. Enhancements include: [0057] a. Reduction of AC
unit sizes based on the reduction of the cooling load [0058] b.
Reduction of electrical service size based on smaller electrical
loads of the smaller AC units [0059] c. Energy reduction of HVAC
system energy use of 25%-40% [0060] d. Improvements of indoor air
quality (IAQ)] [0061] i. Stable CO2 levels [0062] ii. Adequate VOC
dilution [0063] iii. Reduction of space temperature variations
[0064] iv. Noise reduction [0065] e. Reduction of the carbon
footprint with the reduction of required utility generation [0066]
f. Air conditioning system benefits [0067] i. Reduction of entering
air temperatures to the evaporator and the resultant high
differential pressures at the compressor [0068] ii. LEED compliance
for all refrigerant systems if the normal size refrigerant charge
is compared with the reduced unit size charge [0069] iii.
Minimizing excess outside air into the building when occupancy is
not at maximum [0070] iv. Partial outside air economizer use (not
available with conventional heat recovery modules) [0071] v.
Operable in all ambient temperatures from -10.degree. F. to
120.degree. F. [0072] g. Hydrocarbon power generator emitted
pollution reduction at generating plants [0073] h. Water use
reduction for cooling of utility generator equipment [0074] i.
Reduction of global warming [0075] j. Refrigerant volume leakage
reduction in package air conditioning equipment [0076] k. Reduction
of water chemical treatment at industrial cooling towers of utility
generating plants [0077] l. Reduction of ozone depleting and global
warming refrigerant leakage.
[0078] Use of an occupant sensor(s) to manage IAQ and energy
consumption is complimentary to a lighting control system. A
lighting control system is an energy management tool required by
the International Energy Conservation Code as an alternative to
time clocks which use space occupant overrides for the light
control system. One presently preferred occupant sensor utilizes
infrared temperature sensor technology to determine the number of
occupants in a room. Any human entry in to the sensor zone is
detected and turns on light fixtures. EMS systems can control space
lighting and HVAC during present hours of operation. Substantial
energy and cost savings are realized if the sensor determine the
presence of occupants and turn energy consuming systems on or off.
Such an occupancy sensor can be furnished with an auxiliary contact
to enable independent functioning of the lighting system from the
HVAC system. The auxiliary contact determines if a ventilation
adjustment is in order. The occupancy sensor also enables the
"occupied" mode temperature sensor set point to be changed in
response to an "active" status versus an "inactive" status. If, for
example, during a scheduled "occupied" mode of the HVAC unit, the
room sensor detects no human presence for a selected time period of
five minutes, the HVAC unit serving the room can change to
"occupied-inactive" status. This changes the room people and
ventilation set points to zero outside air. When the room sensor
detects human presence, the operating sequence for the DVHR (Demand
Ventilation Heat Recovery) unit 10 of the invention begins. The
first stage of the ventilation air management mode is utilized when
a room is not occupied and is based on the outside ambient air
temperature and includes the base ventilation rate, Rb=(Va)(x).
Since the room is not occupied, (Vp)(Occact)=0. An outside air
source temperature sensor determines if unit 10 operates in the
Cooling-Heat Recovery (CHR) mode, the Heating-Heat Recovery (HHR)
mode, or the Economizer-No Heat Recovery (EHNR) mode. When unit 10
operates either of the CHR or HHR modes, the occupancy sensor
enables the "occupied-active" mode of the HVAC system. The
ventilation ambient air damper 15 and the exhaust air damper 16
(FIG. 1) are opened, closed, or not adjusted in order to direct
into the room the minimum necessary quantities of ventilation air
as calculated by the ventilation algorithm. The velocity sensors
20A, 20B, 21, the indoor and outdoor temperature sensors, and the
CO2 sensor in the room provide inputs to the EMS (Energy Management
System). The indoor air quality (IAQ) and indoor and outdoor
temperature sensors enable the cooling and heating systems to
operate and the ventilation system algorithm determines calculates
the RV set point of the room.
[0079] When operating in the ENHR mode, the bypass damper 17 (FIG.
2) is opened to its design maximum air flow as sensed by the
velocity sensor 20A. The maximum outside air volume is calculated
by the engineer using the peak air flow of the supply fan 13
divided by the number of DVHR units on its system. During the ENHR
mode, the heat recovery module air pressure drop is excluded from
the system losses because it is bypassed. This allows for the
supply fan 13 to ramp up to a higher air flow because it doesn't
have as much system resistance to overcome. This is a higher air
quantity than the maximum fan capability if the sum of the total
ventilation air flow required for proper IAQ is tabulated. This is
a scheduled value on the drawings usually defined by the
engineer.
[0080] The exhaust/relief damper 16 and the heat exchanger damper
15 are closed. Air is relieved from the room via a gravity relief
system. When the ambient air quantity produces a temperature which
is too cold and the room temperature drops to below the desired set
point, the quantity of ventilation air is controlled based on
readings produced by the room CO2 sensor until the IAQ set point
can not be met and the temperature set point continues to drop.
When this occurs, the HHR mode is enabled. In most cases, the
morning warm-up condition shall enable the HHR mode. After the
system begins operating in the HHR mode, the ENHR mode is enabled
once the outside air temperature reaches 60 degrees F. or reaches
another selected temperature. If at any time the ambient air
temperature exceeds the set point of the room by five degrees F.,
the CHR mode is enabled.
[0081] An infrared sensor in the room or other space determines
when the room is occupied. When the room is not occupied, the
ventilation system of the invention is in an `inactive` mode. When
the room is occupied, the sensor generates and transmits signals to
control unit 30. Control unit 30 places the ventilation system in
the active mode, which triggers use of EQ. 1 (and consequently a
graph comparable to that of FIG. 3) as set forth below.
[0082] Control unit 30 communicates with fans 13 and 14 to turn the
fans on and off and to adjust the speed of operation of the
fans.
[0083] The ventilation unit 10 illustrated in FIGS. 1 and 2
includes a housing 23, heat exchange unit 12 mounted in housing 23,
damper(s) 15, 16, and 17 mounted in housing 23, velocity sensors
20A, 20B, and 21 mounted in housing 23, and a controller 30 mounted
in the housing 23. Fans 13 and 14 can be mounted on housing 23, or
can be mounted at locations separate from housing 23 to direct air
through ducts that are connected to housing 23.
[0084] Duct D5 guides incoming ambient ventilation air A1 over one
side of heat exchange unit 12, out into the duct of D1, and through
duct D4 interconnecting unit 10 and air conditioning unit 22 (FIG.
2). Duct D3 guides a portion R2 of the return air over the other
side of heat exchange unit 12 and out into the ambient air as
exhaust/relief air. The return air comes from the room being
ventilated by unit 10. Dampers 15 and 17 are mounted in duct D5.
Damper 16 is mounted in duct D6.
[0085] Velocity sensors 20A, 20B, 21 are shown mounted in ducts D5
and D6, but that need not be the case. Sensors can be mounted at
any desired location in ventilation unit 10 to obtain an accurate
reading of ventilation air A1 entering duct D5 and of return air R2
exiting duct D6 as exhaust/relief air.
[0086] Velocity sensors 20A, 20B, 21 are operatively associated
with control unit 30 and generate and transmit signals to control
unit 30 defining the velocity of ambient air, indicated by arrow
A1, traveling through ducts D5 and D1 into duct D4, and of return
air, indicated by arrow R2, traveling through ducts D1 and D6.
[0087] Control unit 30 also receives signals from a CO2 sensor (not
shown) in the room or other space being cooled (or heated) by the
air conditioning unit 22. Control unit 30 can also, if desired,
receive signals from a sensor that detects ambient temperature,
from a sensor that detects the temperature in the room being cooled
(or heated) by unit 22, from an infrared or other sensor that
detects when one or more individuals are in the room, and from a
sensor that indicates the desired temperature set point in the
room.
[0088] While the shape and dimension of ventilation unit 10 can
vary as desired, and unit 10 can be installed at any desired
location near to or spaced apart from air conditioning unit 22, the
embodiment of the invention illustrated in FIGS. 1 and 2 is a
preferred embodiment because it is constructed to be inserted after
a portion of ducting that leads to and carries return air to a
previously installed air conditioning unit 22 is removed. After the
portion of the return air ducting leading to the air conditioning
unit 22 is removed, unit 10 is installed in-line to replace the
portion of the return air ducting that was removed. Accordingly,
return air R1 and R2 from the room flows into unit 10, portion R1
flows into ducts D3, D1 and D4 and into air conditioner 22, and
portion R2 flows over or through heat exchanger 12 and out through
duct D6. This, as can be seen in FIG. 2, eliminates or minimizes
the amount of duct which must be utilized to install unit 10
in-line along a return air duct that is connected to air
conditioner 22. In FIGS. 1 and 2, it is assumed that unit 10 is
located outdoors. Unit 10 can also, if desired, be installed in a
duct which is located indoors, or can be installed at any other
desired location. And, as would be appreciated by those of skill in
the art, unit 10 can be utilized and installed when a new air
conditioner is being installed on or adjacent a building structure,
or can be installed as an integral part of air conditioning unit
during the manufacture of a new or refurbished air conditioning
unit. Unit 10 is preferably, but not necessarily, manufactured as a
self-contained module with a control unit 30 designed to receive
necessary inputs from air velocity sensors 20A, 20B, 21, from a
room CO2 sensor, from a room infrared occupancy sensor, from an
ambient air temperature sensor, or from any other desired sensor
that is part of self-contained unit or that is remote from unit 10.
Fans 13 and 14 can be incorporated as a part of unit 10, or can be
omitted from unit 10 and installed in or adjacent ducting that
leads to unit 10. Similarly, dampers 15 to 17 can, as illustrated
in FIGS. 1 and 2, be incorporated as part of unit 10, or can be
omitted from unit 10 and installed in ducting leading to unit 10,
as can control unit 30, velocity sensors 20A, 20B, 21, and heat
exchange unit 12. The compact module configuration, with or without
fans 13 and 14, illustrated in FIGS. 1 and 2 is presently much
preferred in the practice of the invention.
[0089] As is illustrated in FIG. 1, a portion, R2, of the return
air from the room is directed by fan 14 from duct D1 over one side
of heat exchange unit 12 and into the ambient air as exhaust/relief
air. The size, in cfm, of portion R2 is controlled by damper 16.
Another portion R1 of the return air from the room continues
through ducts D1 and D4 to air conditioning unit 22, where it
travels over the cooling (or heating) coils and becomes part of the
supply air, indicated by arrow S1, traveling through duct D2 to the
room.
[0090] As is also illustrated in FIG. 1, ambient air, indicated by
arrow A1, is directed by fan 13 over the other side of heat
exchange unit 12 and into duct D1. This ambient air travels over
the cooling (or heating) coils in air conditioning unit 22 and
becomes part of the supply air, indicated by arrow S2, to the
room.
[0091] When the ambient air is warmer than the desired temperature
of the room, heat exchange unit 12 functions to transmit heat from
the ambient air A1 to return air R2. When the ambient air A1 is
cooler than the desired temperature of the room, heat exchange unit
12 functions to transmit heat from the return air R2 to the ambient
air, A1.
[0092] In FIG. 2, damper 15 is closed. Ambient air A2 entering duct
D5 travels through damper 17, through ducts D1 and D4, and into air
conditioning unit 22. The operational configuration of FIG. 2 is
utilized when the ambient air temperature is sufficiently cool to
provide desired cooling to return air R1.
[0093] In FIGS. 1 and 2, D1 is an air duct integrated with D3 for
return air to air conditioner 22; D2 is an air duct directing
cooled (or heated) supply air S1 from air conditioner 22 back to
the room; D3 is a duct through which return air from the room flows
in unit 10; D4 is a duct that directs return air into the coil/fan
section of air conditioner 22; D5 is a duct that directs ambient
air A1 into unit 10 and over one side of heat exchange unit 12; D6
is a duct that directs exhaust/relief air from heat exchanger 12
into the ambient atmosphere; A1 and A2 are ambient air streams
flowing into duct D5; A1 is a fan induced ambient air stream
directed through or over heat exchange unit 12; A2 is a fan induced
ambient air stream that bypasses heat exchange unit 12 and travels
directing in the return air stream in the manner illustrated in
FIG. 2; R2 is a portion of the return air stream that is drawn over
or through heat exchange unit 12; and S1 is a combination of return
air R1 and outside ambient air A1. FIG. 1 illustrates the heat
recovery mode of the ventilation system of the invention. FIG. 2
illustrates the economizer mode of the invention. In the economizer
mode, the temperature of the ambient air stream A2 permits it to be
added directly to the return air stream R1 and obviates the
necessity of passing an ambient air stream A1 over or through heat
exchanger 12.
[0094] A control system ventilation formula is used to calculate
the CO2 ppm target concentration levels that are required to
maintain in a room a maximum 700 ppm CO2 exposure level for
occupants as defined in ASHRAE 62.1-2010 (and earlier versions).
This maximum 700 ppm CO2 exposure is in addition to the existing
CO2 concentration in the ambient air.
[0095] There are two additive variables required to meet the ASHRAE
standards:
a. One variable is the base "area ventilation rate", i.e., the
ventilation rate required for a room. b. The other variable is the
"person" ventilation rate, i.e., the ventilation rate to compensate
for each person in a room.
[0096] The calculation used below approaches each of the additive
variables to achieve a critical steady state result based on
maintaining a maximum CO2 concentration of 700 ppm above the CO2
concentration in the ambient air.
Variables Used in Conjunction with the Control System Ventilation
Formula [0097] x=square footage of the room [0098] Va=area (i.e.,
room) ventilation rate requirement in cubic feet per minute
(cfm/sq. ft), as listed in ASHRAE 62.1-2010, Table 6.1. [0099]
Occmax=maximum code or user defined number of occupants in room
[0100] Vp="per person" ventilation rate requirement, in cfm/person,
as listed in ASHRAE 62.1-2010 Table 6.1. [0101] CRT=rate reset
variable based on outside air temperature during the cooling mode.
This is used in relation to Va. [0102] CRT=1.0 for ambient less
than or equal to 95 F [0103] CRT=0.8 for ambient less than or equal
to 96 F and greater than 95. [0104] CRT=0.6 for ambient temperature
less than or equal to 97 F and greater than 96 F. [0105] CRT=0.4
for ambient temperature less than or equal to 98 F and greater than
97 F. [0106] CRT=0.2 for ambient temperature less than or equal to
99 F and greater than 98 F. [0107] CRT=0.0 for ambient temperature
greater than 99 F. [0108] In other words, if the ambient
temperature is greater than 99 F, ambient air is not utilized to
meet the area ventilation rate requirement, but is still used to
meet the "per person" ventilation requirement. [0109] The CRT
values are adjustable with a plug-in to take into account sensible
cooling excesses associated with extremely high ambient conditions.
[0110] Similar adjustments can be defined for very humid locations
and will be based on a relative humidity--dry bulb temperature
measurement which equals a wet-bulb temperature on the psychometric
chart. [0111] HRT=rate reset variable based on outside air
temperature during the heating mode. This is used in relation to
Va. [0112] HRT=1.0 for ambient temperature greater than 25 F.
[0113] HRT=0.8 for ambient less than or equal to 25 F and greater
than 24. [0114] HRT=0.6 for ambient temperature less than or equal
to 24 F and greater than 23 F. [0115] HRT=0.4 for ambient
temperature less than or equal to 23 F and greater than 22 F.
[0116] HRT=0.2 for ambient temperature less than or equal to 22 F
and greater than 21 F. [0117] HRT=0.0 for ambient temperature less
than or equal to 21 F. [0118] HRT values are adjustable using a
plug-in to take into account sensible heating excesses associated
with extremely low ambient conditions. [0119] OSACO2=concentration
of CO2 in ambient air in ppm. [0120] Occact=count of number of
people in room, usually determined by a CO2 concentration that is
in excess of the CO2 concentration in the ambient air. [0121] IRV
graph=a plot of selected spaced apart reset values (RVs). The units
of measure on the vertical axis of the graph are ppm (parts per
million) CO2. The units of measure on the horizontal axis of the
graph are cfm (cubic feet per minute) ventilation air. [0122]
Rb=base ventilation rate for a room in cfm=(Va)(x). [0123] n=the
number of cfm reset segments selected for and represented on an IRV
graph. Each cfm reset segment s ordinarily of equivalent size to
other segments, although this is not necessarily the case. IRV is
the size of each segment in cfm. [0124] IRVpt=the cumulative number
of calculated persons in a reset segment and any preceding reset
segments. [0125] IRVcfm=a selected cfm point on the horizontal axis
of an IRV graph at which a reset segment ends, at which an
associated reset value (RV) occurs, and which represents a
cumulative quantity (in cfm) of outside (ventilation) air that is
utilized. The value of such a cfm point is equal to:
[0125] (Vp)(IRVpt)+(Va)(x) [0126] IRV=the size in cfm of each
segment in an IRL graph. IRV equals the maximum outside air
quantity (Vp.times.Occmax) divided by the number of reset segments
(n) selected. If, for example, five reset segments are selected,
the reset values (RV), or check points, occur at 0%, 20%, 40%, 60%,
80%, and 100% of the maximum (Vp.times.Occmax) outside air
ventilation (in cfm) that will be utilized to offset the
concentration of CO2 in the room that is above the concentration of
CO2 in the ambient air. Each segment extends from one RV to an
adjacent RV. For example, one segment extends from the cfm
associated with the RV at 0% to the cfm associated with the RV at
20%. If ten reset segments are selected, the reset values occur at
0%, 10%, 20%, 30%, 40%, etc. of the maximum flow of ambient air
that will be utilized to ventilate the room to offset CO2
concentrations above the CO2 concentration in the ambient air.
[0127] RV=RVd+OSACO2=a reset value on an IRV graph. The number of
RVs presently is one greater than the number, n, of segments. Each
set value (RV) represents a desired CO2 concentration which is
noted on the vertical axis of the graph and which is associated
with a selected cfm point (IRVcfm) on the horizontal axis of the
graph. The value of the selected cfm point (IRVcfm) indirectly
indicates the "metabolic equivalent" number of people (Occact) in
the room, i.e., the value of the selected cfm points less the base
cfm of (Va)(x) is divided by Vp to give the "metabolic equivalent"
number of people in the room. A reset value (RV) defines a desired
total room CO2 concentration limit at its associated IRVcfm. A
velocity sensor 20A, 20B in the incoming supply stream of ambient
air indicates the cfm of the incoming air stream. As reset value
(RV) is used to reset the CO2 maximum allowable ppm value for its
associated IRVcfm. The control system of the invention sends a
signal to the outside or ambient air stream damper motors which
modulate the damper blades to adjust the outside air quantity in
response to the CO2 concentration detected by CO2 sensor(s) and in
response to how much the room CO2 deviates from the CO2
concentration defined by the RV. [0128] RVd=the difference, in ppm,
at a selected cfm point on an IRV graph (IRVcfm) between the RV at
that cfm and the ambient air CO2 concentration (OSACO2). Also known
as CO2max. [0129] S.sub.(0, 1, 2, 3, . . . n)=a numerical value (0,
1, 2, 3 . . . n) representing the number of segments used in
calculating, with the formula noted below, both an RV and the
amount by which the RV exceeds the ambient CO2 concentration. For
example, when the first set point RV1 is calculated, a numerical
value of 0 is used for S; when the second set point RV2 is
calculated, a numerical value of 1 is used for S; when the third
set point RV3 is calculated, a numerical value of 2 is utilized,
and so on. When S=0, a segment is not utilized and the RV=OSACO2.
[0130] Altcorr=an altitude correction value. This value increases
the IRV values above those established for sea level and extends
the applicable segment maximum CO2 ppm value to a higher cfm value.
This is a multiplier to the IRV segment values. The value is based
on the specific density of air at sea level divided by the specific
density of air at the altitude of the project site. When the
location of a project is at sea level, the Altcorr is 1.0. [0131]
CO2max=the desired maximum CO2 concentration in ppm in a room above
the CO2 concentration in the ambient air. [0132] CO2target=RVd=the
target CO2 (above ambient) for a segment. [0133] Vamb=the cfm of
ambient ventilation air entering the system as measured by a
velocity sensor. [0134] Vexit=the cfm of supply air that exits into
the atmosphere after passing by the heat exchanger as measured by a
velocity sensor. [0135] CO2act=the actual measured CO2 in a room as
measured by a CO2 sensor. [0136] Tact=the actual temperature in a
room as measured by a thermostat.
Control System Ventilation Formula
[0137] Given the above variables, the target CO2 above ambient, or
RVd, for a segment is:
RVd = [ ( CRT or HRT ) ( Rb ) ( OSACO 2 ) + ( Occact ) ( Vp ) (
OSACO 2 + CO 2 max ) ] ( Rb ) + IRV ( Altcorr ) ( S ( 0 , 1 , 2 , 3
n ) ) - OSACO 2 [ EQ . 1 ] ##EQU00001##
[0138] The following example is presented by way of illustration,
and not limitation, of the invention.
Example
[0139] In this example, it is assumed that a room will be occupied
by school children in the age range of 5 to 8. The ambient
temperature is 88 degrees F. The room is located as sea level. The
size of the room is 900 square feet. The CO2 concentration in
ambient air is 300 ppm. Five segments are selected to use in
preparing an IRV graph. The following values are utilized: [0140]
n=5 [0141] No. of RV points on IRV graph=n+1=6 [0142] No. of
occupants in a segment=(Occmax)/n=30/5=6 [0143] x=900 sq. ft. (size
of room) [0144] Va=0.12 cfm/sq. ft (from ASHRAE 62.1-2010: Table
6.1: Minimum Ventilation Rates In Breathing Zone). [0145]
Rb=(Va)(x)=(900)(0.12)=108 cfm [0146] Occmax=30 (maximum number of
children allowed in room per building code) [0147] Vp=10 cfm/person
(from ASHRAE Table 6.1). [0148] CRT=1.0 (ambient temperature is
less than 95 F) [0149] HRT=N/A, because the ambient temperature
requires cooling, and not heating. [0150] OSACO2=300 ppm. [0151]
IRV=(Vp)(Occmax)/n=(10)(30)/5=60 cfm [0152] Occact=number of people
in the room. This number times (Vp) is added to Rb to determine the
maximum airflow in a segment on an IRV graph. The first segment
includes 6 occupants. Six occupants times (Vp)=6.times.10 cfm=60
cfm. 60+108=a maximum airflow of 168 cfm at the upper end of the
first segment in the IRL graph. The second segment would also
include 6 occupants, producing a total room occupancy equal to the
occupancy in the first segment plus the occupancy in the segment or
6+6=12. Twelve occupants times (Vp)=12.times.10=120 cfm. 120+108=a
maximum airflow of 228 cfm at the upper end of the second segment
in the IRL graph, and so on. [0153] Altcorr=1.0. The project site
is at sea level. [0154] CO2max=700 ppm. This value is a constant
for all building types and occupancies. [0155] S.sub.(0, 1, 2, 3 .
. . n)=S.sub.(0, 1, 2, 3, 4, 5) Since CRT and Altcorr are each
equal to 1.0, the control system formula is simplified to:
[0155] RVd = [ ( Rb ) ( OSACO 2 ) + ( Occact ) ( Vp ) ( OSACO 2 +
CO 2 max ) ] ( Rb ) + IRV ( S ( 0 , , 1 , 2 , 3 , 4 , 5 ) ) - OSACO
2 = [ 32 , 400 ) + ( Occact ) ( 10 , 000 ) ( 108 ) + ( 60 ) ( S ( 0
, 1 , 2 , 3 , 4 , 5 ) ) - 300 [ EQ . 2 ] ##EQU00002##
At the first set point of 0%, Occact=0 (0% of the maximum occupancy
of 30 students=room is not occupied), S.sub.(0, 1, 2, 3, 4, 5)=0,
and the formula is
( Unoccupied condition ) RVd 1 = 32 , 400 108 + ( 60 ) ( 0 ) - 300
= 0 ppm RV 1 = 300 ppm . [ EQ . 3 ] ##EQU00003##
At the second set point of 20%, Occact=6 (20% of the maximum
occupancy of 30 students), S.sub.(0, 1, 2, 3, 4, 5)=1, and the
formula is:
( First occupied segment set point ) Rvd 2 = [ ( 32 , 400 ) + ( 6 )
( 10 , 000 ] ( 108 ) + ( 60 ) ( 1 ) - 300 = 250 ppm RV 2 = 550 ppm
. [ EQ . 4 ] ##EQU00004##
At the third set point of 40%, Occact=12 (40% of the maximum
occupancy of 30 students), S.sub.(0, 1, 2, 3, 4, 5)=2, and the
formula is:
( Second occupied segment set point ) Rvd 3 = [ ( 32 , 400 ) + ( 12
) ( 10 , 000 ) ] ( 108 ) + 60 ( 2 ) - 300 = 368 ppm RV 3 = 668 ppm
. [ EQ . 5 ] ##EQU00005##
At the fourth set point of 60% the formula is:
( Third occupied segment set point ) RVd 4 = [ ( 32 , 400 ) + ( 18
) ( 10 , 000 ) ] ( 108 ) + ( 60 ) ( 3 ) - 300 = 438 ppm RV 4 = 738
ppm . [ EQ . 6 ] ##EQU00006##
At the fifth set point of 80% the formula is:
( Fourth occupied segment set point ) RVd 5 = [ ( 32 , 400 ) + ( 24
) ( 10 , 000 ) ] ( 108 ) + 60 ( 4 ) - 300 = 438 ppm RV 5 = 783 ppm
. [ EQ . 7 ] ##EQU00007##
At the sixth set point of 100%, the formula is:
( Fifth occupied segment set point ) RVd 6 = [ ( 32 , 400 ) + ( 30
) ( 10 , 000 ) ] ( 108 ) + 60 ( 5 ) - 300 = 515 ppm RV 6 = 815 ppm
. [ EQ . 8 ] ##EQU00008##
With reference to FIG. 3: [0156] 1. The reset values (RVs) or
checkpoints in the IRV graph of FIG. 3 are: RV1=300 ppm CO2;
RV2=550 ppm CO2; RV3=668 ppm CO2; RV4=738 ppm CO2; RV5=783 ppm CO2;
RV6=815 ppm CO2. [0157] 2. In the system, when the room is in the
`occupied-inactive` mode at a zero occupancy count (empty room),
the outside air control damper operates to bring in ambient air at
approximately Rb=108 cfm (900 square feet.times.0.12 cfm/square
foot). This air volume, Rb, is equal to (Vb)(x) and is a constant
ventilation flow rate in the overall equation. If no one is in the
room for 5 minutes or more, the ventilation system goes from the
`occupied-inactive` mode to the `unoccupied` mode and is turned off
so there is no ambient ventilation air flowing into the room. The
five minute time element is adjustable as desired. The minute
someone enters the room, the infrared occupancy sensor (or some
other desired sensor) causes control unit 30 to activate the
`occupied-active` mode and control the dampers 15, 16 to establish
the minimum ventilation value, Rb. As the CO2 concentration rises,
the ventilation rate rises to dilute the CO2 concentration. The
amount that dampers 15 and 16 (or 17) open depends on the
difference between the actual CO2 concentration and the set point
RV2, RV3, RV4, etc. The greater the difference, the more the
dampers open. [0158] By way of example, if after the dampers are
opened to increase the flow rate of ambient ventilation air, the
next reading by velocity sensor 20B indicates a flow rate of 190
cfm (in the second segment in FIG. 3) and the CO2 sensor in the
room reads 400 ppm (in the first segment in FIG. 3), then control
unit 30 begins closing damper 15 to reach an ambient air flow rate
that is in the first segment (108 to 168 cfm) in FIG. 3. The CO2
and velocity readings preferably are made every three to five
seconds, although this can vary as desired. [0159] If in the next
reading sensor 20B indicates a flow rate of 175 cfm and the CO2
sensor in the room reads 425 ppm, the control unit 30 continues to
close damper 15 to reach an ambient air flow rate that is in the
first segment toward the goal of raising room CO2 level to the
segment CO2 set point of 550 ppm. [0160] If in the next reading
sensor 20B indicates a flow rate of 160 cfm and the CO2 sensor
reads 425 ppm, the control unit 30 continues to close damper 15
because the CO2 ppm has not reached 550 ppm at set point RV2.
[0161] If at the next reading sensor 20B indicates a flow rate of
110 cfm and the CO2 sensor reads 560 ppm, then the control unit
begins to open damper 15 to increase the ventilation rate to reduce
the CO2 concentration to 550 ppm or less. [0162] If at the next
reading sensor 20B indicates a flow rate of 140 cfm and the CO2
sensor reads 450 ppm, then control unit 30 begins again to close
the damper 15 since the CO2 concentration is once again less than
550 ppm. When the damper cfm is in the first segment (108 to 168),
the desired CO2 set point is 550 ppm (or less). When the damper cfm
is in the second segment (168 to 228), the desired CO2 set point is
668 ppm (or less). And so on. [0163] If at the next reading, the
CO2 ppm in the room is 740 ppm and the velocity sensor 20B reads
150 cfm, control unit 30 opens damper 15 to increase the flow of
ventilation air. [0164] If at the next subsequent reading, the CO2
ppm in the room is 680 ppm and the velocity sensor indicates an
ambient air flow rate of 240 cfm, then the cfm being utilized and
the CO2 concentration are each in the third segment (228 to 288) in
FIG. 3 and the CO2 set point utilized is the set point for segment
three, namely 738 ppm (or less). In addition, since the CO2
concentration is less than 738 ppm, the control unit 30 begins to
close damper 15 toward the minimum flow rate of 228 cfm for the
third segment. [0165] If in the next subsequent reading, the CO2
room sensor indicates a concentration of 670 ppm, and the velocity
sensor 20B indicates a flow rate of 235 cfm, the control 30
continues to slowly close damper 15 toward the minimum flow rate of
228 cfm for the third segment. As long as the ambient air flow (and
the CO2 concentration) is in the third segment, the cfm measured by
sensor 20B should not drop below 228 cfm. And so on. [0166] 3.
Within a short period of time, the cfm value and CO2 value
stabilize and the system modulates as necessary to meet the
appropriate room CO2 sensor setpoint RV2, RV3, RV4, RV5, RV6. The
initial set point concentration values for CO2 control are
relatively low and the ventilation system responds immediately,
overshooting the appropriate set point value. Very quickly, within
a minute or so, the room sensor combines with the velocity sensor,
in cfm, to determine which segment is in reference for the CO2
control set point reset value. [0167] 4. When an individual enters
the room, a CO2 sensor in the room monitors the increase in CO2
above the initial stable RV1=300 ppm in the room (essentially the
ambient air CO2 level) and begins to open the outside air damper to
increase the amount of ventilation air entering the room. The first
`active` occupied CO2 concentration checkpoint RV2 is 250 ppm above
ambient or 550 ppm total. [0168] 4. As the outside air damper
opens, the velocity sensor in the air stream registers the increase
in air flow and sends the value to the control unit 30 to determine
into which segment air flow value the air quantity registers.
[0169] 5. Since one individual will generate a CO2 amount requiring
approximately 10 cfm of outside air for dilution to 700 ppm above
ambient, approximately 6 students can enter into the room at the
first segment upper CO2 limit RVd2 of 250 ppm above ambient. The 6
student load is coincidental with the first segment maximum air
flow rate of [(Vp)(Occact)+(Va)(x)], as it should be. The total
outside air entering the room at this segment limit is 108 cfm
(area ventilation rate)+60 cfm (people ventilation rate)=168 cfm
total ventilation rate. [0170] 6. During all modes of area
occupancy (when the first person enters the room), the initial
checkpoint or segment target CO2 value RVd2 added to the OSACO2
will be the first segment CO2 limit RV2. The only time the 300 ppm
total RV1 (or 0 ppm above ambient) concentration will occur is when
the room is unoccupied. The minute a person enters, the first
segment value will define the limits until its maximum segment air
flow value in cfm is exceeded. By way of example, the maximum air
flow for segment one is, in the example set forth in FIG. 3, 168
cfm. The maximum air flow for segment two is 228 cfm. [0171] 7. As
additional students enter the room, the CO2 sensor will register a
coincidental rise in the CO2 concentration and the control unit 30
will open the outside air damper 15 further if the CO2
concentration exceeds the set or check point value RV2, RV3, etc.
associated with the segment in which the damper ventilation rate is
operating. When the ventilation rate exceeds the first segment 168
cfm value, which also defines the upper limit of the first segment
CO2 value (i.e., 550 ppm), the measured air quantity enters into
the region of the second segment, which defines an upper air flow
rate of 228 cfm and a CO2 concentration upper limit of 368 ppm
above the ambient air CO2 concentration, or, as is shown in FIG. 3,
a total CO2 concentration RV3 of 668 ppm. [0172] 8. The `five
segment` calculation example created above defines the air flow
rates and CO2 concentration limits of each segment. It does not
control the space CO2. The space CO2 is limited by the CO2 sensor
in the room and the operation of the outside air control dampers.
The calculation accumulates the sensed outside air quantity and
redefines the CO2 sensor set point, nothing more. However, this is
the most critical part of Indoor Air Quality management,
maintaining the proper CO2 limits with a moving occupant
ventilation rate target combined with a fixed area ventilation
rate. [0173] 9. As additional students enter the room and the CO2
concentration rises and the ambient air input damper 15 is opened
further, a greater outside air quantity is measured by the velocity
sensor. As the velocity sensor value in cfm continues to change, it
will register into any one of the segment air value limits. When
the CO2 sensor takes a reading and transmits its value to the
control unit 30, the control unit 30 will look at the air quantity
recorded at the velocity sensor, determine which segment it falls
into, and compare the segment CO2 limit to the CO2 concentration
sensed. The controller will send a signal to the outside air
control damper to increase or decrease the air to the room to meet
the segment set point RV2, RV3, RV4, RV5, RV6. Then, as the sensed
air quantity continues to change, in response to the generation of
CO2 (or to a decrease in CO2 when children leave the room) in the
space, it will redefine which segment is applicable and redefine
the CO2 limit as necessary. This is a dynamic function. CO2
measurements are taken, air flow rates are adjusted, CO2
measurements are taken, all the while, the calculations continue to
reset the CO2 concentration target. [0174] 10. And so on.
[0175] Because measurements are taken constantly, it is not a good
control scenario to make continuous adjustments because the control
dampers will `hunt` for a control point and never achieve it.
Creating segments, where the CO2 target value is fixed for more
than a minute amount of change of air quantity, allows for a more
stable control of outside air quantity and helps prevent rapid
cycling of air conditioning equipment in an attempt to meet a room
temperature set point with a `wild` mixed air temperature entering
the cooling or heating coils or furnace.
Discussion of Formula
[0176] Since actual numbers sometimes aide understanding a
calculation process, the values used in the above example are
referenced in the following discussion.
[0177] This particular method of controlling the flow of
ventilation air into a room is to continuously ventilate a room
with ambient air at a base rate equivalent to the Area Outdoor Air
Rate set forth in ASHRAE 62.1-2010: Table 6.1, and to increase the
ventilation rate whenever an individual enters the room, and to
decrease the ventilation rate whenever an individual leaves the
room. For each person entering the room, the ventilation rate is
increased to meet an approximate air quantity based on the People
Outdoor Air Rate set forth in ASHRAE 62.1-2010: Table 6.1. In the
above example, the People Outdoor Air Rate for an individual is 10
cfm. The 10 cfm value per person was set by ASHRAE 62.1-2010 after
completing several studies which determined that for children 5-8
years of age, taking into account their volumetric CO2 generation
and their activity levels, that it takes approximately 10 cfm per
person to properly dilute the space CO2 to 700 ppm above ambient.
700 ppm above ambient CO2 is recognized by ASHRAE as the target CO2
concentration to minimize objectionable odor recognition for 80%+of
occupants newly entering a space who have not become acclimated to
the people generated odors of the space. Therefore, for the sake of
this particular example calculation, it will be established that
for approximately each 10 cfm of air entering the area through the
outside air control damper, one student will be accounted for in
the ventilation calculation. ASHRAE is the American Society of
Heating, Refrigerating, and Air Conditioning Engineers.
[0178] Stated for this calculation, the base ventilation rate is
(x)(Va), which in the above example is (900 sq ft)(0.12 cfm/sq.
ft)=108 cfm. The system would, consequently, ventilate an empty
room at 108 cfm. When the first person enters the room, the
ventilation rate is increased by 10 cfm to 118 cfm. When the second
person enters the room, the ventilation rate is increased to 128
cfm, and so on. Each time a person leaves the room, the ventilation
rate is decreased by approximately 10 cfm.
[0179] Establishing that this control method utilizes the formula
set forth above to control the ventilation of a room with ambient
air, the formula calculates for set checkpoints at desired CO2
levels in the room above the CO2 level in the ambient air.
[0180] Examining the formula further, each air stream ventilation
rate has its actual or maximum allowable CO2 concentration
attribute. The area ventilation rate air stream contributes to the
equation 108 cfm of 300 ppm CO2 concentration. This would be like
comparing 108 gallons of water per minute at 300 degrees F. (under
high pressure of course). The people ventilation rate air stream
CO2 contribution to the equation includes the base 300 ppm of CO2
and allows for an additional 700 ppm CO2 increase. The people
ventilation rate contributes 1000 ppm CO2 (total) for each cfm of
air. When we are establishing the maximum allowable CO2
concentration at its specific target cfm limit, we know that the
300 ppm CO2 air stream will dilute the 1.000 ppm CO2 air stream. We
are adding the air stream CO2 values to quantify the assimilation
of the total CO2 into the total of the two air streams and
determine the influence of the ambient CO2 air quantity on the room
generated CO2. Once assimilated, the resultant CO2 concentration
should represent the discounted CO2 value, which achieves the
ASHRAE defined individual ventilation air flow rate requirements
for area and people.
[0181] In general, the formula has to take into account ventilation
air flow into the room for two purposes: [0182] 1. Area ventilation
of the room. The area ventilation air flow rate is determined using
the Area Outdoor Air Rate Va set forth in ASHRAE Table 6.1 and
using the size of the room in square feet. [0183] 2. Ventilation
air to compensate for additional CO2 produced when individuals are
in the room. This people ventilation air flow rate is determined
using the People Outdoor Air Rate Vp set forth in ASHRAE Table 6.1
and the number of people in the room.
A. Area Ventilation Air Flow Rate for the Room
[0183] [0184] This ventilation rate is represented in the formula
by:
[0184] [(CRT or HRT)(x)(Va) [0185] And, when CRT or HRT and Altcorr
each equal one, this becomes: (x)(Va)
B. Ventilation Air Flow Rate for People
[0185] [0186] This ventilation rate is represented in the formula
by:
[0186] (Vp)(Occmax)
C. Calculation of an IRVcfm.
[0187] The cfm of ventilation air is, as noted, physically measured
to determine the cfm location on the horizontal axis of an IRV
graph. The maximum cfm of a segment (i.e., the IRVcfm) is, on the
IRV graph, associated with an RV. When the IRVcfm of an RV is
reached or exceeded, as determined by the physical measurement of
the incoming ventilation air in cfm, the next IRVcfm is
selected.
[0188] One method of calculating an IRVcfm adding the base room
area ventilation, Rb, to the ventilation for the number of people
in a room, (Occact)(Vp). These terms are seen in EQ. 1 described
above.
[0189] A second method of calculating an IRVcfm is to add the base
rrom area ventilation to a calculation in which the total or
maximum people ventilation rate of (Vp)(Occmax) is divided by the
number of segments, n, and multiplied by the number of segments,
(S.sub.(0, 1, 2, 3, 4, 5)), which are, when moving from left to
right on the horizontal axis of an IRV graph from the base area
ventilation rate in cfm, required to reach the IRVcfm at issue.
Therefore, an IRVcfm=[(Vp)(Occmax)/n](S.sub.(0, 1, 2, 3, 4, 5))
Using either the first or the second method of calculating an
IRVcfm gives the same result.
[0190] The block flow diagram of FIG. 4 illustrates an embodiment
of a ventilation system that can be utilized in the practice of the
invention. The system includes a computer which can be utilized in
the control unit 30 of ventilation unit 10. The computer includes
controller 62 and memory 64. The computer can be a digital
computer, analog computer, hybrid computer, or other programmable
apparatus. In practice, the very large majority of computers
comprise digital computers.
[0191] The memory 64 can be any suitable prior art memory unit such
as are commonly used in digital or other computers. For example,
electromagnetic memories such as magnetic, optical, solid state,
etc. or mechanical memories such as paper tape.
[0192] Velocity sensor(s) 62, indoor and outdoor CO2 sensors 55,
and room thermostat 54 input data to memory 64, and can also input
the data to controller 63. An outdoor temperature sensor, room
temperature sensor, and indoor occupancy sensor, or any other
desired sensor or data input means can also be utilized to input
data to memory 64 or controller 63.
[0193] Controller 63 includes IRVcfm calculation sub-routine 50, RV
calculation sub-routine 51, and damper adjustment sub-routine 52.
IRVcfm calculation sub-routine 50 utilizes variables n, Vp, Va, x,
Occmax input 56 from memory. RV calculation sub-routine 51 utilizes
EQ 1 above (Control System Ventilation Formula) and the variables
57 from memory 64 including n, Vp, Va, x, Ocmax, Occact, CO2max,
CRT, HRT, Altcorr, S.sub.(0, 1, 2, 3 . . . n), and OSACO2 to
calculate RV values like those on the graph of FIG. 3. The damper
adjustment sub-routine 52 utilizes variables 58 from memory 64
including Vamb (the desired velocity of incoming air to achieve the
desired ppm CO2 (RV1, RV2, etc.) at the cfm checkpoints (108 cfm,
168 cfm, etc.) on the graph of FIG. 3. Once control 61 utilizes
sub-routine 52 to calculate the desired cfm, control 61 transmits
the necessary signals to damper(s) 54 to achieve the desired cfm of
incoming ventilation air.
[0194] FIG. 5 is a block flow diagram which illustrates a typical
program or logic function which is executed by the controller 63.
The basic control program consists of commands to "start and
initialize" 70, "read memory" 71, and "transfer control" 72
sequentially to one of subroutines 50 to 52. Each sub-routine 50 to
52 includes the steps of "interpret memory" 75, "perform the
sub-routine function(s)" 76 (i.e., determine IRVcfm, RV. etc.),
followed by "return to control program" 77. The sub-routines are
repeated as indicated by the "repeat to last memory step" 73,
followed by an "end" 74 program step which completes the execution
of the program.
[0195] Control unit 30 controls the flow rate in cfm of ventilation
air through unit 10 by opening and closing dampers 15, 16, 17. Fans
13 and 14 increase or decrease their flow volumes based on a static
pressure sensor in the outside air duct or the exhaust air duct. A
variable speed motor controller increases or reduces the fan speed
to maintain a selected static pressure set point. The control unit
30 changes the speed of the fan motors to try maintain a static
pressure level in each duct.
[0196] An alternate embodiment of the invention is illustrated in
FIGS. 6 and 7. In FIGS. 6 and 7, D10 is an air duct integrated with
duct D30 for return air to air conditioner 220; D20 is an air duct
directing cooled (or heated) supply air S10 from air conditioner
220 back to the room; D30 is a duct through which return air from
the room flows in unit 100; D40 is a duct that directs return air
into the coil/fan section of air conditioner 220; D50 is a duct
that directs ambient air A10 into unit 100 and into one side of
heat exchange unit 120 and between and through finned layers
comprising unit 120; D60 is a duct that directs exhaust/relief air
from heat exchange unit 120 into the ambient atmosphere; A10 and
A20 are ambient air streams flowing into duct D50; A10 is a fan
induced ambient air stream directed through or over heat exchange
unit 120; A20 is a fan induced ambient air stream that bypasses
heat exchange unit 120 and travels through duct D50 and unit 100 to
joint return air stream R10 in the manner illustrated in FIG. 7;
and R20 is a portion of the return air stream that is drawn over or
through heat exchange unit 120. In FIG. 7, S10 is a combination of
return air R10 and outside ambient air A20. In FIG. 6, S10 is a
combination of a portion R10 of the return air and of ambient air
A10 that has passed through heat exchange unit 120. In FIG. 6,
portion R20 of the return air passes through heat exchange unit 120
and out through duct D60. FIG. 7 does not call out a portion R20
because portion R20 is zero, i.e., in FIG. 7 none of the return air
stream is directed through heat exchange unit 120. In FIG. 7,
portion R10 comprises the entire return air stream, minus relief
air which exits the room to outside the building through normal
building relief air paths.
[0197] FIG. 6 illustrates the heat recovery mode of the ventilation
system of the invention. FIG. 7 illustrates the economizer mode of
the ventilation system of the invention. In the economizer mode,
the temperature of the ambient air stream A20 permits it to be
added directly to the return air stream R10 and obviates the
necessity of passing an ambient air stream A10 over or through heat
exchange unit 120.
[0198] In the embodiment of the invention illustrated in FIGS. 1
and 2, air streams A1 and R2 must make ninety degree turns while
traversing ventilation unit 10. Air stream A1 makes a ninety degree
turn to enter heat exchange unit 12. Air stream R2 makes a ninety
degree turn after exiting heat exchange unit 12. Such ninety degree
turns produce increased upstream pressure and increase the energy
required for air streams A1 and R2 to pass through ventilation unit
10. In contrast, in FIGS. 6 and 7, air streams A10 and R20 need not
make ninety degrees turns to while entering or exiting,
respectively, heat exchange unit 120. Heat exchange unit 120 is
rotated such that its faces are canted at angles less than ninety
degrees with respect to walls 80 and 81 (FIG. 11). Air stream A10
need not make a ninety turn to enter unit 120. This decreases the
energy consumed by air streams A10 and R20 while passing through
ventilation unit 100.
[0199] In FIG. 6, damper assembly 150 is in a first open operative
position which permits air stream A10 to flow through duct D50,
through the left side of damper assembly 150, and into heat
exchange unit 120. When angled damper blade 38 is in the first open
operative position, air stream A20 is prevented from flowing into
duct D50, through the right side of damper assembly 150, and into
duct D10 along a path to the right of heat exchange unit 120 to
join return air stream R10 in the manner illustrated in FIG. 7. Air
stream A20 is produced only when damper blade 38 is in the second
open operative position illustrated in FIG. 7. When damper blade 38
is in the second open operative position, air stream A10 is not
produced because damper blade 38 blocks the path of travel
illustrated in FIG. 6. When damper blade 38 is in the first open
operative position, air stream A20 is not produced because damper
blade 38 blocks the path of travel illustrated in FIG. 7.
[0200] When portion R20 of the return air stream travels through
heat exchange unit 120 in the manner illustrated in FIG. 6, damper
assembly 160 is in a first open operative position which permits
air stream R20 to exit through duct D60. Alternatively, when a
portion R20 of the return air stream does not pass through heat
exchange unit 120, damper assembly 160 is in the second closed
operative position illustrated in FIG. 7. Damper assemblies 150 and
160 each rotate or pivot about shafts 31 and 32, respectively
(FIGS. 6 and 7).
[0201] FIGS. 8A, 8B, and 8C further illustrate three general
operative positions of damper 150. In FIG. 8C, damper assembly 150
is in a third closed operative position which prevents ambient air
from flowing into and through duct D50 and past damper 150. In FIG.
8B, damper assembly 150 is rotated from the third closed operative
position of FIG. 8C in the direction of arrow B (FIG. 8B) to the
second open operative position allowing ambient air to follow the
path indicated by arrow A20 in FIG. 8B and FIG. 7. In FIG. 8A,
damper assembly 150 is rotated from the third closed operative
position of FIG. 8C in the direction of arrow A (FIG. 8A) to the
first open operative position allowing ambient air to follow the
path indicated by arrow A10 in FIG. 8A and FIG. 6. As would be
appreciated by those of skill in the art, damper assembly 150 can
be rotated (1) from the second open operative position through the
third closed operative position to the first open operative
position, and vice versa, (2) from the second open operative
position back to the third closed operative position, and (3) from
the first open operative position back to the third closed
operative position. The majority of the time, damper assembly 150
will be in either the first or second open operative position.
[0202] The particular location of damper blade 38 when it is in the
first (or second) open operative position is determined by the
algorithm earlier described herein. The algorithm determines at any
given instant in time a desired flow rate of air, either into the
heat exchange unit 120 via the airflow path generally located by
arrow A10 or bypassing heat exchange unit 120 via the air flow path
generally located by arrow A20. As is indicated in FIG. 11, once
controller 300 determines that damper blade 38 needs to be operated
in, for example, the second operative position of FIG. 8B,
controller 300 is using the previously described algorithm (or
another desired algorithm) to continuously calculate a desired flow
rate of air, and send signals to motor 86 to adjust the position of
damper blade 38 to increase or decrease the flow rate of air along
the path generally indicated by arrow A20 (FIG. 7). Motor 86 turns
shaft 31, and therefore damper blade 38 and shaft 31, in the
direction of arrow B or in a direction opposite that of arrow B.
Minute adjustments of the damper blade 38 rotation in damper
assembly 150 will continue to occur to meet the algorithm
calculated air flow rate requirements.
[0203] FIG. 9 is a top (plan) view illustrating construction
details of damper assembly 150 and its operatively associated
divider panel 35. When ambient air is traveling along the path
indicated by arrow A20, panel 35 (along with associated
circumscribing walls of duct D50) prevents ambient air from
crossing over into the path that is followed by air traveling along
a path indicated by arrow A10. When ambient air is traveling along
the path indicated by arrow A10, panel 35 (along with the
associated circumscribing walls of duct D50) prevents ambient air
from crossing over into the path that is followed by air traveling
as indicated by arrow. A20.
[0204] Damper assembly 150 includes drum arc segments 39A and 39B
with scalloped edges 63A and 63B, and solid contoured panels 64A
and 64B (FIGS. 11 and 13). Damper assembly 150 also includes a
slotted top generally circular panel 36 and a slotted bottom
generally circular panel 37. The shape and dimension of panel 36 is
presently equivalent to that of panel 37, although that need not be
the case. Angled damper blade 38 extends between and interconnects
spaced apart, scalloped edge drum arc segments 39A and 39B (FIG.
9). As is illustrated in FIG. 13, contoured panels 64A and 64B
extend from the interior scalloped edges 63A and 63B approximately
60 degrees away from the scalloped edges, finishing with a linear
edge which is perpendicular to the slotted drum top 36 and slotted
drum bottom 37. Damper assembly 150 can be formed in any desired
manner and can comprise a solid piece of material. It is presently
preferred that damper assembly 150 be fabricated from sheet metal
or sheet plastic in order to reduce the amount of material and
weight required to produce a system in accordance with the
invention. Any desired system can be devised to seal appropriately
the peripheral edges of angled damper blade 38 to prevent air from
flowing between damper blade 38 and scalloped drum segments 39A and
39B unless damper blade 38 is in the first or second open operative
position. In FIG. 12, for example, elongated fixed neoprene or
rubber edge gaskets 84A and 84B sealingly engage the top 36 and
bottom 37 of the damper assembly 150, and elongated neoprene or
rubber edge seals or gaskets 85A, 85B sealingly engage portions of
drum segments 63A and 63B. In FIG. 11, and enhanced in FIG. 12,
angled damper blade 38 is in the third closed operative position.
In the third operative position, the entire length of each
straight/perpendicular edge 84A and 84B and 85A and 85B is in
contact with the interior solid, contoured or flat surfaces of the
damper assembly 150 so that air cannot enter duct D50 and flow past
damper assembly 150. Edge seals/gaskets 84A and 84B are fixedly
attached to the top and bottom of angled damper blade 38 and
seals/gaskets 85A and 85B are fixedly attached to the sides of
angled damper blade 38. Bushings/bearings 69 and 68 sealingly
engage shaft 31. Edge seals/gaskets 84A and 84B sealingly slide
against slotted top and bottom 36 and 37, respectively. Edge
seals/gaskets 85A and 85B sealingly slide against scalloped drum
arcs 39A and 39B contoured interior surfaces
[0205] FIG. 12 depicts how rotatable shaft 31 can extend completely
through and be fixedly attached to angled damper blade 38.
Rotatable shaft 31 can be drilled and tapped axially in angles
separated by 120 degrees to match the angle of the damper blade.
Threaded, locking screws or bolts can engage the tapped and
threaded shaft openings, from the blade side of the shaft, to a
maximum of 75% of the threaded depth to secure the blade to the
shaft at a minimum of three places per angled surface.
[0206] As can be seen in FIGS. 8C and 9, blade segments 33 and 34
of angled damper blade 38 are not co-linear, but instead together
form an inner obtuse angle of less than one hundred and eighty
degrees, typically presently about 120 degrees. This provides space
for scalloped drum segments 39A and 39B such that in FIGS. 8C and
9, edges 85A and 85B of damper blade segments 33 and 34 are in
their entirety on the solid contoured, not scalloped, inner
surfaces of drum arc segments 64A and 64B. In FIG. 8A, angled
damper blade 38 will rotate from the third operative position
through an arc having a length of between 0 degrees and 60 degrees
toward the first operative position, allowing increasing air flow
amounts to pass through the scalloped opening 63A of drum segment
39A in direction of air flow A10. Similarly for FIG. 8B, angled
damper blade 38 will rotate from the third operative position
through an arc of between 0 degrees and 60 degrees toward the
second operative position, allowing increasing air flow amounts to
pass through the scalloped opening 63B of drum segment 39B in
direction of air flow A20.
[0207] During normal operation of shaft 31 and motor 86, when
damper blade 38 is in the first operative position of FIG. 8A,
damper blade segment 34 maintains contact with drum segment 64B and
does not rotate past the perpendicular edge 64C (FIG. 11) of drum
segment arc 64B. In FIG. 8A, damper blade 38 has rotated clockwise
from the position of FIG. 8C through its greatest possible arc of
travel and is in a first "fully open" position. Similarly, during
normal operation of shaft 31 and motor 86, when damper 38 is in the
second operative position of FIG. 8B, damper blade segment 33
maintains contact with drum segment 64A and does not rotate past
the perpendicular edge 64D (FIG. 11) of drum segment arc 64A. In
FIG. 8B, damper blade 38 has rotated counterclockwise from the
position of FIG. 8C through its greatest possible arc of travel and
is in a second "fully open" position.
[0208] The diameter, indicated by arrows F in FIG. 13, of damper
150 is presently ten inches, and the height, indicated by arrows G
in FIG. 13, of damper 150 is presently sixteen inches. In the
majority of cases, the diameter of damper 150 will be in the range
of nine to eleven inches, and the height of damper 150 will be in
the range of fifteen to seventeen inches. The diameter of damper
150 may, however, be in the range of six to twelve inches and the
height of damper may be in the range of sixteen to thirty inches.
The diameter and height of damper 150 are varied to meet desired
air flow requirements, to meet sizing requirements of ducting and
air conditioning units, and/or to meet other design criteria.
[0209] The referenced 10 inches diameter by 16 inches high damper
assembly 150 has a generally cylindrical shape and includes two
contoured panels 64A, 64B each with a scalloped edge 63A, 63B,
respectively, which edge 63A, 63B provides a control surface for
damper blade 38 to regulate air flow through one side of the damper
module while damper blade 38 prevents air flow through the other
side of the damper module. The contoured panels 64A, 64B of damper
150 each are configured with a 10 inches diameter, and extend
through a 120 degree long arc. The 120 degree long arc includes a
scalloped edge 63A, 63B which extends through a 60 degree long arc,
and, also includes an arcuate solid panel with a vertical cut-off
64C, 64D (FIG. 11) which is perpendicular to the top and bottom of
the drum. The solid panel extends through a 60 degree long arc.
Each scalloped edge 63A, 63B is exposed to the air stream in
varying amounts to allow regulation of air flow through the open
areas in edge 63A, 63B using damper blade 38 in its varying
positions contacting a solid portion of the scalloped segment arc
length.
[0210] The top 36 and bottom 37 of the damper assembly 150 are
comprised of generally circular discs which are furnished with
openings of the required size in the center of the discs. The
openings are used to install the actuator shaft bushings/bearings
68 and 69. A slot is provided in each of the top 36 and bottom 37
disc to install the air diverter partition 35, FIG. 15. The air
diverter partition separates the two air streams of A10 and A20 as
required for the first operative position and the second operative
position respectively of damper blade 38. Further, air diverter
partition 35 extends through the top 36 and bottom 37 and attaches
to the inside top and bottom of duct module D50. Air diverter
partition 35 is attached to the top 36 and bottom 37 and sealed to
prevent air leakage between first operative position air stream A10
and second operative position air stream A20.
[0211] When damper assembly 150 is in the economizer mode
illustrated in FIG. 8B, the position of damper blade 38 is, for a
damper assembly 150 with a diameter of ten inches and a height of
sixteen inches, adjusted to vary the air flow A20 between 100 cfm
(cubic feet per minute) and 700 cfm. When the damper assembly 150
is in the heat recovery mode illustrated in FIG. 8A, the position
of damper blade 38 is, for a damper assembly 150 with a diameter of
ten inches and a height of sixteen inches, adjusted to vary the air
flow A10 between 100 cfm and 450 cfm. One way to increase the
airflow A10 or A20 for a given amount of revolution of damper blade
38 is to make the damper assembly 150 taller. Another way to
increase the airflow A10 or A20 for a given amount of revolution of
damper blade 38 is to increase the diameter of the damper assembly
150. Still another way to increase the airflow A10 or A20 for a
given amount of revolution of damper blade 38 is to reduce the
height of damper assembly 150 and increase the diameter of the
damper assembly 150 by a desired amount. Yet another way to
increase the airflow of damper blade 38 is to increase the height
and diameter of damper assembly 150. And yet another way to
increase the airflow of damper assembly 150 is to change the
scallop contours of arc segments 63A and 63B as illustrated by 42A,
42B, 42C, 42E, etc., FIG. 10. Reducing the airflow of damper
assembly 150 is accomplished by carrying out the reverse of the
foregoing size increasing procedures. The minimal desired airflow
A10 or A20 into a classroom is typically 100 cfm.
[0212] The airflow A20 in the economizer mode of FIG. 8B is
increased by rotating damper blade 38 and shaft 31 in the direction
of arrow B (FIG. 8C). The incorporation in scalloped edge 63B of
arcuate edge segments 40, 41, 43, 44 and 42, 42A, 42B, 42C, 42D or
42E, FIG. 9 is important in this respect because with each degree
of rotation of damper assembly 150 in the direction of arrow B, the
amount of increase in airflow A20 is less than if edge segments 40,
41, 43, 44 and 42, 42A, 42B, 42C, 42D or 42E were straight and
parallel to edge 85B of damper blade 38. The rotational centerline
of damper blade 38 is the centerline through shaft 31. As damper
blade 38 begins to open to permit airflow A20, such airflow A20
initially can pass only through the open areas 40A and 41A of
"valleys" 40 and 41 (FIG. 10) of edge 63B. This facilitates being
able to adjust the airflow in small increments. In the practice of
the invention, it is important to be able to adjust the airflow by
increments at least as small as one to two percent of the maximum
airflow in the heat recovery mode and the economizer mode.
Consequently, for example, if the maximum airflow in the economizer
mode is 700 cfm, it is important to be able to adjust the air flow
by 7 to 14 cfm. Scalloped edge 63B facilitates such airflow
adjustments.
[0213] The airflow A10 in the heat recovery mode of FIG. 8A is
increased by rotating damper blade 38 and shaft 31 in the direction
of arrow A (FIG. 8C). The incorporation in scalloped edge 63A of
arcuate edge segments comparable to those illustrated in FIG. 10
for edge 63B is important in this respect because with each degree
of rotation of damper 150 in the direction of arrow A, the amount
of increase in airflow A10 is less than if said arcuate edge
segments were straight and parallel to edge 85A of damper blade 38.
The rotational centerline of damper blade 38 is the centerline
through shaft 31. As damper blade 38 begins to open to permit
airflow A10, such airflow A10 initially can pass only through the
open areas of "valleys" of edge 63A. This facilitates being able to
adjust the airflow in small increments. In the practice of the
invention, it is important to be able to adjust the airflow by
increments at least as small as one to two percent of the maximum
airflow in the heat recovery mode and the economizer mode.
Consequently, for example, if the maximum airflow in the heat
recovery mode is 450 cfm, it is important to be able to adjust the
air flow by four and one-half to nine cfm. Scalloped edge 63A
facilitates such airflow adjustments.
[0214] The shape and dimension of scalloped edges 63A and 63B can
vary as desired. The presently preferred design of edges 63A and
63B utilizes valleys 40 and 41 and peaks 42 which each correspond
to one-half (valleys 40 and 41, and peak 42) or one-quarter (peaks
43 and 44) of the shape of an ellipse. The number and shape of such
peaks and valleys can vary as desired. For example, valleys 40 and
41 may have a circular contour; or, an edge 63A can have a saw
tooth configuration. One or more openings, such as the opening
depicted by dashed line 92 in FIGS. 10 and 13, can be formed though
damper arc segments 39A or 39B near an edge 63A or 63B
respectively.
[0215] In one embodiment of the invention the diameter and/or
height of damper assembly 150 is decreased sufficiently such that
the air flow in the economizer mode is 70 to 450 cfm; and, the air
flow in the heat recovery mode is 70 to 300 cfm.
[0216] In another embodiment of the invention, the diameter and/or
height of damper assembly 150 is increased sufficiently such that
the air flow A20 in the economizer mode is 150 to 2100 cfm; and,
the air flow A10 in the energy recovery mode is in the range of 70
to 1400 cfm.
[0217] The diameter of damper assembly 150 typically corresponds to
the width of the plenum D50 of DVHR module 100. The height of
damper assembly 150 presently typically generally corresponds to
the height of the heat exchange unit 120.
[0218] Accordingly, in general, during the practice of the
invention, the airflow A20 in the economizer mode can be in the
range of 70 to 2100 cfm, and the airflow A10 in the heat recovery
mode can be in the range of 70 to 1400 cfm.
[0219] The maximum possible airflow during the economizer mode is
always be greater than the maximum possible airflow during the heat
recovery mode.
[0220] In FIG. 11, motor 86 is utilized to rotate shaft 31, and
therefore damper blade 38, in the direction of arrow A and in a
direction opposite that of arrow A. Motor 86 can be a stepper motor
or an infinitely modulating motor. Motor 86 preferably is able to
rotate damper blade 38 in increments at least as small as 0.1
degree.
[0221] A particular advantage of the damper blade 38 is that it
enables small incremental changes in air flow while at the same
time enabling and controlling the modulation of two separate
airflows A10 and A20. Airflow A10 is modulated independently of
airflow A20. If airflow A10 is being utilized during operation of
the system of the invention, airflow A20 is not being utilized, and
vice versa.
[0222] One goal of the invention is to make the increase in airflow
A10 or A20 linear with respect to the amount of rotation of damper
blade 38. As damper blade 38 is rotated to permit airflow A10 or
A20 to increase, the cross-sectional area through which airflow A10
or A20 moves increases along with the perimeter of the
cross-sectional area. Preferably, the cross-sectional area should
change proportionally to the perimeter of the cross-sectional area
to permit linear, or substantially linear, control of the volume of
air passing through the cross sectional area. Ideally, a given
increase in the cross-sectional area produces a like increase in
the perimeter of the cross-sectional area, e.g., a 10% increase in
cross-sectional area produces a 10% increase in the perimeter of
the cross-sectional area.
[0223] In the presently preferred embodiment of the invention,
damper blade 38 is rotated a maximum of 60 degrees from the third
operative position of FIG. 8A in the direction of arrow A; and,
similarly is rotated a maximum of 60 degrees from the third
operative position of FIG. 8A in the direction of arrow B. Such
maximum rotation values can be adjusted as desired.
[0224] In FIG. 8B, the cross-sectional area through which airflow
A20 moves is bounded by the edge of damper blade seal 85B of damper
blade segment 34 (FIG. 9), edge 63B of drum arc segment 63B, and
top seal 84A and bottom seal 84B (FIG. 12). In FIG. 8A, the
cross-sectional area through which airflow A10 moves is bounded by
the edge of damper blade seal 85A of damper blade segment 33 (FIG.
9), edge 63A of drum arc segment 63A, and top seal 84A and bottom
seal 84B (FIG. 12). When damper blade 38 is rotated to increase the
flow of air through one of these cross-sectional areas, the
pressure drop produced by the air as it moves through the
cross-sectional areas decreases. If there is a pressure drop
reduction produced when air flow A10 moves past damper 38, then
there is a corresponding increase in the pressure drop produced as
the air passes through heat exchange unit 120.
[0225] In addition to being utilized in connection with air
conditioning (heating/cooling) systems, damper assembly 150 can be
utilized in any atmospheric pressure gas/vapor regulating system
which requires the division and modulation of a single gas/vapor
stream into two separate independent gas/vapor streams.
[0226] While damper assembly 150 and other system components can be
fabricated from any desired material, it is presently preferred
that damper assembly 150 be constructed from a medium to high
strength material such as, for example, carbon steel, aluminum,
polymer or other materials. The particular material selected will
depend on system pressures, corrosivity of the gas/vapor, and the
maximum allowable smoke spread and flame development requirements
of NFPA and local building codes. The preferred maximum leakage for
seals 85A and 85B (FIG. 12) in an air conditioning system when
damper blade 38 is in the third operative position is 2% of the
design air flow at a system pressure of three inches water column
pressure.
[0227] Motor 86, or any other desired actuator system, is
preferably a low voltage (less than 115 volts) or line voltage (115
volts to 600 volts) motor capable of rotating shaft 31 through a
minimum of 180 degrees of rotation, and includes a position
feedback that can recognize when damper blade 38 is in the third
operative position (shut off position) of FIG. 8C and can recognize
any other desired position of damper blade 38. Alternate position
sensing systems can be utilized, such as a magnetic end switch
device attached to damper blade 38 and either the top drum disc 36
or bottom drum disc 37.
[0228] Still another embodiment of the invention is illustrated in
FIGS. 16 and 17. In FIGS. 16 and 17, D10 is an air duct integrated
with duct D30 for return air to air conditioner 220; D20 is an air
duct directing cooled (or heated) supply air S10 from air
conditioner 220 back to the room; D30 is a duct through which
return air from the room flows in unit 100; D40 is a duct that
directs return air into the coil/fan section of air conditioner
220; D50 is a duct that directs ambient air A10 into unit 100 and
into one side of heat exchange unit 120 and between and through
finned layers comprising unit 120; D60 is a duct that directs
exhaust/relief air from heat exchange unit 120 into the ambient
atmosphere; A10 and A20 are ambient air streams flowing into duct
D50; A10 is a fan induced ambient air stream directed through or
over heat exchange unit 120; A20 is a fan induced ambient air
stream that bypasses heat exchange unit 120 and travels through
duct D50 and unit 100 to joint return air stream R10 in the manner
illustrated in FIG. 17; and R20 is a portion of the return air
stream that is drawn over or through heat exchange unit 120. In
FIG. 17, S10 is a combination of return air R10 and outside ambient
air A20. In FIG. 16, S10 is a combination of a portion R10 of the
return air and of ambient air A10 that has passed through heat
exchange unit 120. In FIG. 16, portion R20 of the return air passes
through heat exchange unit 120 and out through duct D60. FIG. 17
does not call out a portion R20 because portion R20 is zero, i.e.,
in FIG. 17 none of the return air stream is directed through heat
exchange unit 120. In FIG. 17, portion R10 comprises the entire
return air stream, minus relief air which exits the room to outside
the building through normal building relief air paths.
[0229] FIG. 16 illustrates the heat recovery mode of the
ventilation system of the invention. FIG. 17 illustrates the
economizer mode of the ventilation system of the invention. In the
economizer mode, the temperature of the ambient air stream A20
permits it to be added directly to the return air stream R10 and
obviates the necessity of passing an ambient air stream A10 over or
through heat exchange unit 120.
[0230] In the embodiment of the invention illustrated in FIGS. 1
and 2, air streams A1 and R2 must make ninety degree turns while
traversing ventilation unit 10. Air stream A1 makes a ninety degree
turn to enter heat exchange unit 12. Air stream R2 makes a ninety
degree turn after exiting heat exchange unit 12. Such ninety degree
turns produce increased upstream pressure and increase the energy
required for air streams A1 and R2 to pass through ventilation unit
10. In contrast, in FIGS. 16 and 17, air streams A10 and R20 need
not make ninety degrees turns to while entering or exiting,
respectively, heat exchange unit 120. Heat exchange unit 120 is
rotated such that its faces are canted at angles less than ninety
degrees with respect to walls 80 and 81 (FIG. 21). Air stream A10
need not make a ninety turn to enter unit 120. This decreases the
energy consumed by air streams A10 and R20 while passing through
ventilation unit 100.
[0231] In FIG. 16, damper assembly 1150 is in a first open
operative position which permits air stream A10 to flow through
duct D50, past the left edge of damper assembly 1150, and into heat
exchange unit 120. When damper assembly 1150 is in the first open
operative position, air stream A20 is prevented from flowing into
duct D50, past the right edge of damper assembly 1150, and into
duct D10 along a path to the right of heat exchange unit 120 to
join return air stream R10 in the manner illustrated in FIG. 17.
Air stream A20 is produced only when damper assembly 1150 is in the
second open operative position illustrated in FIG. 17. When damper
assembly 1150 is in the second open operative position, air stream
A10 is not produced because damper assembly 1150 blocks the path of
travel illustrated in FIG. 16. When damper assembly 1150 is in the
first open operative position, air stream A20 is not produced
because damper assembly 1150 blocks the path of travel illustrated
in FIG. 17.
[0232] When portion R20 of the return air stream travels through
heat exchange unit 120 in the manner illustrated in FIG. 16, damper
assembly 1160 is in a first open operative position which permits
air stream R20 to exit through duct D60. Alternatively, when a
portion R20 of the return air stream does not pass through heat
exchange unit 120, damper assembly 1160 is in the second closed
operative position illustrated in FIG. 17. Damper assemblies 1150
and 1160 each rotate or pivot about shafts 131 and 132,
respectively (FIGS. 16 and 17).
[0233] FIGS. 18A, 18B, and 18C further illustrate three general
operative positions of damper assembly 1150. In FIG. 18A, damper
assembly 1150 is in a third closed operative position which
prevents ambient air from flowing into and through duct D50 and
past damper assembly 1150. In FIG. 18B, damper assembly 1150 is
rotated from the third closed operative position of FIG. 18A in the
direction of arrow B (FIG. 18A) to the second open operative
position allowing ambient air to follow the path indicated by arrow
A20 in FIG. 18B and FIG. 17. In FIG. 18C, damper assembly 1150 is
rotated from the third closed operative position of FIG. 18A in the
direction of arrow A (FIG. 18A) to the first open operative
position allowing ambient air to follow the path indicated by arrow
A10 in FIG. 18C and FIG. 16. As would be appreciated by those of
skill in the art, damper assembly 1150 can be rotated (1) from the
second open operative position through the third closed operative
position to the first open operative position, and vice versa, (2)
from the second open operative position back to the third closed
operative position, and (3) from the first open operative position
back to the third closed operative position. The majority of the
time, damper assembly 1150 will be in either the first or second
open operative position.
[0234] The particular location of damper assembly 1150 when it is
in the first (or second) open operative position is determined by
the algorithm earlier described herein. The algorithm determines at
any given instant in time a desired flow rate of air, either into
the heat exchange unit 120 via the airflow path generally located
by arrow A10 or bypassing heat exchange unit 120 via the air flow
path generally located by arrow A20. As is indicated in FIG. 21,
once controller 300 (FIG. 21) determines that damper assembly 1150
needs to be operated in, for example, the second operative position
of FIG. 18B, controller 300 is using the previously described
algorithm (or another desired algorithm) to continuously calculate
a desired flow rate of air, and send signals to motor 86 to adjust
the position of damper assembly 1150 to increase or decrease the
flow rate of air along the path generally indicated by arrow A20
(FIG. 17). Motor 86 turns shaft 131A, and therefore damper assembly
1150 and shaft 131, in the direction of arrow B to move damper
assembly 1150 from the third operative position of FIG. 18A to the
second operative position of FIG. 18B. Minute adjustments (i.e.,
minute rotation) of the damper drum 138 in damper assembly 1150
continues to occur to meet the algorithm calculated air flow rate
requirements.
[0235] FIG. 19 is a perspective view illustrating construction
details of damper assembly 1150 and its operatively associated
divider panel 135. When ambient air is traveling along the path
indicated by arrow A20, panel 135 (along with associated
circumscribing walls of duct D50) prevents ambient air from
crossing over into the path that is followed by air traveling along
a path indicated by arrow A10. When ambient air is traveling along
the path indicated by arrow A10, panel 135 (along with the
associated circumscribing walls of duct D50) prevents ambient air
from crossing over into the path that is followed by air traveling
as indicated by arrow A20.
[0236] Damper assembly 1150 includes scalloped edges 139 (FIG. 19)
and 163 (FIG. 23). The shape and dimension of edge 139 is presently
equivalent to that of edge 163, although that need not be the case.
Damper 1150 also includes a top generally semicircular panel 136
and a bottom generally semicircular panel 137. The shape and
dimension of panel 136 is presently equivalent to that of panel
137, although that need not be the case. Semicircular wall 138
extends between and interconnects spaced apart, parallel panels 136
and 137. As is illustrated in FIG. 23, contoured panel 64 extends
between scalloped edges 139 and 163. Damper assembly 1150 can be
formed in any desired manner and can comprise a solid piece of
material. It is presently preferred that damper assembly 1150 be
hollow in order to reduce the amount of material required to
produce a system in accordance with the invention.
[0237] The damper assembly 1150A in FIG. 20 is comparable to damper
assembly 1105, provided, however, that damper assembly 1150A is
truncated to produce flat surface 65. If desired, damper assembly
1150A can be truncated to form, instead of flat truncated surface
65, the arcuate concave surface indicated by dashed line 66.
Scalloped edge 139 includes semi-elliptical concave portions 140
and 141, semi-elliptical convex portion 142, and quarter-elliptical
convex portions 143 and 144. The shape and dimension of a scalloped
edge 139, 163 can vary as desired. By way of example, and not
limitation, concave portions 140 and 141 can be semi-circular and
not semi-elliptical.
[0238] Any desired system can be devised to seal appropriately the
periphery of damper assembly 1150 to prevent air from flowing
around damper assembly 1150 unless damper assembly 1150 is in the
first or second open operative position. In FIG. 21, for example,
elongate fixed foam or felt or rubber strips or gaskets 84 and 85
sealingly engage the top 136 and bottom of damper assembly 1150,
and elongate fixed foam or felt or rubber strips sealingly engage
portions of cylindrical outer surface 138. In FIG. 21, damper
assembly 1150 is in the third closed operative position. In the
third operative position, the entire length of each scalloped edge
139, 163 is spaced apart and forwardly from strips 82, 83, 84, 85
so that air cannot enter duct D50 and flow past damper assembly
1150. Consequently, edges 139 and 163 are not visible in FIG. 21
because they are on the other side of and spaced apart from strips
82, 83, 84, 85 as shown in FIG. 24. Seal 82 is fixedly attached to
wall 80. Seal 83 is fixedly attached to wall 81. Seal 84 is fixedly
secured to the top of duct D50. Seal 85 is fixedly attached to the
bottom of duct D50. In FIG. 24, the location of strip 84 is
indicated by dashed line 84A. Bushings 169 and 168 sealingly engage
shafts 131 and 131A, respectively. Outer surface 138 (FIG. 19) of
damper assembly 1150 sealingly slides over strips 82 and 83. Top
136 of damper assembly 1150 sealingly slides over strip 84. Bottom
137 of damper assembly 1150 sealingly slides over strip 85.
[0239] FIG. 22 depicts how a rotatable shaft 131B can extend
completely through and be fixedly attached to a damper assembly
1150.
[0240] In FIG. 24, dashed lines 90 and 91 indicate reinforcing
interior panels, or ribs, that extend from the top 136 to the
bottom 137 of damper assembly 1150. The ribs 90 and 91 are spaced
about one-half inch behind the concave portions 140 and 141 (FIG.
10) of the scalloped edges 139 and 163 of damper assembly 1150.
[0241] As can be seen in FIGS. 18A and 19, the upper edges 133 and
134 of damper assembly 1150 are not collinear, but instead together
form an inner obtuse angle of less than one hundred and eighty
degrees. As a result, damper assembly 1150 is larger than one-half
of a cylinder. This provides space for scalloped edges 139 and 163
such that in FIG. 24, edges 139 and 163 are in their entirety on
the same side of wall 81 and seal 84 as is divider panel 135. No
portion of edges 139 and 163 extends past walls 80 and 81 toward
the opening D50A of duct D50. If desired, damper assembly 1150 can,
as indicated by dashed line 67 in FIG. 20, be formed such that
edges 133 and 134 are collinear. In that case, seals 82, 83, 84, 85
may have to be repositioned to insure that when damper assembly
1150 is in the third operative position illustrated in FIG. 24, no
portion of edges 139 and 163 extends past seals 82 to 85 toward
opening D50A.
[0242] The diameter, indicated by arrows F in FIG. 23, of damper
assembly 1150 is presently ten inches, and the height, indicated by
arrows G in FIG. 23, of damper assembly 1150 is presently sixteen
inches. In the majority of cases, the diameter of damper assembly
1150 will be in the range of nine to eleven inches, and the height
of damper assembly 1150 will be in the range of fifteen to
seventeen inches. The diameter of damper assembly 1150 may,
however, be in the range of six to twelve inches and the height of
damper may be in the range of sixteen to thirty inches. The
diameter and height of damper assembly 1150 are varied to meet
desired air flow requirements, to meet sizing requirements of
ducting and air conditioning units, and/or to meet other design
criteria.
[0243] When damper assembly 1150 is in the economizer mode
illustrated in FIG. 18B, the position of damper assembly 1150 is,
for a damper assembly 1150 with a diameter of ten inches and a
height of sixteen inches, adjusted to vary the air flow A20 between
100 cfm (cubic feet per minute) and 700 cfm. When the damper
assembly 1150 is in the heat recovery mode illustrated in FIG. 18C,
the position of damper assembly 1150 is, for a damper assembly 1150
with a diameter of ten inches and a height of sixteen inches,
adjusted to vary the air flow A10 between 100 cfm and 450 cfm. One
way to increase the airflow A10 or A20 for a given amount of
revolution of damper assembly 1150 is to make the damper assembly
1150 taller. Another way to increase the airflow A10 or A20 for a
given amount of revolution of damper assembly 1150 is to increase
the damper assembly diameter. Still another way to increase the
airflow A10 or A20 for a given amount of revolution of damper
assembly 1150 is to reduce the height of damper assembly 1150 and
increase the diameter of the damper assembly 1150 by a desired
amount. Yet another way to increase the airflow of damper assembly
1150 is to increase the height and diameter of damper assembly
1150. Reducing the airflow of damper assembly 1150 is accomplished
by carrying out the reverse of the foregoing size increasing
procedures. The minimal desired airflow A10 or A20 into a classroom
is typically 100 cfm.
[0244] The airflow A20 in the economizer mode of FIG. 18B is
increased by rotating damper assembly 1150 and shafts 131 and 131A
in the direction of arrow B (FIG. 18A). The incorporation in damper
assembly 1150 of scalloped edge 139 is important in this respect
because with each degree of rotation of damper assembly 1150 in the
direction of arrow B, the amount of increase in airflow A20 is less
than if edge 139 were straight and parallel to the centerline of
damper assembly 1150. The centerline of damper assembly 1150
extends through the center of shafts 131 and 131A. As damper
assembly 1150 begins to open to permit airflow A20, such airflow
A20 initially can pass only through the "valleys" 140 and 141 (FIG.
20) of edge 39. This facilitates being able to adjust the airflow
in small increments. In the practice of the invention, it is
important to be able to adjust the airflow by increments at least
as small as one to two percent of the maximum airflow in the heat
recovery mode and the economizer mode. Consequently, for example,
if the maximum airflow in the economizer mode is 700 cfm, it is
important to be able to adjust the air flow by 7 to 14 cfm.
Scalloped edge 139 facilitates such airflow adjustments.
[0245] The airflow A10 in the heat recovery mode is increased by
rotating damper assembly 1150 and shafts 131 and 131A in the
direction of arrow A (FIG. 18A). The incorporation in damper
assembly 1150 of scalloped edge 163 is important in this respect
because with each degree of rotation of damper assembly 1150 in the
direction of arrow A, the amount of increase in airflow A10 is less
than if edge 139 were straight and parallel to the centerline of
damper assembly 1150. The centerline of damper assembly 1150
extends through the center of shafts 131 and 131A. As damper
assembly 1150 begins to open to permit airflow A10, such airflow
A10 initially can pass only through the "valleys" of edge 163. This
facilitates being able to adjust the airflow in small increments.
In the practice of the invention, it is important to be able to
adjust the by increments at least as small as one to two percent of
the maximum airflow in the heat recovery mode and the economizer
mode. Consequently, for example, if the maximum airflow A10 in the
heat recovery mode is 450 cfm, it is important to be able to adjust
the air flow by four and one half cfm to nine cfm. Scalloped edge
163 facilitates such airflow adjustments.
[0246] The shape and dimension of scalloped edges 139 and 163 can
vary as desired. The presently preferred design of edges 139 and
163 utilizes valleys 140 and 141, and peaks 142 which each
correspond to one-half (valleys 140 and 141, and peak 142) or
one-quarter (peaks 143 and 144) of the shape of an ellipse. The
number and shape of such peaks and valleys can vary as desired. For
example, valleys 140 and 141 may have a circular contour; or, edge
139 can have a saw tooth configuration. One or more openings, such
as the opening depicted by dashed line 192 in FIG. 20, can be
formed though damper assembly 1150 near an edge 139, 163.
[0247] In one embodiment of the invention the diameter and/or
height of damper assembly 1150 is decreased sufficiently such that
the air flow in the economizer mode is 70 to 450 cfm; and, the air
flow in the heat recovery mode is 70 to 300 cfm.
[0248] In another embodiment of the invention, the diameter and/or
height of damper assembly 1150 is increased sufficiently such that
the air flow A20 in the economizer mode is 150 to 2100 cfm; and,
the air flow A10 in the energy recovery mode is in the range of 70
to 1400 cfm.
[0249] Although the diameter and height of damper assembly 1150 can
vary as desired, the diameter of damper assembly 1150 typically
presently corresponds to the width of the plenum D40 of air
conditioning unit 220; and, the height of damper assembly 1150
presently typically generally corresponds to the height of the heat
exchange unit 120. The diameter of damper assembly 1150 can be
based on the available scalloped open air spaces. A larger diameter
provides more air flow. A smaller diameter provides less air
flow.
[0250] Accordingly, in general, during the practice of the
invention, the airflow A20 in the economizer mode can be in the
range of 70 to 2100 cfm, and the airflow A10 in the heat recovery
mode can be in the range of 70 to 1400 cfm.
[0251] The maximum possible airflow during the economizer mode is
always be greater than the maximum possible airflow during the heat
recovery mode.
[0252] In FIG. 21, motor 86 is utilized to rotate shaft 131A, and
therefore damper assembly 1150, in the direction of arrow A and in
a direction opposite that of arrow A. Motor 86 can be a stepper
motor or an infinitely modulating motor. Motor 86 preferably is
able to rotate damper assembly 1150 in increments at least as small
as 0.1 degree.
[0253] A particular advantage of the damper assembly 1150 is that
it enables small incremental changes in air flow while at the same
time enabling and controlling the modulation of two separate
airflows A10 and A20. Airflow A10 is modulated independently of
airflow A20. If airflow A10 is being utilized during operation of
the system of the invention, airflow A20 is not being utilized, and
vice versa.
[0254] One goal of the invention is to make the increase in airflow
A10 or A20 linear with respect to the amount of rotation of damper
assembly 1150. As damper assembly 1150 is rotated to permit airflow
A10 or A20 to increase, the cross-sectional area through which
airflow A10 or A20 moves increases along with the perimeter of the
cross sectional area. Preferably, the cross sectional area should
change proportionally to the perimeter of the cross sectional area
to permit linear, or substantially linear, control of the volume of
air passing through the cross sectional area. Ideally, a given
increase in the cross-sectional area produces a like increase in
the perimeter of the cross-sectional area, e.g., a 10% increase in
cross-sectional area produces a 10% increase in the perimeter of
the cross-sectional area.
[0255] In the presently preferred embodiment of the invention,
damper assembly 1150 is rotated a maximum of 75 degrees from the
third operative position of FIG. 18A in the direction of arrow A;
and, similarly is rotated a maximum of 75 degrees from the third
operative position of FIG. 18A in the direction of arrow B. Such
maximum rotation values can be adjusted as desired.
[0256] In FIG. 18B, the cross-sectional area through which airflow
A20 moves is bounded by seal 83, edge 139 of damper assembly 1150,
seal 85, and seal 84 (FIG. 21). In FIG. 18C, the cross-sectional
area through which airflow A10 moves is bounded by seal 82, edge
63, seal 85, and seal 84. When damper assembly 1150 is rotated to
increase the flow of air through one of these cross-sectional
areas, the pressure drop produced by the air as it moves through
the cross-sectional areas decreases. If there is a pressure drop
reduction produced when air flow A10 moves past damper assembly
1150, then there is a corresponding increase in the pressure drop
produced as the air passes through heat exchange unit 120.
[0257] In addition to being utilized in connection with air
conditioning (heating/cooling) systems, damper assembly 1150 can be
utilized in any atmospheric pressure gas/vapor regulating system
which requires the division and modulation of a single gas/vapor
stream into two separate independent gas/vapor streams.
[0258] While damper assembly 1150 and other system components can
be fabricated from any desired material, it is presently preferred
that damper assembly 1150 be constructed from a medium to high
strength material such as, for example, carbon steel, polymer or
other materials. The particular material selected will depend on
system pressures, corrosivity of the gas/vapor, and the maximum
allowable smoke spread and flame development requirements of NFPA
and local building codes. The preferred maximum leakage for seals
82 to 85 (FIG. 21) in an air conditioning system when damper
assembly 1150 is in the third operative position is 2% of the
design air flow at a system pressure of three inches water column
pressure.
[0259] Motor 86, or any other desired actuator system, is
preferably a low voltage (less than 115 volts) or line voltage (115
volts to 600 volts) motor capable of rotating shaft 131A through a
minimum of 180 degrees of rotation, and includes a position
feedback that can recognize when damper assembly 1150 is in the
third operative position (shut off position) of FIG. 18A and can
recognize any other desired position of damper assembly 1150.
Alternate position sensing systems can be utilized, such as a
magnetic end switch device attached to damper assembly 1150 and a
portion of duct D50 that circumscribes and houses damper assembly
1150.
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