U.S. patent application number 13/768067 was filed with the patent office on 2014-08-21 for dedicated outdoor air system with pre-heating and method for same.
This patent application is currently assigned to Venmar CES, Inc.. The applicant listed for this patent is Venmar CES, Inc.. Invention is credited to Maury Brad Wawryk.
Application Number | 20140235157 13/768067 |
Document ID | / |
Family ID | 51351528 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140235157 |
Kind Code |
A1 |
Wawryk; Maury Brad |
August 21, 2014 |
DEDICATED OUTDOOR AIR SYSTEM WITH PRE-HEATING AND METHOD FOR
SAME
Abstract
An energy exchange system is provided that may include a heater
configured to be disposed within a supply air flow path. A first
pre-heater is configured to be upstream from the heater within the
supply air flow path and configured to pre-heat the supply air with
a first liquid that circulates through the first pre-heater. A
boiler may be operatively connected to the first pre-heater and
configured to heat the first liquid. The system may also include a
second pre-heater configured to be upstream from the heater within
the supply air flow path. A heat transfer device may be operatively
connected to the heater and the second pre-heater. The heat
transfer device is configured to receive flue gas from the heater
and transfer heat from the flue gas to a second liquid within the
heat transfer device.
Inventors: |
Wawryk; Maury Brad;
(Saskatoon, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Venmar CES, Inc. |
Saskatoon |
|
CA |
|
|
Assignee: |
Venmar CES, Inc.
Saskatoon
CA
|
Family ID: |
51351528 |
Appl. No.: |
13/768067 |
Filed: |
February 15, 2013 |
Current U.S.
Class: |
454/233 ;
165/54 |
Current CPC
Class: |
Y02B 30/563 20130101;
F28F 2250/10 20130101; F24H 3/087 20130101; F28D 7/0041 20130101;
F24D 19/1084 20130101; F28D 7/106 20130101; F24D 2200/08 20130101;
F24D 2200/04 20130101; F24D 5/02 20130101; Y02B 30/56 20130101;
F24F 12/001 20130101; F28D 1/02 20130101 |
Class at
Publication: |
454/233 ;
165/54 |
International
Class: |
F24F 12/00 20060101
F24F012/00; F24H 3/06 20060101 F24H003/06; F24D 5/02 20060101
F24D005/02 |
Claims
1. An energy exchange system comprising: an energy recovery device
configured to be disposed within supply and exhaust air flow paths;
at least one first pre-heater configured to be positioned within
one or both of the supply and exhaust air flow paths, wherein the
at least one pre-heater comprises one or more coils configured to
circulate a first liquid that is configured to transfer heat to air
within the one or both of the supply and exhaust air flow paths;
and at least one boiler operatively connected to the at least one
first pre-heater, wherein the at least one boiler is configured to
heat the first liquid.
2. The energy exchange system of claim 1, wherein the at least one
first pre-heater is configured to be upstream of the energy
recovery device within the supply air flow path.
3. The energy exchange system of claim 1, further comprising a
heater configured to be downstream of the energy recovery device
within the supply air flow path.
4. The energy exchange system of claim 3, wherein the at least one
first pre-heater is configured to be positioned within the supply
air flow path.
5. The energy exchange system of claim 1, wherein the at least one
boiler comprises a main tank configured to retain the first liquid,
and a heating element configured to heat the first liquid.
6. The energy exchange system of claim 1, wherein the at least one
first pre-heater comprises multiple first pre-heaters configured to
be positioned within the supply air flow path.
7. The energy exchange system of claim 6, wherein the multiple
pre-heaters are operatively connected to the at least one
boiler.
8. The energy exchange system of claim 7, wherein the at least one
boiler comprises multiple boilers, wherein the each of the multiple
boilers is operatively connected to one of the multiple first
pre-heaters.
9. The energy exchange system of claim 1, further comprising: at
least one second pre-heater configured to pre-heat air within one
or both of the supply and exhaust air flow paths; a heater
configured to be disposed within the supply air flow path, wherein
the heater is configured to generate flue gas; and a heat transfer
device operatively connected to the heater and the at least one
second pre-heater, wherein the heat transfer device is configured
to receive energy from the flue gas from the heater and transfer
heat from the flue gas to a second liquid within the heat transfer
device, and wherein the second liquid is configured to be channeled
to the at least one second pre-heater so that heat is transferred
from the second liquid to supply air within the supply air flow
path before the supply air encounters the energy recovery
device.
10. The system of claim 9, wherein the heater is configured to be
downstream from the energy recovery device within the supply air
flow path.
11. The system of claim 9, wherein the heater is configured to be
upstream from the energy recovery device within the supply air flow
path.
12. The system of claim 9, wherein the at least one first
pre-heater is configured to be positioned with the supply air flow
path.
13. The system of claim 9, further comprising one or more of pipes,
tubes, conduits, or plenum connected between the heat transfer
device and the heater, wherein the flue gas is configured to pass
from the heater to the heat transfer device via the one or more of
pipes, tubes, conduits, or plenum.
14. The system of claim 1, wherein the energy exchange system is a
Dedicated Outdoor Air System (DOAS).
15. The system of claim 1, wherein the energy recovery device is
one or more of an enthalpy wheel, a sensible wheel, a desiccant
wheel, a plate heat exchanger, a plate energy exchanger, a heat
pipe, or a run-around loop.
16. The system of claim 1, wherein the one or more coils are
configured to be disposed within or around a portion of the supply
air flow path.
17. The system of claim 1, further comprising at least one return
air duct configured to fluidly connect the supply air flow path
with the exhaust air flow path.
18. The system of claim 1, further comprising at least one bypass
duct configured to be disposed within the supply air flow path,
wherein the at least one bypass duct is configured to bypass at
least a portion of the supply air around one or both of the at
least one first pre-heater or the energy recovery device.
19. A method of operating an energy exchange system having a supply
air flow path that allows supply air to be supplied to an enclosed
structure and an exhaust air flow path that allows exhaust air from
the enclosed structure to be exhausted to the atmosphere, the
method comprising: heating a first liquid within an internal
chamber of a boiler; pumping the first liquid from the boiler to at
least one first pre-heater disposed within one or both of the
supply air flow path and the exhaust air flow path; pre-heating air
within the one or both of the supply air flow path and the exhaust
air flow path with the first liquid within the at least one first
pre-heater; and pumping the first liquid from the at least one
first pre-heater back to the boiler.
20. The method of claim 19, further comprising: capturing flue gas
generated by a heater; channeling the flue gas to a heat transfer
device; transferring heat from the flue gas to a second liquid
within the heat transfer device; circulating the second liquid to
at least one second pre-heater disposed within one or both of the
supply air flow path and the exhaust air flow path; and
transferring heat within the second liquid to the air within one or
both the supply air flow path and the exhaust air flow path.
21. The method of claim 20, further comprising venting the flue gas
from the heat transfer device after heat from the flue gas has been
transferred to the second liquid within the heat transfer
device.
22. The method of claim 20, further comprising recirculating the
second liquid back to the heat transfer device after the heat
within the second liquid has been transferred to the supply
air.
23. The method of claim 20, further comprising passing the
pre-heated air to an energy recovery device.
24. The method of claim 20, further comprising bypassing at least a
portion of the air around the at least one first pre-heater.
25. A Dedicated Outdoor Air System (DOAS) comprising: a heater
configured to be disposed within a supply air flow path; a first
pre-heater configured to be upstream from the heater within the
supply air flow path, wherein the first pre-heater is configured to
pre-heat the supply air through heat transfer with a first liquid
that circulates through the first pre-heater; and a boiler
operatively connected to the first pre-heater, wherein the boiler
is configured to heat the first liquid.
26. The DOAS of claim 24, further comprising: a second pre-heater
configured to be upstream from the heater within the supply air
flow path; and a heat transfer device operatively connected to the
heater and the second pre-heater, wherein the heat transfer device
is configured to receive flue gas from the heater and transfer heat
from the flue gas to a second liquid within the heat transfer
device, and wherein the second liquid is configured to be channeled
to the second pre-heater so that heat is transferred from the
second liquid to supply air within the supply air flow path.
Description
BACKGROUND OF THE DISCLOSURE
[0001] Embodiments of the present disclosure generally relate to a
dedicated outdoor air system (DOAS) having one or more
pre-heaters.
[0002] Enclosed structures, such as occupied buildings, factories
and animal barns, and the like generally include an HVAC system for
conditioning ventilated and/or recirculated air in the structure.
The HVAC system includes a supply air flow path and a return and/or
exhaust air flow path. The supply air flow path receives air, for
example outside or ambient air, re-circulated air, or outside or
ambient air mixed with re-circulated air, and channels and
distributes the air into the enclosed structure. The air is
conditioned by the HVAC system to provide a desired temperature and
humidity of supply air discharged into the enclosed structure. The
exhaust air flow path discharges air back to the environment
outside the structure, or ambient air conditions outside the
structure. Without energy recovery, conditioning the supply air
typically requires a significant amount of auxiliary energy. This
is especially true in environments having extreme outside air
conditions that are much different than the required supply air
temperature and humidity. Accordingly, energy exchange or recovery
systems are typically used to recover energy from the exhaust air
flow path. Energy recovered from air in the exhaust flow path is
utilized to reduce the energy required to condition the supply
air.
[0003] Conventional energy exchange systems may utilize energy
recovery devices (for example, energy wheels and permeable plate
exchangers) or heat exchange devices (for example, heat wheels,
plate exchangers, heat-pipe exchangers and run-around heat
exchangers) positioned in both the supply air flow path and the
exhaust air flow path. A Dedicated Outdoor Air System (DOAS) is an
energy exchange system that conditions ambient/outside air to
desired supply air conditions through a combination of heating,
cooling, dehumidification, and/or humidification.
[0004] In extremely cold conditions, however, frost may form on one
or more energy recovery devices within a DOAS. For example, in
extremely cold conditions, frost may form on an enthalpy wheel that
first encounters outside air within the DOAS. Frost on the enthalpy
wheel typically reduces the efficiency and effectiveness of the
enthalpy wheel.
[0005] Additionally, in extremely cold conditions, a heater of a
DOAS may draw increased power over a relatively long period of time
in order to adequately heat air that is ultimately supplied to an
enclosed structure. As such, the energy requirements and costs of
operation of the heater may increase.
SUMMARY OF THE DISCLOSURE
[0006] Certain embodiments of the present disclosure provide an
energy exchange system that may include an energy recovery device,
at least one first pre-heater, and at least one boiler. The energy
recovery device is configured to be disposed within supply and
exhaust air flow paths. The first pre-heater(s) is configured to be
positioned within one or both of the supply and exhaust air flow
paths, and may include one or more coils configured to circulate a
first liquid, such as water, that is configured to transfer heat to
air within the supply and/or exhaust air flow paths. The boiler(s)
is operatively connected to the first pre-heater(s) and is
configured to heat the first liquid.
[0007] The first pre-heater(s) may be configured to be upstream of
the energy recovery device within the supply air flow path.
[0008] The system may also include a heater or heat exchanger
configured to be downstream of the energy recovery device within
the supply air flow path. The first pre-heater(s) may be configured
to be positioned within the supply air flow path between the energy
recovery device and the heater.
[0009] The boiler(s) may include a main tank configured to retain
the first liquid. The boiler(s) may also include a heating element
configured to heat the first liquid.
[0010] The first pre-heaters may include multiple first pre-heaters
configured to be positioned within the supply air flow path. The
multiple first pre-heaters may be operatively connected to a single
boiler. Alternatively, each of the first pre-heaters may be
connected to separate and distinct boilers.
[0011] The energy exchange system may also include at least one
second pre-heater configured to pre-heat air within one or both of
the supply and exhaust air flow paths, a heater configured to be
disposed within the supply air flow path, wherein the heater is
configured to generate flue gas, and a heat transfer device
operatively connected to the heater and the at least one second
pre-heater. The heat transfer device is configured to receive
energy from the flue gas from the heater and transfer heat from the
flue gas to a second liquid, such as water, within the heat
transfer device. The second liquid is configured to be channeled to
the second pre-heater(s) so that heat is transferred from the
second liquid to supply air within the supply air flow path before
the supply air encounters the energy recovery device.
[0012] The heater may be downstream from the energy recovery device
within the supply air flow path. Alternatively, the heater may be
upstream from the energy recovery device within the supply air flow
path. The first pre-heater(s) may be positioned with the supply air
flow path between the energy recovery device and the heater.
[0013] The energy exchange system may also include at least one
bypass duct configured to be disposed within the supply air flow
path. The bypass duct(s) is configured to bypass at least a portion
of the supply air around one or both of the at least one first
pre-heater or the energy recovery device.
[0014] Certain embodiments of the present disclosure provide a
method of operating an energy exchange system having a supply air
flow path that allows supply air to be supplied to an enclosed
structure and an exhaust air flow path that allows exhaust air from
the enclosed structure to be exhausted to the atmosphere. The
method may include heating a first liquid within an internal
chamber of a boiler, pumping the first liquid from the boiler to at
least one first pre-heater disposed within one or both of the
supply air flow path and the exhaust air flow path, pre-heating air
within the one or both of the supply air flow path and the exhaust
air flow path with the first liquid within the at least one first
pre-heater, and pumping the first liquid from the at least one
first pre-heater back to the boiler.
[0015] The method may also include capturing flue gas generated by
a heater, channeling the flue gas to a heat transfer device,
transferring heat from the flue gas to a second liquid within the
heat transfer device, circulating the second liquid to at least one
second pre-heater disposed within one or both of the supply air
flow path and the exhaust air flow path, and transferring heat
within the second liquid to the air within one or both the supply
air flow path and the exhaust air flow path.
[0016] Certain embodiments of the present disclosure provide a DOAS
that may include a heater configured to be disposed within a supply
air flow path, a first pre-heater configured to be upstream from
the heater within the supply air flow path, wherein the first
pre-heater is configured to pre-heat the supply air through heat
transfer with a first liquid that circulates through the first
pre-heater, and a boiler operatively connected to the first
pre-heater, wherein the boiler is configured to heat the first
liquid. The DOAS may also include a second pre-heater configured to
be upstream from the heater within the supply air flow path, and a
heat transfer device operatively connected to the heater and the
second pre-heater. The heat transfer device is configured to
receive flue gas from the heater and transfer heat from the flue
gas to a second liquid within the heat transfer device. The second
liquid is configured to be channeled to the second pre-heater so
that heat is transferred from the second liquid to supply air
within the supply air flow path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates a schematic view of an energy exchange
system, according to an embodiment of the present disclosure.
[0018] FIG. 2 illustrates a simplified internal view of a boiler,
according to an embodiment of the present disclosure.
[0019] FIG. 3 illustrates an isometric view of a coil of a
pre-heater, according to an embodiment of the present
disclosure.
[0020] FIG. 4 illustrates an isometric view of a coil of a
pre-heater, according to an embodiment of the present
disclosure.
[0021] FIG. 5 illustrates an isometric view of a coil of a
pre-heater, according to an embodiment of the present
disclosure.
[0022] FIG. 6 illustrates an isometric view of a coil of a
pre-heater, according to an embodiment of the present
disclosure.
[0023] FIG. 7 illustrates a schematic view of the energy recovery
device, according to an embodiment of the present disclosure.
[0024] FIG. 8 illustrates a schematic view of an energy exchange
system, according to an embodiment of the present disclosure.
[0025] FIG. 9 illustrates a schematic view of an energy exchange
system, according to an embodiment of the present disclosure.
[0026] FIG. 10 illustrates a schematic view of an energy exchange
system, according to an embodiment of the present disclosure.
[0027] FIG. 11a illustrates a schematic view of a heat exchanger,
according to an embodiment of the present disclosure.
[0028] FIG. 11b illustrates a schematic view of a heat exchanger,
according to an embodiment of the present disclosure.
[0029] FIG. 12 illustrates an isometric top view of an exemplary
furnace, according to an embodiment of the present disclosure.
[0030] FIG. 13 illustrates a schematic view of an energy recovery
system, according to an embodiment of the present disclosure.
[0031] FIG. 14 illustrates a schematic view of an energy recovery
system, according to an embodiment of the present disclosure.
[0032] FIG. 15 illustrates a schematic view of an energy recovery
system, according to an embodiment of the present disclosure.
[0033] FIG. 16 illustrates a process of operating a direct outdoor
air system, according to an embodiment of the present
disclosure.
[0034] FIG. 17 illustrates a process of operating a direct outdoor
air system, according to an embodiment of the present
disclosure.
DETAILED DESCRIPTION OF THE DRAWINGS
[0035] The foregoing summary, as well as the following detailed
description of certain embodiments will be better understood when
read in conjunction with the appended drawings. As used herein, an
element or step recited in the singular and proceeded with the word
"a" or "an" should be understood as not excluding plural of said
elements or steps, unless such exclusion is explicitly stated.
Furthermore, references to "one embodiment" are not intended to be
interpreted as excluding the existence of additional embodiments
that also incorporate the recited features. Moreover, unless
explicitly stated to the contrary, embodiments "comprising" or
"having" an element or a plurality of elements having a particular
property may include additional such elements not having that
property.
[0036] As explained below, embodiments of the present disclosure
provide an energy exchange system that may include one or more
pre-heaters configured to pre-heat supply air before an energy
recovery device and/or a heat exchanger, such as a heater.
Accordingly, embodiments of the present disclosure provide an
energy exchange system that operates more efficiently than known
systems.
[0037] FIG. 1 illustrates a schematic view of an energy exchange
system 10, according to an embodiment of the present disclosure.
The system 10 is shown as a Dedicated Outdoor Air System (DOAS).
The system 10 is configured to partly or fully condition air
supplied to an enclosed structure 12, such as a building or an
enclosed room. The system 10 includes an air inlet 14 fluidly
connected to a supply air flow path 16. The supply air flow path 16
may channel supply air 18 (such as outside air, air from a building
adjacent to the enclosed structure 12, or return air from a room
within the enclosed structure 12) to the enclosed structure 12.
Supply air 18 in the supply air flow path 16 may be moved through
the supply air flow path 16 by a fan or fan array 20. The fan 20
may be located downstream of an energy recovery device 22 and a
pre-heater 24. Optionally, the fan 20 may be positioned upstream of
the energy recovery device 22 and/or the pre-heater 24. Also,
alternatively, supply air 18 within the supply air flow path 16 may
be moved by multiple fans or a fan array or before and/or after the
pre-heater 24.
[0038] Airflow passes from the inlet 14 through the supply air flow
path 16 where the supply air 18 first encounters the pre-heater 24.
A bypass duct 26 may be disposed in the supply air flow path 16.
The bypass duct 26 may be connected to the supply air flow path 16
through an inlet damper 28 upstream from the pre-heater 24, and an
outlet damper 30 downstream from the pre-heater 24. When the
dampers 28 and 30 are fully opened, supply air 18 may be diverted
or bypassed around the pre-heater 26. The dampers 28 and 30 may be
modulated to allow a portion of the supply air 18 to bypass around
the pre-heater 26. Alternatively, the system 10 may not include the
bypass duct 26.
[0039] Additionally, a damper 32 may be disposed in the supply air
flow path 16 upstream from the pre-heater 24. When fully closed,
the damper 32 prevents supply air 18 from passing into the
pre-heater 24. The damper 32 may be modulated in order to allow a
portion of the supply air 18 to pass through the pre-heater 24,
while a remaining portion of the supply air 18 is bypassed through
the bypass duct 26. Alternatively, the system 10 may not include
the damper 32
[0040] The pre-heater 24 heats the supply air 18 is it passes
therethrough. The pre-heater 24 heats the incoming supply air 18
before it encounters the energy recovery device 22. An additional
pre-heater may be disposed within the supply air flow path 16
downstream from the pre-heater 24 and upstream or downstream from
the energy recovery device 22. The additional pre-heater is
configured to add more heat to the supply air 18 during extremely
cold conditions. The pre-heater 24 may, alternatively, be disposed
within an exhaust air flow path 40 upstream from the energy
recovery device 22. Additionally, alternatively, a pre-heater may
also be disposed within the exhaust air flow path 40 upstream from
the energy recovery device 22. As explained in more detail below
with respect to FIG. 7, the energy recovery device 22 uses exhaust
air 42 from the exhaust flow path 40 to condition the supply air 18
within the supply air flow path 16. For example, during a winter
mode operation, the energy recovery device 22 may condition the
supply air 18 within the supply air flow path 16 by adding heat
and/or moisture. In a summer mode operation, the energy recovery
device 22 may pre-condition the supply air 18 by removing heat and
moisture from the air. While the energy recovery device 22 is shown
downstream from the pre-heater 24 within the supply air flow path
16, the energy recovery device 22 may, alternatively, be positioned
upstream of the pre-heater 24 within the supply air flow path
16.
[0041] After the supply air 18 passes through the energy recovery
device 22 in the supply air flow path 16, the supply air 18, which
at this point has been conditioned, may encounter a heat exchanger
44, such as a heater. The heat exchanger 44 then further heats the
supply air 18 in the supply air flow path 16 to generate a change
in air temperature toward a desired supply state that is desired
for supply air discharged into the enclosed structure 12. For
example, during a winter mode operation, the heat exchanger 44 may
further condition the pre-conditioned air by adding heat to the
supply air 18 in the supply air flow path 16.
[0042] The exhaust or return air 42 from the enclosed structure 12
is channeled out of the enclosed structure 12, such as by way of
exhaust fan 46 or fan array within the exhaust flow path 40. As
shown, the exhaust fan 46 is located upstream of the energy
recovery device 22 within the exhaust air flow path 40. However,
the exhaust fan 46 may be downstream of the energy recovery device
22 within the exhaust air flow path 40. The exhaust air 42 passes
through a regeneration side or portion of the energy recovery
device 22. The energy recovery device 22 is regenerated by the
exhaust air 42 before conditioning the supply air 18 within the
supply air flow path 16. After passing through the energy recovery
device 22, the exhaust air 42 is vented to atmosphere through an
air outlet 48.
[0043] In an alternative embodiment, additional bypass ducts and
dampers may be disposed within the supply air flow path 16 and/or
the exhaust air flow path 40 in order to bypass airflow around the
energy recovery device 22.
[0044] The pre-heater 24 is operatively connected to a boiler 50.
The boiler 50 provides heated liquid, such as water, to the
pre-heater 24 in order to pre-heat the supply air 18 within the
supply air flow path 16. The pre-heater 24 may include one or more
coils 51 that surround a portion of the supply air flow path 16.
The coils 51 are configured to channel heated liquid, such as
water, from an inlet 52 to an outlet 54. The inlet 52 connects to a
liquid outlet 56 of the boiler 50 through a liquid delivery line
57, such as a conduit, tube, duct, or the like. Similarly, the
outlet 54 connects to a liquid inlet 58 of the boiler 50 through a
liquid reception line 59, such as a conduit, tube, duct, or the
like. One or more pumps 60 may be disposed within the liquid
delivery and/or reception lines 57, 59 in order to move the liquid
between the boiler 50 and the coils 51 of the pre-heater 24.
[0045] In operation, the boiler 50 heats liquid within a tank of
the boiler 50. The heated liquid is then delivered to the coils 51
of the pre-heater 24 by way of the liquid delivery line 57. The
boiler may heat the liquid, such as water, to a temperature of
approximately 180.degree. F. As such, the heated liquid may not
boil, but instead remain in a liquid state as it is pumped into the
coils 51. The heated liquid within the coils 51 exchanges energy
with the supply air 18 as the supply air passes through the
pre-heater 24. The heat from the liquid is transferred to the
supply air 18, thereby increasing the temperature of the supply air
18, but reducing the temperature of the liquid within the coils 51.
The reduced-temperature liquid passes out of the outlet 54 into the
liquid reception line 59, which, in turn, channels the
reduced-temperature liquid back to the boiler 50. The boiler 50
then re-heats the reduced-temperature liquid, and the process
repeats. Accordingly, the pre-heater 24 heats the supply air 18
before the supply air 18 encounters the energy recovery device 22.
The boiler 50 provides heated liquid, such as heated water, to the
coils 51 of the pre-heater 24 so that the pre-heater 24 can
pre-heat the supply air 18 before it encounters the energy recovery
device 22 and the heat exchanger 44.
[0046] As shown, the pre-heater 24 is positioned upstream from the
energy recovery device 22 within the supply air flow path 16.
Alternatively, the pre-heater 24 may be downstream from the energy
recovery device 22 within the supply air flow path 16.
Additionally, the pre-heater 24 may be downstream from the heat
exchanger 44 within the supply air flow path 16. As such, the
pre-heater 24 may be a heating device that is a post-heater. Also,
alternatively, additional pre-heaters may be disposed within the
supply air flow path 16. For example, an additional pre-heater may
be disposed between the pre-heater 24 and the energy recovery
device 22 within the supply air flow path 16. Also, additional
pre-heaters may be disposed with the supply air flow path 16
between the energy recovery device 22 and the heat exchanger 44,
and/or downstream from the heat exchanger 44. Each of the
pre-heaters within the system 10 may be operatively connected to
respective boilers. Alternatively, multiple pre-heaters may be
operatively connected to a single boiler.
[0047] Additionally, alternatively, the boiler 50 may be
operatively connected to the heat exchanger 44, such as through
conduits, pipes, or the like, so that flue gas from the boiler 50
is provided to the heat exchanger 44. The higher temperature flue
gas from the boiler 50 may be used to heat fluid, whether air or
water, within the heat exchanger 44. Thus, the boiler 50 may
directly heat air within the supply air flow path 16, as well as
provide heated flue gas to the heat exchanger 44, which also heats
air within the supply air flow path. Moreover, the heat exchanger
44 and/or the boiler 50 may also be operatively connected to a
pre-heater disposed within the exhaust air flow path 40 upstream
from the energy recovery device 22. Accordingly, the heat exchanger
44 and vented flue gas from the boiler 50 may also be used to
condition air within the exhaust air flow path 40.
[0048] FIG. 2 illustrates a simplified internal view of the boiler
50, according to an embodiment of the present disclosure. The
boiler 50 includes a main tank 70 defining an internal chamber 72
that retains a liquid 73, such as water. A heating element 74 may
be positioned proximate the base of the main tank 70 and is
configured to heat the liquid 73 within the internal chamber 72.
The heating element 74 may be an electric or gas heater, for
example. While shown proximate the base of the main tank 74, the
heating element 74 may be positioned at or within any portion of
the main tank 70. For example, the heating element 74 may include
electric heating coils positioned within walls that define the main
tank 70.
[0049] The internal chamber 72 is in fluid communication with the
liquid outlet 56 and the liquid inlet 58. Accordingly, heated
liquid may be pumped through the liquid outlet 56, into the liquid
delivery line 57, and into the pre-heater 24 (shown in FIG. 1).
Similarly, reduced-temperature liquid may be pumped through the
liquid reception line 59, into the liquid inlet 58, and into the
internal chamber 72.
[0050] An exhaust port 76 may be formed through a portion of the
main tank 70. The exhaust port 76 is configured to allow steam
within the internal chamber 72 to pass out of the internal chamber
72. Alternatively, the main tank 70 may not include the exhaust
port 76. Additionally, the boiler 50 may also include a chimney 78
configured to exhaust any combustion gases, such as flue gases,
generated by the heating element 74. Alternatively, the chimney 78
may be connected to a flue gas delivery line, which may be used to
increase the temperature of the supply air, such as through an
additional pre-heater, for example, as explained below.
[0051] The boiler 50 may be one or more of various types of
boilers. For example, the boiler 50 may be a fire tube boiler,
water tube boiler, packaged boiler, fluidized bed combustion
boiler, atmospheric fluidized bed combustion boiler, pressurized
fluidized bed combustion boiler, atmospheric circulating fluidized
bed combustion boiler, stoker fired boiler, pulverized fuel boiler,
waste heat boiler, thermic fluid heater, hydronic boiler, and/or
the like. As noted, FIG. 2 merely illustrates a simplified
configuration for a boiler. Any type of boiler that is configured
to heat liquid may be used. As noted, the boiler 50 may be operated
to heat the liquid below a boiling point in order to provide heated
liquid to the coils 51 (shown in FIG. 1) of the pre-heater 24.
[0052] FIG. 3 illustrates an isometric view of a coil 51a of the
pre-heater 24, according to an embodiment of the present
disclosure. As shown in FIG. 3, the coil 51a may be a tubular
member 80 having a circumferential channel 82 surrounding an air
passage 84, which may be a portion of the supply air flow path 16
(shown in FIG. 1). Liquid, such as water or glycol, is circulated
through the circumferential channel 82. In this manner, liquid L
may flow parallel to the supply air 18 as it passes through the air
passage 84. Optionally, the liquid may flow in a direction counter
to the direction of the air flow (in this example, the lines L
would flow in the opposite direction than shown in FIG. 3).
[0053] FIG. 4 illustrates an isometric view of a coil 51b of the
pre-heater 24, according to an embodiment of the present
disclosure. In this embodiment, a plurality of tubes 86 having
fluid channels 88 surround an air passage 90, which may be a
portion of the supply air flow path 16 (shown in FIG. 1). Liquid L,
such as water or glycol, is circulated through the fluid channels
88. In this manner, liquid may flow parallel to the supply air 18
as it passes through the air passage 90. Optionally, the liquid may
flow in a direction counter to the direction of the air flow.
[0054] FIG. 5 illustrates an isometric view of a coil 51c of the
pre-heater 24, according to an embodiment of the present
disclosure. In this embodiment, the coil 51c may include a series
of fluid-filled plates 92 disposed within an air passage 94 that
forms part of the supply air flow path 16 (shown in FIG. 1). In
this manner, the supply air 18 may flow across and parallel or
counter to the liquid within the plates 92.
[0055] FIG. 6 illustrates an isometric view of a coil 51d of the
pre-heater 24, according to an embodiment of the present
disclosure. In this embodiment, the coil 51d includes a plurality
of liquid-carrying tubes 96 that cross one another. The tubes 96
are disposed within an air passage 98 that forms part of the supply
air flow path 16 (shown in FIG. 1). In this manner, the supply air
18 may flow across and parallel or counter to the liquid L within
the tubes 96.
[0056] Any of the coils shown and described with respect to FIGS.
3-6 may be used with respect to the pre-heater 24, heat exchanger,
heater, or other such heat transfer device.
[0057] Referring to FIGS. 1-6, the pre-heater 24 may be configured
for parallel-flow, counter-flow, cross-flow, or a combination
thereof. The coils 51 shown in FIG. 1 may include any of the coils
51a, 51b, 51c, and/or 51d. In parallel flow, the supply air 18 and
the liquid within the coils 51 enter the pre-heater 24 at the same
end, and travel parallel to one another to the other side. In
counter-flow, the supply air 18 enters at a front end of the
pre-heater 24, while the liquid enters the coils 51 at the back
end. In cross-flow, the supply air 18 and the liquid within the
coil are generally perpendicular to one another within the
pre-heater 24. Therefore, while FIG. 1 shows the liquid delivery
line 57 at a downstream end of the pre-heater 24, and the liquid
reception line 59 at an upstream end of the pre-heater 24, it is
understood that these positions may be reversed.
[0058] The pre-heater 24 and the boiler 50 may be retrofit to any
DOAS, thereby improving the efficiency of the DOAS.
[0059] FIG. 7 illustrates a schematic view of the energy recovery
device 22, according to an embodiment of the present disclosure. A
portion of the energy recovery device 22 is disposed within the
supply air flow path 16, while another portion of the energy
recovery device 22 is disposed within the exhaust air flow path 40.
The energy recovery device 22 is configured to transfer heat and/or
moisture between the supply air flow path 16 and the exhaust air
flow path 40. The energy recovery device 22 may be one or more of
various types of energy recovery devices, such as, for example, an
enthalpy wheel, a sensible wheel, a desiccant wheel, a plate heat
exchanger, a plate energy (heat and moisture) exchanger, a heat
pipe, a run-around loop, or the like. As shown in FIG. 7, the
energy device 22 may be an enthalpy wheel.
[0060] An enthalpy wheel is a rotary air-to-air heat exchanger. As
shown, supply air within the supply air flow path 16 passes in a
direction counter to the exhaust air within exhaust air flow path
40. For example, the supply air may flow through a lower portion,
such as the lower half, of the wheel, while the exhaust air flows
through an upper portion, such as the upper half, of the wheel.
Alternatively, supply air may flow through a different portion of
the wheel, such as a lower 1/3, 1/4, 1/5, or the like, of the
wheel, while exhaust air flows through the remaining portion of the
wheel. The wheel may be formed of a heat-conducting material with
an optional desiccant coating.
[0061] In general, the wheel may be filled with an air permeable
material resulting in a large surface area. The surface area may be
the medium for sensible energy transfer. As the wheel rotates
between the supply and exhaust air flow paths 16 and 40,
respectively, the wheel picks up heat energy and releases it into
the colder air stream. Enthalpy exchange may be accomplished
through the use of desiccants on an outer surface of the wheel.
Desiccants transfer moisture through the process of adsorption,
which is driven by the difference in the partial pressure of vapor
within the opposing air streams.
[0062] Additionally, the rotational speed of the wheel also changes
the amount of heat and moisture transferred. For example, an
enthalpy wheel transfers both sensible and latent energy. The
slower the rate of rotation, the less moisture is transferred.
[0063] The enthalpy wheel may include a circular honeycomb matrix
of heat-absorbing material that is rotated within the supply and
exhaust air flow paths 16 and 40, respectively. As the enthalpy
wheel rotates, heat is picked up from the air within the exhaust
air flow path 40 and transferred to the supply air within the
supply air flow path 16. As such, waste heat energy from the air
within the exhaust air flow path 40 is transferred to the matrix
material and then from the matrix material to the supply air 18
within the supply air flow path 16, thereby raising the temperature
of the supply air 18 by an amount proportional to the temperature
differential between the air streams.
[0064] Optionally, the energy recovery device 22 may be a sensible
wheel, a plate exchanger, a heat pipe, a run-around apparatus, a
refrigeration loop having a condenser and evaporator, a chilled
water coil, or the like.
[0065] Alternatively, the energy recovery device 22 may be a flat
plate exchanger. A flat plate exchanger is generally a fixed plate
that has no moving parts. The exchanger may include alternating
layers of plates that are separated and sealed. Because the plates
are generally solid and non-permeable, only sensible energy may be
transferred. Optionally, the plates may be made from a selectively
permeable material that allows for both sensible and latent energy
transfer.
[0066] Alternatively, the energy recovery device 22 may be a
run-around loop or coil. A run-around loop or coil includes two or
more multi-row finned tube coils connected to each other by a
pumped pipework circuit. The pipework is charged with a heat
exchange fluid, typically water or glycol, which picks up heat from
the exhaust air coil and transfers the heat to the supply air coil
before returning again. Thus, heat from an exhaust air stream is
transferred through the pipework coil to the circulating fluid, and
then from the fluid through the pipework coil to the supply air
stream.
[0067] Also, alternatively, the energy recovery device 22 may be a
heat pipe. A heat pipe includes a sealed pipe or tube made of a
material with a high thermal conductivity such as copper or
aluminum at both hot and cold ends. A vacuum pump is used to remove
all air from the empty heat pipe, and then the pipe is filled with
a fraction of a percent by volume of coolant or refrigerant, such
as water, ethanol, glycol etc. Heat pipes contain no mechanical
moving parts. Heat pipes employ evaporative cooling to transfer
thermal energy from one point to another by the evaporation and
condensation of a working fluid or coolant.
[0068] Referring again, to FIG. 1, as supply air 18 enters the
supply air flow path 16 through the inlet 14, the unconditioned
supply air 18 encounters the pre-heater 24 before the energy
recovery device 22, which may be an enthalpy wheel, flat plate
exchanger, heat pipe, run-around, or the like, as discussed above.
During winter months, when the air is cold and dry, the temperature
and/or humidity of the supply air 18 will be raised as it moves
through the pre-heater 24 and encounters the energy recovery device
22. As such, in winter conditions, the energy recovery device 22
warms and/or humidifies the supply air.
[0069] A similar process occurs as the exhaust air 42 encounters
the energy recovery device 22 in the exhaust air flow path 40. The
sensible and/or latent energy transferred to the energy recovery
device 22 in the exhaust air flow path 40 is then used to
pre-condition the air within the supply air flow path 16. Overall,
the energy recovery device 22 pre-conditions the supply air 18 in
the supply air flow path 16 before it encounters the heat exchanger
44, and alters the exhaust air 42 in the exhaust air flow path 40.
In this manner, the heat exchanger 44 does not use as much energy
as it normally would if the energy recovery device 112 (and/or the
pre-heater 24) was not in place. Therefore, the heat exchanger 44
operates more efficiently.
[0070] The heat exchanger 44 may be or include a gas heater that
coverts gas to heat, for example. Alternatively, the heater
exchanger may be configured to transfer heat from liquid to air,
for example. That is, the heat exchanger 44 may be a liquid-to-air
heat exchanger. In general, the liquid and air are separated so
that they do not mix. The heat exchanger 44 may include radiator
coils that are positioned within or around the supply air flow path
16. Liquid, such as water or glycol, may be circulated through the
coils. As supply air 18 passes by the coils, heat from the liquid
is transferred to the supply air 18, thereby further warming the
supply air 18 before it passes into the enclosed structure 12. The
radiator coils may be heated through combustion, for example, such
as through a gas-fired heater. Heated gas from the heater is vented
as flue gas. As explained below, the vented flue gas may be
channeled to a heating device, such as another pre-heater, in order
to pre-condition the supply air 18 before it encounters the energy
recovery device 22, as described in U.S. patent application Ser.
No. 13/625,912, entitled "Dedicated Outdoor Air System With
Pre-Heating And Method For Same," which was filed Sep. 25, 2012,
and is hereby incorporated by reference in its entirety.
Alternatively, the heat exchanger 44 may not include radiator
coils, but may simply be a gas heater disposed within the supply
air flow path 16, and configured to convert gas to heat and heat
the supply air 18.
[0071] FIG. 8 illustrates a schematic view of an energy exchange
system 800, according to an embodiment of the present disclosure.
The energy exchange system 800 is similar to the system 10, except
that a pre-heater 802, which is operatively connected to a boiler
804, is downstream from an energy recovery device 806 and upstream
from a heat exchanger 808 within a supply air flow path 810. The
pre-heater 802 and the boiler 804 may be configured to operate as
described above.
[0072] Alternatively, the pre-heater 802 may be downstream from the
heat exchanger 808 within the supply air flow path 810. Also, an
additional pre-heater may be positioned within the supply air flow
path 810 upstream from the energy recovery device 806. The
additional pre-heater 802 may be operatively connected to the
boiler 804, or to a separate and distinct boiler.
[0073] FIG. 9 illustrates a schematic view of an energy exchange
system 900, according to an embodiment of the present disclosure.
The energy exchange system 900 is similar to the system 10, except
that the system 900 includes a pre-heater 902 upstream from an
energy recovery device 904 within a supply air flow path 906, as
well as a pre-heater 908 downstream from the energy recovery device
904, but upstream from a heat exchanger 910, within the supply air
flow path 906. The pre-heaters 902 and 908 may both be operatively
connected to a common boiler 912. Separate and distinct liquid
delivery lines 914 and 916 connect the boiler 912 to each of the
pre-heaters 910 and 902, respectively. Optionally, a single liquid
delivery line may extend from the boiler 912 and branch off to the
separate and distinct pre-heaters 910 and 902. Similarly, liquid
reception lines 918 and 920 may connect the pre-heaters 902 and the
908, respectively, to the boiler 912. The liquid reception lines
918 and 920 may merge together, as shown in FIG. 8, into a single
line 922 that channels reduced-temperature liquid from each
pre-heater 902 and 908 into the boiler 912. Alternatively, separate
and distinct liquid reception lines may connect directly to the
boiler 912.
[0074] FIG. 10 illustrates a schematic view of an energy exchange
system 1000 according to an embodiment of the present disclosure.
The system 1000 is configured to partly or fully condition air
supplied to an enclosed structure 1002, such as a building or an
enclosed room. The system 1000 includes an air inlet 1004 fluidly
connected to a supply air flow path 1006. The supply air flow path
1006 may channel supply air 1008 (such as outside air, air from a
building adjacent to the enclosed structure 1002, or return air
from a room within the enclosed structure 1002) to the enclosed
structure 1002. Supply air 1008 in the supply air flow path 1006
may be moved through the supply air flow path 1006 by a fan or fan
array 1010. The illustrated embodiment shows the fan 1010 located
downstream of an energy recovery device 1012 and a gas-fired heater
or heat exchanger 1014. The heat exchanger 1014 may be or include
the gas-fired heater. Optionally, the fan 1010 may be positioned
upstream of the energy recovery device 1012 and/or the heat
exchanger 1014. Also, alternatively, air 1008 within the supply air
flow path 1006 may be moved by multiple fans or a fan array or
before and/or after the heat exchanger 1014.
[0075] Airflow passes from the inlet 1004 through the supply air
flow path 1006 where the supply air 1008 first encounters a
pre-heater 1009 operatively connected to a boiler 1011, as
described above. The pre-heater 1009 may be upstream from a
pre-heater 1016 with the supply air flow path 1006. Optionally, the
pre-heater 1016 may be upstream from the pre-heater 1009 within the
supply air flow path 1006.
[0076] A bypass duct 1017 may be disposed in the supply air flow
path 1006 downstream or upstream from the pre-heater 1009. The
bypass duct 1017 may be positioned in the supply air flow path 1006
between the pre-heaters 1009 and 1016. The bypass duct 1017 may be
connected to the supply air flow path 1006 through an inlet damper
1019 upstream from the pre-heater 1016 (but downstream from the
pre-heater 1009), and an outlet damper 1021 downstream from the
pre-heater 1016. Alternatively, the inlet damper 1019 may be
upstream from the pre-heater 1009 within the supply air flow path
1006. When the dampers 1019 and 1021 are fully opened, supply air
1008 may be diverted or bypassed around the pre-heater 1016 (and/or
the pre-heater 1009). The dampers 1019 and 1021 may be modulated to
allow a portion of the supply air 1008 to bypass around the
pre-heater 1016 (and/or the pre-heater 1009).
[0077] Additionally, a damper 1023 may be disposed in the supply
air flow path 1006 upstream from the pre-heater 1016 and/or the
pre-heater 1009. When fully closed, the damper 1023 prevents supply
air 1008 from passing into the pre-heater 1016 and/or the
pre-heater 1009. The damper 1023 may be modulated in order to allow
a portion of the supply air 1008 to pass through the pre-heater
1016 and/or the pre-heater 1009, while a remaining portion of the
supply air 1008 is bypassed through the bypass duct 1017.
[0078] The pre-heater 1009 heats the air 1008 as it passes
therethrough, as explained above with respect to FIGS. 1 and 2, for
example. Additionally, the pre-heater 1016 heats the air 1008 is it
passes therethrough. The pre-heater 1016 heats the incoming supply
air 1008 before it encounters a process side or portion of the
energy recovery device 1012. An additional pre-heater may be
disposed within the supply air flow path 1006 downstream from the
pre-heater 1016 and upstream from the energy recovery device 1012.
The additional pre-heater is configured to add more heat to the
supply air 1008 during extremely cold conditions. The pre-heater
1016 may, alternatively, be disposed within an exhaust air flow
path 1020 upstream from the energy recovery device 1012.
Additionally, alternatively, a pre-heater may be disposed within
the exhaust air flow path 120 upstream from the energy recovery
device 1012 as well as the pre-heater 1016 within the supply air
flow path 1006. As explained above, the energy recovery device 1012
uses exhaust air 1018 from the exhaust flow path 1020 to condition
the supply air 1008 within the supply air flow path 1006. An
additional energy recovery device (not shown) may be positioned
within the supply air flow path 1006 downstream from the heat
exchanger 1014, and upstream from the enclosed structure 1002.
Additionally, while the energy recovery device 1012 is shown
upstream from the heat exchanger 1014 within the supply air flow
path 1006, the energy recovery device 1012 may, alternatively, be
positioned downstream of the heat exchanger 1014 and upstream of
the enclosed structure 1002 within the supply air flow path 1006.
Additionally, the positions of the pre-heaters 1009 and 1016 may be
reversed, such that the pre-heater 1009 is downstream from the
pre-heater 1016 within the supply air flow path 1006.
[0079] After the supply air 1008 passes through the energy recovery
device 1012 in the supply air flow path 1006, the supply air 1008,
which at this point has been conditioned, encounters the heat
exchanger 1014. The heat exchanger 1014 then further or fully heats
the air 1008 in the supply air flow path 1006 to generate a change
in air temperature toward a desired supply state that is desired
for supply air discharged into the enclosed structure 1002. For
example, during a winter mode operation, the heat exchanger 1014
may further condition the pre-conditioned air by adding heat to the
supply air 1008 in the supply air flow path 1006.
[0080] The exhaust or return air 1018 from the enclosed structure
1002 is channeled out of the enclosed structure 1002, such as by
way of exhaust fan 1022 or fan array within the exhaust flow path
1020. As shown, the exhaust fan 1022 is located upstream of the
energy recovery device 1012 within the exhaust air flow path 1020.
However, the exhaust fan 1022 may be downstream of the energy
recovery device 1012 within the exhaust air flow path 1020.
[0081] The exhaust air 1018 passes through a regeneration side or
portion of the energy recovery device 1012. The energy recovery
device 1012 is regenerated by the exhaust air 1018 before
conditioning the supply air 1008 within the supply air flow path
1006. After passing through the energy recovery device 1012, the
exhaust air 1018 is vented to atmosphere through an air outlet
1024.
[0082] In an alternative embodiment, additional bypass ducts and
dampers may be disposed within the supply air flow path 1006 and/or
the exhaust air flow path 1020 in order to bypass airflow around
the energy recovery device 1012.
[0083] The supply air 1008 encounters the pre-heater 1016 before
the energy recovery device 1012, which may be an enthalpy wheel,
flat plate exchanger, heat pipe, run-around, or the like, as
discussed above. The pre-heaters 1009 and 1016 pre-heat the supply
air 1008, and the energy recovery device 1012 pre-conditions the
supply air 1008 in the supply air flow path 1006 before the supply
air 1008 encounters the heat exchanger 1014. In this manner, the
heat exchanger 1014 does not use as much energy as it normally
would if the pre-heaters 1009, 1016, and the energy recovery device
1012 were not in place. Therefore, the heat exchanger 1014 operates
more efficiently.
[0084] The heat exchanger 1014 may be or include a gas heater that
coverts gas to heat, for example. Heated gas from the heater is
vented as flue gas. As explained below, the vented flue gas is
channeled to the pre-heater 1016 in order to pre-condition the
supply air 1008 before it encounters the energy recovery device
1012.
[0085] In general, flue gas is a gaseous combustion product from a
furnace or heating device. The flue gas may be formed primarily of
nitrogen (for example, more than 2/3) derived from the combustion
of air, carbon dioxide, and water vapor, as well as excess oxygen,
which is also derived from the combustion of air.
[0086] FIG. 11a illustrates a schematic view of the heat exchanger
1014, according to an embodiment. As noted above, the heat
exchanger 1014 is disposed within the supply air flow path 1006.
The heat exchanger 1014 may be a heater that includes a housing
1026 that contains a gas-fired heater 1028, such as a furnace.
Optionally, a boiler as described above may be used in place of the
gas-fired heater 1028. The heater 1028 may generate heat through
combustion. The heater 1028 heats the supply air 1008 as it passes
through the heat exchanger 1014 within the supply air flow path
1006. As supply air 1008 passes through the heat exchanger 1014,
the temperature of the supply air 1008 increases as it is heated by
the heater 1028. Consequently, the temperature of the supply air
1008 is increased as it passes out of the heat exchanger 1014.
[0087] The flue gas from the heater 1028 is vented through a vent
1032 on or within the housing 1026. The heat exchanger 1014 may
include a fan (not shown) that channels the flue gas into the vent
1032. Optionally, the fan may be disposed downstream of the vent
1032 within a conduit 1034. The conduit 1034 may be one or more
pipes, tubes, plenum, or the like. For example, the conduit 1034
may be a series of pipes that connect the vent 1032 to another heat
transfer device. The flue gas from the vent 1032 then passes into
the conduit 1034 that sealingly engages the vent 1032 so that the
flue gas may be channeled to another heat transfer device, as
described below.
[0088] Alternatively, the heat exchanger 1014 may include radiator
coils that contain circulating liquid, such as water, that is
heated by the heater 1028. The heated liquid exchanges heat energy
with the supply air 1008 as it passes through the radiator coils
1030. The radiator coil may be configured as shown and described in
FIGS. 3-6.
[0089] FIG. 11b illustrates a schematic view of a heat exchanger,
according to an embodiment of the present disclosure. The heat
exchanger 1114 may be disposed within a supply air flow path 1106.
The heat exchanger 1114 includes a housing 1126 that contains a
boiler 1128 and radiator coils 1130 that contain a liquid, such as
water, that is heated by the boiler 1128. The boiler 1128 may
generate heat through combustion. The boiler 1128 heats liquid that
circulates through the radiator coils 1130. The radiator coils 1130
are positioned within and/or around the portion of the supply air
flow path 1106 that passes through the heat exchanger 1114. As
supply air 1108 passes through the heat exchanger 1114, the
temperature of the supply air 1108 increases as it passes through
the radiator coils 1130. That is, the heat of the liquid within the
radiator coils 1130 is transferred to the supply air 1108.
Consequently, the temperature of the supply air 1108 is increased
as it passes out of the heat exchanger 1114.
[0090] The flue gas from the boiler 1128 is vented through a vent
1132 on or within the housing 1126. The heat exchanger 1114 may
include a fan (not shown) that channels the flue gas into the vent
1132. Optionally, the fan may be disposed downstream of the vent
1132 within a conduit 1134. The conduit 1134 may be one or more
pipes, tubes, plenum, or the like. For example, the conduit 1134
may be a series of pipes that connect the vent 1132 to another heat
transfer device. The flue gas from the vent 1132 then passes into
the conduit 1134 that sealingly engages the vent 1132 so that the
flue gas may be channeled to another heat transfer device, as
described below.
[0091] FIG. 12 illustrates an isometric top view of an exemplary
furnace 1029, according to an embodiment of the present disclosure.
The furnace 1029 is one example of a heater 1028 (shown in FIG.
11). The furnace 1029 includes a housing 1027 having a plurality of
heating elements 1031 that span between lateral walls 1033 of the
housing 1027. The heating elements 1031 may include channeled rods
having openings through which flames pass, thereby generating heat.
The furnace 1029 may be connected to a source of gas (not shown)
that fuels the furnace 1029. As gas enters the heating elements
1031 and is ignited through an igniting element or pilot light
within a control section 1035, flames are generated. Additionally,
flue gas is also generated from the heating elements. The
temperature of the flame generated by the heating elements 1031 may
be approximately 2700.degree. F., which generates a flue gas
temperature of approximately 400.degree. F. Various other furnaces
may be used as the heater 1028. FIG. 12 merely shows one example of
a furnace.
[0092] The heating elements 1031 may include tubes that contain gas
that is ignited to produce heat. The gas may make several passes
through the tubes before passing to the vent 1032, shown in FIG.
11. As air within the supply air flow path 1006 passes over the
tubes 1031, the air is heated.
[0093] Smaller tubes may be disposed within each of the tubes. For
example, a main gas tube may surround a concentric liquid tube that
contains heat transfer liquid. The liquid tube may be in fluid
communication with the pre-heater 1016 and/or the pre-heater 1009,
shown in FIG. 10. In this manner, the heat transfer liquid may be
directly heated within the furnace and transferred to the
pre-heater 1016 and/or the pre-heater 1009 to heat the supply air
1006. As such, the temperature of the heat transfer liquid may be
increased as it is directly heated within the furnace 1029 and
directly transferred to the pre-heater.
[0094] Referring to FIGS. 10 and 11, flue gas from the heat
exchanger 1014 is vented to the conduit 1034. The conduit 1034
channels the flue gas to a heat transfer device 1060, such as a
heating coil, that may include an internal coil structure, similar
to those described above. Alternatively, the flue gas may be
transferred to a heating element within the boiler 1011 instead of,
or in addition to, the heat transfer device 1060. The heated flue
gas passes through an internal chamber (not shown) of the heat
transfer device 1060 and/or the boiler 1011. As the flue gas passes
through the heat transfer device 1060 and/or the boiler 1011, the
heat from the flue gas is transferred to the liquid within the
radiator coils of the heat transfer device 1060 and/or the internal
chamber of the boiler 1011. The decreased-temperature flue gas (as
heat from the flue gas has been transferred to the liquid) is then
vented to the atmosphere through a vent 1062, for example (or
through a chimney of the boiler 1011, as described with respect to
FIG. 2). However, the liquid within the radiator coil of the heat
transfer device 1060, having an increased temperature through heat
transfer with the flue gas, is channeled to the pre-heater 1016
through a conduit 1064. The heated liquid is then passed from the
conduit 1064 into an inlet 1065 of a coil 1066 of the pre-heater
1016. The pre-heater 1016 may also include radiator coils similar
to those described above with respect to FIGS. 3-6. The liquid
passed into the coil 1066, the temperature of which has risen due
to the heat transfer with the flue gas, then transfers the
increased heat to supply air 1008 that passes through the
pre-heater 1016. Accordingly, the supply air 1008 is pre-heated
(that is, the temperature of the supply air 1008 is increased)
before it encounters the energy recovery device 1012.
[0095] As the liquid within the coil 1066 circulates therethrough,
the temperature of the liquid decreases, as its heat is transferred
to the supply air 1008. The cooled liquid within the radiator coil
1066 passes out of the radiator coil 1066 through an outlet 1067
and into a conduit 1068 that connects back to the heat transfer
device 1060. The liquid is then heated again by heat transfer with
the flue gas, and the process repeats.
[0096] A pump 1070 may be disposed within either of the conduits
1064, 1068, or both. The pump(s) 1070 aids in circulating the
liquid between the heat transfer device 1060 to the pre-heater
1016. However, in at least one embodiment, the system 1000 does not
include the pump.
[0097] While the pre-heaters 1009, 1016, and the heat transfer
device 1060 are described as including liquid-conveying coils, the
pre-heaters 1009, 1016 and the heat transfer device 1060 may be, or
include, various other liquid-carrying and/or heating structures
and components. For example, the pre-heater 1016 may include
fluid-conveying plates. Similarly, the heat transfer device 1060
may be a heating plate(s). Additionally, each of the pre-heaters
1009, 1016 and the heat transfer device 160 may also include
separate and distinct heating devices, similar to the heater 1028
shown in FIG. 11. However, the liquid that is circulated between
the heat transfer device 1060 and the pre-heater 1016 may be
primarily or solely heated by way of heat transfer with the flue
gas. Optionally, the liquid that is circulated between the heat
transfer device 1060 and the pre-heater 1016 may be also heated
through an electric heater.
[0098] Additionally, while the heat transfer device 1060 is shown
as being separate, distinct, and remote from the heat exchanger
1014 and the pre-heater 1016, the heat transfer device 1060 may be
contained within a housing of the heat exchanger 1014 or the
pre-heater 1016. For example, the heat transfer device 1060 may be
mounted directly to the vent of the heat exchanger 1014 inside or
outside of the housing of the heat exchanger 1014. As such, the
heat exchanger 1014 and the heat transfer device 1060 may be
disposed within a common housing.
[0099] The supply air 1008 (for example, air supplied from outdoor
and/or ambient air) is pre-heated by the pre-heaters 1009 and 1016.
The pre-heaters 1009 and 1016 increase the temperature of the
supply air 1008 so that it will not form frost on the energy
recovery device 1012. The pre-heater 1016 may increase the
temperature of the supply air 1008 through a circulating liquid
that has been heated through a transfer of heat from harvested flue
gas, as described above. As such, the efficiency of the system 1000
is increased. Additionally, the pre-heaters 1009 and 1016 provide a
more efficient system, in that they pre-heat the supply air 1008,
thereby reducing the overall energy consumption of the downstream
heat exchanger 1014 to further heat the supply air 1008.
[0100] Moreover, the pre-heaters 1009 and 1016 and the heat
transfer device 1060 may be retrofit to any DOAS, thereby improving
the efficiency of the DOAS.
[0101] FIG. 13 illustrates a schematic view of an energy recovery
system 1380, according to an embodiment of the present disclosure.
The system 1380 is similar to the system 1000, except that a heat
exchanger 1314 is upstream from an energy recovery device 1312
within a supply air flow path 1306. Additionally, a heating device
1301 operatively connected to a boiler 1303 may be downstream from
the energy recovery device 1312 within the supply air flow path
1306. Because the heating device 1301 is downstream from the energy
recovery device 1312 and the heat exchanger 1314, the heating
device 1301 may not be considered a pre-heater. However, the
heating device 1301 may be configured to operate as the pre-heaters
described above. Further, the heating device 1301 may be positioned
at various other portions of the supply air flow path 1036, such as
between a pre-heater 1316 and the heat exchanger 1314, or between
the heat exchanger 1314 and the energy recovery device 1312.
[0102] As shown in FIG. 13, the supply air 1308 is further heated
after the pre-heater 1316 before the supply air 1308 encounters the
energy recovery device 1312. Thus, the possibility of frost forming
on the energy recovery device 1312 is further reduced. The system
1380 may also include an additional heat exchanger downstream from
the energy recovery device 1312 within the supply air flow path
1306.
[0103] FIG. 14 illustrates a schematic view of an energy recovery
system 1490, according to an embodiment. The energy recovery system
1490 is similar to the system 1000, except that an additional heat
exchanger 1492 is positioned upstream the energy recovery device
1412, and a pre-heater 1401 operatively connected to a boiler 1403
is downstream from the energy recovery device 1412 and upstream
from a heat exchanger 1414 within the supply air flow path 1406.
The heat exchanger 1492 may be a liquid-to-gas heat exchanger. Flue
gas from both the heat exchangers 1414 and 1492 is vented into a
shared conduit 1494 that channels the combined flue gas into a coil
heater 1460. The pre-heater 1401 and the boiler 1403 may be
configured to operate as described above. The system 1490 may
include additional pre-heaters 1401 and boilers 1403.
[0104] Alternatively, the pre-heater 1401 may be positioned at
various other portions of the supply air flow path 1406. For
example, the pre-heater 1401 may be positioned between a pre-heater
1416 and the heat exchanger 1492, or between the heat exchanger
1492 and the energy recovery device 1412.
[0105] Additionally, in all of the embodiments of the present
disclosure, an optional return air duct may connect an exhaust air
flow path 1420 with the supply air flow path 1406. For example, an
air duct may be downstream of the energy recovery device 1412 in
the supply air flow path 1406, and upstream of the energy recovery
device 1412 in the exhaust air flow path 1420. Alternatively, or
additionally, an additional return air duct may be upstream of the
energy recovery device 1412 in the supply air flow path 1406 and
downstream of the energy recovery device 1412 within the exhaust
air flow path 1420. The return air ducts may recycle a portion of
the exhaust air 1418, which may be at a much higher temperature
than outdoor air, into the supply air 1408, which further increases
the temperature of the supply air 1408.
[0106] FIG. 15 illustrates a schematic view of an energy recovery
system 1500, according to an embodiment of the present disclosure.
The system 1500 is similar to the system 1000, except that return
air ducts 1502, 1504, and 1506 connect an exhaust air flow path
1520 to a supply air flow path 1506. More or less return air ducts
than those shown may be used. Moreover, the return air ducts may be
used with any of the systems described above.
[0107] Additionally, a pre-heater 1501 operatively connected to a
boiler 1503 may be disposed within the supply air flow path 1506
between an energy recovery device 1512 and a heat exchanger 1514.
The pre-heater 1501 and the boiler 1503 are configured to operate
as described above. The pre-heater 1501 may be disposed at various
other portions of the supply air flow path 1506. For example, the
pre-heater 1501 may be disposed between a pre-heater 1516 and the
energy recovery device 1512. Additional pre-heaters 1501 and
boilers 1503 may also be used.
[0108] The return air duct 1506 connects to the supply air flow
path 1506 upstream of the pre-heater 1516. Thus, the temperature of
the supply air 1508 may be increased even before it encounters the
pre-heater 1516.
[0109] FIG. 16 illustrates a process of operating a direct outdoor
air system, according to an embodiment. At 1620, flue gas from a
heat exchanger or heater is vented and captured within a conduit.
The flue gas may be moved through the use of a fan, for
example.
[0110] At 1622, the flue gas is channeled to a heating device, such
as a heating coil, plate, another heat exchanger, furnace, or the
like. Next, at 1624, the heat within the flue gas is transferred to
liquid contained within the heating device. As the flue gas passes
through the heating device and decreases in temperature (as the
heat from the flue gas is transferred to the liquid within the
heating device), the flue gas is vented from the heating device at
1626. At the same time, at 1628, the liquid, having an increased
temperature due to heat transfer with the flue gas, is circulated
to a pre-heater, which may include a liquid-circulating coil. Then,
at 1630, the heated liquid within the pre-heater is circulated
around supply air flowing through a supply air flow path. Heat
within the liquid is transferred to the supply air. At this time,
the temperature of the liquid decreases, as a portion of its heat
is transferred to the supply air. The liquid fully circulates
through the pre-heater and is then recirculated back to the heating
device at 1632, and then the process returns to 1624.
[0111] Additionally, flue gas and/or liquid may be bypassed to
control the amount of energy transfer. Moreover, the flow of liquid
may be modulated to control the amount of energy transfer.
[0112] FIG. 17 illustrates a process of operating a direct outdoor
air system, according to an embodiment. At 1700, liquid within a
boiler is heated. The liquid may be heated below a boiling point.
Next, at 1702, the heated liquid is pumped from the boiler to one
or more coils of a pre-heater disposed within a supply air flow
path. The pre-heater may be disposed within any portion of the
supply air flow path (and/or within any portion of an exhaust air
flow path). Further, the heated liquid may be pumped to multiple
pre-heaters.
[0113] At 1704, heat from the heated liquid is transferred to air
within the supply air flow path. As the heated liquid moves through
the coil(s), the temperature of the liquid decreases, as the heat
is transferred to the air. As such, reduced-temperature liquid is
pumped from the coil(s) of the pre-heater back to the boiler at
1706. The process then returns to 1700.
[0114] The processes of FIGS. 16 and 17 may occur in conjunction
with one another. Each process may be performed simultaneously, or
one of the processes may occur before the other.
[0115] Thus, embodiments provide systems and methods of heating air
within a supply air flow path. Embodiments provide a system and
method of heating supply air through heated liquid circulating
within one or more coils of a heating device, such as a first
pre-heater. Embodiments may also capture heat energy from exhaust
flue gas, and recycle the heat energy back into the supply air by
way of a second pre-heater. Embodiments provide a system and method
of using heated liquid and recycled flue gas energy to pre-heat an
air stream to reduce the need for defrosting in cold conditions.
Overall, embodiments provide a highly-efficient DOAS.
[0116] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the various embodiments of the disclosure without departing from
their scope. While the dimensions and types of materials described
herein are intended to define the parameters of the various
embodiments of the disclosure, the embodiments are by no means
limiting and are exemplary embodiments. Many other embodiments will
be apparent to those of skill in the art upon reviewing the above
description. The scope of the various embodiments of the disclosure
should, therefore, be determined with reference to the appended
claims, along with the full scope of equivalents to which such
claims are entitled. In the appended claims, the terms "including"
and "in which" are used as the plain-English equivalents of the
respective terms "comprising" and "wherein." Moreover, in the
following claims, the terms "first," "second," and "third," etc.
are used merely as labels, and are not intended to impose numerical
requirements on their objects. Further, the limitations of the
following claims are not written in means-plus-function format and
are not intended to be interpreted based on 35 U.S.C. .sctn.112,
sixth paragraph, unless and until such claim limitations expressly
use the phrase "means for" followed by a statement of function void
of further structure.
[0117] This written description uses examples to disclose the
various embodiments of the disclosure, including the best mode, and
also to enable any person skilled in the art to practice the
various embodiments of the disclosure, including making and using
any devices or systems and performing any incorporated methods. The
patentable scope of the various embodiments of the disclosure is
defined by the claims, and may include other examples that occur to
those skilled in the art. Such other examples are intended to be
within the scope of the claims if the examples have structural
elements that do not differ from the literal language of the
claims, or if the examples include equivalent structural elements
with insubstantial differences from the literal languages of the
claims.
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