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Description  |
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TECHNICAL FIELD
This invention relates generally to a ventilator including a countercurrent
heat exchanger, and more particularly, to a ventilator including a double
pass, countercurrent heat exchanger having a fresh air channel and a stale
air channel which are contiguous to one another, the channels being wound
upon one another so that the fresh air channel is interwoven with the
stale air channel.
BACKGROUND INFORMATION
The trend in building design today is to structures of ever increasing
energy efficiency. In view of the continuing increase in energy costs,
architects, builders and buyers alike are eager to find ways of reducing
the cost of heating their homes and office buildings in winter and cooling
them in summer.
The principal approach taken has been to make the construction of, for
example, a house, more tight fitting and to provide for greater use of
insulation. By reducing the gaps and spaces that arise at such places as
foundations, walls, windows, doors, etc., infiltration of outside air can
be reduced. Additionally, by increasing the amount and quality of the
insulation between walls, in ceilings, etc., heat transfer out of and into
the house can be limited. The result is that less heat is lost in winter
and accumulated in summer, and accordingly, the cost for maintaining the
house at a comfortable temperature is minimized.
However, by making the house "airtight", a potential hazard is created.
Living space generates and accumulates pollutants which if not eliminated,
would, at best, be annoying, and, at worst, create a health hazard. For
example, carbon monoxide and carbon dioxide are generated by the breathing
of house occupants, and operation of gas and wood stoves and fire places.
Chemical vapors such as formaldehyde are given off by building and
furniture materials like plywood, adhesives, insulation and furniture
padding. Further, chemical sprays such as pesticides and cleaning agents
give off noxious fumes. Still further, water vapor and odors are produced
by cooking, showering, bathroom use, and clothes laundering. Additionally,
radioactive gases such as Radon, which arise from natural radioactive
disintegration in soil and building brick and masonry, give rise to
insidious carcinogenic pollution. If left unchecked, these pollutants
could rise to dangerous levels.
To avoid this health threat, while at the some time minimizing energy
costs, architects and builders have resorted to use of special
ventilators. These ventilators don't simply introduce fresh air from
outside the house, for to do so would defeat the energy saving strategy of
tighter construction and increased insulation use. Rather, these
ventilators include heat exchangers which conserve at least some of the
energy expended in maintaining the house at a comfortable temperature. In
operation, the ventilators gather a stream of fresh air from outside the
house, but, before introducing it, preheat or precool it, depending on the
season, with the stale air being exhausted. Most typically, the gathered
fresh air is passed in heat exchange relation to the stale air so that
heat may be transferred from the warmer to the cooler. This enables a
portion of the energy expended in maintaining the room at a comfortable
temperature to be conserved by either extracting heat from or adding heat
to the stale air, before it is exhausted, and, respectively, either adding
heat to or extracting heat from the fresh air being supplied.
William A. Shurcliff, a noted expert in the field of thermal efficiency in
building design, has written on this subject. In his book entitled:
AIR-TO-HEAT EXCHANGERS FOR HOMES, published by Brick Publishing Co., Inc.,
Andover, Mass., he describes in detail the operation and design of heat
exchanging ventilators, and additionally, describes the construction and
operation of a number of currently available types.
As pointed out by Shurcliff, the savings in energy costs that a heat
exchanging ventilator can provide, as for example in time of winter, is
the product of the ventilator's flow rate and the exchange efficiency,
multiplied by, a constant that depends on the cost of energy to heat and
the expected "degree-day" factor; i.e., need for heat, of the geographical
area where the ventilator is to be used.
Shurcliff defines the flow rate of the ventilator as the volume of fresh
air supplied by the ventilator per unit time. Further, he defines
ventilator efficiency as the heat per unit weight of air transferred to
the fresh, incoming air, divided by, the difference in heat per unit
weight of air being exhausted and fresh air outside the house. In the
absence of condensation in the stale air exhaust stream, this reduces to
the difference in temperature between the fresh air introduced into the
ventilated room and the outside air temperature, divided by, the
difference in temperature between the stale air in the room and the fresh
air outside.
Therefore, the greater the flow of air the ventilator can handle, and, in
the case of winter heating, the higher the temperature of the fresh air
supplied, the greater the dollar savings the ventilator can provide.
As also noted by Shurcliff, in order to determine whether a particular
ventilator design will be cost effective, the dollar savings it produces
must be compared to the ventilator's purchase price. According, not only
must the operation of the ventilator be effective, i.e. high flow rate and
high efficiency, but also, its purchase price, and therefore it cost of
construction must be low if one is to maximize the return on investment.
As a further consideration, the ventilator should also have a form factor
that renders its physical integration into the structure to be ventilated
convenient. While, as shown by Shurcliff, a number of heat exchanging
ventilators exist which provide acceptable flow rates and efficiencies,
most are not of a size that permits convenient and unobtrusive
installation; e.g., within the wall of a house or other building to be
ventilated.
SUMMARY OF INVENTION
It is therefore an object of this invention to provide a heat exchanging
ventilator which can supply a stream of fresh air to a living space so as
to maintain pollutants within the space at an acceptable level, and to
further exchange heat between the outgoing stale air and the incoming
fresh air.
It is a further object of this invention to provide a heat exchanging
ventilator that is capable of high flow rate operation.
It is a yet further object of this invention to provide a heat exchanging
ventilator that is capable of high efficiency operation.
It is a still further object of this invention to provide a heat exchanging
ventilator having a combined high flow rate and high efficiency of
operation.
It is yet a further object of this invention to provide a heat exchanging
ventilator or simple construction so as to minimize the cost of
construction.
And it is a yet another object of this invention to provide a heat
exchanging ventilator having a form which may be conveniently fit within a
wall of a house of other structure.
Briefly, the ventilator in accordance with this invention achieves the
desired objects by including a heat exchanger having conduit means which
defines an interwoven fresh air channel and a stale air channel. These
channels are arranged such that incoming fresh air is able to pass in
countercurrent heat exchange relation with the outgoing stale air twice.
In preferred form, the fresh air channel is provided with a first end in
communication with air external to the space to be ventilated; for
example, a house or a room of a house. At this first end, an inlet is
provided for receiving the fresh air. The fresh air channel also includes
a second end in communication with the room to be ventilated. At the
second end, an outlet is provided for exhausting fresh air into the room.
Further, the stale air channel is provided with a first end also in
communication with the room to be ventilated. At the stale air channel
first end, an inlet is provided for receiving air to be exhausted from the
room. Additionally, the stale air channel includes a second end in
communication with air external to the ventilated room. At the stale air
channel second end, an outlet is provided for exhausting the stale air
from the ventilator.
The fresh air and stale air channels are pneumatically isolated from one
another so that air from the respective channels is not commingled. This
prevents the fresh air from being corrupted with pollutants before it is
introduced. Additionally, the two channels are continuous over their
lengths.
Still further, the ventilator heat exchanger includes heat transfer means
in communication with the fresh air and stale air channel that enables
heat to be exchanged between the air in the two channels. In accordance
with this invention, the fresh air channel is contiguous to and wound upon
the stale air channel such that the fresh air channel is interwoven with
the stale air channel, and so that air in the fresh air channel passes in
heat exchange relation to the stale channel twice. Further, the fresh air
channel and stale air channel are oriented relative to one another such
that air in the fresh air channel flows in a direction countercurrent to
air flowing in the stale air channel over a majority of the stale air
channel length.
In preferred form, the heat transfer means of the ventilator heat exchanger
includes a septum having a first surface in heat exchange relation with
the fresh air channel and a second surface in heat exchange relation with
the stale air channel. Also, the first and second septum surfaces are in
thermal communication with one another so that heat flows from the surface
in contact with air of higher temperature to the surface in contact with
air of lower temperature.
In this form, the septum is wrapped in successive and spaced turns to form
alternating sections of the fresh air and stale air channel respectively.
The resulting combination of channel sections has a generally elliptically
shaped profile, and includes two pseudo foci, at one of which the stale
air inlet is located, and at the other of which the fresh air outlet is
located.
In preferred form, the fresh air inlet includes a controllable blower means
for pushing fresh air through the ventilator heat exchanger at variable
rates. Additionally, the stale air outlet also includes a controllable
blower means for drawing stale air through the ventilator heat exchanger
at variable rates.
Continuing, in preferred form, the heat transfer septum is in the form of a
single sheet of material having high thermal conductivity, such as
aluminum or steel, which is wound about the stale air inlet and the fresh
air outlet in successive spaced turns to form the interwoven fresh and
stale air channel sections. Still further, in preferred form, the fresh
air inlet and the stale air outlet as well as the fresh air outlet and the
stale inlet are sufficiently spaced to avoid significant commingling of
the respective air streams.
The foregoing, and other objects features and advantages of the invention
will become apparent from the following more detailed description of a
preferred embodiment, as illustrated in the accompanied figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmented, isometric view of the ventilator in accordance with
this invention as installed within the wall of a house.
FIG. 2 is a front, elevation view of the ventilator in accordance with this
invention.
FIG. 3 is a side section view of the ventilator in accordance with this
invention taken along line 3--3 of FIG. 2.
DETAILED DESCRIPTION
The heat exchanging ventilator in accordance with this invention is shown
in FIGS. 1 to 3.
In FIG. 1, ventilator 1 is seen as it might appear installed in the wall of
a house, the rooms of which are to be ventilated. As shown, ventilator 1
is located in space 3, between interior wall 5, exterior wall 7 and
support beams 9 and 11. Ventilator 1 is arranged to receive fresh air,
schematically shown by arrow 15, from space 13 external to the house, at
the prevailing temperature. Ventilator 1 is further arranged to exhaust
the fresh air to room 21 to be ventilated, at a temperature approaching
that of room 21, as shown schematically by arrow 19. Additionally,
ventilator 1 is arranged to receive stale air, schematically shown by
arrow 23, at room temperature, from room 21, and exhaust it to space 13 at
a temperature approaching that of space 13, as schematically shown by
arrow 25.
Continuing with reference to FIG. 1, ventilator 1 is seen to include a
housing 27. Housing 27 contains the ventilator heat exchanger 29, and its
associated ducting better seen in FIGS. 2 and 3. As shown in FIG. 1,
housing 27 is in the form of a rectangular volume that fits conveniently
between interior wall 5 and exterior wall 7. Housing 27 has a front wall
31, a back wall 33, top wall 35, bottom wall 37 and side walls, 39 and 41,
respectively.
As seen in FIG. 1, ventilator 1 includes a fresh air inlet, shown generally
at 43, for receiving fresh air 15. Inlet 43 is located at upper end 45 of
housing 27, in rear wall 33. Inlet 43 includes a duct 47 having an outer
section 49 which extends through exterior wall 7. A fresh air inlet port
51 is formed by the external open end of duct section 49.
Fresh air inlet 43 also includes a blower 53 mounted within duct 47 for
drawing fresh air 15 through port 51 to heat exchanger 29. In preferred
form, blower 53 is electrical and of conventional type well known in the
art. Blower 53 includes means, also well known in the art, for controlling
blower speed, and with it the fresh air flow rate in heat exchanger 29. To
protect blower 53, fresh air inlet port 51 may be provided with grill work
or screening, which for clarity of the drawing is not shown, to block
entry of debris; e.g., leaves, paper, etc., and animals.
Ventilator 1 also includes a fresh air outlet, shown generally at 55, for
exhausting fresh air 19 to room 21. Outlet 55 is located at the lower end
65 of housing 27 in housing side wall 39. Fresh air outlet 55 includes a
duct 57 having a cylindrical, right angle outer section 59 which extends
through interior wall 5. Fresh air outlet 55 also includes an outlet port
61 at the exterior end of duct section 57. Outlet 55 is in pneumatic
communication with fresh inlet 43 through heat exchanger 29 as shown in
FIGS. 2 and 3.
Like inlet 43, fresh air outlet may include grill work or screening 63 for
restricting access to ventilator 1 from within room 21; as for example, by
children or pets. Filter means, also not shown for the sake of clarity may
be placed either at the fresh air inlet port 51 or outlet port 61 to
filter particulate matter; e.g., soot, dust, etc., from the air before it
enters room 21. In preferred form, the filter is placed at the fresh air
inlet port 51 to protect the ventilator heat exchanger 29 as well as room
21. As would be appreciated by those skilled in the art, blower means 53
could be located at outlet 55 as an alternative to location at inlet 43.
Where blower means 53 is located at outlet 55, blower 53 would be arranged
to draw air through exchanger 29.
Still with reference to FIG. 1, ventilator 1 also includes a stale air
inlet, shown generally at 67, for receiving room stale air 23. Stale air
inlet 67 is located at the upper end 45 of housing 27 in side wall 39.
Inlet 67 includes a duct 71 having an outer section 73 which extends
through interior wall 5. Duct 71 is provided with a port 75 at the
exterior end thereof. Inlet 67 is also provided with grill work or
screening 77 for restricting access to ventilator 1. In preferred form, a
filter, not shown, may be provided at inlet port 75 to prevent
accumulation of lint and grease within heat exchanger 29.
Ventilator 1 further includes a stale air outlet, shown generally at 79,
for exhausting stale air 25 to space 13. Stale air outlet 79 is located at
lower housing end 65 in housing rear wall 33. As shown, outlet 79 includes
a duct 81 having an outer section 83 which extends through exterior wall
7. Outlet 79 is maintained in pneumatic communication with stale air inlet
67 by means of heat exchanger 29. A stale air exhaust port 85 is provided
at the exterior end of duct 81.
Outlet 79 further includes a blower 87 mounted within duct 81 for drawing
stale air 23 through intake port 75 to heat exchanger 29. Like fresh air
intake blower 53, stale air exhaust blower 87 is electrical, and includes
means known in the art for controlling its speed, and subsequently the
flow rate of stale air through heat exchanger 29. As in the case of fresh
air inlet 43, stale air exhaust 79, may include grill work or screening at
port 85, not shown, to limit access to ventilator 1. As would be
appreciated by those skilled in the art, blower means 87 could be located
at inlet 67 as an alternative to location at outlet 79. When located at
inlet 67, blower means 87 would be arranged to push air through exchanger
29.
In preferred form, fresh air inlet 67 and stale air outlet 79 as well as
fresh air outlet 55 and stale inlet 67 are sufficiently spaced to avoid
significant mixing of the respective air streams 15, 25 and 19, 23.
Further, and as would be appreciated by those skilled in the art, the
locations of the inlet--outlet pairs could be exchanged without affection
operation of the ventilator.
As noted, while one of the principal objectives of ventilator 1 is to
provide a stream of fresh air to room 21 in order to maintain pollutants
at a safe level, it is a further objective to conserve energy which has
been expended to maintain the temperature of room 21 at a comfortable
level. Where energy has been expended to raise room temperature, as for
example by heating in winter, or reduce room temperature, as by cooling in
summer, ventilator 1 seeks to conserve that energy by exchanging heat
between the outgoing stale air and the incoming fresh air. Particularly,
in winter, ventilator 1 extracts heat from exhausted stale air 23 and
supplies it to incoming fresh air 15. In summer, the ventilator extracts
heat from incoming fresh air 15 and dumps it to outgoing stale air 23.
To achieve this end, ventilator 1 includes a heat exchanger 29. As best
seen in FIG. 3, heat exchanger 29 includes conduit means 89, arranged
within housing 27. Conduit means 89, in accordance with this invention, is
configured to form a fresh air channel 91 and a stale air channel 93.
Fresh air channel 91 extends from a first end 95, at fresh air inlet 43, to
a second end 97 at fresh air outlet 55. At inlet 43, channel first end 95
is pneumatically coupled to fresh air intake duct 47, at duct section
inner section 99. Duct inner section 99 is located downstream of intake
blower 53, and is in pneumatic communication with above noted fresh air
duct outer section 49 and port 51, which are located upstream of blower
53. With reference to FIG. 2, in preferred form; duct outer section 49 is
rectangular, and located in housing rear wall 33 at housing upper end 45,
extending centrally of, and along a portion of the width of wall 33. Duct
inner section 99, on the other hand, extends the width of exchanger 29 at
fresh air channel first end 95.
With reference to FIG. 3, fresh air outlet 55 at conduit end 97 is seen to
include duct inner section 96. As best seen in FIG. 2, duct inner section
96 is cylindrical in form, and is coupled at a first end 98 to duct
section 59 and outlet port 61. Duct section 96 is closed at second end 94,
as will be more fully described hereafter. Continuing with reference to
FIG. 3, inner section 96 is also provided with a slot which extends the
length of section 96, and defines second end 97 of fresh air channel 91.
As shown in FIG. 3, fresh air channel 91 is seen to include a plurality of
sections, 101, 103, 105, 107, 109, 111, 113, 115, 117 and 119, which are
arranged in end to end relation, and which extend sequentially from first
channel end 95 to second channel end 97. Sections 101 to 119 are seen to
alternate in form between arcuate and linear, starting with semicircular
section 101 and ending with linear section 119. The sections so combined
form a continuous channel having a generally elliptical profile that
spirals inwardly toward the center of the exchanger in a number of wound
and spaced turns.
Stale air channel 93 on the other hand extends from a first end 121, at
stale air inlet 67, to a second end 123 at stale air outlet 79. As shown
in FIG. 3, stale air outlet duct 81 has a duct inner section 125 which is
pneumatically coupled with stale air second channel end 123. Stale air
duct 125 is located upstream of exhaust blower 87, and is in pneumatic
communication with above noted duct outer section 83 and exhaust port 85,
which are down stream of blower 87. As shown in FIG. 2, in preferred form,
duct outer section 83 is rectangular, and located in housing rear wall 33,
at housing lower end 65, extending centrally along a portion of the width
of wall 33. Duct inner section 125, on the other hand extends the width of
exchanger 29, at stale air second channel end 125.
Returning to FIG. 3, stale air inlet 67 at conduit end 121 is seen to
include duct inner section 120. Inner section 120 is cylindrical in form,
and is coupled at one end 122 to duct outer section 73 and inlet port 75,
as best seen in FIG. 2. As shown in FIG. 3, inner section 120 is also
provided with a slot which extends the length of section 120, and defines
first end 121 of stale air channel 93. Duct inner section 120 is closed at
a second end 118, as will be more fully described hereafter.
With reference to FIG. 3, stale air channel 93 is seen to also include a
plurality of sections. The channel sections are designated 127, 129, 131,
133, 135, 135, 139, 141 and 143, and are arranged in end to end relation.
Sections 127 to 143 extend sequentially from first channel end 121, to
second channel 123, and are seen to alternate in form between linear and
arcuate sections, starting with linear section 127 and ending with linear
section 143. The sections so combined form a continuous channel having a
generally elliptical profile that spirals outwardly to the perimeter of
exchanger 27 in a number of wound and spaced turns.
Further, fresh air channel 91 is seen to be contiguous to, and wound upon
stale channel 93 such that the sections of fresh air channel 91 are
interwoven with the sections of the stale air channel 93.
As shown in FIGS. 2 and 3, the various air channel sections each include
outer and inner walls as well as side walls. Since numbering all walls for
all channel sections would overly burden the clarity of the figures, if
has been omitted. However, in order that the sense of "outer" and "inner",
as it applies to the channel walls be understood, reference should be made
to fresh air channel section 103 and stale air channel section 143 in FIG.
3. As seen there, the outer walls of channel sections 103 and 143 are
respectively designated 103a and 143a, and their inner walls designated
103b and 143b.
With regard to the interweaving of channel 91 and 93, and as seen in FIG.
3, fresh air channel section 101 and duct inner section 99 are wound upon
stale air channel section 141 such that the inner wall of section 103 and
duct section 99 overlays the outer wall of stale air channel section 143
in the sense above describes. Likewise, the inner wall of fresh air
channel section 103, 105, 107, 109, 111, 113, and 115 respectively,
overlay the outer wall of stale air channel sections 139, 137, 135, 133,
131, 129 and 127.
Further, and in accordance with this invention, as a result of the fresh
air channel sections being wound upon the stale air channel sections,
sections of stale air channel 93 overlay sections of fresh air channel 91.
For example, the inner wall of stale air channel sections 143, 141, 139,
137, 135, 133, and 131 respectively, overlay the outer wall of fresh air
sections 107, 109, 111, 113, 115 and 119.
Additionally, the inner wall of fresh air channel section 117 overlays at
least a portion of the outer wall of stale air intake duct section 120,
and the inner wall of stale air channel section 129 overlays at least a
portion of the outer wall of | | |
