Note: Descriptions are shown in the official language in which they were submitted.
HEAT RECOVERY DEVICE
Technical Field
[0001] The present invention relates to a heat recovery device for use
with a
clothes dryer.
Background
[0002] Electric and gas heated clothes dryers have become common household
appliances during the past several decades for drying wet clothes inside a
building,
such as a house. As part of the typical clothes drying process, the clothes
dryer
produces hot air. The hot air flows through the wet clothes and is then
exhaust to
the exterior of the house by way of an exhaust vent. The practice of venting
this hot
exhaust air outside is particularly inefficient and results in wasted energy,
which may
result in increased operating costs, especially in recent years with the rapid
rise in
energy costs for homeowners. There are several problems, however, associated
with simply venting the hot exhaust air from the clothes dryer directly back
into the
interior of the house which is why the conventional practice is to vent the
exhaust air
to the exterior of the house. For example, the hot exhaust air from the dryer
typically
contains a certain amount of moisture and lint picked up from the clothes
being
dried. As a result, it is undesirable to re-circulate the hot exhaust air into
the interior
of the house or even back into the dryer.
[0003] What is needed, therefore, is a device and method for recovering at
least
some of the driest hot air that would otherwise be exhausted to the exterior
of the
house and redirecting that hot air either back into the house or even the
clothes
dryer.
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Summary
[0004] A heat recovery device for use on a clothes dryer includes a body
having a
main passageway with a central axis. The body has a first end and a second end
and a dryer exhaust coupling proximate to the first end. The first end has a
main
flow inlet and the second end has a main flow outlet. The heat recovery device
also
includes a return air conduit coupled to the body. The return air conduit has
a return
air inlet and a return air outlet. The return air inlet is disposed within the
main
passageway and facing the main flow inlet. The dryer exhaust coupling is
configured
to be removably coupled to a dryer exhaust outlet of a clothes dryer such that
the
exhaust air discharged from the clothes dryer flows into the main flow inlet.
The
return air inlet is configured to receive a portion of the exhaust air
discharged from
the clothes dryer and discharge that portion through the return air outlet and
a
remainder of the exhaust air being discharged through the main flow outlet.
[0005] In one embodiment, when the heat recovery device is coupled to the
dryer
exhaust outlet, the central axis is substantially horizontal. In this
embodiment, the
return air outlet is configured to discharge the portion of the exhaust air
from the
clothes dryer in a direction substantially perpendicular to the central axis.
[0006] The return air inlet has a cross-section that is one of circular,
semi-circular,
elliptical, rectangular, square, or triangular.
[0007] In one embodiment, the return air inlet is disposed in an upper
half of the
main passageway.
[0008] In another embodiment, a heat recovery device for use on a clothes
dryer,
includes a body having a main passageway with a central axis. The body has a
first
end and a second end and a dryer exhaust coupling proximate to the first end.
The
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first end has a main flow inlet and the second end has a main flow outlet. The
heat
recovery device also includes a return air conduit integrally formed to the
body. The
return air conduit has a return air inlet and a return air outlet. The return
air inlet is
disposed within the main passageway and faces the main flow inlet and the
return air
outlet is disposed outside the main passageway. The body and the return air
conduit
are comprised of a first half and a second half separable from each other
along a
plane extending through the central axis. The dryer exhaust coupling is
configured
to be removably coupled to a dryer exhaust outlet of a clothes dryer such that
the
exhaust air discharged from the clothes dryer flows into the main flow inlet.
The
return air inlet is configured to receive a portion of the exhaust air
discharged from
the clothes dryer and discharge that portion through the return air outlet and
a
remainder of the exhaust air is discharged through the main flow outlet. In
one
embodiment, a portion of the return air conduit external to the body has a T-
shaped
profile. When the heat recovery device is coupled to the dryer exhaust outlet,
the
central axis may be substantially horizontal. In that configuration, the
return air outlet
is configured to discharge the portion of the exhaust air from the clothes
dryer in a
direction substantially perpendicular to the central axis.
[0009] In one embodiment, the heat recovery device further includes one
connector affixed to the body and one connector affixed to the return air
conduit.
Each connector is configured to couple together the first half and the second
half.
[0010] In another embodiment, the return air conduit includes a cover with
openings and the cover is coupled to the return air outlet. The cover may be
slideably removable from the return air outlet and the openings may be
elongated
slots. The return air conduit may include openings on at least one side of the
return
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air conduit. The return air inlet may have a semi-circular cross-section and
the
return air inlet is disposed in an upper half of the main passageway.
[0011] Other features of the heat recovery device are contemplated and
described and claimed below.
Brief Description of the Drawings
[0012] The accompanying drawings, which are incorporated in and
constitute a
part of this specification, illustrate one or more exemplary embodiments of
the
invention and, together with the general description of the invention given
above, and
the detailed description of the embodiments given below, serve to explain the
embodiments of the invention.
[0013] Fig. 1 is side elevational view of the heat recovery device
installed on a
clothes dryer according to one embodiment of the invention.
[0014] Fig. 2 is a perspective view of the heat recovery device of Fig.
1.
[0015] Fig. 3 is a cross-sectional view of the heat recovery device of
Fig. 2 taken
along line 3-3.
[0016] Fig. 4 is a perspective view of a heat recovery device according
to another
embodiment of the invention.
[0017] Fig. 5 is a cross-sectional view of the heat recovery device of
Fig. 4 taken
along line 5-5.
[0018] Fig. 6 is a perspective view of a heat recovery device according
to another
embodiment of the invention.
[0019] Fig. 7 is a cross-sectional view of the heat recovery device of
Fig. 6 taken
along line 7-7.
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[0020] Fig. 8 is a perspective view of a heat recovery device according
to another
embodiment of the invention.
[0021] Fig. 9 is a cross-sectional view of the heat recovery device of
Fig. 8 taken
along line 9-9.
[0022] Fig. 10 is a front prospective view of a heat recovery device
according to
another embodiment of the invention.
[0023] Fig. 11 is rear prospective view of the heat recovery device of
Fig. 10.
[0024] Fig. 12 is a cross-sectional perspective view of the heat recovery
device of
Fig. 10 taken along line 12-12 with the cover slid partially out.
[0025] Fig. 13 is a front elevational view of the heat recovery device of
Fig. 10.
[0026] Fig. 14 is a partial cross-sectional perspective view of the heat
recovery
device of Fig. 10
[0027] Fig. 15 is a side elevational view of a clothes dryer exhausting
dryer air to
the exterior of a building.
[0028] Fig. 16 is a side elevational view of a clothes dryer exhausting
dryer air to
the interior of a building.
[0029] Fig. 17 is a cross-sectional view of the heat recovery device of
Fig. 2 with
the inlet port located near the middle of the main passageway.
[0030] Fig. 18 is a cross-sectional view of the heat recovery device of
Fig. 2 with
the inlet port located near the bottom of the main passageway.
Detailed Description
[0031] The invention is intended to return heat, in the form of hot air,
that is
normally exhausted from a conventional clothes dryer to the exterior of a
building,
such as a house, and into the environment. According to one aspect of the
CA 3050898 2019-07-31
invention, at least some of the hot air may be returned to the interior of the
house,
such as into the room where the clothes dryer is located, to heat at least
part of the
interior of the house. According to another aspect of the invention, at least
some of
the hot air may be returned back into the clothes dryer to enhance the drying
efficiency of the clothes dryer. According to one aspect of the invention,
little or none
of the moisture and lint which may be entrained in the exhausted hot air from
the
clothes dryer is returned to the interior of the house or the clothes dryer.
[0032] With reference to Fig. 1, an exemplary laundry room 10 with a
conventional clothes dryer 12 is illustrating venting hot exhaust air from the
clothes
dryer 12 to the exterior of a building 14, such as a house. A heat recovery
device 20
according to one exemplary embodiment is shown coupled at one end to a dryer
exhaust outlet 22 of the clothes dryer 12 and coupled at another end to an
exhaust
duct 24 which is routed through an exterior wall 26 of the building 14. Hot
exhaust
air 28 flowing through the exhaust duct 24 exits through a vent 30. A conduit
32,
such as pipe or tube, is coupled to the heat recovery device 20. According to
an
aspect of the invention, return hot air 34 exits the conduit 32 into the
interior of the
house 14 as illustrated in Fig. 1. Alternatively, return hot air 34 may also
exit into the
clothes dryer 12 instead of the interior of the house 14 according to another
aspect
of the invention.
[0033] Various embodiments of heat recovery devices are shown in Figs. 2-
12.
Some features of the various embodiments of the heat recovery devices in Figs.
2-
12 are the same or nearly the same. Consequently, the same reference number
for
such a feature will be used on each embodiment where appropriate.
[0034] The heat recovery device 20 is further illustrated in Figs. 2 and
3. The
heat recovery device 20 is comprised of a body 40 having a main passageway 42
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with a main flow inlet 44 and main flow outlet 46. The main flow inlet 44
includes a
dryer exhaust coupling 48, which is configured to be coupled in sealing
engagement
to the dryer exhaust outlet 22 of the clothes dryer 12. The exhaust duct 24 is
coupled in sealing engagement with the main flow outlet 46 of the heat
recovery
device 20. The heat recovery device 20 further includes a return air conduit
50
having a return air inlet 52 and a return air outlet 54, which is in sealing
engagement
with the conduit 32. The return air inlet 52 is positioned in the main
passageway 42,
and more particularly, near the top of the main passageway 42. The return air
conduit 50 and its return air inlet 52 and return air outlet 54 have a
generally circular
cross-section, but could have other cross-sectional shapes as will be
discussed
below.
[0035] With specific reference to Fig. 2, the flow path of the hot exhaust
air from
the clothes dryer 12 through the heat recovery device 20 is illustrated. Hot
exhaust
air being discharged from the dryer exhaust outlet 22 flows into the main flow
inlet 44
and into the main passageway 42 as schematically indicated by arrow A. A
portion
of the hot exhaust air exits through the main flow outlet 46 as schematically
indicated
by arrow B. The remainder of the hot exhaust air exits through the return air
outlet
54 as schematically indicated by arrow C.
[0036] As shown in Figs. 2 and 3, the body 40 of the heat recovery device
20 is
cylindrical in shape, and sized such that the dryer exhaust coupling 48 and
body 40
have similar cross-sectional areas compared to the dryer exhaust outlet 22.
However, the body 40 and the dryer exhaust coupling 48 of the heat recovery
device
20 are not limited to these shapes. The dryer exhaust coupling 48 may be
threaded
or may be sized to produce a frictional or interference fit with the dryer
exhaust outlet
22 of the clothes dryer 12 to couple in sealing engagement with the dryer
exhaust
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coupling 48 of the heat recovery device 20. Similarly, the main flow outlet 46
of the
heat recovery device 20 may be sized to produce a frictional or interference
fit with
the exhaust duct 24. It will be appreciated that tape, a pipe clamp, zip ties,
screws,
rivets, or other mechanical fasteners may be used to couple the heat recovery
device 20 to the dryer exhaust outlet 22 and the exhaust duct 24. In one
embodiment (Fig. 5), the heat recovery device 20 is constructed of polyvinyl
chloride
(PVC), but it may be constructed of any other suitable plastic, rubber, carbon-
fiber,
metal, or any other suitable material. Moreover, the components of the heat
recovery device 20 may each be constructed of different materials as operating
conditions warrant. For example, the body 40 may be constructed of PVC while
the
return air conduit 50 may be constructed of metal.
[0037] The
return air inlet 52 of the heat recovery device 20 in Figs. 2 and 3 has a
circular cross-section with a diameter which is smaller than the diameter of
the
circular cross-section of the main passageway 42 of the body 40. In the
embodiment
in Fig. 3, the diameter of return air inlet 52 is a little more than one-third
the diameter
of main passageway 42 of the body 40. By way of example, but not a limitation,
the
diameter of return air inlet 52 may range from between one-tenth to three-
quarters of
the diameter of the main passageway 42 of the body 40. The size and location
of
the return air inlet 52 may be dictated by how much moist air is desired to be
directed back into the laundry room 10. For instance, someone in drier
climates may
want more of the moist air directed back into the interior of the house 14. To
that
end, a larger return air inlet 52 positioned lower in the body 40 may likely
return more
moist air back into the interior of the house 14 and a smaller return air
inlet 52
positioned at the top of the main passageway 42 of the body 40 may likely
return
less moist air back into the interior of the house 14.
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[0038] In the embodiment of the heat recovery device 20 shown in Figs. 2
and 3,
the return air inlet 52 is sized to remain in the upper half of the main
passageway 42
of the body 40 to capture the dry hot air while the moist air and lint
particulates pass
under return air inlet 52 and are exhausted to the exterior of the building 14
via the
exhaust duct 24. It is believed that placing the return air inlet 52 in the
upper-half of
the main passageway 42 of the body 40 will return the driest air from the
dryer
exhaust outlet 22 back into the laundry room 10. In addition, the force of the
exhaust
airstream exiting from the exhaust outlet 22 is adequate to separate and
return the
dry air via the return air conduit 50 into the laundry room 10. As a result,
no
additional energy is consumed to recover the dry air from the exhaust stream.
[0039] Different shapes and configurations of the return air inlet 52 of
the return
air conduit 50 would be apparent to one skilled in the art in order to alter
the amount
of warm air recovered. As such, the shapes and configurations are not limited
to the
shapes and configurations disclosed herein. In one embodiment shown in Figs. 4
and 5, the heat recovery device 20 includes a return air conduit 60 with a
return air
inlet 62 having a flat surface 64 located in the upper-half of the main
passageway 42
of the body 40 and just below where the return air conduit 60 intersects with
the body
40. The flat surface 64 may be located at different positions relative to the
top of the
main passageway 42 of the body 40 to change the amount of hot air returned to
laundry room 10 via conduit 32. The closer the flat surface 64 is to the top
of the
main passageway 42 of the body 40 (e.g., around 25% of the diameter of the
main
passageway 42 from the top), the less hot air that may be directed into the
interior of
the laundry room 10. Conversely, the further the flat surface 64 is from the
top of the
main passageway 42 body 40 (e.g., around 75% of the diameter of the main
passageway 42 from the top) the warmer air may be directed into the interior
of the
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laundry room 10. The flat surface 64 is shown mounted to the sidewalls of the
main
passageway 42 of the body 40 with a flat, half-moon shaped back portion 66,
curved
to couple it to the upper-half of the main passageway 42.
[0040] In another embodiment shown in Figs. 6 and 7, the heat recovery
device
20 includes a return air conduit 70 with a return air inlet 72 that has an
elliptical
cross-section. The upper-half of the elliptical cross-section of the return
air inlet 72
generally mimics the shape of the main passageway 42 of the body 40 of the
heat
recovery device 20.
[0041] In yet another embodiment shown in Figs. 8 and 9, the heat
recovery
device 20 includes a return air conduit 80 with a return air inlet 82 that has
a
rectangular cross-section. The return air inlet 82 may also have a square
cross-
section. In another embodiment, the cross-section of the return air inlet may
have
triangular cross section.
[0042] Another embodiment of a heat recovery device 90 is shown in Figs. 10-
14.
The heat recovery device 90 is comprised of a body 92 having a main passageway
94 with a main flow inlet 96 and a main flow outlet 98. The main flow inlet 96
includes a dryer exhaust coupling 100 formed from a series of tabs 102, which
are
configured to be coupled in sealing engagement to the dryer exhaust outlet 22
of the
clothes dryer 12. The tabs 102 may be flexible to allow the dryer exhaust
coupling
100 to slip over the dryer exhaust outlet 22 to produce a frictional or
interference fit.
It will be appreciated that tape, a pipe clamp, zip ties, screws, rivets, or
other
mechanical fasteners may be used to couple the heat recovery device 90 to the
dryer exhaust outlet 22 and the exhaust duct 24. The heat recovery device 90
further includes a return air conduit 104 having a return air inlet 106 and a
return air
outlet 108. In one embodiment, the return air conduit 104 is integrally formed
with
CA 3050898 2019-07-31
the body 40. While the return air inlet 106 shown in Fig. 13 has a semi-
circular
cross-section, other cross-sectional geometries may be used, including but not
limited to circular, elliptical, rectangular, square, or triangular. While the
portion of
the return air conduit 104 that is external to the body 92 has a generally T-
shaped
profile as seen in Fig. 13, other profiles may be implemented. The return air
outlet
108 has a generally rectangular shape with a slidable cover 110 with openings
112,
such as elongated slots, fit thereover. The cover 110 may be slid partially
off or
completely removed the return air outlet 108 so that the interior of the
return air
conduit 104 may be cleaned or to allow greater airflow through the return air
outlet
108. The return air conduit 104 has opposing sides 114, 116, with openings
118,
such as elongated slots. The slots 112 and the slots 118 are configured to
allow
return hot air flow through them. It will be appreciated that the return air
outlet 108
may have other shapes such a square or circular, for example. It will be
further
appreciated that through holes and other types of openings may be used in
place of
the slots 112 and/or the slots 118 to allow return hot air to flow through
them. As
shown in Fig. 13, the bottom of the return air inlet 106 is located
approximately one-
third of the diameter of the main passageway 94 from the top of the main
passageway 94. In other words, the return air inlet 106 is disposed within the
upper
portion of the main passageway 94.
[0043] With
specific reference to Fig. 10, the flow path of the hot exhaust air from
the clothes dryer 12 through the heat recovery device 90 is illustrated. Hot
exhaust
air flows through the main flow inlet 96 and into the main passageway 94 as
indicated by arrow A. A portion of the hot exhaust air exits through the main
flow
outlet 98 as indicated by arrow B. A portion of the hot exhaust air exits
through the
return air outlet 108, and more specifically through the slots 112 of the
cover 110, as
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indicated by arrow C. A portion of the hot exhaust air exits through the slots
118 in
opposing sides 114, 116, as indicated by arrows D. Unlike the embodiments
illustrated in Figs. 2-9, the return air conduit 104 is not connected to a
conduit, such
as conduit 32, to direct the return hot air into the laundry room 10. Instead,
the
return hot air enters the laundry room 10 immediately after exiting through
the slots
112, 118.
[0044] In an exemplary embodiment, the heat recovery device 90 may be
constructed of two, separate halves 120, 122, which are held together by three
connectors 124, two on the return air conduit 104 (Figs. 10, 11) and one on
the
bottom of body 92 (Figs. 13, 14). In one embodiment, the two halves 120, 122
are
joined to each other along a plane extending through the central axis of the
main
passageway 94. Each connector 124 includes a flexible member 126 with a
retaining member 128 at its distal end. The flexible member 126 is coupled to
side
122 of the heat recovery device 90. A coupling member 130 is coupled to side
120
of the heat recovery device 90. As the two halves 120, 122 are move toward
each
other, the retaining member 128 contacts the coupling member 130 and flexes
away
from the coupling member 130 as the two halves 120, 122 continue to be moved
toward each other. As the two halves 120, 122 engage one another, the
retaining
member 128 moves past the coupling member 130 the flexible member 126 returns
to it undeflected position and retaining member 128 engages the coupling
member
130 to hold the two halves 120, 122 of the heat recovery device 90. It will be
appreciated that other connectors may be used to hold the two halves 120, 122
together, such as screws, nuts and bolts, adhesive, glue, etc. It will also be
appreciated that the body 92 of the heat recovery device 90 may be formed as a
single, monolithic structure, i.e., as one piece.
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[0045] Each embodiment of the heat recovery devices 20, 90 discussed
above
includes a main passageway 42, 94, which has a central axis. Advantageously,
in
practice, the heat recovery devices 20, 90 will be coupled to the clothes
dryer 12
such that the central axes of the main passageways 42, 94 are substantially
horizontal and each of the return air outlets 54, 108 discharge return air
substantially
perpendicular to the central axis in a substantially vertical direction.
[0046] As mentioned above, the position of the return air inlet in the
main
passageway is likely to influence the amount of moisture in the returned hot
air being
discharged into the laundry room. That is, the return air inlet may be
positioned to
collected drier air or positioned to collect moister air. To evaluate the
position of the
return air inlet on the amount of moist in the returned hot air, the inventor
conducted
five tests. The five tests were conducted to evaluate how the temperature and
humidity inside a laundry room containing a conventional, electric residential
clothes
dryer changed under varying venting configurations. The five tests were
conducted
in a laundry room measuring 5 feet by 6 feet with the laundry room door
closed.
Each test began with removing five beach towels from conventional, residential
clothes washing machine after completing a normal wash cycle and placing them
into the clothes dryer. The dryer was run for 30 minutes on the high heat
setting. A
temperate and humidity monitor made by ACURITErm sitting directly on the top
center of the dryer was used to measure temperature and humidity immediately
before and immediately after the drying cycle. None of the dryer exhaust was
diverted back into the dryer during any of the five tests.
[0047] In Test No. 1, the dryer exhaust was vented directly to the
outside like a
typical clothes dryer is usually set-up and operated as schematically
illustrated in
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Fig. 15. That is, a heat recovery device of the type discussed above was not
used
and no dryer exhaust was intentionally diverted into the laundry room.
[0048] In Test No. 2, all of the dryer exhaust was vented directly into
the laundry
room as schematically illustrated in Fig. 16. In other words, nothing was
attached to
the dryer exhaust pipe.
[0049] In Test No. 3, the heat recovery device 20 similar to the one
shown in
Figs. 2 and 3 was used. The dryer exhaust coupling 48 of the heat recovery
device
20 was attached to the dryer exhaust outlet 22 and the main flow outlet 46 of
the
heat recovery device 20 was attached to the exhaust duct 24 which was attached
to
the vent 30. The return air conduit 50 was positioned such that return air
inlet 52
was in the most upwardly vertical position in the main passageway 42 of the
body 40
of the heat recovery device 20 as illustrated in Fig. 3. In this
configuration, a portion
of the dryer exhaust exited through the vent 30 and a portion of the dryer
exhaust
exited the return air conduit 50 into the laundry room.
[0050] In Test No. 4, the heat recovery device 20 was connected to the
clothes
dryer in the same manner as in Test 3, but the return air conduit 50 was
positioned
such that the centerline of the return air inlet 52 was concentric with the
centerline of
the main passageway 42 of the body 40 of the heat recovery device 20 as
illustrated
in Fig. 17. Like Test No. 4, a portion of the dryer exhaust exited through the
vent 30
and a portion of the dryer exhaust exited the return air conduit 50 into the
laundry
room.
[0051] In Test No. 5, the heat recovery device 20 was connected to the
clothes
dryer in the same manner as in Test 3, but the return air conduit 50 was
positioned in
the most vertically downward position in the main passageway 42 of the body 40
of
the heat recovery device 20 as illustrated in Fig. 18. Again, a portion of the
dryer
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exhaust exited through the vent 30 and a portion of the dryer exhaust exited
the
return air conduit 50 into the laundry room.
[0052] The table below summarizes the data that the temperate and
humidity
monitor collected during the five tests.
Test Test Starting Ending Temp. Starting Ending Humidity Comments
No. Description Temp. Temp. Change Humidity Humidity Change
(F) (F) (F) (%) (%) (%)
1 Typical 75 77 +2 45 46 +1 No visible
connection moisture on
walls or
ceiling of
laundry
room
2 Venting 75 111 +36 42 99 +57 Walls
directly to showed
laundry visible
MOM wetness.
Ceiling
showed
significant
wetness,
including
beads of
water.
3 Inlet port in 75 82 +7 45 49 +4 No
visible
top position moisture on
walls or
ceiling of
laundry
1-00111
4 Inlet port in 75 80 +5 43 53 +10 No
visible
middle moisture on
position walls or
ceiling of
laundry
MOM
Inlet port in 75 81 +6 41 57 +16 Slightly
bottom visible
position wetness on
walls and
ceiling.
[0053] When looking at the data from Test Nos. 3-5, Test No. 3 yielded
the
greatest temperature gain, a rise of 7 degrees, and the lowest increase in
humidity, a
rise of 4 percentage points. Test No. 5 yielded the highest increase in
humidity, 16
percentage points.
CA 3050898 2019-07-31
[0054] While
the present invention has been illustrated by a description of various
preferred embodiments and while these embodiments have been described in some
detail, it is not the intention of the inventor to restrict or in any way
limit the scope of
the appended claims to such detail. Additional advantages and modifications
will
readily appear to those skilled in the art. Thus, the various features of the
invention
may be used alone or in any combination depending on the needs and preferences
of the user.
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