Abstrict A multi-band air curtain forms a separation barrier at an interface
between a first environment having a fluid at a first condition
and a second environment having a fluid at a second condition. A
first stream (55) of a fluid is directed along a first path (45)
generally parallel to the interface between the first environment
and the second environment. A second stream (65) of fluid is directed
along a second path (75) generally outwardly at an angle of divergence
with the first path (45). A third stream (65) of a fluid is directed
along a third path (95) between the first path (45) and the second
path (75) at a first interior angle with said first path (45) and
at a second interior angle with said second path (75). A refrigerated
merchandiser (10) is also disclosed having a display case having
an interior defining a product display region (30) having an open
front and first (34), second (70) and third (58) air outlets for
directing first (55), second (65) and third air (85) streams, respectively,
across the open front of the refrigerated merchandiser in a divergent
manner.
Claims What is claimed is:
1. A method for establishing a separation barrier at an interface
between a first environment having a fluid at a first condition
and a second environment having a fluid at a second condition comprising:
directing a first stream of fluid drawn from the first environment
across the interface between said first environment and said second
environment along a first path generally parallel to the interface,
thereby establishing a primary fluid curtain along the interface;
directing a second stream of fluid drawn from the second environment
across the interface between said first environment and said second
environment along a second path at an angle of divergence with the
first path in a direction towards said second environment, thereby
establishing a tertiary fluid curtain outwardly of said primary
fluid curtain, the angle of divergence between said second path
and said first path ranging from about 10 degrees to about 70 degrees;
and directing a third stream of a fluid along a third path between
said first path and said second path at a first interior angle with
said first path ranging from about 5 degrees to about 35 degrees
and at a second interior angle with said second path ranging from
about 5 degrees to about 35 degrees, thereby establishing a secondary
fluid curtain intermediate said primary fluid curtain and said tertiary
fluid curtain.
2. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 1 wherein
said second interior angle ranges from 15 degrees to 35 degrees.
3. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 1 further
comprising maintaining said third stream of fluid at a temperature
in the range between a first relatively cooler temperature of the
first fluid stream and a second relatively warmer temperature of
the second fluid stream.
4. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 1 further
comprising: directing the first fluid stream along the first path
at a first discharge velocity; directing the second fluid stream
along the second path at a second discharge velocity greater than
said first discharge velocity; and directing the third fluid stream
along the third path at a third discharge velocity greater than
the first discharge velocity and less than the second discharge
velocity.
5. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 4 further
comprising maintaining the ratio of the second discharge velocity
to the first discharge velocity at a magnitude of at least about
1.4.
6. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 5 further
comprising maintaining the ratio of the second discharge velocity
to the first discharge velocity within the range of from about 1.4
to about 2.4.
7. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 5 further
comprising maintaining the ratio of the third discharge velocity
to the first discharge velocity within the range of from about 1.2
to about 2.0.
8. A method for establishing a separation barrier between a first
environment and a second environment as recited in claim 4 further
comprising maintaining the ratio of the third discharge velocity
to the second discharge velocity at a magnitude ranging from greater
than 1.0 to about 1.25.
9. A refrigerated merchandiser comprising: a display case having
an exterior and an interior, said interior defining a refrigerated
product display region having an open front interfacing with an
ambient environment; a first discharge outlet associated with said
display case for directing a first stream of air at a relatively
cooler temperature generally parallely across the open front of
the merchandiser along a first path; a second discharge outlet associated
with said display case for directing a second stream of air a relatively
warmer temperature generally outwardly across the open of the merchandiser
along a second path at a divergent angle with respect to the first
path ranging from about 10 degrees to about 70 degrees; and a third
discharge outlet associated with said display case for directing
a third air stream generally outwardly across the open front of
the merchandiser along a third path, said third air outlet positioned
between said first discharge outlet and said second discharge outlet,
said third path diverging from said first path at an interior angle
ranging from about 5 degrees to about 35 degrees and diverging from
said second path at an interior angle ranging from about 5 degrees
to about 35 degrees.
10. A refrigerated merchandiser as recited in claim 9 wherein said
second interior angle ranges from 15 degrees to 35 degrees.
11. A refrigerated merchandiser as recited in claim 9 wherein said
third stream of fluid has a temperature in the range between the
relatively cooler temperature of the first air stream and the relatively
warmer temperature of the second air stream.
12. A method for operating a refrigerated merchandiser having a
display case defining a refrigerated product display region having
an open front interfacing with an ambient environment, comprising:
directing a first stream of refrigerated air drawn from the product
display region along a first path across the open front of the display
case, thereby establishing a primary air curtain across the open
front of the display case; directing a second stream of ambient
air drawn from exteriorly of the refrigerated merchandiser across
the open front of the display case along a second path at an angle
of divergence with the first path in a direction away from the open
front of the display case, thereby establishing a tertiary air curtain
outwardly of said primary air curtain, the angle of divergence between
said second path and said first path ranging from about 10 degrees
to about 70 degrees; and directing a third stream of air along a
third path between said first path and said second path at a first
interior angle with said first path ranging from about 5 degrees
to about 35 degrees and at a second interior angle with said second
path ranging from about 5 degrees to about 35 degrees, thereby establishing
a secondary air curtain intermediate said primary air curtain and
said secondary air curtain.
13. A method for operating a refrigerated merchandiser as recited
in claim 12 further comprising: discharging the first air stream
from said first discharge outlet along the first path at a first
discharge velocity; discharging the second air stream from the second
discharge outlet along the second path at a second discharge velocity
greater than said first discharge velocity; and discharging the
third air stream from the third discharge outlet along the third
path at a third discharge velocity greater than the first discharge
velocity and less than the second discharge velocity.
14. A refrigerated merchandiser as recited in claim 13 wherein
the ratio of the second discharge velocity to the first discharge
velocity has a magnitude of at least about 1.4.
15. A refrigerated merchandiser as recited in claim 13 wherein
the ratio of the second discharge velocity to the first discharge
velocity has a magnitude within the range of from about 1.4 to about
2.4.
16. A refrigerated merchandiser as recited in claim 15 wherein
the ratio of the third discharge velocity to the first discharge
velocity has a magnitude within the range of from about 1.2 to about
2.0.
17. A refrigerated merchandiser as recited in claim 15 wherein
the ratio of the third discharge velocity to the second discharge
velocity has a magnitude ranging from greater than 1.0 to about
1.25. Description BACKGROUND OF THE INVENTION
The present invention relates generally to air curtains for separating
a first environment from a second environment. The method of the
present invention may be advantageously applied to refrigerated
display merchandisers of the type used in supermarkets, mini-marts,
convenience stores and other commercial establishments for displaying
and merchandising refrigerated or frozen products for sale, wherein
an air curtain separates the open-front, product display area from
the ambient store environment.
Refrigerated display merchandisers, also commonly referred to as
display cases, having open front display regions are commonly used
in supermarkets, mini-marts, convenience stores and other commercial
establishments for displaying and merchandising refrigerated or
frozen products for sale. The open front nature of such display
cases permits the consumer to simply reach into the product display
region to select and remove a product for purchase without the inconvenience
of needing to open a door to access the product. Customarily, a
curtain of cold refrigerated air is passed downwardly at a relatively
high velocity across the open front of the display case to form
an invisible boundary between the product display region and the
region of the store in front of the display case. This air curtain
not only helps retain cool refrigerated air within the product display
region of the display case, thereby cooling the display product
on the shelves of the display case, but also functions to isolate,
to a certain extent, the product display region from the ambient
air within the store. Ambient air that does enter into open product
display region undesirably causes increased energy consumption by
increasing the cooling demand on the refrigeration system associated
with the display case. Further, such ambient air may also cause
a local temperature rise within the product display region sufficient
to result in an undesirable rise in product temperature that could
adversely impact upon product quality.
A problem encountered with when passing a curtain of refrigerated
air downwardly across the open front of the product display region
of the display case lies in the entrainment of ambient air into
the stream of refrigerated air forming the air curtain. Turbulence
exists at the boundary between the relatively high velocity curtain
air and the generally quiescent ambient air lying in front of the
display case. As a result of such turbulence, some ambient air is
undesirably entrained into the air curtain. Multiple air curtain
display cases have been developed in the prior art to address this
entrainment problem. For example, display cases having two adjacent,
parallel, but independently generated, air curtains of refrigerated
air are common in the art. Typically, such as disclosed by Maehara
in U.S. Pat. No. 4,633,677, the outermost air curtain has a slightly
higher temperature than the innermost air curtain, so as to protect
the colder innermost air curtain from the impact of ambient air
entrainment. However, such designs do not completely eliminate the
intrusion of ambient air into the refrigerated air curtain.
Also, it is well known in the art to establish a third air curtain
of relatively high velocity ambient air outwardly of one or two
refrigerated air curtains as a means of reducing entrainment of
ambient air from the store into the refrigerated air curtains. Abraham,
in U.S. Pat. No. 4,267,706, discloses establishing an ambient air
curtain outwardly of an innermost refrigerated air curtain, with
the outer ambient air curtain being directed downwardly parallel
to and adjacent to the inner refrigerated air curtain.
Beckwith et al, in U.S. Pat. Nos. 3,648,482 and 3,850,003, MacMaster
et al, in U.S. Pat. No. 3,827,254 and Roberts, in U.S. Pat. Nos.
5,345,778 and 5,357,767, each disclose establishing an ambient air
curtain outwardly of a pair of refrigerated air curtains. The curtain
closest to the product display region of the display case is coolest,
while the center curtain is at a temperature slightly warmer than
the innermost curtain, but substantially cooler than the outermost
ambient air curtain. The center curtain of warmer refrigerated air
serves to buffer the innermost colder refrigerated air curtain from
warm air intrusion from the outermost ambient air curtain. The outermost
curtain of ambient air is directed substantially vertically downwardly,
either parallel to and adjacent the center air curtain or slightly
inwardly toward the center air curtain, so as to preclude refrigerated
air from the center and innermost refrigerated air curtains from
spilling out of the product display region of the display case.
The outermost ambient air curtain itself ideally spills into the
store near the base of the display case so as to not be drawn into
the air return inlets through which the refrigerated air curtains
return to the evaporator compartment. Although generally quite effective
in reducing intrusion of ambient air into the colder innermost refrigerated
air curtain, some intrusion into the center refrigerated air stream
will occur.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for
establishing a separation barrier at an interface between a first
environment and a second environment. It is a further object of
the present invention to provide a refrigerated merchandiser utilizing
a multi-layer air curtain system across the open front of the display
case.
In one aspect of the present invention, a method is provided for
establishing a separation barrier at an interface between a first
environment having a fluid at a first condition and a second environment
having a fluid at a second condition. The method includes the steps
of: directing a first stream of a fluid drawn from the first environment
along a first path generally parallel to the interface between the
first environment and the second environment, directing a second
stream of a fluid drawn from the second environment between the
first stream of fluid and the second environment along a second
path at an angle of divergence with the first path in a direction
towards the second environment ranging from about 10 degrees to
about 70 degrees, and directing a third stream of a fluid along
a third path between the first path and the second path at an interior
angle with the first path ranging from about 5 degrees to about
35 degrees and at a second interior angle with the second path ranging
from about 5 degrees to about 35 degrees, and most advantageously
from 15 degrees to 35 degrees. The first fluid stream establishes
a primary fluid curtain across the interface, the second fluid stream
establishes a tertiary fluid curtain across the interface outwardly
of the primary fluid curtain, and the third fluid stream establishes
a secondary fluid curtain across the interface intermediate the
primary fluid curtain and the tertiary fluid curtain.
In another aspect of the present invention, a refrigerated merchandiser
is provided having a display case defining a refrigerated product
display region having an open front interfacing with an ambient
environment. A first discharge outlet associated with the display
case directs a first stream of air at a relatively cooler temperature
across the open front of the merchandiser along a first path. A
second discharge outlet associated with the display case directs
a second stream of air at a relatively warmer temperature generally
outwardly across the open of the merchandiser along a second path
at a divergent angle with respect to the first path ranging from
about 10 degrees to about 70 degrees. A third air outlet associated
with the display case directs a third air stream generally outwardly
across the open front of the merchandiser along a third path diverging
from said first path at an interior angle ranging from about 5 degrees
to about 35 degrees and diverging from said second path at an interior
angle ranging from about 5 degrees to about 35 degrees. The third
discharge outlet is positioned between the first discharge outlet
and the second discharge outlet. Advantageously, first, second and
third discharge outlets may be disposed in side-by-side relationship
at the upper front of the display case. The first stream of relatively
cooler temperature air may constitute refrigerated air drawn from
the display case and the second stream of relatively warmer temperature
air may constitute ambient air drawn from the environment exterior
of the refrigerated merchandiser.
In a further aspect of the present invention, the first fluid stream
is directed along the first path at a first discharge velocity,
the second fluid stream is directed along the second path at a second
discharge velocity greater than the first discharge velocity, and
the third fluid stream is directed along the third path at a third
discharge velocity greater than the first discharge velocity, but
not greater than, and advantageously less than, the second discharge
velocity. Advantageously, the second discharge velocity may be maintained
at a magnitude of at least about 1.2 times the first discharge velocity,
and most advantageously within the range from about 1.2 to about
2.4 times the first discharge velocity. Further, the third discharge
velocity may be maintained at a magnitude of at least about 1.2
to about 2.4 times the second discharge velocity.
BRIEF DESCRIPTION OF THE DRAWINGS
The various features and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the currently preferred embodiment with reference
to the accompany drawings wherein:
FIG. 1 illustrates a side elevation profile of a refrigerated merchandiser
having van open-front display case showing an air curtain formed
of three independent, divergent air streams across the open-front
display case; and
FIG. 2 illustrates a close-up view of the three outlets of the
open front display through which air is directed in three independent,
divergent air streams across the open-front display case.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will be described hereinafter in application
on a refrigerated merchandiser for the purpose of establishing a
multi-stream air curtain barrier between the refrigerated product
display area interior to the refrigerated merchandiser and the ambient
area in front of the refrigerated merchandiser. It is to be understood,
however, that the present invention has a much broader application.
Broadly, in one aspect of the present invention, a method is provided
for establishing a separation barrier at an interface between a
first environment having a fluid at a first condition and a second
environment having a fluid at a second condition. For example, for
purposes of illustration, but not limitation, the method of the
present invention could be applied to maintaining a barrier between
at a warehouse door between a environmentally controlled interior
and an exterior loading dock, or at a store entrance between the
temperature controlled store interior and the ambient outdoor environment.
Accordingly, the following description of the present invention
as applied to a refrigerated merchandiser is not intend to limit
the scope of the method of the present invention, but merely to
illustrate the method of the present invention in a particularly
advantageously application thereof.
Referring now to FIG. 1, the refrigerated merchandiser 10 includes
an outer cabinet 12 and an inner cabinet liner 20 that defines within
its bounds an open-front product display region 30. The outer cabinet
has a base 13, a rear wall 14 extending upwardly from the back of
the base 13, a top wall 15 extending forwardly from the rear wall
and a pair of side walls 16 extending vertically from the base 13
to the top wall 15 and forwardly from the rear wall 13. The inner
cabinet liner 20 has a top panel 28, a back panel 26, a bottom panel
24 and opposed side panels 22 which together bound the open-front
product display region 30. Each of the cabinet base 13, rear wall
14, top wall 15 and side walls 16 is insulated, as in conventional
practice, to thermally isolate the interior of the cabinet 12, including
the product display region 30, from excessive heat transfer therethrough.
Perishable product 80 being merchandized may be displayed on shelves
17 disposed within the product display region 30 and upon the upper
surface of the bottom panel 24. The product display region 30 has
an open front 25 so as to permit consumers to not only view, but
also reach into the product display region 30 to select and remove
items of product 80 that they desire to purchase. Product display
region 30 is cooled in a conventional manner to a desired product
temperature, typically to a temperature between -10.degree. F. to
less than about 40.degree. F., depending upon what product is being
merchandised therein and whether the product is frozen or non-frozen.
The refrigerated merchandiser 10 further includes a refrigeration
compartment 40, typically disposed in the portion of the display
cabinet beneath the bottom panel 24, as depicted in FIG. 1, wherein
components of the refrigerant system, typically a tube coil evaporator
50 and a air mover 60, such as for example one or more fans, are
housed. However, it is to be understood that the specific type of
air mover employed is not relevant. As in conventional practice,
refrigerant passing through the tubes of the evaporator 40 refrigerates,
i.e. cools, air passing over the surface of the evaporator tubes.
The refrigerant is typically supplied from a remote refrigeration
unit located elsewhere within the store. However, it is to be understood
that the present invention may also be employed on stand alone refrigerated
merchandisers that include their own refrigeration unit for providing
the cold refrigerant.
A first air circulation duct 32 and a second air circulation duct
52 are formed between the rear wall 14 and the top wall 15 of the
outer cabinet 12 and the back panel 26 and top panel 28, respectively,
of the inner cabinet liner 20. A separation wall 46 spaced intermediate
the rear wall 14 and back panel 26 and the top wall 15 and the top
panel 28 separates the first air circulation duct 32 and the second
air circulation duct 52. The second air circulation duct 52 further
extends along the base 13 of the refrigerated merchandiser beneath
the refrigeration compartment 40. A third air duct 74 is disposed
between the top wall 15 of the outer cabinet 12 and the top panel
28 of the inner cabinet inner 20 outwardly of the first air circulation
duct 32 and the second air circulation duct 52. A separation wall
48 spaced the top wall 15 and the separation wall 46 separates the
third air duct 74 from the second air circulation duct 52.
The first air circulation duct 32 extends in fluid communication
between a first discharge outlet 34 and refrigeration compartment
40, opening thereto at a point downstream of the evaporator 50,
and a first air inlet 42, disposed at the lower front lip of the
refrigerator merchandiser and opening to the refrigeration compartment
40 upstream of the air mover 60. Air mover 60 serves to draw air
from the display region 30 through the first air inlet 42, thence
through the compartment 40 so as to traverse evaporator 50, and
thence through duct 32 to a first air discharge outlet 34. As noted
before, this circulating air has been refrigerated, i.e. cooled,
to a desired temperature as it traverses the evaporator 50.
The third air duct 74 extends between a second discharge outlet
70 and an opening through the top wall 15 to the environment exterior
of the refrigerated merchandiser 10, i.e. the store enviroment.
An air mover 72, such as for example one or more fans, serves to
draw ambient air from the environment exterior of the refrigerator
10 through the third air duct 74 to the second air discharge outlet
70. The second air circulation duct 52 extends in fluid communication
between a third discharge outlet 58 and a second air inlet 54 disposed
at the lower front lip of the refrigerator merchandiser outwardly
of the first air inlet 42. Air mover 62, such as for example one
or more fans, draws air through the second air inlet 54 into and
through the second air circulation duct 52 to the third discharge
outlet 58. The air drawn through the second air inlet 54, which
lies outboard of the first air inlet 42 and adjacent the store environment
will constitute a mix of cool refrigerated air and the warmer ambient
air from the store environment.
Referring now also to FIG. 2, the first discharge outlet 34, the
third discharge outlet 58 and the second discharge outlet 70 are
disposed in side-by-side relationship at the forward lip of the
top front of the cabinet 12. The first discharge outlet 34 lies
closest to the open front of the display region 30 and constitutes
the innermost discharge outlet. The second discharge outlet 70 lies
further from the open front of the display region 30 and constitutes
the outermost discharge outlet. The third discharge outlet 58 lies
between the first discharge outlet 34 and the second discharge outlet
70 and constitutes an intermediate discharge outlet.
From the first discharge outlet 34, the cool refrigeration air
discharging from the first air circulation duct 32 is directed via
guide member 36 provided within the first discharge outlet 34 downwardly
along first path 45 across the open front of the product display
region 30 to air inlet 42, thereby forming a primary air curtain
55 of cool refrigeration air across the open-front product display
region 30. To provide further cooling air directly to the product
display region 30, a plurality of openings 23 may be provided in
the back panel 26 through which a portion of cool refrigeration
air circulating through duct 32 may pass directly into the product
display region 30. This refrigeration air will also be drawn by
the air mover 60 back through the air inlet 42 into the compartment
40 to be recirculated. Thus, the refrigerating air is recycled and
repeatedly recirculated through the compartment 40 and duct 32 to
converse energy expended in cooling the refrigeration air.
From the second discharge outlet 70, ambient air drawn from the
environment exterior of the refrigerated merchandiser 10 and discharging
from the duct 74 is directed by guide member 76 provided within
the second discharge outlet 70 downwardly along a second path 75
across the open front of the product display region, thereby forming
a tertiary air curtain 65. The tertiary air curtain 65 lies outwardly
of the secondary air curtain 85.
From the third discharge outlet 58, the air discharging from the
second air circulation duct 52 is directed via guide member 56 provided
within the third discharge outlet 58 downwardly along third path
95 across the open front of the product display region 30 to the
second air inlet 54, thereby forming a secondary air curtain 85
of cool refrigeration air across the open-front product display
region 30. The secondary air curtain 85 lies outwardly of the primary
air curtain 55 and inwardly of the tertiary air curtain 65. The
guide members 36, 56 and 76 may each comprise a plurality of vanes
defining passages therebetween, a honeycomb matrix defining a plurality
of passageways, or other structure defining a plurality of parallel
passageways through which the air flow discharging through the outlet
is directed along a desired path.
The primary air curtain 55, which constitutes a stream of cool
refrigeration air, has a relatively cool temperature compared to
the tertiary air curtain 65, which constitutes a stream of ambient
air and therefore has a relatively warm temperature. The secondary
air curtain 85 has a temperature lying between the temperature of
the primary air curtain 55 and the tertiary air curtain 65. The
specific temperature of the secondary air curtain 85 will dependent
upon the amount of entrainment of ambient air from the tertiary
air curtain 65 into the secondary air curtain 85. The secondary
air curtain 85 serves as a barrier to significantly reduce entrainment
of ambient air from the tertiary air curtain 65 and the environment
exterior of the open front display case into the primary air curtain
55.
The tertiary, i.e. outer, air curtain 65 of relatively warmer air
drawn from the environment exterior of the refrigerated merchandiser
10 is directed downwardly and outwardly along the second path 75
at an angle of divergence, angle A, away from the first path 45
associated with the primary, i.e. inner, air curtain 55. The secondary,
i.e. intermediate, air curtain 85 is directed downwardly along the
third path 95 at a first interior angle, angle B, with the first
path 45 associated with the primary, i.e. inner, air curtain 55,
and at a second interior angle, angle C, with the second path 75
associated with the tertiary, i.e. outer, air curtain 65. The divergent
angle A has a magnitude ranging from about 10 degrees to about 70
degrees. The first interior angle, angle B, has a magnitude ranging
from about 5 degrees to about 35 degrees. The second interior angle,
angle C, has a magnitude ranging from about 5 degrees to about 35
degrees, and most advantageously ranging from about 15 degrees to
about 35 degrees.
In this manner, a relatively warm outer air curtain 65 is formed
outside, i.e. further away from the product display region 30, of
the relatively cool refrigerated inner air curtain 55 with an intermediate
air curtain 85 that has a temperature intermediate that of the relatively
cool refrigerated inner air curtain 55 and the relatively warmer
outer air curtain 65. The relatively warm outer air curtain 65 serves
as a buffer between the intermediate air curtain 85 and the ambient
environment of the store, while the intermediate air curtain 85
serves as a buffer between the inner air curtain 55 and the relatively
warm ambient temperature outer air curtain 65. Further, as the primary
air curtain 55, the secondary air curtain 85 and the tertiary air
curtain 65 diverge one from another as the respective air curtains
pass generally downwardly, the amount of entrainment of warm air
from the tertiary, i.e. outer air curtain 65, and the store environment
into the cool refrigerated primary, i.e. inner, air curtain 55 is
significantly reduced. Further, when the tertiary air curtain 65
reaches the base region of the display cabinet 12, it passes outwardly
into the store rather than into either of the inlets 42 or 54 in
the forward end of the base portion of the cabinet 12. Consequently,
the entrainment of warm air into the relatively cool inner air curtain
and subsequent passage through inlet 42 into the compartment 40
is minimized, thereby reducing energy consumption in cooling the
recirculating refrigeration air.
In the embodiment of the refrigerated merchandiser depicted in
FIGS. 1 and 2, the third discharge outlet 58, lying intermediate
the first discharge outlet 34 and the second discharge outlet 70,
is disposed at an angle B with the first air outlet 34 in the range
from about 5 degrees to about 35 degrees and provided with axial
guide member 36 such that the secondary air curtain 85 is directed
to diverge away from the primary air curtain 55. Also, the second
discharge outlet 70, lying outwardly of the third discharge outlet
58, is disposed at an angle A with the first air outlet 34 in the
range from about 10 degrees to about 70 degrees and at an angle
C with the third air outlet 58 in the range from about 5 degrees
to about 35 degrees. The second discharge outlet 70 is provided
with axial guide member 76 such that the tertiary air curtain 65
is directed to diverge away from the secondary curtain 85. The first
discharge outlet 34, which lies inwardly of the third discharge
outlet 58, is disposed generally perpendicularly to the open front
of the display region 30 and is provided with axial guide member
36 such that the primary air curtain is directed generally along
the open front of the display region 30.
Alternatively, the first discharge outlet 34, the second discharge
outlet 70 and the third discharge outlet 58 may be disposed in the
front lip at the top front of the cabinet 12 so as to lie in the
same plane. In this arrangement, the guide member 76 of the second
air outlet 70 and the guide member 56 of the third discharge outlet
58 are not axially arrayed within their respective discharge outlets,
but rather would be positioned angularly so as to direct the respective
air streams passing therethrough outwardly away from the open front
of the display region at the desired angle. Thus, the guide member
76 of the second discharge outlet would be positioned so as to direct
the tertiary air curtain 65 along the second path 75 so as to diverge
from the inner air curtain 55 flowing along the first path 45 by
an angle ranging from about 10 degrees to about 70 degrees. Similarly,
the guide member 56 would be positioned within the third discharge
outlet 58 so as to direct the secondary air curtain 85 along the
third path 95 at a first interior angle with respect to the first
path 45 ranging from about 5 degrees to about 35 degrees and at
a second interior with respect to the second path 75 ranging from
about 5 degrees to about 35 degrees. Further, the guide members
56 and 76, may be made adjustable such that the angle at which the
secondary and tertiary air curtains diverges from the first air
curtain and with respect to each other may be selectively adjusted
within a range of preselected angles.
The entrainment of fluid from the second environment into the first
environment across the interface therebetween, for example the entrainment
of ambient air from the store into the display region through the
open front thereof, may be further reduced by controlling the relative
discharge velocities of the respective air curtains. The term discharge
velocity refers to the velocity of the air stream discharging from
its respective air outlet. For the refrigerated merchandiser depicted
in FIGS. 1 and 2, the discharge velocity of the primary air curtain
55 is the velocity of the air stream discharging from first discharge
outlet 34, the discharge velocity of the secondary air curtain 85
is the velocity of the air stream discharging from the third discharge
outlet, and the discharge velocity of the tertiary air curtain 65
is the velocity of the air stream discharging from the second discharge
outlet 70. The discharge velocity of the secondary air curtain should
be maintained greater than the discharge velocity of the primary
air stream, and the discharge velocity of the tertiary air stream
should be maintained greater than the discharge velocity of the
secondary air stream. Advantageously, the discharge velocity of
the secondary air curtain should be maintained in a range from 1.2
to 2.4 times the discharge velocity of the primary air curtain and
the discharge velocity of the tertiary air curtain should be maintained
in a range from 1.2 to 2.4 times the discharge velocity of the secondary
air curtain. Maintaining the respective air curtain velocity ratios
within the aforenoted ranges minimizes the velocity gradient, and
therefore shear instabilities, between the adjacent air curtains
along the length of the interface between the adjacent air curtains,
thereby resulting in less entrainment of air from the higher velocity
air curtain into the lower velocity air curtain. The exact optimal
air curtain velocity ratios in any given application are dependent
upon the absolute discharge velocities of the respective air curtains
and the particular geometry of the application, including the respective
discharge angles of the primary, secondary and tertiary air curtains.
The present invention has been described herein in detail as applied
to a refrigerated merchandiser of the type customarily found in
supermarkets and like establishments. It is to be understood, however,
that the aforementioned description is exemplary, not limiting.
Rather, the present invention may be readily applied in other applications
wherein it is desired to limit passage of fluid between a first
environment that includes a first fluid at a first condition and
interfaces with a second environment that includes a second fluid
at a second condition.
For purposes of this invention, it is to be understood that the
discharge velocity referred to herein may be expressed in conventional
terms as units of distance per unit of time, e.g. meters per second,
or as a mass flow rate, that is in units of kilograms per minute,
or the like.
Many modifications and variations of the present invention may
be recognized by those skilled in the art in light of the above
teachings that will fall within the spirit and scope of the present
invention. The preferred embodiments of this invention have been
disclosed. Accordingly, within the scope of the appended claims,
the invention may be practiced otherwise than as specifically described.
For this reason the following claims should be studied to determine
the true scope and content of this invention. |