EP1587400A2

EP1587400A2 - Method for establishing an air curtain separation barrier

Info

Publication number: EP1587400A2
Application number: EP04700344A
Authority: EP
Inventors: Mary D. Saroka; Abbas A. Alahyari
Original assignee: Carrier Comercial Refrigeration Inc
Current assignee: Taylor Commercial FoodService LLC
Priority date: 2003-01-07
Filing date: 2004-01-06
Publication date: 2005-10-26
Anticipated expiration: 2024-01-06
Also published as: BRPI0406648A; EP1587400A4; WO2004062762A2; WO2004062762A3; MXPA05007351A; HK1089341A1; JP2006514574A; EP1587400B1

Abstract

A method is disclosed 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. A first stream (55) of a fluid is directed along a first path (45) between the first environment and the second environment and a second stream of fluid (65) is directed along a second path (75) between the first stream of fluid and the second environment. A desired parametric relationship is maintained between the first fluid stream and the second fluid stream thereby decreasing passage of fluid from either of the first and second environments to the other of the first and second environments.

Description

METHOD FOR ESTABLISHING AN AIR CURTAIN SEPARATION BARRIER

[001] This application is a continuation-in-part of copending application serial number 10/337,591, filed January 7, 2003. This application is also a continuation-in-part of copending application serial number 10/374,640, filed February 26, 2003.

BACKGROUND OF THE INVENTION

[002] The present invention relates generally to air curtains for separating a first environment from a second environment. The method of the present invention mat 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.

[003] 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.

[004] 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. Patent 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.

[005] 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. Patent 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. Patents 3,648,482 and 3,850,003, MacMaster et al, in U.S. Patent 3,827,254 and Roberts, in U.S. Patent 5,345,778 and U.S. patent 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. Further, providing three separate air flow circuits for generating the three independent air streams increases the complexity and cost of the display case. Consequently, a need exists for a refrigeration system that addresses the problem encountered by the interaction of warm air outside of the display case and the air curtain without significant expense.

SUMMARY OF THE INVENTION

[006] Broadly, the present invention provides 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. The method includes the steps of: directing a first stream of a fluid along the interface between the first environment and the second environment, directing a second stream of fluid between the first stream of fluid and the second environment, and maintaining a desired parametric relationship between the first fluid stream and the second fluid stream thereby decreasing passage of fluid from either of the first and second environments to the other of the first and second environments [007] The step of maintaining a desired parametric relationship between the first fluid stream and the second fluid stream, thereby decreasing passage of fluid from either of the first and second environments to the other of the first and second environments, may include maintaining the ratio of the velocity of the second stream of fluid to the velocity of the first stream of fluid within a desired range, advantageously, by maintaining the ratio of the velocity of the second stream of fluid at a velocity at least about 1.4 times the velocity of the first stream of fluid, and most advantageously within the range from about 1.4 to about 1.8 times the velocity of the first stream of the fluid.

[008] The step of maintaining a desired parametric relationship between the first fluid stream and the second fluid stream, thereby decreasing passage of fluid from either of the first and second environments to the other of the first and second environments, may include maintaining the mass flow rate of the second stream of fluid the ratio of the mass flow rate at a mass flow rate at least about 1.4 times the mass flow rate of the first stream of fluid. The step of maintaining a desired parametric relationship between the first fluid stream and the second fluid stream may also include maintaining the ratio of the second stream of fluid to the mass flow rate of the first stream of fluid within a desired range, advantageously, by maintaining the ratio of the velocity of the second stream of fluid to the velocity of the first stream of fluid within the range of from about 1.4 to about 1.8.

[009] The separation barrier may also be established be directing a first stream of a fluid along a first path between the first environment and the second environment and directing a second stream of fluid along a second path between the second environment and the first stream of fluid at an angle of divergence with the first path, while maintaining the angle of divergence between the first and second paths within a desired range. Advantageously, the angle of divergence is maintained with the range of about 5 degrees to about 50 degrees, and most advantageously within the range of about 35 degrees to about 45 degrees. [010] Further, the first fluid may be drawn from the first environment and the second fluid may be drawn from the first environment. The method of the present invention may be employed to establish a particularly effective dual air curtain for a refrigerated display to provide a separation barrier between the product display area of the refrigerated display case, i.e. the first environment, and the ambient area of the store in front of the display case, i.e. the second environment.

BRIEF DESCRIPTION OF THE DRAWINGS

[011] 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:

[012] Figure 1 illustrates a side elevation profile of a refrigerated merchandiser having an open-front display case showing an outer air curtain and an inner air curtain directed across a product display region of the case in a divergent relationship;

[013] Figure 2 illustrates a side elevation profile of a refrigerated merchandiser having an open-front display case showing an outer air curtain and an inner air curtain directed across a product display region of the case in a parallel relationship;

[014] Figure 3 illustrates graphically the variation in air curtain performance as the relative velocity of two parallel air curtains changes; and

[015] Figure 4 illustrates graphically the variation in air curtain performance as the angle of divergence between the two divergent air curtains changes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[016] The method of the present invention will be described hereinafter in application on a refrigerated merchandiser for the purpose of establishing an 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 method of the present invention has a much broader application. Broadly, the present invention provides 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. 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.

[017] Referring now to Figures 1 and 2, 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 22 and opposed side panels 24 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. [018] Perishable product 80 being merchandized may be displayed on shelves 12 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°F to less than about 40°F, depending upon what product is being merchandised therein and whether the product is frozen or non-frozen.

[019] The refrigerated merchandiser 10 further includes a refrigeration compartment 40, typically disposed in the portion of the display cabinet 12 between the base 13 and the bottom panel 24, as depicted in Figure 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 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 standalone refrigerated merchandisers that include their own refrigeration unit for providing the cold refrigerant.

[020] An air circulation duct 32 is 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. Air mover 60 serves to direct air from air inlet 42 through the compartment 40 so as to traverse evaporator 50, and thence through duct 32 to a first air outlet 34. As noted before, this circulating air has been cooled to a desired temperature as it traverses the evaporator 50. From the first air outlet 34, the cool refrigeration air is directed via vanes 36 provided within the first air outlet 34 downwardly along first path 45 across the open front 25 of the product display region back to air inlet 42. 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. Further, through the afore-described cooling arrangement, a cool air curtain 55 is formed across the open-front product display region 30 from top to bottom thereof. To provide further cooling air directly to the product display region 30, a plurality of openings may be provided in the back panel 26 through which a portion of cold refrigerating air circulating through duct 32 may pass directly into the product display region 30. This refrigerating air will also be drawn by the air mover back through the air inlet 42 into the compartment 40 to be recirculated.

[021] A second air outlet 70 is provided outwardly of the first air outlet 34 at the top front of the cabinet 12. The second air outlet 70 serves to direct relatively warm air drawn from the store environment generally downwardly along a second path 75. In the embodiment illustrated in Figure 1, the second path 75 diverges from the first path 45 followed by the cool refrigerating air. In the embodiment illustrated in Figure 2, the second path 75 lies essentially parallel to the first path 45.

[022] 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 inner air curtain 55. The relatively warm outer air curtain 65 serves as a buffer between the relatively cool inner air curtain 55 and the ambient environment of the store. Further, as the relatively warm outer air curtain 65 diverges from the relatively cool inner air curtain 55 the respective air curtains pass generally downwardly, the amount of entrainment of warm air from the outer air curtain 65 into the cooler inner air curtain 55 is minimized. Further, when the outer air curtain 65 reaches the base region of the display cabinet 12, it passes outwardly into the store rather than into the air inlet 42 in the forward end of, the base portion of the cabinet. 13 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. [023] As shown in greater detail in Figure 2, the first air outlet 34 and second air outlet 70 are located at top and forward region of display case 12, with the second air outlet 70 being located outwardly of the first air outlet 34, that is, closer to the front of the display cabinet 12. As noted previously, first air outlet 34 is in communication with duct 32 and directs relatively cool air driven by air mover 60 downwardly along path 45 across open front of the product display region 30 to form the inner air curtain 55. The second air outlet 70 is in fluid communication with a source of relatively warm air and directs relatively warm air driven by a second air mover 72 associated therewith downwardly along path 75 to form an outer air curtain 65 that diverges from the inner air curtain 55.

[024] In the embodiment depicted in Figure 1 , a plenum chamber 72 provided at the forward lip of the top wall 15 of the cabinet 12. The second air outlet 70 and an ambient air inlet 74 open into the plenum chamber 72. An air mover 76, such as an axial flow fan, is provided in operative association with the inlet 74. In operation, the air mover 74 draws ambient air from the store into and through the plenum chamber 72 and thence out the second air outlet 70 to form the relatively warm outer air curtain 65. The second air outlet 70 may, as shown in Figure 1 , lie in the same plane as the first air outlet 34. In this case, the second air outlet 70 is provided with guide vanes 78, positioned so as to direct the relatively warm air passing therethrough to form the outer air curtain 65 along path 75 so as to diverge from the inner air curtain 55 flowing along path 45. The guide vanes 78 may be adjustable such that the angle at which the second air curtain diverges from the first air curtain may be selectively adjusted within a range of preselected angles. Alternatively, the second air outlet 70 may be disposed at an angle with the first air outlet 34 and provided with axial guide vanes 78 such that the outer air curtain 65 is naturally directed to diverge away from the inner air curtain 55.

[025] In accordance with one aspect of the method of the present invention, the outer air curtain of relatively warmer air is directed downwardly and outwardly away from the inner air curtain at a divergent angle A of about 5 degrees to about 55 degrees, and more advantageously at a divergent angle A of about 25 degrees to about 50 degrees, and even more advantageously at an angle A about 35 degrees to about 45 degrees. Referring now to Figure 4, the vertical axis thereof represents an entrainment factor developed to qualitatively determine the degree of entrainment of warm air into the cool air. The entrainment factor is the ratio of the difference between the measured temperature of the return air passing through the return air inlet 42 and the measured temperature of the cool refrigerated air discharging through the first air outlet 34 to the difference between the measured temperature of the warm air discharging through the second air outlet 70 and the measured temperature of the cool refrigerated air discharging through the first air outlet 34. The lower the magnitude of the entrainment factor, the lesser the degree of entrainment of warm air into the return air. The horizontal axis represents the divergent angle A, that is the included angle between the inner air curtain 55 and the outer air curtain 65 as these air curtains diverge as they flow generally downwardly from the first air outlet 34 and the second air outlet 70, respectfully. As seen in Figure 4, the entrainment of relatively warm air into the return air stream entering the return air inlet 42 was minimized when the divergent angle A between the inner and outer air curtain was about 40 degrees. However, significant reductions in entrainment occurred over a wide range of divergent angles.

[026] In the embodiment depicted in Figure 2, the second air outlet 70 is provided with guide vanes 78 positioned so as to direct the relatively warm air passing therethrough to form the outer air curtain 65 along path 75 that is essentially parallel to the path 45 along which the inner air curtain 55 flows. The second air curtain flows downwardly along but to the outside of the first air curtain and is directed so as to spill over back into the store rather than enter the compartment 40 through the return air inlet 42. In accordance with another aspect of the method of the present invention, the outer air curtain 65 is directed downwardly at a discharge velocity that is at least 1.4 times greater than the discharge velocity of the inner air curtain 55. The term discharge velocity refers to the velocity of the air stream discharging from its respective air outlet at the top of the display case 30. Ergo, the discharge velocity of the inner air curtain 55 is the velocity of the air stream discharging from air outlet 34 and the discharge velocity of the outer air curtain 65 is the velocity of the air stream discharging from air outlet 70. [027] Referring now to Figure 3, the vertical axis thereof represents the load reduction factor , which is the refrigeration load of the dual air curtain compared to the load for an inner air curtain only, and the horizontal axis represents the ratio of the velocity of the outer air curtain in that of the inner air curtain. Accordingly, the lower the load reduction factor, the more effective is the dual air curtain. As illustrated in Figure 3, the effectiveness of a dual curtain flow barrier in reducing passage of flow across the air curtain is maximized by maintaining the ratio of the discharge velocity of the outer curtain to the discharge velocity of the inner curtain within the range of from about 1.4 to about 1.8. Maintaining the air curtain velocity ratio within this range 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. Therefore, an very effective separation barrier may be maintained between two environments through use of the present invention through a dual air curtain of parallel streams of a first and a second fluid by maintaining the discharge velocity of the outer air stream a level of about 1.4 to about 1.8 times faster than the discharge velocity of the inner air stream.

[028] The method of 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 method of 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.

[029] Various other parameters, other than velocity or angle of divergence, may also be employed in formulating a desired parametric ration. For example, the relative mass flow rate may be used. That is, a separation barrier may be established between a first environment and a second environment by directing the first stream of fluid along the interface at a first mass flow rate, directing the second stream between the first stream of fluid and the said second environment at a second mass flow rate, and maintaining the ratio of the mass flow rate of the second stream of fluid to the mass flow of the first stream of fluid within a desired range. Advantageously, the mass flow rate of the of the second fluid stream would be at 1.4 times the mass flow rate of the first fluid stream and, most advantageously, within the range of 1.4 to 1.8 times grater than that of the first fluid stream.

[030] 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.

Claims

CLAIMSWhat 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 a fluid along the interface between said first environment and said second environment; directing a second stream of fluid between said first stream of fluid and said second environment; and maintaining a desired parametric relationship between said first fluid stream and said second fluid stream thereby decreasing passage of fluid from either of said first and second environments to the other of said first and second environments.

2. 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 stream of fluid along the interface at a first velocity; directing the second stream between the first stream of fluid and the fluid from said second environment at a second velocity; and maintaining the velocity of the second stream of fluid at a velocity at least 1.4 times the velocity of the first stream of fluid.

3. 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 stream of fluid along the interface at a first velocity; directing the second stream between the first stream of fluid and the fluid from said second environment at a second velocity; and maintaining the ratio of the velocity of the second stream of fluid to the velocity of the first stream of fluid within a desired range.

4.. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 3 further comprising maintaining the ratio of the velocity of the second stream of fluid to the velocity of the first stream of fluid within the range of from about 1.4 to about 1.8.

5. 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 stream of fluid along the interface at a first mass flow rate; directing the second stream between the first stream of fluid and the fluid from said second environment at a second mass flow rate; and maintaining the ratio of the mass flow rate of the second stream of fluid to the mass flow of the first stream of fluid within a desired range.

6. 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 mass flow rate of the second stream of fluid to the mass flow rate of the first stream of fluid within the range of from about 1.4 to about 1.8.

7. 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 stream of fluid along a first path; directing the second stream between along a second path between said second environment and the first stream of fluid and the fluid from said second environment along a second path at an angle of divergence with the first path; and maintaining the angle of divergence between the first and second paths within a desired range.

8. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 6 further comprising maintaining the angle of divergence between the first and second paths within the range of from about 5 degrees to about 50 degrees.

9. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 6 further comprising maintaining the angle of divergence between the first and second paths within the range of from about 35 degrees to about 45 degrees.

9. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 1 further comprising: directing a first stream of a fluid drawn from said first environment along a first path between said first environment and said second environment; directing a second stream of fluid drawn from said second environment along a second path between said second environment and said first stream of fluid drawn from said first environment; and maintaining a desired parametric relationship between said first fluid stream and said second fluid stream thereby decreasing passage of fluid from either of said first and second environments to the other of said first and second environments

10. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 9 further comprising: directing the first stream of fluid along the interface at a first velocity; directing the second stream between the first stream of fluid and the fluid from said second environment at a second velocity; and maintaining the ratio of the velocity of the second stream of fluid to the velocity of the first stream of fluid within a desired range.

11. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 9 further comprising: directing the first stream of fluid along the interface at a mass flow rate velocity; directing the second stream between the first stream of fluid and the fluid from said second environment at a second mass flow rate; and maintaining the ratio of the mass flow rate of the second stream of fluid to the mass flow of the first stream of fluid within a desired range.

12. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 9 further comprising: directing the first stream of fluid along a first path; directing the second stream between the first stream of fluid and the fluid from said second environment along a second path at an angle of divergence with the first path; and maintaining the angle of divergence between the first and second paths within a desired range.

13. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 12 wherein the divergent angle ranges form about 5 degrees to about 50 degrees.

14. A method for establishing a separation barrier between a first environment and a second environment as recited in claim 12 wherein the divergent angle ranges form about 35 degrees to about 45 degrees. 1/3

FIG.1 2/3

FIG.2 3/3

FIG.3

FIG.4