US20130316635A1

US20130316635A1 - Module, Device and Method for Providing a Fluid Curtain

Info

Publication number: US20130316635A1
Application number: US13/903,780
Authority: US
Inventors: Tomi Sipilä; Kimmo Heinavaara
Original assignee: Norpe Oy
Current assignee: Norpe Oy
Priority date: 2012-05-28
Filing date: 2013-05-28
Publication date: 2013-11-28
Also published as: EP2668875A1; EP2668875B8; TR201809561T4; EP2668875B1; FI125239B; RU2013125360A; LT2668875T; FI20125567A; PL2668875T3; DK2668875T3

Abstract

A module with a flow channel for providing a fluid curtain, such as an air curtain, between different environments, comprises an inlet for introducing a fluid flow through said flow channel of the module and an outlet for introducing said fluid curtain. In addition the module comprises a honeycomb structure with plurality of parallel conduits before the outlet in order to laminarize the flow for the fluid curtain, and guiding the flow and suppressing instabilities in the flow downstream of it. Furthermore the module comprises a mechanical structure before the outlet. The mechanical structure is configured to change the velocity profile of the flow before the honeycomb structure or during the honeycomb structure so that the velocity profile of the flow after the honeycomb structure or outlet is a smooth skewed parabolic velocity profile with a peak shifted from the centre line of the symmetrical parabolic velocity profile.

Description

FIELD

The invention relates to a module, method and arrangement for providing a fluid curtain, such as an air curtain, between different environments, such as between two spaces with different temperatures and/or concentrations.

BACKGROUND

Devices with fluid curtains separating two different environments having common opening interface but different conditions, such as temperature or concentration, are previously known for example in technical fields of refrigeration apparatuses but also a clean work area. The separation barrier is needed to minimize the mixing of different conditions with each other, such as temperature, different types of particles like microbes, concentration or the like. It is noticed that entrained ambient air into the cold air curtain in the refrigeration apparatuses is the largest thermal load of a multi-deck type or “vertical” refrigerated display case and according to some estimates 75% of the refrigeration load comes from the air curtain entrainment. In addition different types of air curtains are also used in laminar air flow work stations, such as is described in U.S. Pat. No. 4,927,438 A.
As an example the patent publication U.S. Pat. No. 7,162,882 B2 (see Prior Art FIG. 1) discloses a multi-band air curtain forming 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 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 generally outwardly at an angle of divergence with the first path. A third stream (85) of a fluid is directed along a third path between the first path and the second path. 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 (68) air outlets for directing air streams across the open front of the refrigerated merchandiser.
There are however some disadvantages relating to the known prior art, such as turbulent transition layer between the air curtain and at least another environment. The more turbulent transition layer the more entrainment of the ambient air into the air curtain occurs. In addition the need of at least two or even more air curtains is clear disadvantage.

SUMMARY

An object of the invention is to alleviate and eliminate the problems relating to the known prior art. Especially the object of the invention is to provide a method and module for providing a fluid curtain between different environments such as environments with different temperatures, contents and/or concentrations, like bacterial content, so that the entrainment of the ambient fluid into the fluid curtain is minimized.
The object of the invention can be achieved by the features of independent claims.
The invention relates to a module according to claim 1. In addition the invention relates to an arrangement of claim 7, and method of claim 8.
According to an embodiment of the invention a fluid curtain, such as an air curtain, between different environments is provided via a honeycomb structure comprising plurality of parallel conduits. The conduits are configured to laminarize the flow for the fluid curtain, and to guide the flow and suppressing instabilities in the flow downstream of it. The suppressing of instabilities is performed at least in perpendicular direction to walls of said conduits. According to an example the Reynolds number of flow when flowing out from the honeycomb structure is advantageously below 6000, more advantageously below 5000 and most advantageously around 1000. However, it is to be noted that these ranges or values are only examples and that the invention is not limited only to those.
In addition according to an embodiment the velocity profile of the flow before the honeycomb structure or during the honeycomb structure is changed so that the velocity profile of the flow after the honeycomb structure is a (advantageously smooth) skewed parabolic velocity profile with a peak shifted from the centre line of the symmetrical parabolic velocity profile. According to an exemplary embodiment the peak is shifted towards the first environment, such as towards inside of the refrigerated display case. The invention offers clear advantages over the known prior art, when the inventors have noticed that the shape of vertical velocity profile and the turbulence intensity present at the outlet nozzle will remarkably control the fluid curtain entrainment rate. For example when applying the velocity profile as proposed by the present invention the relative velocity and change of relative velocity in the transition layer with the second environment fluid (such as warm ambient air) is small, which keeps the transition layer with the second environment fluid as laminar as possible thereby minimizing entrainment of the ambient fluid into the fluid curtain. By minimizing the entrainment of the ambient fluid the thermal or particle load of the systems and thereby the refrigeration or cleaning costs of the display case can be remarkable reduced.
The term entrainment is used in this document for example to the purpose of to transfer air or other fluid (or even particles) into an organized fluid current (such as an air curtain) from the surrounding atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

Next the invention will be described in greater detail with reference to exemplary embodiments in accordance with the accompanying drawings, in which:

FIG. 1 illustrates a prior art device for providing air curtains;

FIG. 2 illustrates an exemplary module for providing fluid curtain according to an advantageous embodiment of the invention; and

FIG. 3 illustrates an exemplary arrangement (a refrigerated display case) for providing fluid curtain according to an advantageous embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a prior art device for providing air curtains described in U.S. Pat. No. 7,162,882 B2. FIG. 1 is already handled in connection with the background of the invention chapter above. Anyway it is to be understood that the module and inventive concept of the present invention can also be implemented with similar devices as described in FIG. 1, where the air curtain providing means can be replaced for example by the module of the invention described in FIG. 2 or with the means of said module, such as an appropriate mechanical structure before the outlet for the air curtain, where said mechanical structure is configured to change the velocity profile of the flow before the honeycomb structure or during the honeycomb structure so that the velocity profile of the flow after the honeycomb structure or outlet is a smooth skewed parabolic velocity profile with a peak shifted from the centre line of the symmetrical parabolic velocity profile.
FIG. 2 illustrates an exemplary module 100 for providing a fluid curtain, and especially an air curtain 101 between different environments (Environment I, Environment II) according to an advantageous embodiment of the invention, where the module comprises a flow channel 102. The module 100 comprises an inlet 103 for introducing an air flow through the flow channel of the module and an outlet 104 for outputting said air curtain. In addition the module 100 comprises a honeycomb structure 105 before the outlet in order to laminarize the flow for the air curtain. The honeycomb structure comprises plurality of parallel conduits 106 for guiding the flow and suppressing instabilities in the flow downstream of it and at least in perpendicular direction to walls of said conduits 106.
In addition the module 100 comprises a mechanical structure 105, 107 before the outlet 104, which is configured to change the velocity profile of the flow 101 before 107 the honeycomb structure or during 105 the honeycomb structure so that the velocity profile of the flow after the honeycomb structure 105 or outlet 104 is a smooth skewed parabolic velocity profile with a peak 108 shifted from the centre line 109 of the symmetrical parabolic velocity profile or the centre line 109 of the honeycomb structure 105.
According to an embodiment the mechanical structure before the outlet is a deflector 107, such as an S-shaped (described in FIG. 2) or convex-shaped deflector, where the convex is configured to protrude towards the honeycomb structure (not shown in Figures). The deflector 107 is advantageously configured to guide the air flow 110 from the inlet 103 to the honeycomb structure 105 so that greater dynamic pressure and thereby the greater fluid velocity is introduced to the distance from the centre line 109 of the honeycomb structure, and most advantageously so that the greater dynamic pressure and thereby greater fluid velocity is introduced to the point before the centre line 109 of the honeycomb structure in the direction of the inlet flow 103.
According to an embodiment the form of the deflector 107 in the downstream direction 110 of the inlet flow is convergent, advantageously continuously convergent, and most advantageously continuously but non-linearly convergent towards the honeycomb structure 105. Due to the rounded shapes and smooth surface of the deflector 107 it does not significantly generate turbulence in flow upstream of the honeycomb structure 105, In addition the honeycomb structure 105 itself is a very effective device to suppress the fluid curtain instabilities immediately downstream of it.
In addition according to an embodiment the first curve 107 a of the S-shaped deflector 107 or the peak or apex of the convex-shaped deflector (not shown) is configured to protrude towards the honeycomb structure 105 is located in the downstream direction of the inlet flow 110 before the centre line 109 of the honeycomb structure 105. Furthermore, according to an embodiment the second curve 107 b of the S-shaped deflector 107 is configured to protrude into the opposite direction than the first curve, and is located in the downstream direction of the inlet flow 110 after the centre line 109 of the honeycomb structure 105. According to these embodiment the greater dynamic pressure and thereby the greater fluid velocity can be introduced to the point before the centre line 109 of the honeycomb structure in the direction of the inlet flow 103, and thereby the smooth skewed parabolic velocity profile with a peak 108 shifted from the centre line 109 of the symmetrical parabolic velocity profile or the centre line 109 of the honeycomb structure 105 can be achieved, as is described in FIG. 2.
According to an embodiment the mechanical structure before the outlet 104 is the honeycomb structure 105 with plurality of parallel conduits 106, wherein the cross sectional area of the conduits of the honeycomb structure 105 located in the downstream direction of the inlet flow 110 before the centre line 109 of the honeycomb structure 105 is greater than the diameters of the conduits after the centre line 109 of the honeycomb structure. Also according to this embodiment the smooth skewed parabolic velocity profile with a peak 108 shifted from the centre line 109 of the symmetrical parabolic velocity profile or the centre line 109 of the honeycomb structure 105 can be achieved, as is described in FIG. 2.
FIG. 3 illustrates an exemplary arrangement 200, such as a refrigerated display case, for providing fluid curtain according to an advantageous embodiment of the invention. The device may comprise a display space 201, an access opening 202 in the front of said display space, and a flow curtain providing means 100 for establishing the flow curtain 101 across the access opening 202. Even if the refrigerated display case is described here as an example, it is to be noted that the inventive concept, namely the module 100 or the means and features 101-110 of the module described e.g. in FIG. 2 can be utilized also in other devices separating at least two different environments with the fluid curtain, such as laminar air flow work stations.
The refrigerated display case 200 described in FIG. 3 comprises only one means for producing the fluid curtain, such as only one channel 102, and therefore only one fluid curtain 101. In addition the device 200 comprises a fluid suction means or portion 203 located adjacent the lower edge of the access opening 202, an air duct 204 communicating with said fluid suction means or portion 203 having a fluid discharge outlet 205 near the upper edge of the access opening 202.
The deflector 107 and the honeycomb structure 105, 106 described e.g. in connection with FIG. 2 can be implemented in connection with the fluid discharge opening 205 to provide the fluid curtain 101. However, it is to be noted that the deflector 107 and the honeycomb structure 105, 106 described e.g. in connection with FIG. 2 can also be implemented into the device described in FIG. 1 or 3 as a module described e.g. in connection with FIG. 2.
In addition the device 200 advantageously comprises circulating means 206 for circulating fluid through said fluid duct 204, 205 and again through the deflector 107 and the honeycomb structure 105, 106, as well as through the refrigeration means 207 for example for refrigerating the fluid for the fluid curtain 101.
The device 200 described in FIG. 3 is a recirculated type refrigerated display case, since it comprises the fluid suction means or portion 203 for collecting the chilled fluid of the fluid curtain 101 and recirculating it again. However, the inventive concept and embodiments of the present invention can also be implemented in connection with non-recirculated type devices, such as is described in FIG. 1, where the refrigerated display case comprises also one or more fans 72 or the like to draw ambient air from the environment exterior of the refrigerator 10 through the fluid duct 74 to the second air discharge outlet 70.
According to an advantageous embodiment the flow curtain 101 is created by forcing chilled flow in the duct 205 at the top of the display case 200 into the deflector 107, such as S-shaped deflector. The deflector 107 turns the chilled fluid flow 110 downward through the honeycomb structure 105 and thereby produces a smooth skewed parabolic velocity profile with peak shifted towards the inside of the display case 200 having low temperature (Environment I) compared to the ambient temperature (Environment II).
The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the inventive idea and scope of the inventive thought and the following patent claims. For example the different environments separated by the fluid curtain comprise different conditions, such as temperatures, bacterial contents, humidity, concentration or the like. In addition even though the air curtain is described as an example of the fluid curtain, the same inventive concept can also be applied with other fluids for providing other type fluid curtain, such as gas, like nitrogen, gas mixture or vapour or stream.

Claims

1.-16. (canceled)

17. A module for providing a fluid curtain between different environments, the module comprising:

an inlet configured to introduce a fluid into a flow channel of the module;

an outlet for the fluid, the outlet configured to create a fluid curtain between different environments;

a honeycomb structure located before the outlet and configured to laminarize the flow of the fluid in the fluid curtain, wherein the honeycomb structure comprises a plurality of substantially parallel conduits configured to guide the flow of the fluid and suppress instabilities in the flow of the fluid; and

a mechanical structure located before the outlet, wherein the mechanical structure is configured to change the velocity profile of the flow before or in the honeycomb structure so that the velocity profile of the flow after the honeycomb structure or the outlet comprises a skewed parabolic velocity profile with a peak shifted from the center line of the symmetrical parabolic velocity profile.

18. The module of claim 17, wherein the mechanical structure comprises a deflector configured to guide the fluid flow from the inlet to the honeycomb structure so that a greater dynamic pressure and greater fluid velocity is introduced at a distance from the center line of the honeycomb structure.

19. The module of claim 18, wherein the deflector comprises an S-shaped or convex-shaped deflector.

20. The module of claim 18, wherein the form of the deflector downstream of the inlet flow is convergent, continuously convergent, or continuously but non-linearly convergent towards the honeycomb structure.

21. The module of claim 18, wherein a first curve of the S-shaped deflector or the peak of the convex-shaped deflector towards the honeycomb structure is located downstream of the inlet flow before the center line of the honeycomb structure.

22. The module of claim 21, wherein a second curve of the S-shaped deflector in the opposite direction of the first curve is located downstream of the inlet flow after the center line of the honeycomb structure.

23. The module of claim 17, wherein the mechanical structure comprises the honeycomb structure and wherein the cross sectional area of the conduits of the honeycomb structure located in the downstream direction of the inlet flow before the center line of the honeycomb structure are greater than the diameter of the conduits after the center line of the honeycomb structure.

24. The module of claim 17, wherein the fluid is air, nitrogen, vapor, stream, or combinations thereof.

25. An apparatus, comprising:

a display device containing a display space and an access opening; and

a module located in front of the display space, the module configured to supply a fluid curtain across the access opening, wherein the module comprises:

an inlet configured to introduce a fluid into a flow channel of the module;

26. The apparatus of claim 25, wherein the mechanical structure comprises a deflector configured to guide the fluid flow from the inlet to the honeycomb structure so that a greater dynamic pressure and greater fluid velocity is introduced at a distance from the center line of the honeycomb structure.

27. The apparatus of claim 26, wherein the deflector comprises an S-shaped or convex-shaped deflector.

28. The apparatus of claim 26, wherein the form of the deflector downstream of the inlet flow is convergent, continuously convergent, or continuously but non-linearly convergent towards the honeycomb structure.

29. The apparatus of claim 26, wherein a first curve of the S-shaped deflector or the peak of the convex-shaped deflector towards the honeycomb structure is located downstream of the inlet flow before the center line of the honeycomb structure.

30. The apparatus of claim 29, wherein a second curve of the S-shaped deflector in the opposite direction of the first curve is located downstream of the inlet flow after the center line of the honeycomb structure.

31. The apparatus of claim 25, wherein the mechanical structure comprises the honeycomb structure and wherein the cross sectional area of the conduits of the honeycomb structure located in the downstream direction of the inlet flow before the center line of the honeycomb structure are greater than the diameter of the conduits after the center line of the honeycomb structure.

32. The apparatus of claim 25, wherein the fluid is air, nitrogen, vapor, stream, or combinations thereof.

33. A method for providing a fluid curtain between different environments, the method comprising:

introducing a fluid flow into an inlet of a module, the module comprising an outlet configured to create a fluid curtain between different environments;

laminarizing the fluid flow of the fluid curtain via a honeycomb structure which contains a plurality of substantially parallel conduits configured to guide the flow of the fluid and suppress instabilities in the flow of the fluid; and

changing the velocity profile of the flow before or in the honeycomb structure so that the velocity profile of the flow after the honeycomb structure or the outlet comprises a skewed parabolic velocity profile with a peak shifted from the center line of the symmetrical parabolic velocity profile.

34. The method of claim 33, wherein the velocity profile is changed by a deflector configured to guide the fluid flow from the inlet to the honeycomb structure so that a greater dynamic pressure and greater fluid velocity is introduced at a distance from the center line of the honeycomb structure.

35. A method of claim 33, wherein the cross sectional area of the conduits of the honeycomb structure located in the downstream direction of the inlet flow before the center line of the honeycomb structure is greater than the diameters of the conduits after the center line of the honeycomb structure.

36. The method of claim 33, wherein the fluid is air, nitrogen, vapor, stream, or combinations thereof.