GB2563468A

GB2563468A - Open refrigerated display case and flow stabilising device

Info

Publication number: GB2563468A
Application number: GB1719416.8A
Authority: GB
Inventors: J P Wirth Nicholas
Original assignee: Wirth Research Ltd
Current assignee: Wirth Research Ltd
Priority date: 2017-11-22
Filing date: 2017-11-22
Publication date: 2018-12-19
Anticipated expiration: 2037-11-22
Also published as: WO2019102182A1; GB2563468B; GB201719416D0

Abstract

An open refrigerated display case comprising a display volume, an air outlet 120 and an air inlet 118 between which an air curtain is formed and a flow stabilising beam 128 extending transversely across the display volume wherein a leading edge of the beam is positioned in a region where a notional flow velocity is 87% of a notional peak flow velocity. A plurality of beams may be attached to a plurality of shelves 117 and each may have inner and outer stabilising beams which form two slots. The inner beam may be arranged at a slight angle to a line extending between the shelf it is on and the one below and the inner and outer beams may converge towards each other. Also disclosed is a method of fitting a beam which may involve simulating an air curtain to identify where to position a stabilising beam.

Description

OPEN REFRIGERATED DISPLAY CASE AND FLOW STABILISING DEVICE

The present invention relates to an open refrigerated display case and a flow stabilising device for an open refrigerated display case.

The display of chilled or frozen items is prevalent in many retail environments, most notably in supermarkets. Historically, such items have been displayed in refrigerated display cases having glass doors to allow customers to browse items before opening the doors to access the items. However, the presence of such doors has been seen as problematic in that they make it difficult for several customers to access the contents of the case simultaneously, as well as creating an obstruction when open, narrowing the usable aisle space.

It is therefore commonplace in more recent years for supermarkets to use open-fronted display cases (Open Refrigerated Display Cases; herein “ORDCs”). ORDCs utilise an air curtain which is cooled to below ambient temperature and propelled generally downward, across the open front of the display case. The air curtain separates the refrigerated interior of the display case from the ambient air surrounding the display case. The air curtain thus minimises cool air spillage from inside the display case due to buoyancy effects, and also provides a barrier from other external motions of air around the display case, which could otherwise disturb or displace the cooler air in the display case. ORDCs therefore do not need any physical barrier separating customers from the contents of the display case. Accordingly, ORDCs provide a desirable method of displaying food and other perishable goods as they allow both easy access and clear visibility of merchandise.

However, as a direct consequence of their open design, ORDCs do have significantly higher energy consumption compared to the closed-fronted alternative. The main energy losses occur within the air curtain, and are caused by the entrainment of warm ambient air into the air curtain and the turbulent mixing which occurs within the air curtain itself. The entrainment of warm ambient air causes an increase in temperature within the air curtain, and this warmer air must be cooled as it re-circulates through the system. It has been estimated that 70% to 80% of the cooling load of an ORDC is due to such effects.

In recent years, multi-decked designs have become commonplace to maximise the display space per unit of floor space. Consequently, the air curtains of such ORDCs must seal a larger display volume. This has exacerbated entrainment issues and the resulting energy losses, as well as making the design of air curtains more challenging, particularly in respect of ensuring product integrity and temperature homogeneity while attempting to minimize their energy consumption.

The invention thus seeks to improve the efficiency of ORDCs by reducing entrainment within the air curtain.

According to a first aspect, there is provided an open refrigerated display case comprising: a refrigerated display volume; an air outlet configured to direct airflow out of the air outlet across the display volume toward an air inlet to thereby form an air curtain across the display volume, the air outlet and air inlet defining a notional flow velocity profile; a flow stabilising device comprising a stabilising beam extending transversely across the display volume and located within the air curtain; wherein the stabilising beam is positioned such that a leading edge thereof is located in a region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

The refrigerated display volume is a volume generally defined between the walls of the ORDC. The air outlet and the air inlet may be connected by a duct such that air can be recirculated from the air inlet back to the air outlet. The duct may comprise a fan or pump for moving air from the air inlet to the air outlet. The duct may also comprise a refrigeration unit for cooling air passing through the duct.

The notional flow velocity profile may be a flow velocity profile of a notional air curtain which would be generated between the air outlet and air inlet if all or one or more of the flow stabilising device or devices were not present. It should be understood that the flow stabilising devices, and in particular the stabilising beams, will alter the actual flow velocity profile of the air curtain. Accordingly, the positioning of the stabilising beams should be based upon the region of the notional flow velocity profile which would otherwise be generated if they were not present. The notional flow velocity profile may never actually be generated by the air outlet and inlet, but it should be understood that it nevertheless can be simulated in order to educate the positioning of the stabilising beams.

The notional flow velocity profile may be measured through a depth or thickness of the notional air curtain in a horizontal direction. The notional flow velocity profile may change with increasing distance from the air outlet. The notional flow velocity profile may generally be described as having a bell-curve profile (having a single peak), although it may be symmetrical or asymmetrical. The notional peak flow velocity is the fastest flow velocity within the notional flow velocity profile at a specific height or distance from the air outlet i.e. at the level at which the flow stabilising device is located.

The stabilising beam may have a length, which extends in the transverse direction across the display volume. The cross-sectional shape of the stabilising beam may be substantially constant along its length. The cross section of the beam may have a height and a thickness. The height may be greater than the thickness such that the cross section of the beam is generally elongate. The beam may be arranged such that the height generally extends in a vertical direction or in a prevailing flow direction of the air curtain.

The refrigerated display volume may comprise a shelf, and the flow stabilising device may be associated with the shelf such that the stabilising beam is arranged outwardly of the shelf in the refrigerated display volume to thereby form an inner slot between the shelf and the stabilising beam.

The display volume may comprise a plurality of shelves. Each shelf may be provided with an associated flow stabilising device.

The stabilising beam may have a cross-section which extends between the leading edge and a trailing edge.

The leading edge of the beam may be the part of the beam which is arranged closest to the air outlet. The leading edge may be the furthest-upstream part of the beam with respect to the air curtain. It should be understood generally that the leading edge of the stabilising beam is the first part of the beam with which the air curtain interacts. Conversely, the trailing edge of the beam may be the part of the beam which is arranged closest to the air inlet. The trailing edge may be the furthest-downstream part of the beam with respect to the air curtain. It should be understood generally that the trailing edge of the stabilising beam is the last part of the beam with which the air curtain interacts. The trailing and leading edges may extend across the majority of the beam.

The cross-section of the stabilising beam may have a width which increases from the leading edge to a maximum thickness and then tapers from the maximum thickness to the trailing edge. The location of the maximum thickness may be located closer to the leading edge than the trailing edge. The stabilising beam may define a chord line which extends between the leading edge and trailing edge of the stabilising beam. The cross-section of the stabilising beam may be symmetrical about the chord line or may be asymmetric. The leading edge may be radiused. The trailing edge may be pointed or may be radiused but with a smaller radius of curvature than the leading edge.

Where multiple flow stabilising devices are provided, at least one of the flow stabilising devices may be arranged such that the chord line of the stabilising beam extends at an angle of around 1.5 to 16.5 degrees to a line or plane defined between a front edge of its associated shelf and the front edge of the subsequent shelf, or in particular at an angle of around 4 to 14 degrees, or at approximately 9 degrees. The subsequent shelf may also be described as the below shelf. Generally, the subsequent shelf is the next shelf away from the air outlet in a prevailing flow direction of the air curtain. For the lowermost shelf (or the lowermost shelf fitted with a flow stabilising device), the angle may be defined with respect to a line or plane formed between the front edge of the shelf and the air inlet. Further, if there is stock which overhangs the flow path, then the angle may be defined with respect to a line or plane formed between the front edge of the shelf and the front edge of the stock.

The stabilising beam may be an inner stabilising beam. The flow stabilising device may further comprise a second outer stabilising beam arranged outwardly from the inner stabilising beam to thereby form an outer slot between the inner and outer stabilising beams.

The inner and outer stabilising beams may be arranged such that the inner and outer beams converge towards their respective trailing edges. The outer slot may therefore be a narrowing or wedge-shaped slot.

The air outlet may comprise at least one of a nozzle, or a flow-straightening device.

The stabilising beam may be positioned such that the leading edge is located in a region in which the notional flow velocity is at least 94% of the notional peak flow velocity.

The stabilising beam may be positioned such that the leading edge is located in a region in which the notional flow velocity is substantially equal to the notional peak flow velocity.

In a second aspect, there is provided a method of configuring an open refrigerated display case, comprising: providing a refrigerated display volume; forming an air curtain across the display volume by directing airflow out of an air outlet across the display volume toward an air inlet, wherein the air outlet and air inlet define a notional flow velocity profile; and arranging a flow stabilising device comprising a stabilising beam extending transversely across the display volume such that a leading edge of the stabilising beam is the stabilising beam is positioned in a region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

The method may further comprise, prior to arranging the flow stabilising device, forming or simulating a preliminary air curtain having the notional flow velocity profile to thereby locate the region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

The refrigerated display volume may comprise a shelf. The flow stabilising device may be associated with the shelf and arranged such that that the stabilising beam is arranged outwardly of the shelf in the refrigerated display volume to thereby form an inner slot between the shelf and the stabilising beam.

Arranging the flow stabilising device may comprise arranging the inner and outer stabilising beams such that they converge towards their respective trailing edges.

The flow stabilising device may be arranged such that the leading edge of the stabilising beam is positioned in a region in which the notional flow velocity is at least 94% of the notional peak flow velocity.

The flow stabilising device is arranged such that the leading edge of the stabilising beam is positioned in a region in which the notional flow velocity is substantially equal to the notional peak flow velocity.

The skilled person will appreciate that, except where mutually exclusive, a feature described in relation to either of the above aspects may be applied mutatis mutandis to any other aspect. Accordingly, any feature described with respect to the open refrigerated display case of the first aspect may be applied in a method according to the second aspect, and vice versa. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.

Embodiments will now be described by way of example only, with reference to the Figures, in which:

Figure 1 is a side cross-sectional view of a conventional open refrigerated display case (ORDC);

Figure 2 is a schematic cross sectional view of an open refrigerated display case (ORDC) according to the invention;

Figure 3 is a schematic detailed view of a shelf and flow stabilising device of an open refrigerated display case (ORDC) according to the invention; and

Figure 4 is a representative graph of convective performance loss against velocity.

Figure 1 shows a conventional ORDC 2. The ORDC 2 comprises a cabinet portion formed by a lower wall 4, a back wall 6, an upper wall 8, and left and right side walls (not shown). A lower panel 10, a back panel 12 and an upper panel 14 are disposed within the cabinet portion.

The lower, back and upper panels 10, 12, 14 form a display volume 15 which is provided with a plurality of shelves 17 (six are shown) on which items may be displayed. The shelves 17 are affixed to the back panel 12.

As shown, the lower, back and upper panels 10, 12, 14 are spaced from the respective lower, back and upper walls 4, 6, 8 to form a duct 16. An air inlet 18 is provided at the lower panel 10 to form an inlet to the duct 16. Similarly, an air outlet 20 is provided at the upper panel 14 to form an outlet from the duct 16. The air inlet 18 and the air outlet 20 are thus fluidically coupled to one another by the duct 16. The air inlet 18 and the air outlet 20 are spaced from the back panel 12 toward the front of the cabinet portion and ahead of the shelves 17.

A fan 22 and a heat exchanger 24 are located within the duct 16 adjacent to the air inlet 18 and thus are disposed between the lower wall 4 and the lower panel 10. The fan 22 draws air into the duct 16 via the air inlet 18 which then passes through the heat exchanger 24 where it is cooled to well below the ambient temperature.

After passing through the heat exchanger 24, the air continues through the duct 16 between the back wall 6 and the back panel 12. The back panel 12 may be perforated allowing air to pass from the duct 16 into the display volume 15 where it cools items located on the shelves 17 and on the lower panel 10.

The remaining air flows through the duct 16 to the air outlet 20. The air is ejected from the air outlet 20 and descends over the open front of the display volume 15 to form an air curtain 26. The air curtain 26 passes from the air outlet 20 to the air inlet 18, where it is drawn in by the fan 22 and re-circulated through the duct 16. The air curtain 26 thus forms a non-physical barrier which separates the display volume 15 from the ambient air surrounding the ORDC 2.

As shown in Figure 1, the air curtain 26 may be angled away from vertical by around 510°. This may be achieved by angling the air outlet 20. In particular, the air outlet 20 may be provided with a honeycomb panel (not shown) which rectifies the air flow as it exits the air outlet 20 to provide laminar flow. In other examples, the air outlet 20 may be directly above the air inlet 18 such that the air curtain 26 is substantially vertical.

Figure 2 shows a schematic cross-sectional view of an ORDC 102 according to an embodiment of the invention. The ORDC 102 shares many features with the ORDC 2 of Figure 1, and these features are denoted by reference numerals differing by 100 from the features of Figure 1. For example, the ORDC 102 of Figure 2 comprises a lower wall 104 which corresponds to lower wall 4 of the ORDC 2 of Figure 1.

The ORDC 102 comprises a total of eight shelves 117a-h arranged between the air outlet 120 and the air inlet 118. As described with reference to Figure 1, although not necessary, the air curtain 126 of the ORDC 102 is angled away from vertical such that the air inlet 118 is positioned forward of the air outlet 120. As shown in Figure 2, this path is replicated by the ends of the shelves 117a-h with the end of each subsequent shelf projecting forward of the previous shelf. This arrangement is generated by the back panel 112 which is angled away from vertical and so allows the lengths of the shelves 117a-h to be uniform.

ORDC 102 comprises a plurality of flow stabilising devices 128. In particular, each shelf 117a-h has an associated flow stabilising device 128a-h. Each flow stabilising device 128 is spaced forwardly of the front edge of its respective shelf 117 and generally within the flow path of the air curtain 126.

For clarity, a detailed view of a generic shelf 117 and flow stabilising device 128 are shown in Figure 3. In particular, Figure 3 shows an area F demarked in Figure 2, which includes the front edge of a shelf 117 and the flow stabilising device 128. Although the area F in Figure 2 is indicated around a particular shelf 117d and flow stabilising device 128d, it should be understood that Figure 3 generally shows and describes any of the shelf/flow stabilising device pairings117a-h/128a-h. Accordingly, reference numerals in Figure 3 do not include a suffix a-h, but any features of Figure 2 having the same reference numeral should be understood to have the features described in Figure 3.

Referring to Figure 3, the shelf 117 has a front edge defined by a front face 130. In this example, the front face 130 is angled to the vertical, but it should be understood that the face 130 could be vertical or angled the opposite way to the vertical. The front face

130 is planar, but it could equally be curved or another shape which reduces interference with the air curtain 126.

As can be seen in Figure 3, the flow stabilising device 128 comprises a first or inner stabilising beam 132 and a second or outer stabilising beam 134 which extend transversely across the display volume 115. The stabilising beams may be referred to simply as “beams” for brevity.

As Figure 3 shows a cross section looking transversely across the ORDC 102, it will be understood that the beams 132,134 extend into the page, and their cross sectional shape is shown. The inner and outer stabilising beams 132, 134 are each connected to a plurality of supporting arms 136 either via their ends or partway along the lengths of the beams 132, 134. The supporting arms 136 generally extend outwardly from the front edge of the shelf 117 in order to position the beams 132, 134 forward of and spaced apart from the shelf 117.

The inner beam 132 is so-named as it is positioned closer to the shelf 117 than the outer beam 134. The inner beam 132 is spaced outwardly from the shelf 117 by a distance D1 such that a first inner slot 138 is formed between them. The distance D1 in this example is approximately 70mm, although, as will be explained in more detail below, in other examples, other values for D1 may be appropriate.

The inner beam 132 has a cross sectional shape which defines a leading edge 140 and a trailing edge 142. The leading edge 140 of the inner beam 132 is directed upstream in the air curtain 126, while the trailing edge 142 generally faces downstream. A chord line 144 extends between the leading and trailing edges 140,142. Front and rear surfaces are formed between the leading and trailing edges 140, 142 either side of the chord line 144, with the front surface of the beam 132 facing outwardly and a rear surface facing inwardly. The width of the inner beam 132 increases from the leading edge 140 to a maximum thickness and then tapers from the maximum thickness to the trailing edge 142. The location of the maximum thickness is located closer to the leading edge 140 than the trailing edge 142. The leading and trailing edges 140, 142 are radiused, with the leading edge 140 having a larger radius of curvature than the trailing edge 142. Other arrangements and shapes of beam 132 are possible, which have leading and trailing edges. In other examples, the front and rear surfaces may meet at a point at the trailing edge 142 or may be truncated such that an additional surface is disposed at the trailing edge 142 between the front and rear surfaces.

Furthermore, the flow stabilising device 128 is arranged such that the chord line of the inner stabilising beam 132 extends at an angle of around 1.5 to 16.5 degrees (in particular 4 to 14 degrees or in particular approximately 9 degrees) to a line or plane defined between the front edge of its associated shelf 117 and the front edge of the subsequent or below shelf 117. Generally, the subsequent shelf is the next shelf away from the air outlet in the prevailing flow direction of the air curtain 126. For the lowermost shelf (or the lowermost shelf fitted with a flow stabilising device 128), the angle may be defined with respect to a line or plane formed between the front edge of the shelf and the air inlet 118. Further, if there is stock which overhangs the flow path, then the angle may be defined with respect to a line or plane formed between the front edge of the shelf and the front edge of the stock. It is noted that a positive angle for the stabilising beam 132 denotes that the trailing edge is further from the shelf than the leading edge.

The outer beam 134 is spaced outwardly from the inner beam 132 by a further distance D2 such that a second outer slot 146 is formed between the beams 132,134. Accordingly, a transverse slot is formed either side of the inner stabilising beam 132. The outer stabilising beam 134 does not have an aerofoil cross-section like the inner beam 132. However, the outer beam 134 has a leading edge 148 and a trailing edge 150 with respect to the air curtain 126, and a chord line 152 extending between the leading and trailing edges 148, 150. The outward facing surface 154 of the outer beam 134 generally faces outward from the display volume 115 at approximately the same height as the shelf 117. Accordingly, the surface 154 may be provided with a product information strip (not shown) or other features for attaching and displaying information relating to the product which is stored at that transverse position on the shelf 117. Accordingly, it may be desirable to arrange the outer beam 134 such that its outer surface 154 is substantially vertical, or tilted to provide easy viewing of the product information.

In this example, a beam convergence angle of approximately 10-20 degrees is formed between the chord lines 144, 152 of the inner and outer stabilising beams 132,134. In particular, the beam convergence angle is around 13.6 degrees. However, in other embodiments, the beams may not converge and may instead be arranged parallel to one another or diverge (i.e. increase in separation away from their leading edges 140, 148).

In other examples, there may be no outer stabilising beam provided, so the inner stabilising beam is the only stabilising beam. Alternatively, further stabilising beams may be provided outward of the outer stabilising beam in yet further examples.

A pair of axes V, x are shown in Figure 3. The x axis generally denotes a distance in the horizontal direction inwardly/outwardly with respect to the display volume 115. The V axis generally indicates velocity at the position on the x axis. The V axis is arranged such that the downward direction is positive. Therefore, the velocity at a given point on the x axis is depicted by the vertical distance downward on the V axis.

The curve Vn represents a notional flow velocity profile along the x axis at the vertical position of the leading edge 140 of the inner stabilising beam 132 in the display volume 115. The notional flow velocity profile Vn can be understood as the flow velocity profile along the x axis at the given vertical position for a notional air curtain that would be present if the flow stabilising device 128 were not present. In other words, the notional flow velocity profile Vn represents the flow velocity profile of an air curtain which would be created by the air outlet 20 and inlet 18 absent any interference by the flow stabilising device 128. In order to understand or identify the notional flow velocity profile Vn, the notional air curtain may be formed by running the ORDC without the flow stabilising devices 128 present, or may be simulated, for example with computational fluid dynamics (CFD).

As can be clearly seen, the notional flow velocity profile Vn has a notional peak flow velocity Vm which is arranged at or towards the middle of a curve having a single peak and which may be described generally as a bell-curve (although not necessarily symmetrical about the peak). The notional flow velocity inward or outward of the peak Vm reduces. This is representative of the notional air curtain, which would have a central fast-flowing core, bordered by inner and outer shear layers with the relatively still air inside the display volume 115 and the external environment respectively.

As will be appreciated, the presence of the flow stabilising device 128, and in particular, the beam 132, will cause the actual flow velocity profile to be different from the notional flow velocity profile Vn.

As can now be appreciated, the inner stabilising beam 132 is positioned in the air curtain 126 such that its leading edge 140 is substantially coincident with the region in which the notional peak flow velocity Vm occurs. Of course, as explained above, due to the presence of the flow stabilising device 128, the actual peak velocity Vm does not actually occur in this region, but it would save for the presence of the device 128. Although the optimum position for maximum flow stabilisation is in the region of notional peak flow velocity Vm, it has been found that a substantial improvement in flow stabilisation occurs provided that the leading edge 140 is located within a region in which the notional flow velocity is at least 87% of the notional peak flow velocity Vm. Outside of this range, the flow stabilising improvements provided by the invention may fall away.

Generally, regardless of the number of stabilising beams provided with the flow stabilising device 128, the innermost beam (which in this case is inner beam 132) should be provided in the region of notional maximum flow velocity Vm as described above.

In this example, the outer beam 134 is located away from the region of notional peak velocity Vm. Accordingly, the difference between the notional flow velocity and the actual flow velocity at this location is relatively small. However, as the outer stabilising beam 134 also lies within the air curtain 126, its positioning can also provide improvements in the air curtain flow stability.

Turning back to Figure 2, it will now be evident that, for each of the flow stabilising devices 128a-h, the local notional flow velocity profile Vn is illustrated. The notional profile Vn for each device 128a-h is substantially similar to the notional profile Vn described in Figure 3 above.

When considering the notional flow velocity profiles Vn for each flow stabilising device 128a-h, it will be apparent that the bell curve shape generally flattens with increasing distance away from the air outlet 120. This is because the notional air curtain which would be present in the absence of the devices 128a-h would gradually lose stability and entrain air either side of the notional curtain to an increasing extent.

It can be seen that each of the flow stabilising devices 128a-h is located at or immediately proximate the region of maximum notional flow velocity Vm for its respective notional flow velocity profile Vn. It may be apparent that in the example of Figure 2, the distance D1 between each shelf 117a-h and the inner beam 132 of the respective device 128a-h is equal. Similarly, the distance D2 between the inner 132 and outer 134 beams is equal. Accordingly, each of the flow stabilising devices 128a-h is identical in construction. Owing to the design of the air outlet 120 and inlet 118, and the flow velocity, the notional flow velocity profiles are all arranged such that, at the distance D1 forward from the shelf 117a-h, a notional flow velocity of at least 87% of the notional peak flow velocity Vm is exhibited. Accordingly, despite the differences in the region of the notional peak flow velocity Vm throughout the height of the display volume 115 (i.e. the location of the peak of the notional profiles Vn), an identical flow stabilising device 128 can be used for each shelf 117a-h and the leading edges 140 still fall within the acceptable region in which the notional flow velocity is at least 87% of the notional peak flow velocity Vm. However, it will be appreciated that in other arrangements, only some of the shelves 117a-h may be provided with flow stabilising devices or only some of the shelves 117a-h may be provided with flow stabilising devices which have their inner beam 132 located at this position. Nevertheless, the air curtain should substantially follow the notional flow velocity profile (with no intermediate disturbances) at least until it reaches the first shelf provided with a flow stabilising device which has a stabilising beam positioned such that its leading edge is located within the region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

In other examples, the flow stabilising devices may be configured or configurable such that the distance D1 between the inner stabilising beam 132 and the respective shelf varies from shelf to shelf.

Accordingly, the inner stabilising beam 132 of each flow stabilising device 128a-h can be configured such that its leading edge 140 is located precisely in the region of notional peak flow velocity Vm at its respective vertical position in the display volume 115. Accordingly, each flow stabilising device 128a-h can be positioned in its optimum position.

The flow stabilising devices 128 can be connected to a standard shelf 117 and thus allow the flow stabilising devices 128 to be retrofitted to existing ORDCs. The flow stabilising devices 128 may, however, be integrally formed with the shelves 117 or the ORDC 102.

Although each shelf 117 of the ORDC 102 has been described as having a flow stabilising device 128, this need not be the case and only some of the shelves 117 may be provided with flow stabilising devices 128.

Although the flow stabilising devices 128 have been described as being connected directly to the shelves 117, they may instead be connected to other parts of the ORDC. For example, the arms 136 of the flow stabilising devices may connect to the back panel 12 such that the flow stabilising devices are positioned between adjacent shelves 117 (or between the lowermost shelf 117 and the lower panel 110). In particular, the flow stabilising devices 128 may be positioned just below each of the shelves 117. Alternatively, the flow stabilising devices 128 may be connected to the left and right side walls of the ORDC 102. In this case, the arms 136 could be omitted and the stabilising beam or beams connected directly to the ORDC.

The stabilising beam or beams also need not lie in the plane of the shelf. For example, the stabilising beam may be offset from the shelf. This may be achieved by using arms which are stepped or otherwise configured so that the connection to the shelf.

It should be understood that, regardless of the vertical position at which the flow stabilising device or devices are positioned, the notional flow velocity profile at the leading edge of the innermost stabilising beam should simply be placed within the region of peak flow velocity at that particular vertical position.

The performance of the ORDC may be expressed in terms of “Convective Heat Flux” which is a measure of the energy loss in the cabinet through heat transfer caused by the movement of air. Reductions in the magnitude of this parameter correlate closely with savings in the electrical power consumption of the ORDC. It is convenient to use Convective Heat Flux in this instance as, unlike electricity consumption, it can be directly determined using simulations (e.g. CFD).

Figure 4 shows a representative graph of convective performance loss against position in terms of the percentage of the peak flow velocity at the leading edge. As shown, it has been found that locating a stabilising beam within 87% of the peak flow velocity leads to an acceptable performance which is within approximately 20% of the fully optimised position found at the peak flow velocity. Locating the stabilising beam within 94% of the peak flow velocity has been found to provide a performance which is within approximately 10% of the fully optimised position. It will be appreciated the curve of Figure 4 may become asymmetric as the stabilising beam approaches the shelf and aerodynamic interference effects begin to occur. A similar graph to that shown in Figure 4 would also be seen for the angle of the stabilising beam, where angles within

7.5 degrees of the fully optimised angle of 9 degrees (i.e. angles between 1.5 and 16.5 degrees) have been found to provide a performance which is within approximately 20% of the fully optimised angle and angles within 5 degrees (i.e. angles between 4 and 14 degrees) have been found to provide a performance which is within approximately 10% of the fully optimised angle.

To assess whether a flow stabilising device has a stabilising beam which is positioned such that the leading edge thereof is located in a region in which the notional flow velocity is at least 87%, the air curtain velocity profile of the ORDC may be physically measured. Specifically, the air curtain velocity profile may be determined using the following procedure. Before commencing, all flow stabilising beams (if present) should be removed, along with any items such as temporary signage that could be expected to influence the behaviour of the air curtain.

The flow velocity may be measured by means of a hot-wire anemometer mounted to an adjustable arm in such a way that it can traverse the air curtain horizontally in a direction perpendicular to the width of the ORDC. The anemometer should be positioned vertically as close as possible to each shelf in turn, with the mounting arm arranged in such a way that disturbance to the air curtain is minimised. Starting with the anemometer adjacent to the shelf, velocity measurements should be taken at regular intervals of approximately 15mm, passing through the region of peak velocity and terminating when the velocity is close to zero at the forward extent of the air curtain. Because the air curtain is unsteady in nature, each velocity measurement should consist of a time average over a period of at least 20 seconds. The resulting velocity values can then be plotted as a function of horizontal distance from the shelf in order to identify the location of peak velocity at the level of each shelf.

Generally, if flow stabilising devices have been provided previously, they have been provided away from the peak flow velocities of the air curtain, usually outwardly of the peak flow, so as to entrain escaping flow from the air curtain back into the main flow.

However, the inventors have surprisingly identified that, if placed at or proximate to the region of peak flow velocity, the air curtain can be stabilised to an increased extent and warm air entrainment thereby reduced.

It will be understood that the invention is not limited to the embodiments abovedescribed and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or 15 more features described herein.

Claims

1. An open refrigerated display case comprising:

a refrigerated display volume;

an air outlet configured to direct airflow out of the air outlet across the display volume toward an air inlet to thereby form an air curtain across the display volume, the air outlet and air inlet defining a notional flow velocity profile;

a flow stabilising device comprising a stabilising beam extending transversely across the display volume and located within the air curtain;

wherein the stabilising beam is positioned such that the leading edge thereof is located in a region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

2. An open refrigerated display case as claimed in claim 1, wherein the refrigerated display volume comprises a shelf, and wherein the flow stabilising device is associated with the shelf such that the stabilising beam is arranged outwardly of the shelf in the refrigerated display volume to thereby form an inner slot between the shelf and the stabilising beam.

3. An open refrigerated display case as claimed in claim 2, wherein the display volume comprises a plurality of shelves, each shelf being provided with an associated flow stabilising device.

4. An open refrigerated display case as claimed in claim 3, wherein at least one of the flow stabilising devices is arranged such that a chord line of the stabilising beam extends at an angle of around 1.5-16.5 degrees to a line defined between a front edge of its associated shelf and the front edge of the subsequent shelf, and optionally around 4-14 or 9 degrees to the line defined between the front edge of the associated shelf and the front edge of the subsequent shelf.

5. An open refrigerated display case as claimed in any preceding claim, wherein the stabilising beam is an inner stabilising beam and the flow stabilising device further comprises a second outer stabilising beam arranged outwardly from the inner stabilising beam to thereby form an outer slot between the inner and outer stabilising beams.

6. An open refrigerated display case as claimed in claim 5, wherein the inner and outer stabilising beams are arranged such that the inner and outer beams converge towards their respective trailing edges.

7. An open refrigerated display case as claimed in any preceding claim, wherein the air outlet comprises at least one of a nozzle, or a flow-straightening device.

8. An open refrigerated display case as claimed in any preceding claim, wherein the stabilising beam is positioned such that the leading edge is located in a region in which the notional flow velocity is at least 94% of the notional peak flow velocity.

9. An open refrigerated display case as claimed in any preceding claim, wherein the stabilising beam is positioned such that the leading edge is located in a region in which the notional flow velocity is substantially equal to the notional peak flow velocity.

10. A method of configuring an open refrigerated display case, comprising:

providing a refrigerated display volume;

forming an air curtain across the display volume by directing airflow out of an air outlet across the display volume toward an air inlet, wherein the air outlet and air inlet define a notional flow velocity profile; and arranging a flow stabilising device comprising a stabilising beam extending transversely across the display volume such that a leading edge of the stabilising beam is the stabilising beam is positioned in a region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

11. A method of configuring an open refrigerated display case as claimed in claim 10, further comprising, prior to arranging the flow stabilising device, forming or simulating a preliminary air curtain having the notional flow velocity profile to thereby locate the region in which the notional flow velocity is at least 87% of the notional peak flow velocity.

12. A method of configuring an open refrigerated display case as claimed in claim 10 or 11, wherein the refrigerated display volume comprises a shelf, and wherein the flow stabilising device is associated with the shelf and arranged such that that the stabilising beam is arranged outwardly of the shelf in the refrigerated display volume to thereby form an inner slot between the shelf and the stabilising beam.

13. A method of configuring an open refrigerated display case as claimed in claim 12, wherein the display volume comprises a plurality of shelves, each shelf being provided with an associated flow stabilising device.

14. A method of configuring an open refrigerated display case as claimed in any of claims 10-13, wherein the stabilising beam is an inner stabilising beam and the flow stabilising device further comprises a second outer stabilising beam arranged outwardly from the inner stabilising beam to thereby form an outer slot between the inner and outer stabilising beams.

15. A method of configuring an open refrigerated display case as claimed in claim 14, wherein arranging the flow stabilising device comprises arranging the inner and outer stabilising beams such that they converge towards their respective trailing edges.

16. A method of configuring an open refrigerated display case as claimed in any of claims 10-15, wherein the flow stabilising device is arranged such that the leading edge of the stabilising beam is positioned in a region in which the notional flow velocity is at least 94% of the notional peak flow velocity.

17. A method of configuring an open refrigerated display case as claimed in any of claims 10-16, wherein the flow stabilising device is arranged such that the leading edge of the stabilising beam is positioned in a region in which the notional flow velocity is substantially equal to the notional peak flow velocity.