EP3412996B1

EP3412996B1 - Refrigerated display unit and refrigerated air flow distribution system

Info

Publication number: EP3412996B1
Application number: EP18175915.0A
Authority: EP
Inventors: Igor LAURI
Original assignee: ARNEG SpA
Current assignee: ARNEG SpA
Priority date: 2017-06-08
Filing date: 2018-06-05
Publication date: 2021-07-14
Anticipated expiration: 2038-06-05
Also published as: PT3412996T; PL3412996T3; DK3412996T3; RU2018120698A; AU2018204034B2; AU2018204034A1; US20180352973A1; RU2018120698A3; EP3412996A1; BR102018011374A2; CA3007237A1; ES2894271T3; RU2759646C2; IT201700063123A1; LT3412996T

Description

The present invention relates generally to a refrigerated display unit and, in particular, to a system for distributing refrigerated air flows in a closed refrigerated display unit.
Nowadays, particular display units provided with refrigerating systems, usually called commercial refrigerated counters, are very widespread. These refrigerated display units, or commercial refrigerated counters, are typically used in the retail sector to display and store particular types of perishable products. In particular, these refrigerated display units are often used in supermarkets, canteens, etc. to offer the opportunity to buy fresh products and keep the products in an environment with adequate temperature. In general, a commercial refrigerated counter may be either open-type, that is to say, without any solid barrier between the products contained therein and the external environment, or closed-type, i.e. provided with one or more doors or walls, usually partially or completely transparent, which isolate the refrigerated volume from the external environment.
Regardless of the type, a commercial refrigerated counter has the primary purpose of keeping the temperature of the products contained therein within a predefined range of values. Many technical product standards classify refrigerated counters according to the position of such a temperature range. For positive temperature refrigerated counters and in accordance with the EN 23953-2 (2015) standard, some temperature limits are identified as follows:

1) -1/+7 °C: temperature class M2;
2) -1/+5 °C: temperature class M1;
3) -1/+4 °C: temperature class M0.

The energy consumption of a refrigerated counter is therefore a function of the selected temperature range. For example, a class M0 refrigerated counter consumes more energy than a similar class M2 refrigerated counter. However, the energy consumption of a refrigerated counter is even more dependent on the average temperature of the products it contains. In fact, the higher the average temperature of the products, the lower the energy requirement of the refrigerated counter, and vice versa. It is therefore evident that the search for maximum energy savings in a refrigerated counter is strictly correlated with the increase in the average temperature of the products contained in such a refrigerated counter.
The aforementioned energy saving strategy is unfortunately not completely feasible, since the products normally placed in the vicinity of the heat exchange battery of the refrigerated counter, which usually operates at temperatures below 0°C, contribute in greatly decreasing the average temperature. Raising the operating temperature of the heat exchange battery could therefore be a solution for raising the average temperature of the products. However, this would also entail the inevitable increase in the temperature of the products in its highest values, that is to say, for those products placed far from the heat exchange battery, and therefore already at the limit with respect to the upper threshold referred to the temperature class considered.
Relevant prior art can be found in JP 2007 163020 A , US 4 367 632 A , JP 2005 241136 A .
The object of the present invention is therefore to provide a refrigerated display unit, in particular a system for distributing the flow of refrigerated air into a closed refrigerated display unit, which is able to solve the aforementioned drawbacks of the prior art in a manner extremely simple, cost-effective and particularly functional.
In detail, it is an object of the present invention to provide a system for distributing the flow of refrigerated air that is able to minimise the gradient between the hottest and the coldest points within the refrigerated volume. A refrigerated display unit provided with this system for distributing the flow of refrigerated carrier fluid (air), while respecting the limits imposed by the respective temperature class (which may be, for example, M2: -1/+7°C), strongly compresses the temperature range, increasing its lower value (which in the example considered can be +5/+7°C), with the obvious increase in average temperature and the consequent decrease in energy requirements.
This and other objects according to the present invention are achieved by implementing a refrigerated display unit as outlined in claim 1.
Further features of the invention are highlighted in the dependent claims, which are an integral part of the present description.
The features and advantages of a refrigerated display unit according to the present invention will be more apparent from the following description, which is to be understood as exemplifying and not limiting, with reference to the accompanying schematic drawings, in which:

figure 1 is a schematic view of a generic refrigerated display unit of the closed type made according to the prior art, in which the air flows are highlighted;
figure 2 is a schematic view of a refrigerated display unit of the closed type made according to the present invention, in which the air flows are highlighted;
figure 3 is another schematic view of a refrigerated display unit of the closed type made according to the present invention, in which a detail of the relative back panel is highlighted;
figure 4 is a sectional view of a refrigerated display unit of the closed type made according to the present invention, in which the heat exchange battery and the relative accessories are highlighted;
figure 5 is another sectional view of a refrigerated display unit of the closed type made according to the present invention, in which the heat exchange battery and the relative accessories are highlighted;
figure 6 is a perspective view of a component of the refrigerated display unit of the closed type made according to the present invention;
figure 7 is a side elevation view of the component in figure 6;
figure 8 shows, for a generic refrigerated display unit of known type, the field of the velocity modules of the carrier fluid both in the plenum between the fans and the heat exchange battery and in the volume located downstream of said heat exchange battery; and
figure 9 shows, for the refrigerated display unit according to the present invention, the field of the velocity modules of the carrier fluid both in the plenum between the fans and the heat exchange battery and in the volume located downstream of said heat exchange battery.

With reference in particular to figures 2 to 7, a refrigerated display unit according to the present invention is shown, indicated as a whole with reference numeral 10. The refrigerated display unit 10 is provided with at least one refrigerating machine (not shown) that can be either incorporated in the refrigerated display unit 10 itself or remotely installed to operate with a plurality of separate refrigerated display units.
The refrigerated display unit 10 is therefore internally provided with at least one refrigerated volume 12 configured for containing a plurality of products to be kept at a temperature lower than the room temperature by means of the refrigerating machine. In the embodiment shown in the figures, the refrigerated display unit 10 is of the so-called vertical type. In the respective refrigerated volume, one or more horizontal shelves 14 are installed on which the products to be refrigerated are placed. Alternatively, the refrigerated display unit 10 could also be of the so-called "island" type, that is to say, mainly horizontal and internally provided with or without vertical dividing walls.
The refrigerated display unit 10 is furthermore internally provided with at least one technical volume intended to contain an air treatment unit operatively connected to the refrigerating machine. As shown in figures 4 and 5, the air treatment unit comprises at least one heat exchange battery 16, through which a cooling fluid and a carrier fluid (typically consisting of air) exchange heat, and a plurality of fans 18 placed at the inlet surface 16A of such a heat exchange battery 16, with reference to the direction of the carrier fluid flow. The fans 18 are configured to move both the carrier fluid to be refrigerated to the heat exchange battery 16, and the refrigerated carrier fluid to the refrigerated volume 12.
Irrespective of the embodiment, the refrigerated display unit 10 is of the closed type, that is to say, provided with one or more doors or walls 20, partially or completely transparent, which isolate the refrigerated volume 12 from the external environment. Inside the refrigerated display unit 10 one or more conduits 22 of an air flow system are provided, placed in fluid connection with the heat exchange battery 16 and configured for conveying the refrigerated carrier fluid, moved by the fans 18, towards the refrigerated volume 12.
Each conduit 22 is provided with at least an outlet opening 24 placed in fluid communication with the refrigerated volume 12, such as to diffuse a flow of refrigerated carrier fluid, according to a predefined direction, within such a refrigerated volume 12. In particular, as shown in figure 2, the outlet openings 24 are positioned at a single door or wall 20, so that the flow of refrigerated carrier fluid is diffused from the respective outlet openings 24 into a portion of refrigerated volume 12 placed at the doors or walls 20. This flow of refrigerated carrier fluid generates a so-called curtain or knife of air which, among other effects, acts as a physical barrier to the inlet of ambient air into the refrigerated volume 12 in the condition of open doors or walls 20.
The refrigerated display unit 10 comprises at least one distributor device 26 for distributing a flow of carrier fluid, placed at the inlet surface 16A of the heat exchange battery 16 and between at least two fans 18. In order to optimise the heat exchange between the refrigerating fluid and the carrier fluid, it is in fact desirable that the motion field of such a carrier fluid be as uniform as possible when the inlet surface 16A of the heat exchange battery 16 is intercepted. In this way, the useful heat exchange surface is maximised.
The portion of recovered power can be used to raise the temperature of the heat exchange battery 16, with obvious advantages in terms of overall efficiency of the refrigerated display unit 10 and of a decrease in the temperature gradient of the refrigerated products. Due to a mapping of the field of motion of the refrigerated carrier fluid, which has taken place in the plenum between the fans 18 and the heat exchange battery 16, the shape of the carrier fluid flow distributor device 26 to be located at the inlet surface 16A of the heat exchange battery 16 is determined. In the embodiment shown in the figures, the carrier fluid flow distributor device 26 consists of a plate oriented according to a plane that is substantially vertical and perpendicular to the inlet surface 16A of the heat exchange battery 16.
Figure 8 shows, for a generic refrigerated display unit of known type, the field of the velocity modules of the carrier fluid (air) both in the plenum between the fans and the heat exchange battery and in the volume located downstream of said heat exchange battery. The areas indicated with R represent the higher speeds, while the areas indicated with B represent the speeds close to zero. Because of the mutual interference between the flow rates processed by each individual fan, in the plenum there are sums or subtractions of flow of the carrier fluid. This phenomenon involves a maldistribution of the total flow of carrier fluid which intercepts the inlet surface of the heat exchange battery. A maldistribution of the total flow of carrier fluid implies that some parts of the heat exchange battery do not carry out any heat exchange (inlet speed equal to zero).
Figure 9 instead represents the field of the velocity modules of the carrier fluid (air) for the refrigerated display unit 10 according to the present invention, once again measured both in the plenum between the fans 18 and the heat exchange battery 16, and in the volume placed downstream of such a heat exchange battery 16. The presence of one or more carrier fluid flow distributor device 26 prevents the overlapping of the carrier fluid flow rates of the fans 18 located at the sides of each carrier fluid flow distributor device 26, eliminating or reducing the mutual interference of these fans 18. The result, shown in figure 9, is a better distribution of the velocity of the carrier fluid at the inlet surface 16A of the heat exchange battery 16. Obviously, a variable number of carrier fluid flow distributor devices 26 can be applied according to requirements.
Each conduit 22 is divided into at least one first conduit portion 22A with substantially vertical development, placed at a vertical wall 28 of the refrigerated volume 12 that is opposite the doors or walls 20, and into at least one second conduit portion 22B with substantially horizontal development, hydraulically placed downstream of the respective first conduit portion 22A, as well as above the refrigerated volume 12. The second conduit portion 22B is hydraulically connected to the outlet opening 24.
The vertical wall 28 is provided with a plurality of slots 30 with substantially horizontal development, which put the first conduit portion 22A in fluid communication with the refrigerated volume 12 and, consequently, directly send part of such a refrigerated carrier fluid flowing in each conduit 22 to said refrigerated volume 12. Each slot 30 has a width equal to ten times the respective height, as shown in figure 3. Even more preferably, each slot 30 has a width of about 20 mm and a height of about 2 mm.
Still preferably, a plurality of slot 30 rows, superimposed to each other and spaced according to a predefined dimension A, is provided on the vertical wall 28, wherein each row of slots 30 comprises a plurality of slots 30 which are side-by-side and arranged along a substantially horizontal axis. Even more preferably, such a dimension A is about 50 mm. The first conduit portion 22A, on the other hand, has a passage cross section having a width preferably equal to about 60 mm.
The particular drilling of the vertical wall 28 contributes to the decrease of the temperature gradient between the coldest point and the hottest point of the refrigerated volume 12. The size and the shape of each slot 30, combined with the specific dimensioning of the first substantially vertical conduit portion 22A, allow splitting the flow of refrigerated carrier fluid in such a way that each product, independently of the shelf 14 on which it is placed, exchanges the correct amount of thermal energy with the refrigerated carrier fluid. In particular, the products that are in sight, and which are therefore also subject to irradiation, benefit from an additional convective exchange due to the effect of the front air curtain or knife. In contrast, products that are in shadow with respect to the radiating surface are only partially involved in the flow of refrigerated carrier fluid. For irradiating surface it is meant the surface belonging to the external environment with respect to the refrigerated display unit 10 and which exchanges heat by irradiation due to a temperature difference. Typically, the irradiating surface consists of the walls, floors and/or ceilings of the room in which the refrigerated display unit 10 is located.
In a generic closed-type refrigerated display unit, that is to say, provided with doors like that in figure 1, ventilation is generally reduced since it is assumed that the barrier effect is not carried out by the refrigerated carrier fluid curtain, as in an open refrigerated display unit, but by the doors themselves. Even if this corresponds to what has been experimentally found, the refrigerated carrier fluid curtain produced by reduced ventilation tends to assume a curved shape that does not adequately brush all the product to be refrigerated (see figure 1, where the vortices of air between the curtain of refrigerated carrier fluid and the door are highlighted). This means that, at the same temperature of the refrigerated carrier fluid, some products are warmer than others, with the obvious consequence of increasing the overall gradient of the stored goods.
In the refrigerated display unit 10 according to the present invention, the fans 18 have been sized so as to exploit the doors or walls 20 as straightening surfaces of the air curtain or knife, which is vertically guided, uniformly impinging the products to be refrigerated (see figure 2). In other words, the flow of the air curtain or knife provided by the outlet openings 24 is substantially parallel to the developing plane of the door or wall 20 in its closed configuration. In this way, the swirling movements that occur in the refrigerated volume area between the air curtain or knife and the doors or walls of traditional refrigerated display units are eliminated or at least reduced (see figure 1).
In addition to the suitably perforated vertical wall 28, the element which allows the use of the doors or walls 20 as straightening surfaces of the air curtain or knife is the sizing of the flow rate of the refrigerated carrier fluid (air), i.e. the quantity and type of fans 18 installed on the refrigerated display unit 10. The optimal flow range is calculated as a compromise that allows:

1) on the one hand, obtaining sufficient verticality of the air curtain or knife by using the doors or walls 20 as straightening elements of the flow lines; and
2) on the other hand, not excessively increasing the effect of convective exchange against such doors or walls 20 and, consequently, not excessively increasing the electric consumption of the motor of fans 18.

In fact, the flow rate of the refrigerated carrier fluid is sized so as to use the doors or walls 20 as straightening surfaces for creating the air curtain or knife.
Preferably, the optimum flow rate of the refrigerated carrier fluid (air), with the passage sections of the conduit 22 and of the slots 30, is obtained in a velocity range of such a refrigerated carrier fluid ranging from 1.65 m/s to 2.0 m/s, where the speed is measured at the intake grid of fans 18. For flow rates smaller than the design ones, the fluid vein detaches from the doors or walls 20, starting to "sway" and losing the efficiency of standardizing the temperature of the products.
In particular, the open-type refrigerated display units of the known type, that is, the open-type wall-mounted refrigeration counters of the known type, generate a refrigerated carrier fluid flow at the opening such as to generate a frontal vertical air curtain which is capable of separating the internal environment from the external environment.
Specifically, the flow must be dimensioned in a way, on the one hand, as to avoid excessive turbulence with the external environment (in the case of too high speed and/or flow), and on the other hand to prevent the breaking of the air curtain and of the relative fluid barrier (in case of too low speed and/or flow).
In closed refrigerated display units of the known type, that is to say in closed wall-mounted refrigeration counters, the presence of the closing door has made the need to create a fluidic barrier useless, since the barrier is defined by the door itself.
However, the generation of a refrigerated carrier fluid is provided which, however, performs only the cooling function and therefore not necessarily the generation of the air curtain acting as a fluid barrier, if not in the brief moments of opening the door. Figure 1 shows an example of the flows of the refrigerated carrier fluid in a closed display unit.
Conventionally, if it is assumed that the flow rate of a refrigerated carrier fluid in an open display unit is equal to 1, the flow rate of a refrigerated carrier fluid in a closed display unit of the same size, geometry, external environmental conditions and performances is around 0.5 - 0.6.
The flow rate of refrigerated carrier fluid generated in the refrigerated display unit, according to the invention, is dimensioned so as to be significantly greater than that of a closed display unit of a known type, but also than that of an open display unit of a known type, with the same dimensions, geometries, external environmental conditions and performances.
In particular, if it is assumed that the flow rate of a refrigerated carrier fluid in an open display unit is equal to 1, and that the flow rate of a refrigerated carrier fluid in a closed display unit of known type is around 0.5 - 0.6, according to the invention, with the same dimensions, geometries, external environmental conditions and performances, the flow rate is around 1.3 - 1.4.
In this way, as already described, the increased curtain tension, by ensuring a good quality in the heat exchange with the goods and the door 20, is used as a current rectifier for verticalizing and stabilizing the air curtain.
It has thus been seen that refrigerated display unit according to the present invention achieves the objects described above.
The refrigerated display unit of the present invention thus conceived is susceptible to many modifications and variants, all falling within the scope of the invention, which is defined by the appended claims.

Claims

Refrigerated display unit (10) comprising:
- at least one refrigerating machine;

- at least one refrigerated volume (12) configured for containing a plurality of products to be kept at a temperature lower than the room temperature by means of the refrigerating machine;

- at least one technical volume configured for containing an air treatment unit operatively connected to the refrigerating machine, said air treatment unit comprising at least one heat exchange battery (16), by means of which a cooling fluid and a carrier fluid exchange heat, and a plurality of fans (18) placed at the inlet surface (16A) of said heat exchange battery (16);

- one or more ducts (22) of an air flow system, placed in fluid connection with the heat exchange battery (16) and configured for conveying the refrigerated carrier fluid, moved by the fans (18), towards the refrigerated volume (12), wherein each conduit (22) is provided with at least one outlet opening (24) placed in fluid communication with the refrigerated volume (12), such as to diffuse a flow of refrigerated carrier fluid, according to a predefined direction, inside such refrigerated volume (12), wherein each conduit (22) is divided into at least one first conduit portion (22A) with substantially vertical development, placed at a vertical wall (28) of the refrigerated volume (12) that is opposite the doors or walls (20), and into at least one second conduit portion (22B) with substantially horizontal development, hydraulically placed downstream of the respective first conduit portion (22A), as well as above the refrigerated volume (12), wherein said second conduit portion (22B) is hydraulically connected to said at least one outlet opening (24), wherein said vertical wall (28) is provided with a plurality of slots (30) which put the first conduit portion (22A) in fluid communication with the refrigerated volume (12) and, consequently, directly send part of the refrigerated carrier fluid flowing in each conduit (22) to said refrigerated volume (12),

- at least one carrier fluid flow distributor device (26), placed at the inlet surface (16A) of the heat exchange battery (16) and between at least two fans (18), said at least one carrier fluid flow distributor device (26) being arranged to avoid the overlapping of the carrier fluid flows of the fans (18) placed at the sides of said carrier fluid flow distributor device (26), eliminating or reducing the mutual interference of such fans (18),
the refrigerated display unit (10) being characterised in that it comprises one or more doors or walls (20) isolating the refrigerated volume (12) from the external environment and in that said flow of said refrigerated carrier fluid is substantially parallel to the developing plane of said one or more doors or walls (20) in a closed configuration and in that each slot (30) has a substantially horizontal development and a width that is equal to ten times the respective height.
Refrigerated display unit (10) according to claim 1, characterised in that each carrier fluid flow distributor device (26) consists of a plate oriented according to a plane that is substantially vertical and perpendicular to the inlet surface (16A) of the heat exchange battery (16).
Refrigerated display unit (10) according to claim 1, characterised in that the outlet openings (24) are positioned at a single door or wall (20), such that the refrigerated carrier fluid, delivered by said outlet openings (24), forms an air curtain or knife whose flow is substantially parallel to the development plane of the door or wall (20) in its closed configuration.
Refrigerated display unit (10) according to claim 1, characterised in that each slot (30) has a width of about 20 mm and a height of about 2 mm.
Refrigerated display unit (10) according to any one of the preceding claims, characterised in that a plurality of slot (30) rows, superimposed to each other and spaced according to a predefined dimension (A), is provided on the vertical wall (28), wherein each row of slots (30) comprises a plurality of slots (30) which are side-by-side and arranged along a substantially horizontal axis.
Refrigerated display unit (10) according to claim 5, characterised in that said predefined dimension (A) is equal to about 50 mm.
Refrigerated display unit (10) according to any one of the preceding claims, characterised in that the first conduit portion (22A) has a passage cross section equal to about 60 mm.
Refrigerated display unit (10) according to any one of the preceding claims, characterized in that the flow rate of said refrigerated carrier fluid is obtained in a velocity range of such a refrigerated carrier fluid ranging from 1.65 m/s to 2.0 m/s, where the speed is measured at the intake grid of said fans (18), so as to use the doors or walls (20) as straightening surfaces for creating the air curtain or knife.