EP0717945A2 - Method for improvement of the operation of refrigerators - Google Patents

Abstract

A typical cabinet freezer (1) displays products for sale on several shelves (2) above a chest container (3). Air circulated by a fan (6) up a concealed passage (4), containing the evaporator (5), falls down the front of the shelves as a cold air curtain. To prevent migration of water vapour from the ambient atmosphere into the curtain, and the consequent frost build-up, a separate air supply, with humidity lying between 0 and 2g/kg, is provided from an overhead outlet (8), to fall on either side of the cabinet. Additionally, air supplied (7) to the circulating fan (6) is itself of similar quality. Applications to various single and multiple freezer installations, including provision for recirculating the dehumidified air, are described. curtain. To prevent

Description

The present invention relates to the operation of display furniture for products equipping stores with large sales areas and, more particularly, the operation of refrigerated display cabinets present in the area reserved, in these stores, for fresh products and food cold, as well as in transit locations and cold rooms.

• les meubles verticaux à plusieurs niveaux d'étagères avec face ouverte,
• les meubles verticaux à plusieurs niveaux d'étagères avec bac et face ouverte,
• les meubles verticaux à service arrière,
• les meubles mixtes avec gondole dissymétrique sur laquelle est posée une armoire à portes vitrées,
• les gondoles murales équipées d'une superstructure à étagères,
• les gondoles de type dissymétrique ou mural avec bandeau vitré ou non,
• les gondoles du type "îlot" symétriques,
• les gondoles à groupe frigorifique incorporé,
• les doubles gondoles composées de deux gondoles dissymétriques dos à dos, formant un ensemble symétrique,
• les vitrines frigorifiques,
• les comptoirs frigorifiques.

The refrigerated display cabinets installed in big box stores and to which the process according to the present invention applies include in particular:

• vertical furniture with several levels of shelves with open sides,
• vertical furniture with several levels of shelves with tray and open face,
• vertical furniture with rear service,
• mixed furniture with asymmetrical gondola on which is placed a cupboard with glass doors,
• wall gondolas fitted with a shelf superstructure,
• asymmetrical or wall-mounted gondolas with a glass strip or not,
• symmetrical "island" type gondolas,
• gondolas with incorporated refrigeration unit,
• the double gondolas composed of two asymmetrical gondolas back to back, forming a symmetrical whole,
• refrigerated display cases,
• refrigeration counters.

These refrigeration units, which allow products to be kept at low temperatures, are said to be "positive cold" when the evaporation temperatures are between -15 ° C and -5 ° C, and "negative cold" when the temperatures evaporation are between -40 ° C and -15 ° C.

In these refrigerated cabinets, one or more air curtains protect their enclosures against the warmer ambient air, the cooling of the air stream or streams forming these curtains being ensured by means of refrigerant evaporators supplied with a fluid refrigerant which can be a gas, glycol water or a synthesis fluid.

The evaporators and / or exchangers with water or synthetic fluid, which are traversed by the ambient air, capture the humidity of the air intended for the curtain (s) protecting against the warmer ambient air. Below 0 ° C, the water contained in the air in the form of tiny droplets will freeze and form micro-crystals which, entrained by natural or forced convection air, will be fixed on the fins of the exchanger coils -evaporators. This is the icing process.

The myriads of micro-crystals will form a kind of snow which will gradually obstruct the spaces between the fins, and will become, with prolonged contact with the fins, ice of a greater or lesser density, depending on the duration fixed for the cycles. defrost, resulting in a gradual reduction in the refrigerated air flow.

In addition, the micro-crystals will also be deposited on the walls of the refrigerated cabinets and on products presented to customers, making them commercially less attractive.

To overcome this drawback and limit the total icing of the heat exchanger-evaporator batteries, the refrigeration units are equipped with defrosting systems by reheating. The exchangers are then heated in different ways, either natural or activated, by electrical resistances or reverse cycle. Some pieces of furniture are even equipped with permanent defrosts.

This results in a significant energy consumption to melt the frost, and it seems more abnormal to heat in a refrigeration cabinet that you want to keep low, see very low temperature.

The times between each defrost are variable depending on the sites, indoor or outdoor climatic conditions, type of equipment and brands. In general, the defrosting time is approximately 20/25 minutes every four hours. Thus, every four hours, the refrigeration unit will stop refrigeration for about 20 minutes. Some pieces of furniture are designed to undergo defrosting every six hours. In this case the duration of defrosting is of the order of 30 to 35 minutes.

The temperature inside the cabinet, maintained at -20 ° C for example, may during defrost rise up to + 10 ° C or + 15 ° C, a temperature difference of 30 to 35 ° C. During this period, frozen products are no longer maintained at heart and their good conservation is therefore altered, in contradiction with the regulations in force and those in preparation in the European context.

By document FR-A-2 679 988 it has been proposed, in order to limit the icing of the refrigeration coil of an open refrigerated cabinet, to provide, between the aeraulic refrigeration circuit of the cabinet and the atmosphere, an air curtain protector whose the air which constitutes it has been dehumidified. Practice has shown that the process proposed by this document is not very effective, since it does not prevent the existence of a large difference in partial pressure of water vapor between the interior of the cabinet and the outside (the ambiance). As a result, significant humidity remains available and is introduced inside the cabinet, to be condensed and frozen on the evaporators, the walls and the channels of the cabinet.

The object of the present invention is to remedy the drawbacks due to icing encountered in refrigerated display cabinets fitted in large surface stores and it proposes, for this purpose, a method of using these refrigerated display cabinets which makes it possible to almost completely eliminate the formation of frost in this furniture.

According to the method of the invention, it is proposed to maintain in the immediate environment of the furniture, that is to say in an area of less than one meter from the opening of this furniture, a partial vapor pressure of weak water, of the order of 4 g / cm2 to 7.5 g / cm2, by blowing air in this zone whose specific humidity is less than or at most equal to 2 g / kg of dry air. Full efficiency for dry air from 0.7 g / kg to 1.5 g / kg.

Thus, according to the invention, a "micro-climate" with low water vapor pressure is created in the area located in front of the opening of the refrigeration cabinet, which isolates the interior of the refrigerated cabinet from the ambient air at high specific humidity content and therefore prevents the migration of water vapor contained in the ambient air inside the furniture.

Thus, in the absence of a relatively dry micro-climate, when the specific humidity of the outside air corresponds to a water vapor content of 12 g / kg and the atmosphere of an air-conditioned store corresponds at a water content of 9 g / kg, the immediate environment of the refrigerated cabinets of store sales are around 7.5 g / kg of dry air.

By maintaining, according to the invention, in the close environment of the refrigerating cabinet located in front of the opening thereof, a water vapor content of the ambient air of 3.5 g / kg by blowing dry air with a moisture content of less than 2 g / kg of dry air, the humidity available inside the cabinet is then reduced by 7.5 g / kg - 3.5 g / kg = 4 g / kg, i.e. a reduction of more than 50% of water, and therefore of frost and ice.

The implementation of the method according to the present invention can be accompanied by the introduction of dry air of 0 to 2 g / kg into the refrigerated air streams of the refrigerated display cabinets, by connection of these air streams on air supply networks for dry air. It can also be accompanied by the connection of refrigeration cabinet fans to air supply networks for dry air from 0 to 2 g / kg in addition to the specific treatment of the furniture environment.

According to another arrangement according to the invention, a thin layer of dry air of 0 to 2 g / kg is blown in front of the curtain for protection against the warmer ambient air. This thin layer of dry air can, depending on the type of furniture, have a speed identical to that of the curtain scrolling, or a faster speed in order to carry out a phenomenon of entrainment and accompaniment of the air of the curtain, or a slower speed so that the curtain captures the dry air so that it mixes and protects the interior of the furniture from the aggression of humid air.

According to yet another arrangement of the invention, the dry air is blown in a specific manner above or below the refrigerating cabinet so as to wrap it in a "bubble" of dry air protecting it from humid ambient air.

Finally, according to another provision of the invention, a dry air blowing is carried out globally above or below the refrigerated cabinets, so as to globally maintain the volume of the zone where these cabinets are located in an air climate. dry which absorbs the humidity in which these pieces of furniture work.

The air supply networks for the supply of dry air and, if necessary, the return air are of the sealed type, in order to prevent dry air from being charged with moisture during transport.

Dry air is prepared by air dehumidifiers which, depending on the case, the sites and the installation possibilities, can be installed either outside the building, on the roof for example, or inside, in specific premises or in the same atmosphere.

The processes for manufacturing dry air can be those of dehumidification by cooling the air passing through them, with heating by heat exchanger or by recovery.

The most effective devices are air desiccation which allow to obtain dry air less than 2 grams per kilo of dry air. These materials are equipped with absorbent wheels, composed of silicate gel or lithium chloride, or other absorbent or regenerable materials.

• soufflage dans l'environnement et dans le meuble frigorifique :
     150 à 400m³/h par mètre linéaire
• soufflage devant le rideau seul :
     50 à 300m³/h par mètre linéaire
• soufflage dans l'ambiance à
  1 mètre au-dessus des meubles
  frigoriques, ce qui implique la réalisation d'un faux-plafond isolant la zone de froid alimentaire des meubles frigorifiques de vente du volume supérieur général, s'il est de grande hauteur (et dans tous les cas s'il est supérieur ou
  égal à 3 mètres) : 200 à 600m³/h par mètre linéaire.

The dry air flow rates to be used depend on the climatic conditions prevailing in the store and on the water content of the dry air. With a store atmosphere at 26 ° C, 50% RH (relative humidity), or 10.5 grams per kilo of dry air, the air flow rates to be blown will be as follows:

• blowing in the environment and in the refrigeration unit:
  150 to 400m ³ / h per linear meter
• blowing in front of the curtain alone:
  50 to 300m ³ / h per linear meter
• blowing in the mood to
  1 meter above the furniture
  refrigerators, which implies the realization of a false ceiling insulating the cold food zone of the refrigerated sales cabinets of the general upper volume, if it is of great height (and in all cases if it is higher or
  equal to 3 meters): 200 to 600m ³ / h per linear meter.

In all cases, the dry air must be blown between 0 and 2 gr / kg of dry air

• soufflage devant le rideau protecteur de 0,2 à 7m/s
• surface de couverture du rideau de 90 à 100%.

The air diffusers will be designed and determined as follows:

• blowing in front of the protective curtain from 0.2 to 7m / s
• curtain cover area from 90 to 100%.

The air intake, after introduction or distribution of dry air, will depend on the composition of the outside air. When the specific humidity of the air is low, below 8 gr / kg of dry air, a more or less significant quantity will be used to limit energy consumption.

A regulation system will make it possible to adjust the relative humidity rate, based on the analysis of the specific humidity outside, in the atmosphere and the recovery of the room treated.

The air will be filtered using filters placed either in the machines or on the duct networks. Extensive filtration will guarantee perfect hygiene in refrigerated cabinets that will operate with clean, dehumidified air, providing a high degree of hygienic quality.

The blown air will therefore be dehumidified and blown to a water content of 0 to 2 grams per kilo of dry air, and filtered using standard filters, or high efficiency or very high efficiency.

The supply air temperature can be negative or positive; in any event, in summer, air cannot be introduced at more than 26 ° C in an air-conditioned store and at more than 30 ° C in a non-air-conditioned store.

When dry air is blown in front of the protective air curtain, its temperature will be regulated from 0 ° C to + 25 ° C. When the air is blown into the atmosphere, depending on the atmosphere in the store, its temperature will be maintained between + 8 ° C and + 28 ° C.

• la figure 1 est une vue schématique en coupe verticale transversale d'un meuble frigorifique vertical à cinq niveaux, avec introduction d'air sec dans la gaine de circulation du rideau et soufflage d'air sec dans l'ambiance ;
• la figure 2 est une vue schématique en coupe verticale transversale d'un meuble frigorifique vertical à cinq niveaux à double ou triple rideau d'air, avec soufflage d'air sec par raccordement au ventilateur du meuble ;
• la figure 3 est une vue schématique en coupe verticale transversale d'un meuble frigorifique vertical à cinq niveaux avec soufflage d'un rideau d'air sec devant la vitrine ;
• la figure 4 est une vue schématique en coupe verticale transversale d'un meuble frigorifique vertical à cinq niveaux avec soufflage d'air sec autour du meuble ;
• les figures 5 à 7 montrent trois réalisations de soufflage d'air sec de façon globale dans une zone contenant plusieurs meubles frigorifiques ;
• la figure 8 est une vue schématique en coupe verticale transversale d'un meuble frigorifique vertical à cinq niveaux avec soufflage d'air sec dans le deuxième ou le troisième rideau, devant le meuble et dans l'ambiance ;
• la figure 9 est une vue schématique en coupe verticale transversale d'un meuble frigorifique à cinq niveaux à double ou triple rideau d'air, avec soufflage d'air sec dans l'ambiance et reprise de l'air soufflé ;
• La figure 10 est une vue schématique en coupe verticale transversale d'un meuble frigorifique à cinq niveaux, avec soufflage d'air sec par le ventialteur du meuble ;
• la figure 11 est une vue schématique en coupe verticale transversale d'un meuble frigorifique mixte avec soufflage d'un volume d'air sec devant le meuble et soufflage d'air sec dans l'ambiance ; et
• la figure 12 est une vue schématique en coupe verticale transversale d'un meuble frigorifique vertical cinq niveaux avec soufflage dans le double ou le triple rideau d'air par raccordement sur le ventilateur du meuble, et soufflage d'un volume d'air sec extérieur.

In order to make the invention clear, we will describe below, by way of non-limiting examples, preferred modes of implementation with reference to the appended schematic drawing in which:

• Figure 1 is a schematic cross-sectional vertical view of a vertical refrigeration cabinet with five levels, with the introduction of dry air into the circulation duct of the curtain and the blowing of dry air into the atmosphere;
• FIG. 2 is a schematic view in transverse vertical section of a vertical refrigeration cabinet with five levels with double or triple air curtain, with blowing of dry air by connection to the ventilator of the cabinet;
• FIG. 3 is a schematic view in vertical transverse section of a five-level vertical refrigeration unit with the blowing of a curtain of dry air in front of the display case;
• Figure 4 is a schematic vertical cross-sectional view of a five-level vertical refrigeration cabinet with blowing dry air around the cabinet;
• Figures 5 to 7 show three embodiments of blowing dry air generally in an area containing several refrigerated cabinets;
• Figure 8 is a schematic vertical cross-sectional view of a five-level vertical refrigeration cabinet with blowing dry air into the second or third curtain, in front of the furniture and in the atmosphere;
• FIG. 9 is a schematic view in vertical transverse section of a refrigerating cabinet with five levels with double or triple air curtain, with blowing of dry air in the atmosphere and return of the blown air;
• Figure 10 is a schematic cross-sectional vertical view of a five-level refrigeration cabinet, with blowing dry air through the cabinet ventialteur;
• FIG. 11 is a schematic view in transverse vertical section of a mixed refrigeration unit with blowing a volume of dry air in front of the cabinet and blowing dry air into the atmosphere; and
• Figure 12 is a schematic vertical cross-sectional view of a five-level vertical refrigeration cabinet with blowing in the double or triple air curtain by connection to the cabinet fan, and blowing a volume of dry air outside .

Referring to Figure 1, there is shown a vertical refrigeration cabinet 1 comprising four rows of shelves 2 and, at the base, a tray 3. The protection of the enclosure of the cabinet 1 against warmer and humid ambient air is provided by an air curtain which circulates inside the sheath 4 fitted to the cabinet and containing the evaporator 5 and the fan 6 ensuring convection.

Above the cabinet 1 opens a pipe 8 blowing dry air at less than 2 g / kg of dry air which tends to envelop the cabinet by isolating the enclosure from it from the warmer ambient air and more humid. Thanks to this arrangement, the humidity captured by the evaporator 5 will be completely negligible, thus avoiding the formation of frost, both on the fins of the evaporator and on the products placed on the shelves 2 and in the tank 3.

In addition, the sheath 4 is connected to a duct 7 for supplying dry air between 1 and 2 gr / kg of dry air, this connection being made upstream of the evaporator 5. The dry air used is manufactured from an air desiccation device (not shown in the drawing) connected to the pipe 7 by a sealed type network in order to prevent dry air from being loaded with parasitic humidity during transport.

The refrigeration unit 11 shown in FIG. 2 is of the general type with double or triple air curtain, including an external curtain intended to be supplied by the ambient air under the action of a fan 12. The other two curtains are obtained by forced convection in two circuits respectively containing fans 13,14 and evaporators 15,16.

According to the invention, the fan 12 is connected to a sealed pipe 18 for supplying dry air between 1 and 2 gr / kg of dry air, thereby blowing an external curtain of dry air 17 which isolates the enclosure. furniture 11 warmer and wetter ambient air.

We schematized in 19, above the cabinet 11, a socket for the return of the blown air.

In the embodiment shown in FIG. 3, a curtain of dry air 32, between 0 and 2 g / kg of dry air, is blown in front of the cabinet display cabinet 31, from a duct airtight dry air outlet 33 opening above the cabinet. There is provision in the atmosphere, above the windows of the cabinet 31, a device 34 for taking up the air reinjected into the desiccation system.

According to the embodiment shown in Figure 4, the refrigeration unit 41 is placed under a dry air blowing pipe 42 so that the dry blown air, between 1 and 2 gr / kg of dry air, passes in front of and behind the furniture, being taken up by an appropriate system 43 placed in the ground (or on the ground, or in elevation). The cabinet 41 is thus enveloped in a "bubble" of dry air which completely isolates the enclosure of the cabinet from the warmer and more humid ambient air.

This implies the existence of a ceiling or false ceiling located at a height of about three meters, since the dry air flow must be as low as possible.

In FIG. 5, the zone of a store where the refrigerated cabinets 51, 52 and 53 are grouped together is diagrammed at 50. In zone 50, above the cabinets 51 to 53, runs a conduit 54 for supplying dry air comprising vents 55 blowing dry furniture above the furniture between 1 and 2 gr / kg of dry air. The zone 50 is thus generally maintained in a climate of dry air which isolates the furniture 51 to 53 from the humid atmosphere of the rest of the store.

As a variant, in FIG. 6, upper vertical wall elements 61, 62 have been shown which partially close the area 50. Inwardly, the wall elements 61, 62 have arrivals 63, 64 d at their lower part. dry air between 1 and 2 g / kg of dry air blowing near the door air curtains 65, 66. As shown in this figure, the return of the blown air can be carried out by sockets 67, 68 associated with arrivals 63, 64 and by sockets 69 arranged in the upper part of zone 50.

In another variant shown in FIG. 7, the recovery of the blown dry air (between 1 and 2 g / kg of dry air) is carried out by intakes 71, 72, 73 placed in the ground, between the pieces of furniture 51 to 53. These sockets 71 to 73 could as well be placed on the ground, or behind the refrigerated cabinets.

In the embodiment shown in Figure 8, the double or triple refrigeration unit 81 air curtain has its fan 82 connected to a sealed duct 83 for supplying dry air to blow an external curtain of dry air between 0 and 2 gr / kg of dry air. In addition, the pipe 83 is extended at 84 to open towards the front of the cabinet 81, blowing a dry air veil 85. Finally, the pipe 83 is extended at its upper part to provide dry air outlets 86 , 87 which provide a blowing of dry air in front of and behind the cabinet, surrounding it.

In the embodiment shown in Figure 9, the dry air inlet pipe 92 between 1 and 2 gr / kg of dry air is disposed above the refrigeration unit 91 which is of the general double or triple air curtain including an ambient air curtain. Dry air blown into the atmosphere through line 92 is taken up by means of the fan 93 to create an external curtain of dry air. In addition, the dry air blown from the pipe 92 isolates the cabinet 91 towards the front and is taken back towards the rear of the cabinet by a socket 94 arranged in the atmosphere at the top. Full efficiency is obtained with a ceiling or false ceiling whose height above the ground is close to three meters.

The embodiment shown in FIG. 10 constitutes a variant of the device in FIG. 2, in which the external curtain of dry air 102 blown into the fan 103 of the second or third curtain is taken up on the ground, under the refrigerating cabinet 101 , by a suitable plug 104.

In the embodiment of FIG. 11, the piece of furniture 111 represented is of the mixed type composed of an asymmetrical gondola on which is placed a cupboard with glass doors, each of the two enclosures having its evaporator and its ventilation system. Above the cabinet 111 is disposed a duct 112 for the arrival of dry air between 0 and 2 gr / kg of dry air which blows in front of the cabinet a volume of dry air 113 which protects the two enclosures of the cabinet.

Optionally, at the upper part of the atmosphere, the inlet pipe 112 has an upper extension 114 blowing dry air into the atmosphere.

Finally, the embodiment of FIG. 12 constitutes a variant of the device of FIG. 8, in which the volume of dry air 122 between 1 and 2 g / kg of dry air blown in front of the second or third air curtain dry is taken up below the refrigeration unit 121 by an appropriate outlet 124 placed on the ground (the recovery could however be in the upper part).

It will be understood that the above description has been given by way of example, without limitation, and that additions or constructive modifications could be made without departing from the scope of the invention.

Claims (11)

Process for improving the operation of refrigerated display cabinets in shops, transit places and cold rooms, characterized in that dry air is blown around the refrigerated cabinet with a maximum of 0 to 2 grams of water per kilogram of dry air, considerably reducing the formation of frost on the evaporator and on the products presented in the cabinet. Method according to claim 1, characterized in that said dry air is blown above or below the refrigeration unit so as to surround it with a dry air envelope protecting it from the humid ambient air. Process according to Claim 1 or 2, characterized in that dry air is blown from the outside with 0 to 2 grams of water per kilogram of dry air. A method according to claim 3 characterized in that said dry air is introduced into the air stream constituting at least one of the protective air curtains of the refrigeration unit. Method according to Claim 3, characterized in that, to form at least one of the protective curtains of the refrigerating cabinet with dry air, the ventilator of the cabinet is connected to a dry air inlet duct. Process according to any one of Claims 1 to 5, characterized in that a volume of said dry air is blown in front of the air curtain protecting the enclosure of the refrigerating cabinet against the warmer and more humid ambient air. Method according to any one of the preceding claims, characterized in that the said dry air is blown in a general manner into an area where the refrigerated cabinets are placed, maintaining this area in a climate of dry air. Method according to any one of claims 1 to 7, characterized in that one proceeds, at the base and / or above the refrigerated cabinets, to a recovery of said dry blown air. Process according to any one of Claims 1 to 8, characterized in that the dry air is produced by dehumidification or by drying. A method according to claim 9, characterized in that the dehumidified air undergoes extensive filtration. Process according to any one of Claims 1 to 10, characterized in that the dry air is blown laminarly when the volumes of ambient air above the refrigerated display cabinets are large for ceiling heights greater than 3 meters, and / or when dry air is blown in the immediate vicinity of the refrigerated display cabinets, so as not to disturb the insulating air curtains.

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