WO2006079618A1

WO2006079618A1 - Alternate de-icing of air coolers in refrigerated sales cabinets by means of electrical resistors

Info

Publication number: WO2006079618A1
Application number: PCT/EP2006/050388
Authority: WO
Inventors: Christophe Borlein; Denis Clodic
Original assignee: Auchan France
Priority date: 2005-01-27
Filing date: 2006-01-24
Publication date: 2006-08-03
Also published as: FR2881215A1

Abstract

The invention relates to a system for the de-icing of a plurality of tubes (90, 91, 92, 93) through which a coolant circulates, which is included in at least one battery of an air cooler (30) in a refrigerated sales cabinet (1) and which comprises a plurality of flexible electrical resistors (160, 161, 162, 163). According to the invention, at least one of the flexible electrical resistors (160, 161, 162, 163) is inserted into a de-icing tube (100, 101, 102, 103) which is solidly connected inside one of the above-mentioned circulation tubes (90, 91, 92, 93) at least over a substantial part of the length thereof.

Description

ALTERNATING FRESH AIR FRIGORIFIED FURNITURE FRESH AIR FRIGORIFIERS BY ELECTRICAL RESISTORS

The invention relates to a defrosting system by flexible electrical resistors inserted inside the refrigerant circulation tubes or the refrigerant of finned batteries integrated in the refrigerated sales cabinets.

1. BACKGROUND OF THE INVENTION

In the sales areas of medium and large areas, many refrigerated sales cabinets are open, only air curtains integrated into the refrigerated sales cabinet separate the indoor atmosphere of the furniture from that of the sales area. . One of the consequences of such a design is the rapid formation of ice on the finned batteries where circulates either a refrigerant circulated by a compressor or a coolant circulated by a pump. This formation of frost is all the more important as the level of storage temperature of the product is low. Such frost formations exist both in the furniture where the fresh products are placed, whose storage temperature is between 0 and 5 ° C, but even more frozen products, storage temperature between - 20 and - 18 ⁰ C .

Frost obstructs the air passage on the fins, which requires defrosting at regular intervals. The number of defrosts varies between 3 and 6 in 24 hours. Each of these defrosts lasts between 20 and 45 minutes depending on the temperature level and the amount of ice to be defrosted. These defrosts lead to an increase in the temperature of the air circulating on the products, a temperature that rises to 10 ° C, which leads to two undesirable phenomena, a very significant rise in temperature of the products of several degrees Celsius and a abrupt transfer of moisture into the cabinet via the hot air which causes re-condensation and frosting not only on certain parts of the furniture but also on the products.

2. STATE OF THE ART

Effective defrosting of refrigerated cabinets has been the subject of numerous patents. The present invention differs from the state of the art in solving poorly resolved problems. For example, there are systems where flexible electrical resistors are included in tubes where the refrigerant does not circulate and where moreover these tubes are not intimate contact with the fins. This system has several drawbacks, in particular a low deicing efficiency both because of the small number of heating tubes and by poor contact of the tubes and fins. 3. SOLUTION ACCORDING TO THE INVENTION

The present invention relates to a system for defrosting a plurality of cooling fluid circulating tubes, included in at least one battery of an aerofrigerifer included in a commercial refrigerating cabinet, and comprising a plurality of flexible electrical resistances.

According to the invention, at least one of said flexible electrical resistances is inserted into a deicing tube secured within and at least a substantial part of the length, of one of said circulation tube.

Thus, the general principle of the invention consists in using flexible electrical resistances inserted in tubes dedicated to defrosting in conductive contact with the circulation tubes of one or more battery (s) of refrigerant. This conductive contact is essential to limit the thermal contact resistance in order to obtain a transfer of heat by conduction between this defrosting tube incorporating the electrical resistance and the circulation tube of the aerofrigerator generally provided with fins. A simple criterion for defining the conductive contact is furthermore that the temperature difference between the tube dedicated to deicing and the tube of the aerofrigerator is very small, of the order of 0.1 Kelvin.

Advantageously, the deicing tube is secured by brazing or welding with said at least one of said circulation tubes.

According to another advantageous variant of the invention, the deicing tube is secured by bonding with said at least one of said circulation tubes.

Preferably, the deicing tube is secured to said at least one of said circulation tubes over a length equivalent to at least eighty percent of the total length of said at least one of said circulation tubes.

Advantageously, the aerofrigerifer comprises: a first battery and a second battery, said second battery of said air-cooler being independent of said first battery and separated from said first battery by an insulating partition; and

- A lower motorized shutter and a motorized upper shutter, alternately ensuring the passage of air to be cooled on said first battery or on said second battery;

, and in that said lower motorized flap has a shape such that it acts as an element for collecting and discharging the defrosting water via a perforated tube-shaped hinge.

Advantageously, said first battery and said second battery are controlled by a programmable controller using:

for triggering a defrosting mode of the first battery, comparing the temperature difference between the air temperature measured by a first probe at the output of said aerofreigeriger and the temperature measured by a second probe temperature at the coldest point of said first battery with a first set point;

for triggering a de-icing mode of the second battery, comparing the temperature difference between the air temperature measured by said first probe at the output of said aerofrigerator and the temperature measured by a third probe temperature at the coldest point of said second battery with said first setpoint;

- For stopping said defrost mode of said first battery, the comparison of the temperature measured by said second temperature sensor with a second temperature setpoint.

for stopping said deicing mode of said second battery, comparing the temperature measured by said third temperature sensor with said second temperature setpoint.

According to another preferred feature, said second setpoint value is equal to 7 degrees Celsius.

The proposed system aims on the one hand to defrost the refrigeration battery without raising the temperature of the air circulating in the furniture and products and to perform this defrosting by flexible electrical resistances placed in dedicated defrosting tubes which are in conductive contact with the inner wall of the air circulation tube of the aerofrigerifer, where circulates the cooling fluid (a refrigerant or a coolant) , and in particular by brazing for at least 80 percent of the length of the air-cooling tube. The design is such that the flexible electrical resistances are easily removable. To obtain an almost constant temperature of the cold air blown on the products to be preserved, the aerofrigorifère is composed of two finned batteries arranged in parallel on the air circuit and operating alternatively in cold mode and in mode defrosting. To enable such an operation, flaps are arranged upstream and downstream of these two air batteries to allow the passage of air only on the battery in refrigerating operation and prohibit the flow of air on the battery in defrost.

A detailed description makes it possible to better understand the interest of the system according to the invention.

Figure 1 gives a sectional view of a refrigerated sales unit 1 comprising among others a series of fans 2 to ensure the circulation of cold air both on the aerofrigorifère 30 and in the furniture structure. This aerofrigerent 30 comprises a first battery 3 operating in parallel and alternately with a battery 4. The air passes on one or the other of the two batteries depending on the position of the flaps 5 and 6. When the battery 3 produces the cold, the battery 4 is either stopped or in defrosting and vice versa, when the battery 4 is in operation, the shutters 5 and 6 seal the air passages of the battery 3 which is then either defrosting or judgment. This alternating operation makes it possible not to modify the temperature of the air blown on the installed products 400, 401, 402 and following on the shelves 50 and 51 and following of the refrigerated furniture of sale.

FIG. 2 shows an end and detailed view of the aerofrigerator 30 composed of the two batteries 3 and 4. The motorized shutters 5 and 6 are recognized with their respective drive motors 7 and 8. The detail shows that an insulating partition 11 separates the batteries 3 and 4 and that each of the tubes 90, 91, 92, and following comprise the inside of each of them a brazed tube 100, 101, 102 and following, dedicated to defrosting, in conductive contact, receiving a flexible electrical resistance.

FIG. 3 shows a view of a circuit of a battery comprising two tees 131 and 132 through which then enters the refrigerant or refrigerant, the circuit formed by the finned tubes 90, 91, 92 and 93 and following, where circulates the refrigerant or coolant, and wherein are brazed the tubes dedicated to defrost 100, 101, 102 and 103 where the flexible electrical resistors 160, 161, 162 and 163 flexible are inserted.

FIG. 4 gives the detail of an inlet tee 130. The refrigerant or the refrigerant enters via the pipe 120 entering through a tee 130 into the circulation tube 90 containing the tube 100 whose diameter is significantly smaller than the tube 90 and containing resistance 160.

FIG. 5 shows that the tubes dedicated to defrosting 100 and 101 are fixed in conductive contact on opposite generatrices of the circulation tubes of the aerofrigerator. This is indeed essential to allow adequate closure by the elbow 140 of the circulation tubes of the aerofrigerator containing the tubes dedicated to defrosting. FIG. 6 shows the detail of the blanks 150 and 151 which must be extremely precise in order to fit both the circulation tubes 90 and 91 of the aerofreigerifer and the tubes dedicated to defrosting 100 and 101. These blanks 150 and 151 are made in such a way that the solder joint between the bend 140 and the tubes 100 and 101 makes it possible to obtain a seal necessary for air-cooled refrigerants operating with refrigerants under pressure up to 25 bars. The assembly of the tube 100 and 101 on the opposite generatrices of the tubes 90 and 91 of the aerofrigorifère as well as the cutouts 150 and 151 of the tube 140 constitute the repetitive pattern of the assembly on the whole of the aerofrigerifer and are a element of the overall concept of conductive fixing tubes dedicated to the tubes of the aerofrigorifère while leaving the flexible resistors 160 and 161 so that they can be electrically connected.

FIG. 7 is a sectional view showing the circulation tube 90, the defrosting tube 100 incorporating the resistor, the electrical resistance 160, the tube 100 being in conductive contact inside the tube 90 by a solder joint 170 almost continuous over at least 80 percent of the generatrix of the tube 100. Of course, the Conductive contact can be made by any other known means without departing from the scope of the invention.

Figure 8 shows a detailed view of the lower flap 5 which has several features. To take account of the fact that the battery 3 may be a larger main battery and the battery 4 a smaller secondary battery, the battery 3 operating longer in cooling mode, the battery 4 essentially operating during the defrost cycle of the battery 3. In this case, the two walls 18 and 19 of the flap 5 are unsymmetrical, the largest 18 to close the section where is inserted the largest battery 3. The lower flap 5 has a particular role of recovery of the defrosting water. To do this, the lower hinge of the flap consists of a tube 20 having a series of orifices 210, 211 and following through which the defrosting water is both recovered and drained outside. The tube 20 comprises a heating cord to keep de-iced water always above the freezing point. Figure 9 shows a detail of the tube-shaped hinge where we see the succession of orifices 210, 211 and following. 4. OPERATION OF THE SYSTEM ACCORDING TO THE INVENTION

The air is sucked by the fan or fans 2 in a specific circuit 60 of the refrigerated sales cabinet as shown in FIG. 1. In the example taken from FIG. 1, the air circulates on the main battery 3 where it cools and deposits under Frost shape some of its moisture. When the temperature difference between the temperature of the surface of the battery 3 and the temperature of the exit of the air of the battery increases, it indicates that the exchange is deteriorating and that it is necessary to launch the cycle of defrosting the battery 3. The flaps 3 and 5 will therefore switch to close the air circuit on the battery 3 and allow the flow of air on the battery 4. A regulation of the refrigerant flow that will be explained later allows to stopping the circulation of the refrigerant or refrigerant in the battery 3 and allow the contrary circulation of this fluid in the battery 4 which then operates as an evaporator and produces cold. Once the battery 3 is aeromagnetically isolated and emptied of its refrigerant or refrigerant, the flexible electrical resistors 160 and following inserted into the tubes 100 and following are then put into operation and raise the temperature of the tube 100 and following and therefore the tube 90 and following with a very small temperature difference, of the order of 0.1 Kelvin, and almost instantaneously, and that of the fins crimped on these tubes. When the wall temperature is above 0 ° C, the water frost begins to melt. The battery is thus defrosted, the water is collected by the shutter 5 which also has a suitable slope to allow gravity evacuation of the defrosting water through the tube 20. When the temperature of the fins is greater than 7 ° C, the experiment shows that the frost is completely melted. A dewatering time is then provided and the refrigerating operation of the battery 3 can then resume either as soon as the defrosting is finished, or until a critical layer of frost is formed on the battery 4. The system thus designed allows a rapid defrosting, typically of the order of 7 to 10 minutes, due to the conductive contact between the tubes 100 and following and the tubes 90 and following, while it usually takes about twenty minutes and as the refrigeration production was initiated on the battery 4, the air temperature has not varied, thus solving the known difficulties of the usual defrosts. In fact, in this case, the hygrometry of the blown air remains stable as well as its temperature, so no deposit of moisture or frost is formed inside the refrigerated sales cabinet. 5. SYSTEM FOR CONTROLLING SUCCESSIVE DEFROSTING OF BOTH

BATTERY

The table below shows the successive times and the actions to be performed to manage the control system of the successive de-icing of the two batteries.

The time TO is the start of operation of the battery 3 in cooling mode, the solenoid valve 23 of FIG. 10 is open, that is to say in position 1 in table 1, allowing the arrival of the refrigerant or the refrigerant. refrigerant in this battery while the solenoid valve 24 is in the closed position, position 0, and therefore prohibits the flow of refrigerant or refrigerant on the battery 4.

At time T1, which is at least two hours distant from the time TO, this minimum time is also controlled by a clock, the defrosting cycle of the battery 3 begins, the solenoid valves 23 and 24 are then open both , positions 1 of Table 1, which allows the temperature of the battery 4. The flaps 5 and 6 are always in the same position. In addition to the clock control, which manages the minimum time, the defrosting is triggered when the temperature difference between the probe 72, placed in the air leaving the aerofrigerator 30, and the probe 70, placed at the point the coldest of the battery 3, is greater than 5 K. When the defrost is performed on the battery 4, the temperature difference is measured between the probe 72 and the probe 71 also placed at the coldest point of the battery 4, that is to say on a fin near the inlet of the refrigerant or refrigerant, as is also the probe 70 on the cold battery.

At time T2, the solenoid valve 23 is closed, position 0 of Table 1, interrupting the supply of refrigerant or refrigerant battery 3, allowing this battery to empty. The emptying time, fixed experimentally, is 1 to 2 minutes.

At time T3, the flaps 5 and 6 change position and obstruct the passage of air on the battery 3 and allow the passage of air on the battery 4.

At time T4, the battery 3 is isolated from the air circuit and the flexible resistances come into operation, position 1 of the flexible resistors 160 and following. The defrosting time is controlled by the temperature sensor 70 which verifies that the temperature of the coldest blade is not greater than 7 ° C. When this temperature is reached, the supply of the flexible electric resistances is cut off, position 0 of table 1. The defrosting time is short, less than 10 minutes. For the battery 4 it is the temperature sensor 71 which controls the higher temperature level of the colder fin.

At time T5, the flexible resistors 160 and following are stopped and a dewatering time of about 10 minutes is left, the heating cord of the water discharge pipe 20 is put into operation.

At time T6, the solenoid valve 23 is open, the refrigerant or coolant is recirculated on the battery 3.

At time T7, the flaps 5 and 6 switch to the initial position and the cycle can start again.

All of these successive actions opening and closing of the solenoid valves 23 and 24, positional change of the flaps 5 and 6, switching on and off of the flexible electric defrost heaters are programmed actions in a control unit which uses as input data, for triggering defrost, a first temperature setpoint (500) equal to the temperature difference between the probe 72 and either the probe 70 for the battery 3 or the probe 71 for the battery 4 and, for stopping defrosting, the probes 70 and 71 as soon as the temperature measured by these probes is greater than a second temperature set point value (501), preferably equal to 7 ° C. A timer integrates the different time sequences of emptying the battery of its fluid and dripping and the minimum time between two defrosting.

Claims

1. Defrosting system of a plurality of circulation tubes (90, 91, 92, 93) of a cooling fluid, included in at least one battery of an aerofiigerifer (30) included in a refrigerating cabinet ( 1), and comprising a plurality of flexible electrical resistors (160, 161, 162, 163)

, characterized in that at least one of said flexible electrical resistances (160, 161, 162, 163) is inserted into a deicing tube (100, 101, 102, 103) secured inside and at least on a substantial part the length of one of said circulation tubes (90, 91, 92, 93).

2. Defrosting system according to claim 1, characterized in that said deicing tube (100, 101, 102, 103) is secured by soldering or welding with said at least one of said circulation tubes (90, 91, 92, 93).

3. Defrosting system according to claim 1, characterized in that said defrosting tube (100, 101, 102, 103) is secured by bonding with said at least one of said circulation tubes (90, 91, 92, 93).

4. Defrosting system according to any one of claims 1 to 3, characterized in that said defrosting tube (100, 101, 102, 103) is secured to said at least one of said circulation tubes (90, 91, 92 , 93) over a length equivalent to at least eighty percent of the total length of said at least one of said circulation tubes (90, 91, 92, 93).

5. Defrosting system according to any one of claims 1 to 4 characterized in that said aerofrigorifere (30) comprises: a first battery (3) and a second battery (4), said second battery (4) of said aerofrigorifere (30) ) being independent of said first battery (3) and separated from said first battery (3) by an insulating partition (11); and a lower motorized shutter (5) and an upper motorized shutter (6), alternately ensuring the passage of the air to be cooled on said first battery (3) or on said second battery (4);

, and in that said lower motorized flap (5) has a shape such that it acts as an element for collecting and discharging the defrosting water via a perforated tube-shaped hinge (20).

6. Defrosting system according to claim 5 characterized in that said first battery (3) and said second battery (4) are controlled by a programmable controller using: for triggering a defrosting mode of the first battery (3), comparing the temperature difference between the air temperature measured by a first probe (72) at the output of said aerofluoriger (30); ) and the temperature measured by a second temperature probe (70) at the most fioid point of said first battery (3) with a first setpoint (500);

for triggering a defrosting mode of the second battery (4), comparing the temperature difference between the air temperature measured by said first probe (72) at the output of said aerofligerigère (30); ) and the temperature measured by a third temperature probe (71) at the most fioid point of said second battery (4) with said first setpoint (500);

for stopping said defrosting mode of said first battery (3), comparing the temperature measured by said second temperature sensor (70) with a second temperature reference value (501);

for stopping said deicing mode of said second battery (4), comparing the temperature measured by said third temperature sensor (71) with said second temperature set point value (501).

7. Defrosting system according to claim 6, characterized in that said second setpoint value (501) is equal to 7 degrees Celsius. (501).