RU2623242C1 - Tunnel freezing device - Google Patents

Abstract

FIELD: heating system.

SUBSTANCE: air coolers in the freezer compartment are installed at the top and bottom of the metal perforated conveyor belt carrying the product to be cooled. The electro-convective device of the apparatus in the form of an electrogasdynamic system connected to the voltage source contains two electrode blocks arranged parallel to each other, one of which is located in the freezer compartment area under the upper cooler and the other - in the freezer compartment area below the lower cooler. Each of the blocks consists of wire type electrodes: generating and grounding. In the version of the unit, the generating electrode can be provided with EHD needle-shaped elements. When high voltage is applied to the unit electrodes, a corona discharge arises and, as a result, an electric wind appears forming the conditions for forced electroconvection. The areas of electrode blocks location are connected by a bypass, which has built-in electrode blocks at its input and output to intensify convection. Air humidity and frost formation adjustment is ensured by an electrode unit with EHD wire-type elements placed between the upper cooler and the bypass output channel area, connected to a voltage source via a voltage divider.

EFFECT: economic and technological efficiency of the device is increased due to reduction of energy consumption, reduction of freezing process duration, product shrinkage reduction, and provision of its electro-antiseptization.

3 cl, 4 dwg

Description

The invention relates to the field of rapid freezing of a wide range of different products, specifically to the design of tunnel-type freezers, and can be used in the agricultural sector, in the food and meat and dairy industries, in medicine and pharmacology.

Known tunnel freezer (SU No. 1210020, F25D 13/06, 1984), containing a freezer in a heat-insulated casing and installed in it in separate boxes two closed belt conveyors: the upper and lower, the first of which has a section located outside the housing for laying the product, as well as air coolers containing cooling batteries and fans, and air distribution devices with guiding arcuate fins. The process of freezing the products in it is ensured both due to convective cooling by air, and due to contact heat exchange of the product with a metal conveyor belt in contact with the cooling batteries of the air coolers. However, the presence of two conveyors located in the ducts and the corresponding construction of an air-cooling and air-distribution system constructively complicate the apparatus, increasing its material consumption.

Known tunnel freezing apparatus for freezing a small piece of product (RU No. 2101629, F25D 13/06, 1998), in the upper part of the freezer of which two belt conveyors with boxes are placed one below the other, and in the lower part - air coolers, including cooling batteries and fans. One of the boxes covers the upper branch of the upper conveyor, the other - the lower branch of the upper conveyor and the upper branch of the lower conveyor. The air distribution device in this analogue is simplified in comparison with the previous analogue, and at the same time it provides intensive blowing of the product with counter-directed transverse flows of cold air.

Common disadvantages of these analogues are:

- increased energy consumption due to the technology of two-stage freezing of the product and the use of a group of high-pressure fans to create a powerful air flow;

- and the likelihood of a quick formation of frost on the surface of the cooling elements, which leads to an increase in thermal resistance and, consequently, to a decrease in the air flow rate and, as a consequence, to an increase in the duration of product processing.

In addition, they do not provide funds to reduce microorganisms on the surface of the product with a bactericidal effect.

The closest analogue (prototype) of the invention is a tunnel freezer for freezing products using forced circulation of chilled air (GB 2141813 A, F25D 13/06, 1985), containing a freezer in a thermally insulated case with windows for loading and unloading products, the upper and lower coolers and a closed belt conveyor, the upper (working) branch of the metal strip of which, designed to accommodate the processed product, passes inside the freezer, and the lower (return) a branch is outside its enclosure. Product freezing in the prototype is carried out mainly due to contact heat exchange with a cooled working branch of the conveyor belt. Therefore, the lower cooler is adjacent to the bottom of this branch of the conveyor belt with a minimum clearance and has ends at the ends of the sections with a wound flat wire made of a material with a low coefficient of friction, for example, copper, serving as a support for the belt and ensuring its smooth sliding. To improve cooling from below, an additional flow of cooling gas (circulat ING) is provided, circulating simultaneously along the cooler and the belt, using a device consisting of a fan and longitudinal guide walls located directly below the lower cooler. The upper cooler is designed to cool the product from above and, according to the description of the patent, the upper zone of the freezer can be additionally equipped with means for ensuring the forced circulation of the cooled air in the product placement zone.

The absence in the prototype of a closed, uniform for the entire volume of the freezer, circuit of the cooled air circulation (the conveyor belt passing inside the chamber separates its upper volume from the lower one), circulation in the lower zone of the chamber of additional refrigerant provided by the fan device, and rapid frost formation on the cooling elements should attributed to the disadvantages of the prototype, because they are the cause of increased energy consumption, uneven air distribution and an increase in the duration of the process, reducing its technological efficiency. So, for example, rapid frost formation on the surface of the coolers leads to an increase in thermodynamic resistance and a decrease in the boiling point of the refrigerant, and, accordingly, an excessive consumption of electricity, as it is well known that lowering the boiling point of the refrigerant by 1 ° C leads to an excessive consumption of electricity by the refrigeration machine by 4-5%. In addition, the short operating time of the cooling apparatus, due to the need for periodic defrosting of the cooling elements, does not allow long-term processing of products, i.e. reduces the performance of the device. The prototype does not provide bactericidal processing of products.

The problem solved by the invention is aimed at creating a tunnel freezer, which reduces energy consumption, shortens the duration of the freezing process, reduces the drying of the product, which allows electro-antiseptizing of the processed product.

The technical result obtained by the implementation of the invention is to increase the energy and technological efficiency of the freezer.

The technical result is achieved by the fact that the tunnel freezer for freezing products by forced circulation of chilled air, containing a freezer in a thermally insulated case having windows for loading and unloading products, a belt conveyor located inside the freezer with access to the outside of the case through the said windows, and the upper and lower coolers located in the freezer, respectively, above and below the metal belt of the conveyor, according to the invention is provided with forcing forced circulation of cooled air by an electro-convective device made in the form of an electro-gas-dynamic system connected to a voltage source, containing two electrode blocks located parallel to each other, one of which is located in the freezer area under the upper cooler, and the other in the freezer area under the lower cooler, and connecting the zone of placement of the electrode blocks of the bypass, having at the input and output built-in electrode blocks that intensify convection, and a means to control air humidity and reduce frost formation in the form of an electrode block placed between the upper cooler and the output channel bypass zone, connected to a voltage source through a voltage divider, each of the said electrode blocks consisting of wire type electrodes: generating and ground with a dielectric insert between them , and the conveyor belt is perforated.

Additional differences of the invention are that in particular cases of execution of the apparatus:

the generating electrode of the electrode block of the electro-gas-dynamic system is made with needle-shaped elements, the tips of which are turned towards the grounded electrode, and counter to the points of the counter elements of the opposite block;

the generating electrode of the bypass electrode unit is made with needle-shaped elements whose tips face the grounded electrode, which is the bypass metal duct.

The electro-gasdynamic (EHD) system, containing electrode blocks with distributed elements of wire and needle type, connected to a high voltage source, makes it possible to provide forced circulation of chilled air with a pressure sufficient for the efficiency of the cooling process without using high-pressure and, accordingly, energy-intensive fans. In the known analogues, the uniformity of the air flow created by the fans is achieved due to air distribution devices (often complicated), while the proposed energy-intensive EHD system ensures uniform air flow throughout the entire volume of the freezer.

Reducing the duration of freezing of products is provided due to the greater mobility of the ions formed in the electroconvective medium, destroying the boundary layer at the surface of the product, which allows to increase the external heat transfer coefficient, and directed frost formation on the surface of the cooling elements, turbulent air flow, and, as in contact with the surface of the product, the boundary layer is destroyed at the surface of the cooling elements and the thermodynamic resistance, defined as R = δ / λ, where δ is the thickness of hoarfrost (ice), λ is the thermal conductivity coefficient of hoarfrost (ice), which reduces the temperature difference between the cooled and cooling medium and leads to an increase in the external heat transfer coefficient of 1.2 ÷ 1 9 times.

The decrease in shrinkage is associated with a reduction in the duration of the freezing process and the possibility of regulating moisture in the air stream during the refrigeration process due to the EHD unit with wire-type electrodes connected to a voltage source through a voltage divider.

To clarify the invention presented drawings, where:

in FIG. 1 shows a General view of the freezer in the context (example); in FIG. 2 - general view of the electrode block; in FIG. 3 is an embodiment of an electrode unit with needle elements; in FIG. 4 - bypass.

In the freezer 1 with a thermally insulated casing 2, a closed belt conveyor is placed with an exit outside the casing 2 through windows 3 designed for loading and unloading processed products 4. The conveyor belt 5 is made of metal, for example, stainless steel, and is perforated.

The coolers upper 6 and lower 7 are located in the chamber 1, respectively, above and below the conveyor belt 5. The forced circulation of the air cooled by them is ensured by an electroconvective device containing an electro-gasdynamic (EHD) system with two identical electrode blocks 8 and 9 parallel to each other and bypass 10 In this case, block 8 is installed under the upper cooler 6, and block 9 is under the lower cooler 7. Each of the blocks 8 and 9 is made (Fig. 2) in the form of two electrode connected by a dielectric insert 11, each in wire-type: generating 12 and 13 grounded.

In a variant embodiment of the blocks (Fig. 3), the generating electrodes 12 are provided with needle-shaped elements 14 arranged so that their tips face the grounded electrode 13 and are opposite the points of the response elements of the generating electrode of the opposite block.

The placement zones of blocks 8 and 9 are connected by bypass 10, at the inlet and outlet of the air duct of which (Fig. 4) there are built-in electrode blocks 15 and 16, which contribute to the enhancement of convection of the air flow, and are made similarly to blocks 8 and 9, with the only difference being that The generating electrode always has needle elements. A grounded bypass can be a metal duct.

Blocks 8, 9 and 15, 16 are connected to a voltage source 17.

In the upper zone of the freezer 1 below the output channel of the bypass 10, a wire-type electrode block 18, similar to blocks 8 and 9, is installed, by which air humidity and frost growth are regulated by periodically connecting it using switch 19 to voltage source 17 through a divider 20.

In order to ensure the safe operation of the apparatus, as well as to prevent the accumulation of static electricity during its operation, grounding is provided for the heat-insulated casing 2, the freezer 1, the bypass duct 10 and the metal conveyor belt 5 (not shown conventionally in the drawing).

The operation of the freezer is as follows.

The product 4 is placed on the conveyor belt 5, and through the window 3 for loading the product enters the refrigeration processing in the freezer 1.

When a high voltage is supplied from the voltage source 17 to the EHD, the elements of the electrode unit 8 cause a corona discharge and, as a result, an electric wind, which forms the conditions of forced electroconvection. Cold air moves in a closed cycle in the entire volume of the thermally insulated freezer from the cooling element 6 to the product, then through the holes in the perforated metal conveyor belt 5 the air enters the zone of action of the cooling element 7. Here, the EHD by the elements of the electrode unit 9 creates an increased pressure due to the electric wind pushing air into the bypass 10, inside which the EHD of the electrode blocks 15 and 16 transport it into the zone of action of the cooling element 6 and the cycle repeats.

To regulate the air humidity during the refrigeration processing of the product and reduce the intensity of the frost formation process, it is necessary to switch on the electrode block 18, consisting of a generating electrode 12 and a grounded electrode 13 (Fig. 2), with the frozen out moisture contained using a switch 19 and a voltage divider 20 in air, under the action of an ion flux, it will be deposited on wire EHD elements of the electrode block. The reduced voltage on the EHD of the electrode block eliminates the possibility of influencing the process of air circulation in conditions of forced electroconvection.

The advantages of the proposed freezer are that in it, in comparison with known analogues, it is provided:

- reduction of energy consumption by 20-25% due to the fact that the power consumption of the air cooler engines is several times greater compared to the power consumption of the electro-gas-dynamic system with the same efficiency, and, unlike the air cooler motors, the electrodes do not heat up, therefore, there is no consumption parts of the produced cold to cool them;

- increase operational reliability, because EHD system with distributed electro-gas-dynamic elements of needle and wire elements, in comparison with air coolers, does not have moving parts;

- reducing the duration of the refrigeration processing of the product, ceteris paribus, by 20-25%, respectively, increased productivity of the apparatus;

- uniform movement of the air at any point in the apparatus, i.e. there are no so-called dead zones, which, in turn, has a positive effect on the quality of the refrigeration processing of the product;

- reduced drying of the product, achieved by increasing the speed of freezing and reducing the total time of refrigeration processing.

Due to electro-antiseption by airflow ions, aseptic conditions were created in the freezer of the apparatus during the entire processing time of the product, which reduces the bacterial contamination of the product. As the experiments showed, the bacteria of Escherichia coli E. coli are completely destroyed and the bacterial contamination of the unpacked product is significantly (80-90%) reduced.

Claims (3)

1. A tunnel freezer for freezing products by forced circulation of chilled air, comprising a freezer in a thermally insulated case having windows for loading and unloading products, a belt conveyor located inside the freezer with access to the outside of the case through the said windows, and upper and lower coolers located in the freezer, respectively, above and below the conveyor belt made of metal, characterized in that it is equipped with a forced circulation of chilled air by an electroconvective device made in the form of an electro-gas-dynamic system connected to a voltage source, containing two electrode blocks located parallel to each other, one of which is located in the freezer area under the upper cooler, and the other in the freezer area under the lower cooler, and connecting the zone of placement of the electrode blocks of the bypass, having at the input and output built-in electrode blocks that intensify convection, as well as a means for adjusting air humidity and reduce frost formation in the form of an electrode block placed between the upper cooler and the output channel bypass zone, connected to a voltage source through a voltage divider, each of these electrode blocks consisting of wire type electrodes: generating and ground with a dielectric insert between them, and wherein the conveyor belt is perforated. 2. The apparatus according to claim 1, characterized in that the generating electrode of the electrode block of the electro-gas-dynamic system is made with needle-shaped elements whose tips face the grounded electrode and meet the points of the counter elements of the opposite block. 3. The apparatus according to claim 1, characterized in that the generating electrode of the bypass electrode unit is made with needle-shaped elements whose tips face the grounded electrode, which is the bypass metal duct.

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