Industrial microwave ovens. Equipment for industrial microwave heating

Industrial microwave ovens are used in catering establishments for prompt warming up, as well as preparation and defrosting of various products and ready meals using a high-frequency current of an electromagnetic field. Industrial microwave ovens operate in the following modes:

• microwave,
• convection,
• grill.

In addition, they can be combined for a more varied preparation of common dishes. Today, mechanical, electronic, and electromechanical control of microwave ovens is used.

As for the differences between professional equipment and household equipment, in general, professional ovens are similar to household ones, but they cook, heat up and defrost food much faster and in large quantities. That is why most entrepreneurs are trying to buy branded food equipment, and not be content with much less productive household counterparts.

In addition, industrial microwave ovens are more reliable and durable than household ones. They are able to withstand intensive use, that is, they can work continuously for a long time. Often they are equipped with additional programs, and almost always have a larger internal chamber.

Another distinguishing feature of professional microwave ovens from household ones is ultra-reliable shielding. It is for this reason that such ovens practically do not emit harmful electromagnetic waves. The door mechanism has a reinforced structure, and the professional microwave ovens themselves are built very rationally, which makes it possible to use the working volume of the chamber most efficiently.

Microwaves are not an essential piece of equipment for professional kitchens, as they are less heavily involved in the cooking process. But lately, professional microwaves are increasingly being used in high-traffic bars, restaurants and fast food outlets.

Such equipment is already absolutely indispensable for restaurants and cafes offering full meals. Industrial microwave ovens are successfully used in large kitchens in hotels and airports.

Professional ovens, like any other similar equipment, are distinguished by increased wear resistance and the highest productivity. They are designed for really tough operation, and in an almost round-the-clock mode. The quality of such equipment is ensured by an extremely careful selection of materials of construction with excellent performance characteristics. Also, a great advantage of professional ovens is the greater mobility of heating and defrosting dishes, which becomes an indispensable quality when there is a need to increase the throughput of a particular catering enterprise.

Compared to other professional equipment, the advantage of microwave ovens is the economy in power consumption, since most models operate on a single-phase current network and bring products to readiness in a very short time. Most microwave ovens are made of stainless steel, lined with plastic or the same stainless steel on the outside. The inner chamber is made without seams, which greatly facilitates its maintenance.

Which is better: infrared wood dryer or microwave analog? To understand, you need to understand how they work, as well as compare the main indicators. What we are going to do.

Wood is a hygroscopic material that contains moisture and is able to absorb it from the outside. Lumber on sale comes in two types: with natural moisture and dried. The latter are more expensive, since they are ready for use immediately after purchase. Therefore, many sawmill owners are interested in purchasing wood dewatering equipment.

The market offers several options for wood drying plants. Today we will consider infrared dryers and microwave installations, we will understand the principle and parameters of their operation, we will determine how to organize the production process using them. Having detailed information about different types of equipment, it will be much easier to decide which one will be optimal for a particular production.

Principle of operation

Infrared Dryers suggest drying wood by heating it with infrared rays. This method does not require the use of a coolant, the organization of the ventilation system and the presence of complex control automation. Drying does not lead to internal stress and warping of the wood. It is possible to change the drying mode depending on the quality of the source material.

The principle of operation of the microwave dryer is similar to the operation of a microwave oven. Drying occurs under the influence of microwave radiation: the moisture in the wood heats up and boils, the excess pressure created by the hot steam squeezes it out. Excess moisture is removed by reversible fans.
The mode of attenuation of the microwave wave makes it possible to regulate the drying temperature.

Appearance

Infrared Dryers are a set of thermoactive cassettes, only 1.5 mm thick. These cassettes are stacked in a certain sequence in a pile of lumber prepared for drying.


Microwave dryers look like a closed metal container, in most cases equipped with a motorized cart with an electric drive for more convenient placement of a pile of sawn timber inside the structure. Additionally, a control unit is installed.

Size and weight

One of the main advantages of infrared dryers is their portability. Standard thermosetting cassette has a size of 1230 x 650 x 1.5 mm and a weight of 5.7 kg, which allows you to easily transport the entire set of equipment for drying wood in the trunk of a car. The weight of a set of 12 cassettes is 69 kg, and in a crate with a shield and cable routing - no more than 130 kg.

Microwave installation has much larger dimensions and weight. So, the chamber, designed for drying 6-9 cubic meters of sawn timber, has a length of more than 6 meters, a width of 1 meter and a height of about 2 meters. At the same time, its weight is 9 tons, and the area required for the installation of equipment is 3x17 m. To transport the microwave installation from place to place, you will need to use special equipment.

Autonomy of work

Infrared dryer completely autonomous, with its correct installation and connection, you will not need to constantly monitor the drying process.

Microwave installation, in which the material is dehydrated by high-frequency currents (915-2500 MHz), requires regular monitoring by the operator to prevent the wood from burning inside the chamber.

Drying time

Naturally, the drying time of sawn timber depends on its moisture content in its original state and the type of wood.

By using infrared thermoactive cassettes any kind of wood can be dried. Drying time to 8% pine moisture is 3-7 days. The thinner the boards and the higher the moisture content to be achieved, the less time it will take to dry.

Regarding Microwave dryers it is known that the "SHCh-LES" installation of the "INVESTSTROY" company is able to dry pine timber 200x200 mm with a humidity of 50-70% to 18% in 22 hours (after the material has cooled down, the moisture content decreases to 10.2%).

Power supply

Infrared cassettes work from an ordinary household power supply network of 220 V.

For work Microwave drying plant power supply 380V, 50 Hz will be required.

Power and electricity consumption

Maximum power of the installation from infrared cassettes: 3.3 kW / m³. Electricity consumption during the drying of 1m³ of wood: 100-400 kW * h.

Average power consumption microwave installations: 58 kW, and the specific energy consumption for the drying process is 200-230 kW * h / m³.

Price

One of the most significant indicators when purchasing new equipment for work is its market value.

The prices for infrared dryers FlexiHIT are very democratic:

• equipment for drying 1 m³ of a three-meter board will cost 59,288 rubles;
• equipment for drying 1 m³ of a four-meter board will cost 69,329 rubles;
• equipment for drying 1 m³ of a six-meter board - 70,007 rubles.

Moreover, the prices are indicated for the entire set of equipment, which contains 12 thermoactive cassettes, a control panel, cabling and crate.

In Russia Microwave installations, as noted above, is produced by the company "INVESTSTROY". Such a dryer costs from 1,300,000 rubles. In addition, when planning to purchase it, you need to take into account that a magnetron (a device that generates microwaves) is a consumable item. It will need to be replaced at least once a year. The cost of the magnetron is 150,000 rubles.

conclusions

It is worth noting that both options of the considered dryers are new technologies, but already successfully used in our country.

Undoubtedly the convenience of infrared equipment is the possibility of using it, both indoors and outdoors, mobility and low price. Such equipment can be used in production and in everyday life. Ease of installation allows you to completely assemble the dryer within one day, and if necessary, quickly disassemble it and transport it to another place. At the same time, the drying quality meets the most stringent requirements.


The advantage of the microwave installation k is the ability to quickly dry thick beams and rounded logs with a diameter of up to one meter. Their use is justified in production, where it is a question of preparing for the further use of large workpieces. But with a less impressive scale, this technology is practically inaccessible due to its high cost and size.

Microwave unit for drying bulk materials.
Our company specializes in the development, design, engineering and testing of equipment in order to obtain a reliable and high-quality product for drying and heat treatment of bulk materials. A sample with a maximum power of 2 kW (power controlled by software) and water cooling has successfully proven itself in the technological process. Application in various industries is possible.

Microwave heating and its application:
Technological processing of a wide variety of objects almost always includes heat treatment and primarily heating or drying. With traditional methods of heating and drying (convective, radiation and contact), the object is heated over the surface. If the thermal conductivity of the object is low, which is the case with dielectrics, then the heat treatment of the object occurs slowly, with local overheating of the heating surface, which may cause burning of this surface, the occurrence of internal mechanical stresses. All this can ultimately lead to the failure of the facility.
Super-high-frequency heating of an object is called the energy of the electromagnetic field of ultra-high frequencies. An electromagnetic wave, penetrating into an object, interacts with charged particles. The combination of such microscopic processes leads to the absorption of field energy in the object. A complete description of the effect can be obtained only with the help of quantum theory. We restrict ourselves to taking into account the macroscopic properties of the material medium described by classical physics.
Depending on the location of charges in them, the molecules of the dielectric medium can be polar and non-polar. In some molecules, the arrangement of charges is so symmetrical that in the absence of an external electric field, their electric dipole moment is zero. Polar molecules have a certain electric dipole moment even in the absence of an external field. When an external electric field is applied, non-polar molecules are polarized, that is, the symmetry of the arrangement of their charges is violated, and the molecule acquires a certain electric moment. Under the action of an external field, polar molecules not only change the magnitude of the electric moment, but also rotate the axis of the molecule in the direction of the field. Usually, a distinction is made between electronic, ionic, dipole and structural polarization of a dielectric. At microwave frequencies, dipole and structural polarizations have the greatest specific gravity, so that heat release is possible even in the absence of a conduction current.

Microwave devices for technological purposes operate at frequencies established by international agreements. For heat treatment in the microwave range, electromagnetic oscillations are most often used at frequencies of 433, 915, 2375 (2450) MHz.
The table provides information on the depth of penetration of an electromagnetic wave into some of the dielectrics with losses.

Depth of penetration of an electromagnetic wave in a dielectric with losses at 20-25Со

So, if instead of traditional heating methods, heating using the energy of microwave oscillations is used, then due to the penetration of the wave into the depth of the object, this energy is converted into heat not on the surface, but in its volume, and therefore it is possible to achieve a more intense increase in temperature with greater uniformity heating compared to traditional heating methods. The latter circumstance in some cases leads to an improvement in the quality of the product. Microwave heat treatment has a number of other advantages. So, the absence of a traditional heat carrier ensures the sterility of the process and the inertia-free heating control. By changing the frequency, you can achieve heating of various components of the object. Microwave electrothermal installations occupy a smaller area than similar installations with a traditional power drive, and have less harmful impact on the environment with better working conditions for the service personnel. Microwave installations and their working chambers.

For any purpose of the microwave electrothermal installation, it has a structural diagram shown in Figure 1.

A prototype of a microwave oven manufactured for Polisorb LLC

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No matter how fans of a healthy lifestyle advocate for the valuable properties and a storehouse of vitamins in fresh vegetable salads, most people still prefer to combine them with hot meals. Compact, powerful, professional microwave ovens for restaurants and cafes from the WhiteGoods online store will heat up meat, side dishes, soups, pies, hot dogs, pizza, hot sandwiches and any prepared dishes in a matter of seconds. It is a reliable, convenient and affordable solution for catering enterprises of any level.

Microwave oven is a wise compromise in confined spaces

Microwaves have become a reasonable compromise for cafes and food service outlets, where the lack of production space barely allows you to place a refrigerator, coffee maker, etc., and not just an oven and, even more so, in a hot workshop. This compact appliance is able to meet the hot food needs of customers and get you the sales you deserve. Modern microwave ovens for restaurants from the line of advanced models combine innovative technologies such as convection function, multi-level power control, several defrosting modes, pre-programmed programs for up to 360 recipes, an exhaust air purification system (catalytic converter), etc. Extensive functionality turns these small appliances into versatile pieces of equipment that will become a lifesaver in your restaurant, diner or cafe.

Express-class heating equipment for a successful business!

Professional microwave ovens are absolutely indispensable equipment for grocery stores with hot snack counters, cafes without their own kitchen, bistros, food courts based on semi-finished products and other ready-made food outlets. Due to the ergonomic shape of the case, the devices are easy to maintain and maintain hygiene standards. The main differences between a professional microwave oven and household models:

• increased power, thanks to which you will reduce the heating time by 42% -60% (hot sandwich / pizza in 4-9 seconds, cheeseburger - 20 seconds);
• uniform heating of dishes without drying out the edges or undercooking the middle, inherent in household microwave ovens, will exclude marriage or dissatisfied reviews of restaurant visitors;
• increased useful volume of the working chamber;
• extended timer up to 60 min;
• many combined modes: microwave technology, grill, defrosting, cooking, convection, etc.;
• Glassy enamelled hard-wearing restaurant microwave oven casing is robust and designed for heavy use in commercial kitchens. Plus durable reliable parts of the mechanism.

Thanks to its stylish design and rich color range, a microwave oven for a cafe will become an interesting addition to the interior and will take its rightful place on the bar counter. A good model of a professional microwave will help you pamper your visitors with both juicy meat or fish with a delicate taste, as well as aromatic pastries with an appetizing golden crust that will look fresh, as if fresh from the oven.

Where to buy good microwave ovens for restaurants and cafes?

Flexibility and versatility, with the greatest preservation of usable space, explain the high demand for equipment of this class. A high-speed, easy-to-operate restaurant microwave will provide significant time savings for cooks and add extra convenience to the professional kitchen. Prompt customer service will have a beneficial effect on the profitability of the establishment.
In the WhiteGoods online store you can buy the most popular, universal, professional microwave ovens for cafes, restaurants and other catering establishments. Stunning reliability and high efficiency - these are the distinctive features of professional equipment from the WhiteGoods catalog. Our microwave ovens will perfectly fit into the concept of any kitchen, save time and money!

The main areas of application of microwave heating can be identified - food, rubber and textile industries. Here, characteristics such as process efficiency, automation capability and high product quality play an important role. There are prospects for the introduction of microwave heating and drying in the pharmaceutical industry, wood processing and agriculture. The use of fast heating technology in canteens, hospitals, schools, etc. is expanding, the massive use of microwave ovens in everyday life is already well known to our readers.
The microwave heating effect is based on the absorption of electromagnetic energy in dielectrics. Microwave fields penetrate to a considerable depth, which depends on the properties of materials. Interacting with matter at the atomic and molecular level, these fields affect the movement of electrons, which leads to the conversion of microwave energy into heat.
UHF energy is a very convenient source of heat, which in a number of applications has undoubted advantages over other sources. It does not introduce contaminants when heated, and when it is used, there are no combustion products. In addition, the ease with which microwave energy is converted into heat allows very high heating rates to be obtained, while no destructive thermomechanical stresses arise in the material. The generating equipment is completely electronic and works practically inertialessly, due to which the microwave power level and the moment of its supply can be instantly changed. The combination of microwave heating with other heating methods (steam, hot air, infrared radiation, etc.) makes it possible to design equipment to perform various functions, i.e. Microwave heating allows you to create new technological processes, increase their productivity and improve product quality. To correctly assess the applicability of microwave energy in special processes, detailed knowledge of the properties of the material at various frequencies and at all stages of the process is required. The absorbed power and the depth to which this power penetrates are determined by three factors: dielectric constant, frequency and geometry of the microwave system.
The dielectric constant of lossy materials is a complex quantity:
,
where ε is the relative dielectric constant, tgδ = ε1 / ε is the dielectric loss factor of the material, or the tangent of the loss angle.
The depth of penetration in microwave energy is understood as the distance d at which the power density decreases to 37% of the value on the surface, i.e. in other words, 63% of the initial energy of the electromagnetic wave is absorbed in the material and converted into heat. With a small value of tgδ, the penetration depth is determined by a simple expression:

where d is the depth of penetration, cm; f - frequency, GHz.
The power absorbed per unit volume will be, W / cm3:
P = 2.87 10-4 E2f tgδ,
where E is the electric field strength, V / cm; f - frequency, GHz.
The calculated values ​​of the depth of penetration of microwave energy into food products at the widely used frequency of 2.45 GHz are given in Table 1. If tanδ decreases with temperature, then the heating process is stable (absorption of microwave energy decreases with temperature). This automatic temperature limitation occurs when dielectrics are heated, in which losses are due to the water content with its special dependence of dielectric properties on temperature.
Heating by infrared or light sources works, in comparison with microwaves, at higher (by about 2-3 orders of magnitude) frequencies. Accordingly, the penetration depth decreases and only the surface of the object to be treated is heated. The rest of the volume receives heat only due to the slower heat conduction process. This can lead to thermomechanical overvoltages and loss of material quality. Where time is of the essence (cooking, drying or reheating), microwaves have a decisive advantage over radiant heat. For example, when cooking vegetables or fruits, microwave heating helps to maintain a fresh look and taste, and the vitamin content is slightly reduced.
Microwave heating is economically effective when drying hard wood, since a temperature rise at a rate of up to 1000 ° C / s can be realized at a field strength of 5 kV / cm.
Compared to infrared heating, the use of microwaves has a great advantage - almost instantaneous switching on and off, as well as precise temperature control. High power density and better focusing result in great energy savings. Waste radiation and the need for concomitant cooling of surrounding parts are eliminated.
The integration of an electronic microwave generator into an automatic production line is easy due to its reasonable cost, economy and compactness. A combination with other treatments is also possible. For example, when processing poultry carcasses, microwaves and steaming are used simultaneously.
Of course, for a particular application, factors such as product quality, processing speed, space required, energy cost, and investment must be carefully evaluated to determine if microwave heating will be superior to traditional methods.

Industrial magnetrons
Magnetrons and klystrons are used as high-power generators. Magnetrons dominate due to their higher efficiency below 50 kW. Most often, two frequencies are used - 915 and 2450 MHz. Since the frequency of 915 MHz can not be used in all cases, the frequency of 2450 MHz is usually considered optimal in international practice. Table 2 gives an idea of ​​the modern Russian magnetrons produced by CJSC NPP Magratep in comparison with foreign devices.
Magnetron М-116-100 (Fig. 1) is used in installations for defrosting fish, softening rocks and in other cases where an increased depth of penetration into the material is required.

The world's only magnetron M-137 with a power of 50 kW at a frequency of 433 MHz (Fig. 2) was successfully used in experimental installations for soil softening in Yakutia. Such a low operating frequency provides the required penetration depth of microwaves into the frozen rocks.
Magnetron M-168 with a power of 5 kW (Fig. 3) is widely used in installations for rubberizing cables, vulcanizing rubber parts, and polymerizing plastic.
Microwave treatment plants
Microwave heating processes are divided into two groups: continuous processes and batch processing. In continuous processes, for example on a conveyor, the "raw" material continuously passes through the processing zone, while the load on the output of the microwave generator is practically unchanged. When processing in batches, the heated material is in the processing zone until the required temperature is reached, therefore, with a change in temperature, the dielectric constant and the loss factor change significantly. This leads to a change in the load (and within a wide range) for which the microwave generator must operate. Even in waste economical installations, the VSWR of the load can exceed 4. In this case, magnetrons are preferred because of their ability to operate on a load with high VSWR.

Fig. 4. Scheme of the installation for heating oil products in railway tanks ("Elvis" enterprise, Nizhny Novgorod). The microwave generator goes down from the top

The new technology of high-intensity heat treatment consists in heating the grain in a combined way: first, convectively - up to a temperature of 95 ° C and then - in an electromagnetic microwave field up to a temperature of 120–150 ° C (Fig. 6). With the rapid heating of the grain "from the inside", capillary moisture boils, the partial pressure of water vapor increases and the starch shells break. At the same time, starch that is difficult to digest is broken down into dextrins - easily digestible forms. With this treatment of grain, which contains about 40% starch, its nutritional value increases by 20-30% and the palatability improves.
Other promising microwave technologies are drying, disinsection and disinfection of grain, thermal stimulation of grain during pre-sowing treatment, improvement of baking qualities, and a number of others. Pasteurization and sterilization of liquid food products using microwave energy are possible. These methods are distinguished by high productivity of the process and compactness of installations. Among other things, installations for microwave processing of materials have the ability to accurately maintain technological modes, which makes it possible to obtain high quality products, for example, when drying medicinal herbs (Fig. 7).
In some cases, one has to deal with such large-sized objects that resonators or conveyor processing cannot be used. Then, for example, a package of a wooden bar for drying is loaded into a box, inside which it is processed with microwave energy using a system of special waveguide-slot emitters (Fig. 8).
Radiant systems are especially suitable for heating thin films or microwave hyperthermia of malignant neoplasms.
The essence of the method consists in heating the tumor with the help of electromagnetic radiation to a temperature level of 42–44 ° C. The advantages of microwave hyperthermia are that the zone of influence is heated from the inside, heating the tissues at the same time, without damaging the skin. The modern device for local microwave hyperthermia "Yakhta-3" (FSUE "NPP" Istok ", Fryazino) allows creating and long-term maintenance of a zone of hyperthermia in a tumor of almost any configuration with minimal impact on surrounding organs and tissues. in an independent form, and as a means of enhancing the effect of chemotherapy and radiation therapy.

Literature
1. Microwave energy / Per. from English. Ed. Shlifera E.D., vol. 2. - M .: Mir, 1971.
2. IR, 2008, No. 12;