SU1748294A1 - Resonant chamber for microwave heating of dielectrics - Google Patents

Abstract

Use: for drying products. SUMMARY OF THE INVENTION: A resonator chamber for microwave heating of dielectrics comprises a housing in the form of a rectangular parallelepiped, whose inlet and outlet pr-1 rectangular tubes are connected to the opposite side walls of the dielectric to move through the chamber of the heated dielectric. On the upper wall of the housing there is a communication slot with a source of microwave energy, oriented along the longitudinal axis of the housing. Determining the ratio between the height of the body and its length, as well as the height of the rectangular tubes, allows to ensure uniform heating of the dielectric and exclude radiation from the input and output rectangular tubes, t sludge. l about and

Description

The invention relates to microwave technology, specifically to the installation of devices for microwave heating of dielectrics, and can be used for leveling the moisture profile of paper web, vulcanizing rubber products, drying products of various industries: radio engineering (ceramics), construction (ceramic tiles, brick, cement), food (freeze drying of maca, dried fruit, tea), wood processing, woodworking (parquet, pencils, furniture and musical pieces), textile (colorful coating of fabrics), cotton processing (raw cotton), etc.

Various designs are known, resonator chambers, for example, slow-moving systems such as a diaphragmed waveguide, or spiral systems.

However, such chambers are applicable only to dielectric products with a small cross section. The electric field in them is uniformly along the radius, which leads to non-uniform heating of the dielectric.

Also known prismatic multimode resonator. The dimensions of the resonator are chosen so that when the resonator is operating in a certain frequency range in the resonator, these types of oscillations are excited, the total effect of which on the dielectric

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would lead to the most uniform heating. Such chambers are used, for example, in commercially available cooking facilities.

Multimode excitation mode essentially leads to non-uniform heating. Chamber loading mode (open door) determines low productivity since the generator must be turned off at the time of opening. The size of the chamber cannot be chosen arbitrarily, since this violates the condition of maximum homogeneity of the heating of the dielectric.

Closest to the present invention is a chamber with inlet and outlet pipes for moving the heated products about

However, this camera is multi modal. In addition, the input and output pipes are not non-radiative for Emno modes of oscillation, which excludes the use of these types of oscillations and, accordingly, obtaining a uniform heating of products.

The aim of the invention is to increase the heating uniformity and reduce the radiation into the surrounding space.

This goal is achieved by the fact that a cavity chamber for microwave heating of dielectrics, comprising a housing in the form of a rectangular parallelepiped, inlet and outlet rectangular pipes for moving a heated dielectric, connected to opposite side walls of the housing, and a communication element with a microwave energy source. made in the form of a slit located on the upper wall of the body has a length a and a body and its height b selected in accordance with the ratio:

a ra ((2f / c) + 1 / b) rf /, where f is the operating frequency; c is the speed of light; go - the number of variations of the floor along

shell length ,, m 1,2,3, ... height d of the inlet and outlet rectangular tubes selected from the condition: (2f), with the slot being oriented parallel to the longitudinal axis of the shell.

Such a constructive solution allows increasing the uniformity of heating of dielectrics due to the camera operation in a single-mode mode in the form

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fluctuation E№10; to increase the productivity of the installation due to the possibility of organizing the conveyor method of heating (or drying) during continuous operation of the installation.

The drawing shows the proposed resonator chamber for the installation of microwave heating of dielectrics.

The resonator chamber contains a housing 1 in the form of a rectangular parallelepiped, a microwave power input unit 2, an inlet 3 and an outlet pipe ;, a dielectric 5 moving through the cavity of the housing 1

Resonator chamber works as follows.

The microwave power input unit is tuned to a critical connection of the supply line to the resonator chamber with the dielectric inside. The drawing shows a slotted power input unit with supplying microwave power through a rectangular waveguide. The power input unit can also be made loopback with the supply of microwave power via a coaxial line. When microwave power is supplied through the input unit 2 into the housing 1 in the latter, oscillations of the type Et10 are excited, having a field along the edge b of the housing 1 and a floor variation, along the edge a - the floor variations along the third edge determining the width of the housing 1, a constant field . The latter condition determines an arbitrary choice of the chamber width, based on the given width of the heated dielectric. In the general case, the camera can operate in the form of oscillations E, where n is the number of variations of the floor along the height of the chamber, n 1,2,3, ... In this case, the dimensions a and b are chosen from

((2f / c) 2 + (n / b) 2r1 / z.

Such a camera can be used in special purpose installations, for example, when a displacement system is not placed in the chamber (for example, in the form of dielectric rolls), taking into account that when a dielectric is introduced into the chamber at a constant installation frequency j, the overall dimensions of the chamber decrease . The heated dielectric can either be pulled through the inlet 3 and the outlet pipe of the housing 1 (for example, paper), or move through the cavity of the housing 1 on the dielectric conveyor. Dielectric 517 interacts in case 1

ka with electric microwave field and the transfer of energy to the field dielectric due to - dielectric losses in it and due to the resistive conductivity of the electrician. The required microwave power depends on the amount of dielectric mass that needs to be heated to a predetermined temperature and evaporated (if required) per unit of time, and on the chamber efficiency, defined as the ratio of microwave power scattered in the dielectric, to microwave power, entered the chamber. The input 3 and output k pipes of the housing 1 are out-of-limit waveguides for oscillation at the operating frequency. Since in the plane of the face to which the tube is attached, there is only a component of the magnetic field, directed parallel to the edge b

case 1, then the inlet 3 and outlet C pipes are out of limit if their transverse dimension d in the direction of the rib b of the housing 1 satisfies condition (2f). The lengths of the inlet 3 and outlet A of the pipes are chosen from the condition of the necessary weakening of the electromagnetic field in them from the working value in the chamber to the maximum permissible value in the room from the point of view of safety engineering.

The calculations show that, for example, for heating to 80 ° C and evaporation of 1 kg of water per 1 second, a power of 2.6 MW is required. The estimated calculations of the drying chamber for the paint coating of the wallpaper surface 0.65 m wide with a water flow rate of 2 g / ma allow you to choose a chamber with dimensions of 40 and 75 m, operating at a frequency of 915 MHz and having 75. With a web speed of 350 m / min, the required power of the microwave generator is 26 kW. The amplitude of the magnetic field strength in the chamber

near the entrance to the pipe, it is equal to 950 A / m. If we assume that the transverse dimension of the inlet and outlet pipes cm and the maximum permissible energy flux density in the room should be no more than 10 W / m2, then the required attenuation of the floor in the pipes, equal to 100 dB, is achieved with a pipe length of 75 mm.

Thus, the proposed resonator chamber allows to increase the uniformity of heating of dielectrics and reduce radiation into the surrounding space.

Claims (1)

Invention Formula 1 A resonator chamber for microwave heating of dielectrics, comprising a housing in the form of a rectangular parallelepiped, inlet and outlet rectangular tubes for moving a heated dielectric, connected to opposite side walls of the housing, and a communication element with a microwave source of energy, made in the form of a slit, located on the upper wall of the case, revealing; that, in order to increase the uniformity of heating, reduce the radiation into the surrounding space, the ratio of the length a of the hull and its height b was chosen in accordance with the (2f / c) 2 + (1 / b), where f is the operating frequency; c is the speed of light; m is the number of floor variations along the length of the body; , 2, 3, ..., The height d of the inlet and outlet rectangular pipes is selected from the condition: wherein the slot is oriented parallel to the longitudinal axis of the housing.  BUT .