KR20040026954A - Microwave tempering system using the two-frequency microwave heating - Google Patents

Abstract

PURPOSE: A microwave tempering system is provided to reduce costs of the system, while achieving improved heating speed and uniformity of heating operation. CONSTITUTION: A microwave tempering system comprises a first microwave generating unit(101) for generating a frequency of 915MHz±25MHz which is mainly used for finishing a tempering; a second microwave generating unit(102) for generating a frequency of 2450MHz±50MHz which is mainly used for raising the temperature of an object to a predetermined level; waveguides(103,104) connected to the output terminals of the first and second microwave generating units, respectively, in such a manner that the waveguides transmit the microwaves generated from the first and second microwave generating units; and a chamber(105) connected to the output terminal of the waveguide, wherein the chamber provides a shielded space for permitting the microwave transmitted through the waveguides to be radiated to the object to be heated.

Description

Microwave tempering system using the two-frequency microwave heating

The present invention relates to a microwave tempering system, and more particularly, by using a large output microwave generator having a frequency of 915 MHz ± 25 MHz and a low output microwave generator having a frequency of 2450 MHz ± 50 MHz to share the microwave output required for tempering frozen foods. The present invention relates to a microwave tempering system using microwave heating at two frequencies that can improve the uniformity of microwave tempering and lower the cost of the microwave tempering system.

Conventional microwave tempering systems used only one frequency for tempering frozen food using microwave heating. That is, as the size (volume) of the frozen food increased and the throughput increased, a large power microwave generator having a deep penetration depth and a frequency of 915 MHz ± 25 MHz was used. However, as the output of the microwave generator increases, the price increases significantly, and there is a problem in that heating is not uniform due to a long wavelength of about 33 cm.

The present invention was created in view of the above, by using a high output microwave generator having a frequency of 915 MHz ± 25 MHz and a low output microwave generator having a frequency of 2450 MHz ± 50 MHz by sharing the microwave output required for tempering frozen foods. It is an object of the present invention to provide a microwave tempering system using microwave heating of two frequencies that can improve the uniformity of microwave tempering and lower the cost of the microwave tempering system.

1 is a schematic block diagram of a microwave tempering system using microwave heating at two frequencies in accordance with the present invention.

2 shows another embodiment of a microwave tempering system using microwave heating at two frequencies in accordance with the present invention.

<Explanation of symbols for the main parts of the drawings>

101 ... first microwave generator 102 ... second microwave generator

103,104 Waveguide 105 Chamber

106 ... Conveyor System 107,108,116 ... Shield Curtain

109,110 Absorber 115 Bulkhead

120.Heat to be heated

In order to achieve the above object, a microwave tempering system using microwave heating of two frequencies according to the present invention,

A first microwave generator for generating a frequency of 915 MHz ± 25 MHz, which is mainly used for tempering finishing;

A second microwave generator for generating a frequency of 2450 MHz ± 50 MHz, which is mainly used to raise the temperature of the object to be heated;

A waveguide connected to output terminals of the first and second microwave generators and transmitting microwaves generated from the first and second microwave generators; And

It is characterized in that it comprises a chamber that is connected to the output of the waveguide and provides a shielding space for irradiating the heating object microwaves transmitted through the waveguide.

Furthermore, it is installed in the lower part of the chamber, the conveyor system for enabling microwave irradiation while continuously moving the heated object, the inlet through which the heated object is introduced into the chamber by the conveyor system and the outlet drawn out from the chamber And a shielding curtain for reducing the amount of microwaves leaking out of the chamber, and an absorber provided at the periphery of the conveyor runway in front of the inlet and the outlet of the chamber, and for absorbing and removing the microwaves leaking out of the chamber. It has that feature.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram of a microwave tempering system using microwave heating of two frequencies according to the present invention.

Referring to FIG. 1, a microwave tempering system using microwave heating of two frequencies according to the present invention includes a first and second microwave generators 101 and 102, waveguides 103, 104, and a chamber 105. Basically provided, the conveyor system 106, shielding curtains (107) 108, absorbers (109) 110 may be further installed.

The first microwave generator 101 generates a frequency of 915 MHz ± 25 MHz. This 915MHz ± 25MHz frequency is used throughout the process from tempering start to finish.

The second microwave generator 102 generates a frequency of 2450 MHz ± 50 MHz. Here, the microwave at a frequency of 2450 MHz ± 50 MHz is used as an aid in raising the temperature of the object to be heated from -10 degrees Celsius to minus several degrees Celsius. The operating temperature criteria for this 2450 MHz ± 50 MHz frequency may vary depending on the type, size and shape of the material to be heated. In addition, the second microwave generator 102 may be directly connected to the chamber 105 without passing through the waveguide 104 described later.

The waveguides 103 and 104 are respectively connected to output terminals of the first and second microwave generators 101 and 102, and transmit microwaves generated from the first and second microwave generators 101 and 102. do.

The chamber 105 is connected to the output end of the waveguides 103 and 104, and provides a shielding space for allowing microwaves transmitted through the waveguides 103 and 104 to be irradiated to the heated object 120. The wall of the chamber 105 is made of a metal conductor, so that the microwaves are irradiated to the heated object 120 while being reflected in various directions.

Conveyor system 106 is installed below the chamber 105 and enables microwave irradiation while continuously moving the heated object 120.

The shielding curtains 107 and 108 are installed at the inlet through which the heated object 120 enters the chamber 105 and the outlet from the chamber 105 by the conveyor system 106, and the microwaves 105. ) To reduce the amount of leakage. The shielding curtains 107 and 108 are made of a thin metal conductor, and are installed to be freely rotatable back and forth so as not to interfere with the movement of the heated object 120.

Absorbers 109 and 110 are installed at the periphery of the conveyor running paths in front of the inlet and the outlet of the chamber 105, and absorb and remove microwaves leaked out of the chamber 105. As the absorbers 109 and 110, ferrite, carbon powder, iron oxide, or the like, which is cured by mixing cement or plastic, water, saline, or the like may be used. In addition, a shutter or a choke may be used instead of the absorbers 109 and 110.

On the other hand, Figure 2 shows another embodiment of a microwave tempering system using microwave heating of two frequencies according to the present invention, there is no significant difference in the configuration thereof with the embodiment of FIG. However, in the case of the embodiment of FIG. 1, the chamber 105 is single, whereas in the other embodiment of FIG. 2, the partition 105 is divided into two chambers 105 by placing the partition wall 115 in the middle of the chamber 105. One side of the chamber 105 is configured so that microwaves generated from the first microwave generator 101 are irradiated, and the other side of the chamber 105 is irradiated with microwaves generated from the second microwave generator 102. It is only. In FIG. 2, reference numeral 116 denotes a shielding curtain.

According to the microwave tempering system of the present invention having the configuration as described above, microwaves having a frequency of 2450 MHz ± 50 MHz and 915 MHz ± 25 MHz are irradiated to food frozen at a temperature of minus 20 ° C to minus 40 ° C simultaneously or sequentially. In general, heating by heat conduction is heated to the inside by heat conduction after the surface of the object to be heated is heated, whereas heating by microwaves causes the heated object 120 to be heated at the same time as a whole by the principle of dielectric heating. In addition, by using the microwave at a frequency of 2450 MHz ± 50 MHz having a short wavelength of only about one third of the wavelength of the microwave at the frequency of 915 MHz ± 25 MHz, the microwave distribution in the chamber 105 is evened, thereby increasing the heating uniformity. At this time, the microwave having a relatively shallow penetration depth of 2450 MHz ± 50 MHz is mainly used to raise the temperature of the heated object from -10 ° C to -0 ° C.

When sequentially irradiating the microwaves of the two frequencies to the heating target 120, the tempering starts at 2450MHz ± 50MHz and finishes at 915MHz ± 25MHz. In addition, when irradiating microwaves of two frequencies to the heating target 120 at the same time, the temperature of the heating target 120 before reaching the temperature at which the penetration depth of the microwave of 2450MHz ± 50MHz is not sufficient is reached at a frequency of 2450MHz ± 50MHz. Terminate the microwave irradiation, or finish tempering with a frequency of 915 MHz ± 25 MHz with the output lowered.

As described above, the microwave tempering system using microwave heating of two frequencies according to the present invention is a tempering of frozen food by using a high power microwave generator having a frequency of 915 MHz ± 25 MHz and a low power microwave generator having a frequency of 2450 MHz ± 50 MHz By dividing the microwave output required for the circuit, the requirement for a microwave generator with a frequency of 915 MHz ± 25 MHz is lowered, which lowers the cost of the microwave tempering system. In microwave heating, the shorter the wavelength of the microwave (or the higher the frequency), the higher the uniformity of the heating and the larger the dielectric loss counter. Therefore, the microwave having the frequency of 915 MHz ± 25 MHz is used by using the microwave of 2450 MHz ± 50 MHz and 915 MHz ± 25 MHz Compared with using alone, there is an advantage that high heating uniformity and fast heating rate can be obtained.

Claims (3)

A first microwave generator for generating a frequency of 915 MHz ± 25 MHz, which is mainly used for tempering finishing; A second microwave generator for generating a frequency of 2450 MHz ± 50 MHz, which is mainly used to raise the temperature of the object to be heated; A waveguide connected to output terminals of the first and second microwave generators and transmitting microwaves generated from the first and second microwave generators; And And a chamber connected to an output end of the waveguide, the chamber providing a shielding space for irradiating the heated object with the microwaves transmitted through the waveguide. 2. The method of claim 1, A conveyor system installed below the chamber and configured to enable microwave irradiation while continuously moving the heated object; A shielding curtain installed at an inlet through which the heated object is drawn into the chamber and an outlet from the chamber by the conveyor system, the shielding curtain for reducing the amount of microwaves leaking out of the chamber; It is installed in the periphery of the conveyor runway in front of the inlet and the exit of the chamber, the microwave tempering system using microwave heating of two frequencies further comprising an absorber for absorbing and removing the microwave leaked out of the chamber. The method of claim 1, A bulkhead for dividing the chamber into two chambers is provided in a substantially central portion of the chamber, and microwaves generated from the first microwave generator are disposed in one chamber of the divided chamber, and second microwave generators are arranged in the other chamber of the divided chamber. Microwave tempering system using microwave heating of two frequencies, characterized in that the generated microwave is irradiated.