A ventilation device for improving the uniformity of radio frequency heating drying

Abstract

The present invention relates to a ventilation device for improving the uniformity of radio frequency heating and drying. The device adopts a dual-chamber ventilation structure with inner and outer chambers. The inner and outer chambers are each connected to a hot air blower. The two chambers correspond to the center and edge areas of a material tray above a lower electrode plate through a limiting frame, ensuring that the hot air generated by the two hot air blowers passes through the two chambers and enters the edge and center areas of the material tray respectively. During the drying process, the controller of the hot air blower automatically adjusts its heating temperature based on the temperature monitoring results of the material in the edge and center areas of the material tray, so that the temperature of the material in the edge area of ​​the material tray is the same as that of the material in the center area. The ventilation system modification cost of the present invention is low, the method is simple to operate, and it avoids excessively high temperature of the material in the edge area of ​​the material tray during the radio frequency drying process, thereby ensuring uniform drying of the material.

Description

Technical Field

[0001] The invention relates to the field of agricultural products and food processing, and in particular to a ventilation device for improving the uniformity of radio frequency heating and drying. Background Art

[0002] Radio frequency heating technology was first applied in the light industry and pharmaceutical industry in my country, and has only been gradually introduced into the field of agricultural products or food processing in the past two decades. Radio frequency heating technology is mainly used as a heat treatment technology. It takes advantage of its selective heating, rapid heating, deep penetration, overall heating, and moisture self-balance to achieve the purpose of efficient insecticide, sterilization, bleaching and color protection. It has been applied to the processing of grain, nuts, wood and other fields. However, the radio frequency heating process often has the common problem of overheating of materials in the edge area of ​​the tray, which can easily cause the product to burn and deteriorate in quality, restricting its application in agricultural products or food processing. When it is used for drying, it will inevitably lead to uneven drying. Therefore, the research and development of a ventilation device that improves the uniformity of radio frequency heating drying is of great significance to the industrial application of radio frequency heating drying technology. Summary of the Invention

[0003] In view of the defects existing in the prior art, the purpose of the present invention is to provide a ventilation device that improves the uniformity of radio frequency heating and drying. The modification cost of the ventilation system is low, and the supporting operation method is simple to operate, thereby achieving uniform heating and drying of agricultural products or food.

[0004] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0005] A ventilation device for improving the uniformity of radio frequency heating drying, comprising: an inner air chamber 9-1, an outer air chamber 9-2, an inner air chamber inlet 8-1 and an outer air chamber inlet 8-2; the inner air chamber inlet 8-1 is connected to the inner air chamber 9-1, the outer air chamber inlet 8-2 is connected to the outer air chamber 9-2, and the outer air chamber 9-2 and the inner air chamber 9-1 are isolated from each other; the inner air chamber inlet 8-1 is used to connect to a hot air blower, and the outer air chamber inlet 8-2 is used to connect to another hot air blower; the outer air chamber 9-2 is used to dry materials in the corner areas, and the inner air chamber 9-1 is used to dry materials in the middle area.

[0006] A radio frequency heating and drying device includes: a radio frequency generator, a radio frequency controller, the ventilation device described above, two infrared thermometers, an upper electrode plate, a lower electrode plate, two hot air blowers, and a material tray. The ventilation device is located below the lower electrode plate, and the material tray is placed above the lower electrode plate. The material tray is used to place the material.

[0007] Each hot air blower is equipped with a controller and an infrared thermometer. The controller is used to adjust the heating temperature and wind speed of the hot air blower. The infrared thermometer connected to the outer air chamber is used to monitor the material temperature in the edge area of ​​the material tray, and the infrared thermometer connected to the inner air chamber is used to monitor the material temperature in the center area of ​​the material tray and feed back to the controller to realize automatic adjustment of the heating temperature of the hot air blower.

[0008] A limit frame is installed on the lower electrode plate to achieve precise correspondence between the position of the material tray and the wind chamber area in the vertical direction.

[0009] The mesh holes of the material tray are in the same position as the ventilation holes of the lower electrode plate. The hot air from the inner and outer air chambers enter the middle and edge areas of the material tray respectively through the mesh holes of the lower electrode plate and the material tray, heating and drying the materials in the two areas respectively.

[0010] The infrared thermometer is installed above the upper electrode plate to avoid electromagnetic field interference between the upper and lower electrode plates. During measurement, infrared rays pass through the holes on the upper electrode plate and illuminate the surface of the material in the material tray to measure the temperature.

[0011] During the drying process, when the infrared thermometer detects that the material temperature in the edge area or the material temperature in the center area of ​​the tray deviates from the set material temperature, its controller lowers or increases the heating temperature of the corresponding hot air blower to make the material temperature in the edge area of ​​the tray the same as that in the center area.

[0012] Beneficial effects of the present invention:

[0013] The ventilation device adopts a double-chamber ventilation structure, with the inner and outer air chambers respectively connected to a hot air blower. The two air chambers correspond to the central area and edge area of ​​the material tray above the lower electrode plate through a limit frame, ensuring that the hot air generated by the two hot air blowers passes through the two air chambers into the edge area and center area of ​​the material tray respectively; during the drying process, the controller of the hot air blower automatically adjusts its heating temperature according to the material temperature monitoring results of the edge area and center area of ​​the material tray, so that the material temperature in the edge area of ​​the material tray is the same as the material temperature in the center area, thereby avoiding the uneven drying, deterioration of product quality and poor consistency caused by the excessively high edge temperature of the material tray during the drying process, which is of great significance to the industrial application of radio frequency drying. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention has the following accompanying drawings:

[0015] Figure 1 This is a schematic diagram of the existing radio frequency heating dryer architecture.

[0016] Figure 2 It is a structural schematic diagram of the ventilation device of the radio frequency heating drying device of the present invention.

[0017] Figure 3It is a structural schematic diagram of the lower electrode plate of the present invention. DETAILED DESCRIPTION

[0018] The following is combined with Figure 1-2 The present invention is described in further detail.

[0019] like Figure 1 As shown, a conventional RF heating dryer mainly includes an RF generator 1, an RF controller 2, an upper electrode plate 3, a lower electrode plate 4, a hot air blower 5, a ventilation chamber 9 and a material tray 10, wherein the hot air blower is provided with a controller 6 and an infrared thermometer 7. The material tray above the lower electrode plate corresponds to the position of the ventilation chamber below. During the drying process, the RF controller sets an appropriate distance between the upper and lower RF electrode plates, and the RF generator and the hot air blower are turned on in turn. The hot air is evenly blown through the ventilation chamber, and then enters the material tray through the ventilation holes of the lower electrode plate and the mesh of the material tray to heat and dry the material 11. The infrared thermometer connected to the hot air blower monitors the material temperature in the center area of ​​the material tray. The controller 6 adjusts the heating temperature and wind speed of the hot air blower according to its monitoring results to make the material temperature reach the required temperature.

[0020] The present invention improves the single air chamber ventilation system of the conventional radio frequency heating dryer. The improved double air chamber ventilation structure is as follows: Figure 2 As shown, it includes an inner air chamber 9-1 and an outer air chamber 9-2. The inner air chamber inlet 8-1 and the outer air chamber inlet 8-2 are connected to a hot air blower respectively. A limit frame 12 is installed to achieve accurate correspondence between the position of the material tray and the air chamber area below. The appropriate distance between the upper and lower RF electrode plates is set by the RF controller, and the RF generator and the two hot air blowers are turned on in turn. The hot air enters the inner air chamber and the outer air chamber respectively for uniform wind, and then passes through the lower electrode plate (such as Figure 3 Air enters the tray through ventilation holes (shown), heating and drying the material at the edges and center of the rectangular tray. Infrared thermometer 1 7-1 and infrared thermometer 2 7-2 monitor the temperature of the material in the center and edges of the tray, respectively. Based on these monitoring results, the controllers of the two hot air blowers automatically adjust the heating temperature and wind speed to ensure that the temperature of the material at the edges of the tray is the same as that in the center.

[0021] The material tray and the limiting frame are both made of non-metallic materials such as polypropylene, have low dielectric parameters, and are electrically insulating.

[0022] The material to be dried in the tray is agricultural products or food, especially granules and small pieces. The following is a detailed description using corn kernels as an example:

[0023] In a specific implementation, a 2 kg corn tray with a wet basis moisture content of 26.8% was prepared in a 30 cm × 20 cm × 4.5 cm tray. A 6 kW, 27.12 MHz radio frequency heating machine and a 5 kW hot air blower were used. The spacing between the upper and lower electrode plates of the radio frequency generator was adjustable. In this embodiment, the spacing between the upper and lower electrode plates was 110 mm. The hot air velocity was 1.5 m / s. The relative humidity at room temperature was 15% at 25°C, and the corn layer thickness was 2 cm. For example, to achieve a corn kernel temperature of 65°C during the drying process, the present invention automatically adjusted the heating temperature of the two hot air blower controllers based on the corn kernel temperature monitoring results in the center and edge regions of the tray, respectively, to achieve a corn kernel temperature of 65°C. A control treatment used a conventional single-chamber ventilation system, in which the heating temperature of the hot air blower was automatically adjusted based only on the corn kernel temperature in the center region of the tray, to achieve a corn kernel temperature of 65°C in the center region. When dried to a safe moisture content of 14%, the temperature and moisture content of corn kernels at different positions in the two treatment trays were measured, and the temperature uniformity index and moisture uniformity index of the two were compared. The uniformity index (UI) was calculated as follows:

[0024]

[0025] Where n is the number of sampling data points, X i is the value of the i-th sampling data point, X ave It is the average value. The smaller the uniformity index is, the better the uniformity is.

[0026] Table 1 Temperature uniformity index and moisture uniformity index at the end of corn drying

[0027]

[0028] As can be seen from Table 1, compared with the conventional single-chamber radio frequency hot air dryer, the temperature uniformity and moisture uniformity of the corn after drying in the double-chamber radio frequency drying device adopted in the present invention are significantly better.

[0029] The above is only one embodiment of the present invention. The device can also be applied to the heating and drying process of other materials. All equivalent changes and modifications made within the scope of the patent application of the present invention are within the scope of the present invention.

[0030] In order to solve the problem of poor uniformity in the radio frequency heating drying of existing agricultural products and food materials, the present invention introduces a dual-chamber ventilation system for the first time, especially for granular or small-block materials, which can differentially heat the materials in the center and edge areas of the tray. During the drying process, the hot air temperatures of the inner and outer air chambers are adjusted respectively in combination with the information feedback from material temperature monitoring, so that the hot air temperature of the outer air chamber is lower than that of the inner air chamber, avoiding overheating of the materials in the edge area of ​​the tray, ensuring uniform drying of the materials in the tray, and effectively protecting the consistency of the processing quality of food and agricultural products. It has broad market prospects and considerable economic benefits, and has a positive role in promoting the application of radio frequency drying technology.

[0031] The above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the essence and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of protection of the present invention.

[0032] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A radio frequency heating drying device, characterized in that: It includes a ventilation device, a radio frequency generator, a radio frequency controller, two infrared thermometers, an upper electrode plate, a lower electrode plate, two hot air blowers and a material tray; the ventilation device is located below the lower electrode plate, and the material tray is placed above the lower electrode plate, and the material tray is used to place the material; The ventilation device includes: an inner air chamber, an outer air chamber, an inner air chamber inlet, and an outer air chamber inlet; the inner air chamber inlet is connected to the inner air chamber, the outer air chamber inlet is connected to the outer air chamber, and the outer air chamber and the inner air chamber are isolated from each other; the inner air chamber inlet is used to connect to a hot air blower, and the outer air chamber inlet is used to connect to another hot air blower; the outer air chamber guides hot air to heat and dry the materials in the edge area of ​​the material tray, and the inner air chamber guides hot air to heat and dry the materials in the middle area of ​​the material tray; Each hot air blower is equipped with a controller and an infrared thermometer. The controller is used to adjust the heating temperature and wind speed of the hot air blower. The infrared thermometer connected to the outer air chamber is used to monitor the material temperature in the edge area of ​​the material tray, and the infrared thermometer connected to the inner air chamber is used to monitor the material temperature in the center area of ​​the material tray. The infrared thermometer is fed back to the controller to achieve automatic adjustment of the heating temperature of the hot air blower. The material of the material tray is polypropylene.

2. The radio frequency heating drying device according to claim 1, wherein: A limit frame is installed on the lower electrode plate to achieve precise correspondence between the position of the material tray and the wind chamber area in the vertical direction.

3. The radio frequency heating drying device according to claim 1, wherein: The mesh holes of the material tray are in the same position as the ventilation holes of the lower electrode plate. The hot air from the inner and outer air chambers enter the middle and edge areas of the material tray respectively through the mesh holes of the lower electrode plate and the material tray, heating and drying the materials in the middle and edge areas respectively.

4. The radio frequency heating drying device according to claim 1, wherein: The infrared thermometer is installed above the upper electrode plate to avoid electromagnetic field interference between the upper and lower electrode plates. Infrared rays pass through the holes in the upper electrode plate and irradiate the surface of the material in the tray to measure the temperature.

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