MICROWAVE LIQUID HEATER Russian patent published in 1998 - IPC

FIELD: microwave engineering. SUBSTANCE: microwave liquid heater has section of rectangular waveguide 1 with cross-section of AxB, where A and B are wide and narrow walls of waveguide, respectively. Two tubes 3,4 for liquid circulation are positioned inside waveguide section. Tubes are made of dielectric of low losses, with internal diameter D=(0.14- 0.13)A. They are spaced at 0,367λ, where λ is wave length in vacant space. Dielectric tubes are positioned in rectangular waveguide section at angle of 45+-2 to its wide walls, and their axes are in plane passing through axis of rectangular waveguide section in parallel to its narrow walls. U-shaped projection 2, 0.3A wide, is provided in section of rectangular waveguide along its axis, symmetrically on one of the wide walls. This projection together with rectangular waveguide section forms input transition 2.1 from waveguide of rectangular cross-section AxB to waveguide of U-shaped cross-section, section of U-shaped waveguide with variable height of U-shaped projection 2.2 and output transition 2.3 from U-shaped cross-section waveguide to rectangular waveguide of AxB cross-section. Height of projection in input transition 2.1 on length of 0,68λ increases linearly from 0 to 0.67B. Projection height in output transition 2.3 on length of 0,49λ decreases linearly from 0.57B to 0. Section of U-shaped waveguide 2.2 has seven segments. First segment 2.2.1 is 0.8D long, with projection height of 0.67B. Second segment 2.2.2 is 45 deg. linear transition from projection, 0.67B high, to projection, 0.57B high. Third segment 2.2.3 is 0,2λ long, with projection height of 0.57B. Fourth segment 2.2.4 is linear transition on length of 0,1λ from projection, 0.57B high, to projection, 0.67B high. Fifth segment 2.2.5 is 0.8D long, with projection height of 0.67B. Sixth segment 2.2.6 is 45 deg. linear transition from projection, 0.67B high, to projection, 057B high. Seventh segment 2.2.7 is 0,1λ long, with projection height of 0.57B. Axes of first and second dielectric tubes are in plane of second and sixth segments of 45 deg. linear transition, respectively. Value of voltage standing-wave ratio of heater with treated liquid in tubes does not exceed 1.25, and value of voltage standing-wave ratio of heater with no liquid in tubes and with matched output load is not over 1.2. Microwave power attenuation in heater when heating the water is at least 20 dB. To obtain higher attenuation value, pasteurizer construction allows several heaters to be connected in series. EFFECT: more effective heating. 1 wdgl