Patent ID: 6917022

Claim:
A continuous flow microwave heater for heating fluids, comprising: a microwave source, an applicator ( 1 ) having opposite front walls ( 8 ) and side walls ( 3 , 4 ) with a microwave in-coupling opening ( 5 ) connected to said microwave source ( 11 ) directly or by way of a hollow conductor, a dielectric tube ( 2 ) extending through said applicator ( 1 ) parallel to the axis of said microwave in-coupling opening ( 5 ) in said applicator ( 1 ) and normal to two opposite side walls ( 3 , 4 ) of said applicator ( 1 ), of which one includes said in-coupling opening ( 5 ), a metallic tube stub ( 6 , 7 ) sealingly connected to each of opposite ends of said dielectric tube ( 2 ) outside said applicator ( 1 ) for conducting a fluid to be heated through said applicator ( 1 ), which fluid forms a load ( 2 ), said tube stubs ( 6 , 7 ) being also joined to said opposite side walls ( 3 , 4 ) of the applicator ( 1 ) in a microwave-tight manner, wherein said applicator ( 1 ) has a rectangular shape which is adapted to the wavelength λ of the microwave supplied by the microwave source ( 11 ) in such a way that, in the applicator ( 1 ), the linearly polarized base mode TE 10 of the microwave is excited, the axis of said dielectric tube ( 2 ) extends parallel to the field polarization of the linearly polarized TE 10 mode and is disposed at a distance of about λ/4 from the respective nearest front wall ( 8 ) of said applicator ( 1 ), and the axis of the dielectric tube ( 2 ) coincides with the field maximum of the linearly polarized TE 10 mode, the distance between the center point of the incoupling opening ( 5 ) and the axis of the dielectric tube ( 2 ) is so selected that field energy coupled into the applicator ( 1 ) is completely or nearly completely absorbed in the dielectric tube ( 2 ) through which the fluid to be heated is conducted and converted therein to heat, such that no or only negligable reflections occur in the applicator, and said tub stubs ( 6 , 7 ) have an open width adjacent the side walls ( 3 , 4 ) of the applicator ( 1 ), which equals the outer diameter of the dielectric tube ( 2 ) over a length of λ/4 to λ/2, and their diameter becomes then smaller over a length of >λ/4 so as to provide a blocking structure preventing an escape of any microwaves from said applicator ( 1 ).