| 摘要 |
Apparatus for heating water (12) in a tank (10) comprising a radio frequency energy source, such as a magnetron (14). Radio frequency energy is supplied from the source (14) to the water (12) in the tank (10) via a substantially conical waveguide. The radius of the waveguide (16) at the point (18) at which the radio frequency energy is first incident from the magnetron (14) is beneficially greater than lambda/4, where lambda is the wavelength of the radio frequency energy. A PTFE plate or membrane (20) is provided between the distal end of the waveguide (16) and the body of water (12), at least portion of the upper surface plate (20) being substantially conical so as to provide a non-uniform interface between the water (12) to be heated and the radio frequency energy. The plate (20) is substantially transparent to the radio frequency energy, i.e. it does not absorb or reflect such energy. In use, RF energy emitted perpendicularly from the magnetron (14) strikes the conical waveguide (16) at points (18), and is reflected upwards towards the water (12). The energy passes through the first surface of the PTFE plate (20) with minimal absorption and strikes the interface between the plate (20) and the water (12). As a result, the angle of reflection of the RF energy is such that little, if any, thereof is reflected back to the magnetron (14). Instead, it simply 'bounces' around the inside of the waveguide (16) until it is returned to the water (12). An angled, microwave reflective plate (30) may be provided on an upper portion of the tank (10). |
