EFFECTS OF ELECTRICAL SHIELDING AND SALT CONCENTRATION ON MICROWAVE HEATING IN CYLINDRICAL CONTAINERS

摘要

Time-temperature distributions in water and salt solutions were collected in a cylindrical container with and without electrical top shielding during microwave heating. A cold spot was found to exist for both water and salt solutions close to the bottom of the container with and without electrical top shielding. Surface heating was observed in unshielded salt solutions and resulted in a stagnant layer close to the top of the container. Surface heating was eliminated in salt solutions with electrical shielding at the top of the container. Flow profiles within the container were monitored using a potassium permanganate dye tracer and a video camera. The flow profiles for water showed an upward flow in the central region and a descending flow along the side walls. An upward flow along the side walls and a downward flow along the central axis was observed for salt solutions.