EFFECT OF ELECTRICAL SHIELDING ON TIME-TEMPERATURE DISTRIBUTION AND FLOW PROFILES IN WATER IN A CYLINDRICAL CONTAINER DURING MICROWAVE-HEATING

Time-temperature distribution data was collected with water in a cylindrical container under different types of electrical shielding. With no shielding or bottom shielding, the temperature profiles in the radial direction were relatively uniform and the axial temperatures decreased from the top to the bottom of the container. The cold spot was along the central axis close to the bottom of the container. When the top was shielded and microwave energy was allowed to enter from the bottom, a uniform temperature distribution was observed throughout the container. A flow pattern visualization technique for liquid products heated in a microwave oven was developed. When the top of the container was shielded, good mixing of the liquid was observed due to convection heating.