|Institution:||University of Johannesburg|
|Full text PDF:||http://hdl.handle.net/10210/13327|
The heating and drying of products is a process which is essential to improve the quality. This process has been around since the beginning of the industrial age. Most industries use natural energy sources, e.g. coal, to generate the energy that is needed. This energy is then used to heat air and this in turn is used to dry the products. Heat transfer is used to dry the materials and it is a known fact that this mechanism is not effective due to huge losses. A certain company identified this problem and decided to investigate microwave energy as an alternative energy source. The aim of the project was to determine if microwave energy could dry the phosphate and to do an economic feasibility study on such a microwave oven. The operation of microwave sources was examined and the magnetron was found to be the most effective source. Magnetrons that operate at a frequency of 2.45GHz, are easily obtainable and therefore also more economical than magnetrons that operate at other frequencies. The loss mechanisms that are associated with microwave heating as well as the parameters associated with volumetric heating were then investigated. It was found that the complex permittivity and permeability of the material to be heated, are important properties associated with microwave heating and these were not known and needed to be determined. After examlnlng several methods to determine these properties, the measurements were done by means of a network analyser. From the results it was evident that the phosphate losses were relatively high enabling most of the microwave energy to be absorbed. These results were confirmed after further tests were done.