Browsing by Author "Burcher-Jones, Jordan"
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- ItemContinuous flow microwave sterilisation focussing on aqueous media(Stellenbosch : Stellenbosch University, 2020-03) Burcher-Jones, Jordan; De Swardt, J. B.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: This thesis contains details regarding the research and development of a continuous flow, temperature controlled, microwave heating sterilisation unit. The microwave hardware design promotes the propagation of the fundamental 𝑇𝐸10 mode for rectangular waveguide structures at 2.45 GHz. The system design incorporates a single mode applicator chamber which considers the microwave heating patterns within the system. The heating patterns were predicted through rigorous electromagnetic thermal coupled simulations. The temperature control system operates by maintaining output magnetron power whilst varying the media flow rate. The system has a controllable temperature range between 60 C and 95 C resulting in a variable system output flow rate between 3.3 l/h and 6 l/h. The constant output power produced by the magnetron can be set to either 700 W, 350 W or 210 W, using a technique called saturable reactor control and this is demonstrated and explained in the project. The magnetron and high voltage supply were obtained from a conventional microwave oven. Calibration techniques for various stages in the system are discussed and implemented to ensure measured data obtained is accurate and repeatable. The materials used to transport the targeted media inside the treatment chamber were selected based on a low dissipation factor ( 𝑡𝑎𝑛 ), effectively making the materials “invisible” to microwave radiation. This allows for selective heating of the media to be treated inside the system. The microwave sterilisation treatments were conducted with a strain of Lactococcus lactis (NZ9000) with an antibiotic marker (chloramphenicol at 10 μg/ml) suspended in sterile saline. The experiments conducted and observations made during development suggest that the designed system is a successful, effective, sterilisation solution.