Department of Mechanical and Mechatronic Engineering

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Browsing Department of Mechanical and Mechatronic Engineering by Author "Allen, Tamara Candice"

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    Towards a mobile, cost-effective neonatal brain cooling device
    (Stellenbosch : Stellenbosch University, 2022-04) Allen, Tamara Candice; Owen, Michael ; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH SUMMARY: Hypoxic-ischemic Encephalopathy is the brain damage caused as a result of decreased oxygen and blood flow to the brain of a baby during birth. This brain damage is one of the leading causes of cerebral palsy and other disabilities worldwide. In order to reduce the damage created, therapeutic hypothermia treatment is given to the affected neonate. This treatment reduces the core temperature of the neonate to below homeostasis in order to allow the brain sufficient chance to recover from the decreased oxygen and blood flow. Therapeutic hypothermia, however, must be administered within six hours of birth. This proves challenging for developing countries with minimal resources and rural settings. Therefore, this project aimed to assist in the development of a mobile and cost-effective device that can be used during transport. This will allow therapeutic hypothermia to begin en-route to the destination hospital, where the therapy can be continued. To aid towards the design of such a device, this project followed a phased design approach, which included design requirement development, concept development and evaluation, detailed design and analysis, design implementation, and design evaluation. A thermoacoustic refrigerator was the concept chosen for further development due to its low-cost components, potential small and lightweight nature, and promising research potential. A thermoacoustic refrigerator produces heat transfer potential from acoustic power through the use of a resonator, a loudspeaker, a stack, and heat exchangers. A standing wave is formed within the resonator at a specific design frequency, which allows for the desired air particle movement. The interaction of the moving particles with the stack then enables the transfer of heat from one side of the resonator to the other. The subsequent placement of heat exchangers on either side of the stack allows heat transfer to/from thermal reservoirs. A thermoacoustic prototype was built and evaluated through various experimental phases, by comparison to DeltaEC - a thermoacoustic modeling tool. The experiment tested the response of the system at various operating conditions by changing the electrical power input, the mean pressure, and a simulated environmental temperature. The acoustic aspects of the model were well validated, however the thermal aspects were not. The main reason for this seems to be attributed to the over-prediction of the heat transfer coefficient within the DeltaEC model. The model therefore assumes a much more effective heat exchanger than the one that is practically implemented, due to certain assumptions that the model makes about the heat exchanger. The model is therefore not validated, and the recommendation is to split any further research into two streams: thermoacoustic development, and the development of a mobile therapeutic hypothermia device. This is further supported by the various practical limitations experienced by the prototype, including the need for a specialised speaker to improve the electro-acoustic efficiency. In addition, the loud sound of the system proves impractical within the use scenario, and the difficult manufacture of the stack is impractical at the current stage of development. The overall recommendation is therefore to discontinue the investigation of thermoacoustics within this use scenario.