Mr. Charles Waithaka Gachara enrolled in the Master of Science (Nuclear Science) program at the Institute of Nuclear Science & Technology - the University of Nairobi in 2014. He holds a degree in Bachelor of Science in Physics from the University of Nairobi (graduated in 2009). His master’s thesis project earned him a chance to collaborate with other researchers at the NHL University of Applied Sciences in the Netherlands for one year. He has gained and demonstrated good knowledge in research, especially in liquid atomization using electrospray and applications of nuclear science techniques in medicine, nuclear power, non-destructive test, and air pollution assessment. Nevertheless, Charles has experience in power electronics and microprocessors technology.

Project Summary

Thesis Title: Electrohydrodynamic Atomization Of Non-Newtonian Liquids With High Solid Content : A Case Study For The Production Of Powder

Electrohydrodynamic atomization (EHDA) is now a well-known technique among researchers as a potential technique for industries. The technique uses electric fields to produce mono-dispersed charged droplets and ensures controlled production. The current work investigated the intrinsic aspects of EHDA atomization of non-Newtonian liquids with high solid content made from infant milk formula (IMF) powder. The aim was to determine the characteristics of sprays of IMF solutions with high solid content, compare them with characteristics of EHDA atomization of Newtonian liquids, and investigate the possibilities of out-scaling. The electrospray characteristics were conducted in the dripping and in the jetting regime using a grounded nozzle and charged counter electrode. The visualization of sprays was done using a high-speed camera with backlight illumination. The obtained modes for solid content less than 40% w/w in the dripping regime were possible to correlate to conventional electrospray modes. The simple jet mode was obtained in the jetting regime with whipping break-up producing smaller droplets compared to varicose break-up. The out-scaling experiments using 55% w/w IMF solution led to the development of a single nozzle with four orifices and each orifice having 300 µm internal diameter. This nozzle configuration achieved a throughput of ~3 L h-1 and droplets with broad size distribution (13 µm ≤ d ≤ 1900 µm). The broad distribution was attributed to the whipping break-up mechanism of the IMF electrospray jets. Further studies are necessary to determine the properties of the powder product that can be obtained when electrospraying in an evaporator.