Browsing by Author "El-Mesery, Hany S."

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    The drying of onion slices in two types of hot-air convective dryers
    (Academic Journals, 2012-08-07) Gikuru, Mwithiga; El-Mesery, Hany S.
    Drying experiments were carried out using two types of convective hot-air dryers such that the hot air passed perpendicularly through a thin layer of onion slices in one dryer while the air passed parallel to the thin layer in the second dryer. The drying air temperatures were 50, 60 or 70°C, while air velocity was set at 0.5, 1.0 or 2.0 m/s. The drying behavior of onion slices under the aforementioned experimental parameters was fitted using Newton, Henderson and Pabis, Page and Modified Page models. The results were compared for their goodness of fit in terms of coefficient of determination (R2) and standard error (SE). The Page model was the best in describing the drying behavior of onion slices when compared to the other models. The drying time in the case of the horizontal convective hot-air dryer in comparison with vertical convective hot-air dryer was considerably less while onion slices dried at higher temperatures generally had higher rehydration ratios.
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    Performance of a convective, infrared and combined infrared-convective heated conveyor-belt dryer
    (Springer, 2015-05) Gikuru, Mwithiga; El-Mesery, Hany S.
    A conveyor-belt dryer was developed using a combined infrared and hot air heating system that can be used in the drying of fruits and vegetables. The drying system having two chambers was fitted with infrared radiation heaters and through-flow hot air was provided from a convective heating system. The system was designed to operate under either infrared radiation and cold air (IR-CA) settings of 2000 W/ m2 with forced ambient air at 30 °C and air flow of 0.6 m/s or combined infrared and hot air convection (IR-HA) dryer setting with infrared intensity set at 2000 W/m2 and hot at 60 °C being blown through the dryer at a velocity of 0.6m/s or hot air convection (HA) at an air temperature of 60 °C and air flow velocity 0.6 m/s but without infrared heating. Apple slices dried under the different dryer settings were evaluated for quality and energy requirements. It was found that drying of apple (Golden Delicious) slices took place in the falling rate drying period and no constant rate period of drying was observed under any of the test conditions. The IR-HA setting was 57.5 and 39.1 % faster than IR-CA and HA setting, respectively. Specific energy consumption was lower and thermal efficiency was higher for the IR-HA setting when compared to both IR-CA and HA settings. The rehydration ratio, shrinkage and colour properties of apples dried under IR-HA conditions were better than for either IR-CA or HA.