Browsing by Author "Adeyemi, Samuel Ayobami"

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    Numerical and Experimental Studies on Mixedmode Solar Dryer for Cocoa Beans
    (Obafemi Awolowo University, 2016) Adeyemi, Samuel Ayobami
    Cocoa beans dried undeIn this study a mixed-mode solar dryer was numerically modeled. The modeled solar dryer was designed, fabricated and evaluated for its performance. This was with a view to optimizing the design of the dryer and hence improve the performance. The mixed-mode solar dryer was numerically modelled for performance optimization using ANSYS software. The simulation is based on ANSYS solar load model. Based on optimized geometry obtained, a mixed-mode solar dryer was designed, fabricated and evaluated. The dryer was used to dry cocoa beans under free convective and forced convective (varied airspeed of 1.2m/s and 1.5m/s) drying. The drying was carried out during the wet and dry season of the year. Drying air temperature, ambient temperature, relative humidity, air velocity and drying time were measured until the beans reached equilibrium moisture content. Grade and physico-chemical test such as pH, acetic acid content and FFA of the dried beans were determined. Results of the model show that temperature within drying chamber increases with increase in solar collector area and decreases with increase in drying bed height. Maximum solar energy is obtainable at solar collector inclination angle of 14˚. This angle corresponds to angle ranges (α-6.5) ≤ β ≥ (α+6.5) of the earth polar system. The data obtained from the fabricated optimized dryer without loading were compared with numerically modeled dryer results with good agreement. The dryer dried 50 kg of wet cocoa beans to equilibrium moisture content within average drying period of 57 hours. Quality tests of the dried beans show that all the dried beans are grade 1, irrespective of drying method. However, Cocoa beans dried under forced convective process are more acidic with acetic acid value of 3.23 mg/g and 3.19 mg/g at airspeed 1.2 m/s and 1.5 m/s, respectively. The corresponding acetic acidic value for cocor free convective process was 3.38 mg/g. The pH for cocoa beans dried under free convective is higher than forced convective drying. The FFA for cocoa beans dried under free and forced convective drying (at airspeed 1.2 m/s and 1.5m/s) are 0.4 mg/g, 0.42 mg/g and 0.43 mg/g, respectively. Hence, cocoa bean samples dried under free convective drying are superior. In addition, samples dried during wet-season have less free fatty acid and acetic acid content with higher pH value compared to dry-season dried sample. Hence, cocoa bean samples dried during wet-season are also less acidic than dry-season dried samples. In conclusion, the study established that adequately modeled mixed mode solar dryer is a viable tool for extracting maximal energy from solar system of the earth planet. Mixed mode solar dryer is adequate to dry wet cocoa bean to safe moisture level irrespective of seasonal variation in weather condition of the year with good quality produce