Effect of Moisture Content and Grain Variety on Frictional Properties and Specific Heat Capacity of Acha (Fonio) Grains

There are many varieties of acha, but the most prominent two are white acha (Digitaria exilis) and brown acha (Digitaria iburua). This study was undertaken to determine the static coefficient of friction, kinetic coefficient of friction and specific heat of the grains as influenced by moisture content. The moisture levels considered were 5, 11, 23 and 28% db for the white variety and 5, 9, 21 and 30% db. The study revealed that increase in moisture content resulted to increase in the value of the properties considered for both varieties, with the white acha showing the highest values. Static coefficient of friction increased linearly with moisture content and had maximum values of 0.49 - 0.62 for the brown variety and 0.52-0.66 for the white variety all on steel sheet, while the minimum values for both varieties were on glass surface. Kinetic coefficient of friction increased linearly with moisture content and the highest value was obtained on hessian bag material (0.62-0.66) with the least being on steel sheet (0.58-0.64) for the two acha grain varieties. The study further revealed that, specific heat capacity of acha grains increased with increase in moisture content from 2.93 – 11.29 kJ/kgK (5 – 28% db) for the white variety and from 2.33 – 13.88 kJ/kgK (5 – 30% db) for brown variety. This study concludes that variety and changes in moisture content significantly affected the determined properties of acha

Effect of Moisture Content on some Engineering Properties of African Mahogany (Afzelia Africana) Seed

Some engineering properties of Afzelia africana, namely axial dimensions, one thousand seed mass, surface area, particle density, bulk density, porosity, angle of repose, static and kinetic coefficients of friction, coefficient of restitution and specific heat were determined as a function of moisture content in the moisture range of 6.1 – 32.3% (d.b). Results showed that in the above moisture range, major, intermediate and minor axial dimensions of the seed increased from 25.4 – 26.2mm, 13.2 – 13.95mm and 10.2 – 11.2mm, respectively. One thousand seed mass, surface area, particle density, porosity, angle of repose, static coefficient of friction, kinetic coefficient of friction and specific heat capacity of the seeds all increased with increase in moisture content. Seed bulk density decreased with increase in moisture content and coefficient of restitution decreased as drop height and moisture content increased. The relationship existing between the engineering properties and seed moisture content, established using regression analysis showed high coefficient of determination. These properties would be useful in the design of Afzelia africana seed handling, storage and processing equipment

Development of a Guna Seed Extractor

Guna seed extraction presents an onerous task and has been the labour and time consuming operation that militates against the large scale production and processing of this important oil crop. To overcome this problem, a guna seed extractor that works on the principle of impact from breaker arms and macerators was developed. The seed extractor consists of a hopper equipped with flow rate control device, a seed extraction unit, winnowing unit and power system. Performance tests were conducted on the seed extractor using the fruits of two varieties of guna crop namely citrullus colocynthis and citrullus lanatus in the moisture ranges of 87.21-92.45% (wb) and 85.07-89.74% (wb) respectively, obtained by varying the fruit storage duration. Result of tests and analyses showed that the performance indicators (percentage effective seed extraction, cleaning efficiency, cleaning loss, percentage seed loss at concave, material retention and percentage seed retention) were significantly affected by fruit moisture content (storage duration), material feed rate and machine speed at 1 and 5% levels. Percentage effective seed extraction and percentage seed loss at concave increased with increase in fruit moisture content, material feed rate and machine speed Maximum percentage effective seed extraction of 95.1% at the moisture content of 92.45% for the colocynthis fruit, and 96.0% at 89.74% moisture content for the lanatus, was obtained at the material feed rate of 375 kg/h and machine speed of 939 min – 1. Maximum percentage seed loss at concave was less than 5%. Cleaning efficiency, cleaning loss and material retention in the seed extraction chamber, decreased with the increase in the fruit moisture content for both varieties of guna fruits, but increased with increase in material feed rate and machine speed, while percentage seed retention decreased with increase in moisture content, material feed rate and machine speed. Maximum cleaning efficiency of 94.15% and 91.28% for the colocynthis and lanatus varieties respectively, was obtained at the material feed rate of 375 kg/h, machine speed of 939 min -1, and fruit moisture contents of 87.21% and 85.07%. Maximum cleaning loss was less than 30% and percentage seed retention was high at low fruit moisture content, material feed rate and machine speed. Practically no seed damage was recorded. Regression models that could be used to express the relationship existing between the seed extractor performance indices and fruit moisture content, material feed rate and machine speed were established for each variety of guna crop

Physical properties of four varieties of sorghum (Sorghum bicolor L. Moench) grain at different moisture contents

This study was undertaken to determine the physical properties of four varieties of sorghum grain and investigate their variation with moisture content. The properties studied include: axial dimensions, arithmetic mean and geometric mean diameters, one thousand grain weight, particle density, bulk density, porosity and angle of repose. Each property was investigated at four moisture levels in the range of 3.5-18.25% d.b (brown variety), 3.04-25.49% d.b (red variety), 3.5-20% d.b (reddish brown variety) and 3.4-25.49% d.b (white variety). The major, intermediate and minor dimensions all increased with increase in moisture content from 4.25-5.04mm, 4.10-4.76mm and 2.80-2.99mm for brown, 3.78-4.32mm, 2.96-3.43mm and 1.95-2.85mm for red, 4.25-5.21mm, 4.11-4.99mm, 3.61-3.77mm for reddish brown, 4.0-5.38mm, 3.20-4.99mm and 3.00-3.48mm for white variety. The arithmetic mean diameter had higher values for the four varieties than the geometric mean diameter. One thousand grain weight, bulk density, true density, porosity, and angle of repose of all the varieties of sorghum studied, increased linearly with increase in moisture content. Regression models with high coefficients of determination were used to express the relationship existing between the physical properties of the grains with moisture content

Design, Construction and Performance Evaluation of a Small Scale Biofuel Distiller

A biofuel distiller of 20 L feed capacity was designed fabricated and used to distill bioethanol from a biomass broth. The distiller consists of a 40 L volume boiler unit integrated to the combustion chamber as a cylindrical column; and a counter current cylindrical condenser of length, tube and shell internal diameter of 88 cm, 0.0191/0.15 m, inclined at 450.  The reactor is a Top Lit Updraft (T-LUD) type fired with charcoal of moderate lump. Its performance evaluation was conducted using 20 L palm bunch broth as the distiller feed. The palm bunch collected from Siat Nigeria Ltd, Ubima, Rivers State, Nigeria, was physically pretreated by grinding to powder, hydrolyzed with 1.2 % dilute H2SO4, at 160°C for 30 min and fermented for 72 h with S.cerevisiae separated from palm wine. The broth was then separated from the slurry by filtering before distillation. The result of the machine evaluation showed that 817 ml bioethanol was obtained per batch at 20 min from the bubble point which took 95 min. Actual combustion efficiency was found to be 55 % with reactor power rating of 12.2 kW. The machine vaporized bioethanol fuel from the boiler feed fed at 27°C, and released the distillate at 28.3°C. Distillation efficiency was found to be greater than 90 % while the maximum productivity occurred at 10 min from the bubble point. The machine is economical, reliable, convenient to use and can stand diverse environmental conditions. It can be integrated as a waste management step in the downstream end of palm mill operations

Computational Fluid Dynamics (CFD) Analyses of Energy and Exergy in Thin Layer Drying of Okra (Abelmoschus esculentus) Slices using Centre Shaft Rotary Tray Cabinet (CSRTC) Dryer

This paper presents a simulation of the drying process of okra (Abelmoschus esculentus) in a Center Shaft (CS) Rotary Tray Cabinet Dryer using three drying temperatures (50, 60 and 70 °C). ANSYS 14.5 Workbench was used to simulate the dryer model in 2D (2 Dimensional). The detail of the CFD simulation was utilized to investigate the energy and exergy of the dryer. The ANSYS Design Modeler was used to model the 2D representation of the dryer and the meshing was done using ANSYS ICEM. ANSYS Fluent CFD solver was then used to calculate the alternative using the normal turbulence-realizable k-epsilon model in a steady-state system with improved wall temperature treatment. The simulation outcome was used in calculating the dryer's exergy and energy analysis based on the thermal efficiency. It was noted that the simulated temperature from the experiment is greater than that of the experiment. The results indicated that the experimental energy utilization (EU), energy utilization ratio (EUR) and energy efficiency increased from 14.1 to 57.93 J/s, 0.15 to 0.20 and 18.89 to 33.98 percent, while the simulated energy utilization ratio increased from 23.91 to 57.68 J/s, 0.19 to 0.20 and 26.21 to 33.40 percent, respectively, and as the drying air temperature increased from 50 °C to 70 °C. Experimental exergy inflow, outflow, exergy loss and exergy efficiency increased from 4.01 J/s to 6.98 J/s, 1.83 J/s to 1.9 J/s, 3.18 J/s to 5.07 J/s and 21 to 27%, while simulated air temperatures increased from 5.01 J/s to 7.49 J/s, 1.33 J/s to 2.20 J/s, 3.66 J/s to 5.29 J/s and 27 to 29% respectively with respect to the drying air temperature range (50–70 °C). Model equations were derived from the plotted graphs to express the energy and exergy parameters as a function of drying temperature

Performance Evaluation of a Bambara Ground Nut Sheller

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 6 (2004): A. Atiku, N. Aviara, and M. Haque. Performance Evaluation of a Bambara Ground Nut Sheller. (July 2004)