OPTIMAL OPERATION OF OPA DAM – RESERVOIR WATER SUPPLY SYSTEM

Dynamic programming technique was used in the simulation of Obafemi Awolowo University Campus water supply system to generate the maximum cumulative returns from sales of water to the people around for a seasonal planning period of a year. Major parameters necessary in the optimization of the reservoir system viz: reservoir size: rates of evaporation, siltation and seepage; streamflow characteristics and scheduled release of water, were considered as constraints. The cost functions expressed in Monetary Unit (MU) were derived for the sales of water. The objective function was optimized taking into consideration the probabilistic inflow of water into the reservoir. The maximum cumulative returns for the various combinations of: the state of the reservoir at the beginning of the planning period (SI); the inflow into the reservoir during the rainy season (11) and the inflow into the reservoir during the dry season (12), were computed and analyzed, with the optimal policies for the various possible combinations obtained. The maximum cumulative return from sales of water from the computer simulation result was found to be 8,868,570MU. This occurred when there was peak seasonal inflow into the reservoir and a decision to release 3,878,935 m3 of water, made during the planning period

PREDICTIVE MODEL FOR EVALUATING CORROSION RATE OF MILD STEEL IN SIX ENVIRONMENTS

Experiments were carried out in six environments for 90 days to determine the levels of corrosion rates on AISI 1021 mild steel rods. The environments were: Sodium hydroxide fumes sulphuric acid fumes; nitric and fumes; Sodium sulphate fumes; Sodium Chloride solution; and water from borehole. Weight losses in the rods were determined at intervals of 5 days as these rods were exposed to the environments. The relationships between loss in weight of the exposed steel and exposure period were determined. Corrosion rate models were developed as a function of total surface area and exposure period. The theoretical corrosion rates were compared to rates determined from theoretical considerations. It was found that the corrosion effect is rapid in Na0H environment. Its effect was noticed after about 2 hours of exposure. The samples exposed to Sulphuric acid fumes environment had the highest mean corrosion rates of 0.5488 cm/yr (for established) and 0.5201 cm/yr (for predicted). Water from borehole environment had the least mean corrosion rates of 0.1249 cm/yr (for established) and 0.1277 cm/yr (for predicted). There is no significant difference between the calculated values of corrosion rates using established model and predictive models, thus indicating the reliability of the models

MOISTURE – SOLID TRANSFER DURING OSMOTIC DEHYDRATION OF BANANA (MUSA SAPIETUM) VARIETIES

Moisture-Solids transfer during the osmotic dehydration of three banana (Musa Sapietum) varieties was investigated. Cavendish, Omini-red and Cooking banana were transversely sliced into 10, 15 and 200m thicknesses. Sample of each thickness were immersed in 250, 600 and 680B sucrose solutions. A fruit: solution ratio of 1:20 (w/w) was maintained. The fruit-solution mixtures were kept at 270, 340 and 400C for 12 hours. Samples were evaluated gravimetrically at 2 hours interval. Moisture and total solids contents were determined and expressed as g water/g dry matter (DM) and g solids/g initial mass respectively. Moisture contents on dry basis of the banana slices were found to decrease with increased immersion time, solution concentration and temperature. However, moisture contents decreased with decreased slice thickness. Total solids content increased with increased immersion time, solution concentration and temperature, but decreased with decreased slice thickness. Omini red cultivar had the lowest moisture content and the highest total solids content at the end of 12 hours of osmotic treatment. Complex polynomial equation showing the relationship with moisture and total solids contents with immersion time showed high correlation (R2 = 0.9919 – 1.000)

DISCRETE ELEMENT MODELLING OF THE IMPACT PARAMETERS OF A SELECTED FRUIT: MODEL VALIDATION AND EFFECT OF DAMPING

The Discrete Element Method has been applied to numerical modelling of the impact process in fruit with a view to obtain information on damages due to impact. A DE code which incorporated a non-linear viscoelatic contact law, real containing walls and particle deformation developed from an existing code using a linear elastic contact law without containing walls was used. The code was validated with available theoretical and experimental results on impact behaviour of rubber spheres. The parametric variations with different damping coefficients were then simulated for a selected fruit dropped from a height of 10, 15, 20 and 30 cm onto a hard flat surface. The parameters investigated include variation in the force, time, velocity, deformation and the peak force during contact in relation to the height drop. The experimental and the simulated were found to be in good agreement (p>0.05) with no significant differences. The peak forces predicated by the simulation were 42.5, 85.2 and 137.7 N as compared to 40, 87 and 136 N from the experiment for spheres weighting 29.4, 95 and 190.7 g respectively. The predicted time of contact was however slightly lower in all the cases but there is no significant difference between the experimental and the predicted (p>0.05). The study with the fruits also showed good agreement with the existing data, indicated by the features of the curves, which showed that the non-linear viscoelatic contact model is a good approximation for predicating the contact behaviour of viscoelatic materials. Information on the parameters required in the selection of appropriate materials and range of parameters useful in the design of handling equipment were provided. The model is therefore a useful tool in the study of impact process for agricultural particulate (discrete) materials

EVALUATION OF A PEDAL – OPERATED CASSAVA GRATER

A pedal – operated cassava grating machine was developed and evaluated. The grater is to bridge the gap between the motorized grater and the labour-intensive, traditional cassava grating device, and to ameliorate the tedium of cassava grating at the village level. The grater’s component parts are: the grating unit, power and transmission unit, the housing, the hopper and the discharge chute. The cassava grater output capacity ranged between 28.50kg/h and 45.00kg/h depending on cassava variety. The particle size distribution in the end product representing medium fine, fine and powdery materials is 1:3:6. The grater capacity has a comparative advantage ratio of more than 220% over traditional grating device. One average person of between 25 – 45 years of age can comfortably operate the continuously for about 16 minutes to produce an output of about 4kg

BENCHMARKING AND VALIDATION OF HOT ROLLING SIMULATION MODELS

Mathematical models representing the various stages in the hot rolling process of steel production were produced. Simulated models used were validated using the EXCE: package and then subjected to a sensitivity analysis under identical conditions to predict the optimum operating conditions under which the essential process steps can be carried out. The results showed that ferrite grain size is more sensitive to the retained strain than to the cooling rate or the austenite grain size. It was also inferred from the work that a drop in the austenite-ferrite (y – a) transformation temperature leads to an increase in the tensile strength of the steel. This is an agreement with industrial practices

ANALYTICAL APPROACH OF EARTH MASONRY INFILL-PANEL SUBJECT TO SEISMIC LOADS

Earth wall has been observed to be a structural, flexible and inexpensive element in construction. In this work an investigation was carried out on the earth (laterite) wall as an infill panel to determine its hysteric parameters, strength degradation and stiffness decay due to seismic loading. Prediction formulation, for the lateral strength and stiffness parameters of the panel was obtained. Equivalent strut model was found to be appropriate in the analysis, while Bouc-Wen model was employed for hysteresis behaviour. The multistory frame structure with the earth wall in-fills behaves purely as braced element in which the lateral loads are resisted by a truss mechanism, formed by the compression in the earth wall infill panels and tension in the column. The force-displacement response for this element may be employed to assess the overall structural damage and its distribution to a sufficient degree of accuracy

THE INFLUENCE OF INGOT GEOMETRY ON TEMPERATURE DISTRIBUTION IN HCSS316 DURING HOT ROLLING

The effects of material geometry on rolling parameters such as yield stress, rolling load and torque have been studied. In this work, geometrical variation is intruded into the Reverse Sandwich Rolling Model (RSM) for high carbon stainless steel type 316 (HCSS316). The modification affords evaluation of the possible effect of geometry of the in-going strip of HCSS316 on temperature distribution in the material during hot rolling. Simulation of the model was carried out using FORTRAN 77. The computer code was validated with hot rolling experimental data from two high-reversing hot rolling mills with different roll diameter. Results of the simulation revealed a symmetrical temperature distribution from the rolling surfaces, to the mid-thickness of the specimen where in peaked. Thos pattern was consistent for specimens with different geometry. The results showed agreement with experimental inferences

AN INVESTIGATION INTO THE EFFECTS OF IRRIGATION DEVELOPMENT ON SOME CLIMATIC FACTORS IN TWO IRRIGATION SCHEMES IN NIGERIA

An analysis of climatic data for two irrigation projects in Nigeria was carried out. The schemes investigated are Itoikin Rice Project (IRP) and Zauro Polder Project (ZPP located in the rain Forest and Sudan Savanna zones of Nigeria respectively. At IRP, an annual mean rainfall of 1332mm with low variability between the years at coefficient of variation (Cv) of 17% level was recorded. Post0irrigation development relative humidity (RH) records for Itoikin indicate an annual mean 77.9% with a Cv of 1.6%. These results show that irrigation development in this area is associated with unusual scanty rainfalls in the dry months of the year due to large volume of water. There was consistent high relative humidity during the usual irrigation periods. Post-irrigation development maximum and minimum temperature records at Itoikin indicate annual means of 31.60C and 22.60C respectively. All these micro-climatic data affirm the effect of irrigation during the supposedly dry months of the year. At ZZP, climatic data were largely unavailable, only the data for a few pre-irrigation development years (1974-79) were obtained. These data indicate an annual mean rainfall of 568.4mm and annual mean of 35.10C and 21.30C, respectively at ZZP. These micro-climatic data for ZPP area may be used as baseline for monitoring of the impact of the full blown project when it commences. &nbsp