Alexis Kuitche

Variation of the Physical Properties of Sheanut (Vitellaria Paradoxa Gaertn.) Kernels during Convective Drying

The effect of moisture content and drying temperature of Vitellaria paradoxa Gaertn kernels on some of its physical properties was investigated. The kernels which were harvested at a moisture content of about 60% (wet basis) and hence prone to high post harvest losses from two ecological zones of Cameroon (Bangoua in West province and Tchabal in Adamawa province) were dried in a forced convection dryer at 40oC, for 6, 20, 48, 72 and 96 hours to give moisture contents ranging from 10 to 60% wet basis. Ten trees from each of the zones were carefully selected to serve as sources for the ripe kernel bearing shea fruits that were used as samples for this study. For each parameter studied, a sample population of 30 kernels selected at random per tree was used. The results obtained revealed that there was a significant difference in the physical properties of the kernels from different trees irrespective of the locality. The bulk density, true density, sphericity and porosity varied non-linearly with the moisture content. Kernels with larger masses showed a different variation pattern of bulk density and porosity with moisture content compared to the lighter kernels. The variation of the bulk density, sphericity, porosity of sheanut kernels with moisture content and temperature was satisfactorily modelled with empirical equations. The samples underwent considerable shrinkage (up to 35%) during the drying process. Three empirical models were used to describe the shrinkage behaviour of the kernels and it is proposed that these models could be incorporated in drying models.

Simulations Based on Experimental Data of the Behaviour of a Monocrystalline Silicon Photovoltaic Module

The performance of monocrystalline silicon cells depends widely on the parameters like the series and shunt resistances, the diode reverse saturation current, and the ideality factor. Many authors consider these parameters as constant while others determine their values based on the characteristic when the module is under illumination or in the dark. This paper presents a new method for extracting the series resistance, the diode reverse saturation current, and the ideality factor. The proposed extraction method using the least square method is based on the fitting of experimental data recorded in 2014 in Ngaoundere, Cameroon. The results show that the ideality factor can be considered as constant and equal to 1.2 for the monocrystalline silicon module. The diode reverse saturation current depends only on the temperature. And the series resistance decreases when the irradiance increases. The extracted values of these parameters contribute to the best modeling of a photovoltaic module which can help in the accurate extraction of the maximum power.

Potential of Wind Energy Development for Water Pumping in Ngaoundere

The modelling of wind energy conversion systems is of great importance if one intends to develop water pumping applications for a sustainable development. This paper presents a technical assessment based on the measured wind data in which we investigate the possibility of coupling piston pump, roto-dynamic pump and electric pump with wind rotors for water pumping applications. Weibull distribution is used to model the monthly mean wind speed for a location in the town of Ngaoundere. It is found that there is a good agreement between the predicted values of the mean wind speed and those obtained from data suggesting that the Weibull distribution can be used to provide accurate estimation of the mean wind speed. The mean electric power and energy are computed based on the power curves of Vestas V25 and V100. Taking into account the wind regime characteristics of our site, we provide the amount of water which can be expected from each type of wind pumps. The monthly amount of water has minimum and maximum average values of 422 m3 and 674 m3 for the piston pump, 1275 m3 and 1982 m3 for the roto-dynamic pump and 31334 m3 and 100042 m3 for the electric pump. From the results, it is clear that electric pump offer better performances than piston and rotodynamic pumps.

NUMERICAL SIMULATION OF CONVECTIVE HEAT TRANSFER COEFFICIENT IN CHANNEL WITH CORRUGATED WALLS

The present work is a contribution to study of convective heat transfer coefficient inside a rectangular channel with corrugated walls. Triangular, square and rectangular shaped configurations were studied for a range of geometric parameters during simulation. The Navier-Stokes equations were numerically solved using the finite volume method through the Easy CFD_G package code in its V.4.1.0 version. With prescribed temperatures and velocities, the model predicts the behavior of the airflow inside the device. The temperature and velocity distributions are first predicted. From these distributions, the convective heat transfer coefficients along the surface of the objects placed inside the system are determined. Also, from the pressure distribution, the pressure drops along the channel are predicted. The results show that the triangular corrugated-shaped configuration with h = 5 [cm] and α = β = 60° enable to obtain the best value of convective heat transfer coefficient on the surface of the objects which is 2.70 [Wm-2°C-1] resulting in a pressure drop of 0.11 [Pa], while for parallel-plate channel configuration this same coefficient is 1.12 [Wm-2°C-1]. The energy balance enabled to conclude that the energy gain by convection air/objects is superior to the air pump energy to overcome the pressure drop.

Fatigue Safety Coefficient Based Mutual Comparison of the Simple Working Regime of Hermetic Compressor Suspension Springs

Compressors suspension made up of helical suspension spring system has a significant importance on the operation of hermetic compressors, considering the aspects of noise and vibration. These springs are loaded by harmonic forces very often. High cycles fatigue damage and failure can be found during its service loading. The severity of lading regime has been studied for three typical loading regimes of springs using the fatigue safety factor. The spring fails by fatigue not yielding; infinite life is not predicted. All cases are demonstrated in the Haigh diagram. Finite life is predicted. It has been showed that loading cases with constant mean shear give lowest safety factor than the proportional or constant middle stress regimes.