Asian Journal of Physical and Chemical Sciences

The accumulation of dust on solar panels affects the transmittance of solar panel glazing which leads to the degradation of its efficiency due to low levels of irradiance reaching the cells. In this work, the response of polycrystalline silicon solar panels toward dust in a natural dusty environment was experimentally investigated at a location in Calabar close to the Calabar river. The experimental measurements were carried out in real-time outdoor conditions where human activities take place. An automatic dust wiping/cleaning mechanism to ensure the panel surface was kept clean was deployed in the study. An intelligent maximum power point (MPP) trackers for tracking the maximum power points of the panels were also utilized for this work. Results obtained revealed that the accumulation of dust on polycrystalline solar panel adversely affects its power output and efficiency. From the results, it was also revealed that the average panel temperature of the photovoltaic system with the automatic dust wiping mechanism was 5.30⁰C lower than the other system without the mechanism. This lower panel temperature led to an increase of 16%, 32.5%, 43.40% and 43.37% in average voltage, average current, average power and average efficiency respectively over the dusty panel. It was demonstrated that solar panel efficiency plummets as panel temperature rises due to heat dissipation caused by the accumulation of dust.

This study seeks to propose a new model of hearth for the consumption of biogas produced by a biodigester of 4 m^-3. The cylindrical furnace is used to heat an empty pot for 3 hours. To do this, the system is subdivided into two sub-systems, the first is the flame, which heats the bottom of the pot. The latter is the second hottest point. The developed network is composed of 8 isothermal points, interconnected by thermal resistances, each of which represents a particular type of heat transfer mode. The resolution of the system required 8 differential equations. The modeling allowed us to appreciate the temperatures governing the system. The experimental study proves an agreement with the model temperatures. Studies show that the cook stvoe’s optimal thickness and height are respectively 18 mm and 09 cm. The heat ide the internal air of the kettle is 220⁰C and the flame temperature is 900⁰C. The instantaneous efficiency of the cook stove obtained is 65%. In addition, a validation with literature data to confirm this study with maximmum gap of 5%, therefore its adoption will lead to reducing the consumption of biogas and therefore have a positive impact on the woodcut.

Aim: A subsurface geotechnical investigation was carried out for the purpose of establishing the depth of competent soil for foundation design and construction of a one-storey building.

Study Design: The study was aimed at assessing the subsoil competence for a foundation design in the Eastern Niger Delta using engineering geology and geotechnics.

Place and Duration of Study: The research was conducted in three locations along the Rumuokwuta axis of Port Harcourt (the eastern Niger Delta) between April and September 2019.

Method: The study involved both field sampling and laboratory analysis. This involved soil boring for the retrieval of disturbed and relatively undisturbed samples for analysis, which involves grain size analysis, the Atterberg limits, moisture content, and unit weights. Also, Oedometer consolidation Oedometer and undrained, unconsolidated triaxial tests were carried out.

Results: The study revealed two main stratigraphic layers that are mostly fine within the shallow foundation level (0.0–3.0m). From the results, the soil exhibited the following geotechnical properties: liquid limit (41-46%), plastic limit (21-23%), plasticity index (18-24%), and moisture content range (20.6-24.7%). The undrained cohesion value is 55 kPa, and the average frictional angle is 5^o. The coefficients of compression (Mv) and consolidation (Cv) were 0.20 m² /MN and 40.7 m²/yr, respectively.

Conclusion: With the moderate bearing and settlement values within the shallow foundation level, the feasibility of adopting a shallow foundation for the purposed structure is tolerable. A shallow foundation (1.4m minimum) with an allowable bearing pressure of 100 kPa is therefore recommended.

In the current energy context, geothermal systems are highly developed in the building field. Among these interesting systems on the energy plan, one finds in particular the earth-to-air heat  exchanger commonly called ‘Canadian or Provençal well’. It consists of tubes buried in which the ambient air is pushed in order to be refreshed in contact with the ground whose temperature is quasi-constant throughout the year. In this work, a study of the performance of an earth-to-air heat exchanger was undertaken by means of numerical modeling of heat exchange by forced convection in a buried tube. The transfer equations in the tube are discretized using the finite volume method in turbulent regime and solved using the Thomas algorithm. For the determination of the ground temperature, the model of the semi-infinite mass subjected to a periodic excitation was adopted. The soil temperature was used as a boundary condition for the buried tube.

The results show that the interest of the earth-to-air heat exchanger is major, since it improves throughout the year, the thermal conditions sought. It intervenes in an effective way on the damping of the thermal amplitudes in the building. The variation of the diameter and the length of earth-to-air heat exchanger does not influence notably the distribution of the streamlines and isotherms but affect significantly the values of stream function and temperature inside de tube of the earth-to-air heat exchanger. When diameter of the pipe increases, the outlet temperature increases. The increase of the length of the earth-to-air heat exchanger leads to the isotherms increase as a result of the intensification of heat exchange between the walls and the convective jet. The temperature in the air outlet compartment is lower as the length of the earth-to-air exchanger increases.

A numerical study of the natural heat and mass transfer in a cavity with a straight isoscele cross-section containing air is made in this paper. The two inclined side walls are kept in natural convection with the surrounding environment. The upper horizontal wall is subjected to a heat flux of constant density, while the lower one is adiabatic. Under the Boussinesq assumption, the thermodynamic conditions are numerically studied using the unsteady convection equations formulated as a secondary variable of vorticity and a stream function, energy and moisture. The system of equations discretised by the implicit finite difference method is solved by the Thomas algorithm. The results show a flow structure, isotherms and isohumidities dependent on the study parameters. Thus, on one hand, an increase in the inclination angle of the walls is accompanied by an increase in the velocity of the fluid. On the other hand, an increase in the aspect ratio or Lewis number leads to a decrease in the fluid’s velocity. The average Nusselt number, which is independent of the Rayleigh number, increases slightly as the inclination angle of the walls decreases. The increase of the Lewis number results in the decrease of the flow velocity components values. It is observed that the maxima values of velocity components were reached for Rayleigh number equal to 7.10³.