Thermal Engineering

This study presents a novel natural convection process. A prototype of an indirect solar dryer, with its collector made of hemispherical concentrators had been realized and studied with the idea of obtaining higher temperature in the drying chamber, and this with a steady non tracking collector. The patented collector is based on the hot-spot theory. Measurements had been conducted for all critical period of the year. The result seemed conclusive with temperature improvement in steady non tracking collectors, and suggests further investigation of the hot-spot theory, by conceiving a mathematical model and by deepening the experiment outcomes for a best thermodynamic study.

Our work relates to a numerical and experimental study of a solar exchanger designed and tested in Laboratory of Renewable Thermal Energy. This device is a unit for transforming solar radiation into thermal energy. The objective of our work is to study the evolution of temperature in the solar collector-water system. Our results show that this device makes it possible to heat the water during the day. The numerical results show that the temperature rise of the water is 47.84 °C in March and 46.34 °C in April.

Development of eco-friendly systems and energy efficient systems has been a great concern for sustainable development. In the present research paper, we are using a two-stage evaporative cooler (TSEC) consisting of two evaporative cooling chambers. The temperature drop through TSIEC can be achieved to be about 100K or below by applying the combined concept of bootstrap air refrigeration cycle and evaporative air refrigeration cycle. In this system we are using indirect evaporative cooling of compressed air in two stages of compression followed by cooling to attain very low temperature which can be used for scientific researches and cryogenics.

The conventional double pipe heat exchanger has less heat transfer rate, so to overcome this problem, this paper focuses on establishing the Triple Tube Heat Exchanger (TTHE) is modified constructive version of double concentric tube heat exchanger by adding an intermediate tube for hot fluid. In this paper the experimental data obtained during the test in a double and triple concentric tube heat exchangers are very much impressive. However, U valve also fitted and were analyzed and the experiment results conforms the effectiveness of the triple tube heat exchanger.

We have conducted a meta-analysis, a detailed literature review has been studied on hydrogen economy and it’s important in both regions. We have also seen that how useful a hydrogen can be and how it can affect the overall economy of both regions (China and Pakistan). The reason for conducting meta-analysis is to compare the hydrogen economy performance in both countries. This analysis would also give a wider perspective that how hydrogen economy with its different functions, especially hydrogen in the energy sector can enhance the overall growth of the economy. In our analysis, we have compared the different statistics of hydrogen with different factors of economy and tried to assess the impact of hydrogen in those sectors. Our findings indicate that large-scale use of hydrogen is not a significant environmental hazard. If appropriate technical standards and safety standards are used, hydrogen is no longer hazardous to conventional fuels. The hydrogen economy has the potential to provide many benefits for the country, including reduced dependence on imported oil, environmental sustainability, and economic competitiveness. But without serious effort, there is no serious difficulty. Recommendations are made to guide Pakistan towards the path to the hydrogen economy. It must be a clear political support for the development of hydrogen. We need to establish a partnership with countries related to hydrogen technology. In order to overcome the technical obstacles, investment in the research and development of hydrogen and fuel cells is necessary. Current study is not only beneficial for policymakers but also for scholars.

Excessive wood consumption in Burkina Faso has led not only to deforestation, but also to soil degradation. The preservation of ecosystem balances, the management of soil fertility and the safeguarding of forests are major issues for future generations. It is in this context that our work has focused on the development of an energy conversion technology that effectively uses little-used agricultural residues (cotton stalks, bare corn cobs, rice husks, etc.). This device is a multifunction family furnace that produces biochar for soil amendment and provides alternative energy for household needs. The physical and mathematical modeling of the oven based on the nodal method whose equations were solved by implicit finite differences allowed to describe its thermal behavior. K-type thermocouples were used for the experimental study to validate the mathematical model. Indeed, the pyrolysis temperature of the bare corn cobs is on average 450 °C. The model allowed us to show that the thickness of the pyrolysis chamber influences the pyrolysis temperature and reduces the pyrolysis time. For a thickness of 8 cm of the pyrolysis chamber, the average pyrolysis time is 1 hour 30 minutes. The study also showed that the variation of the ambient temperature does not influence the pyrolysis temperature. Moreover, the thickness of the insulation chamber affects the external wall temperature but not the pyrolysis temperature.

An experimental and numerical study of the operation of an adsorption solar refrigerator using the zeolite-water couple is presented. The experimental consists of measuring the solar radiation incident on the collector-absorber, the temperature of the collector-adsorber, of the condenser and the one of the evaporator. The numerical part concerns a modeling and a simulation of the functioning of this refrigeration system. Transfer equations are deduced from thermal and mass balances established at each component of the refrigerator. The Dubinin-Astakhov equation is adopted for the adsorption kinetics of the zeolite-water pair. The results are presented by the evolution over time of the temperatures of the components of the solar refrigerator (absorbent plate, condenser, evaporator, etc.), as well as the pressure adsorbed, adsorbate mass and SCOP.

In Burkina Faso, the increase in energy consumption in habitat can be expected to become even more marked, not only because of the expansion of air conditioning and the number of electrical appliances. In this work, we proceeded to a modeling and a simulation of the thermal behavior of the envelope of the habitat F1 (studio apartment) built in concrete block from the software COMSOL Multiphysics Simulation 5.3a. We have noted that the concrete block habitat has a high internal temperature (temperature above 35°C) with a low thermal phase shift of 02 hours during the hot months (March and April) of the year. Block constructions would require a very large daytime air conditioning load to keep the interior at a comfortable temperature. We can therefore say that for sustainable or bioclimatic design, the concrete block is not a material adapted to the climatic context of the city of Koudougou.

In this work, we simulate the global solar radiation received by a horizontal surface and vertical surfaces of different orientations on the ground from theoretical models considering the diffusion and absorption of solar radiation through the atmospheric layer. We have to generate results of the global radiation by the model of Liu and Jordan for thermal systems optimization, particularly in the field of the building in the city of Ouagadougou. This work shows that the solar radiation on a surface, in addition to the seasonal variability, also varies according to the orientation and the inclination of the sun. Thus, in the case of buildings, for example, exposing the large surfaces of the building according to the southern orientation will be avoided in favor of the northern orientation. It is also necessary to consider the scenario of use of the building to situate it in space and time in order to minimize the thermal contributions.

An analytical solution to the problem of an MHD oscillatory boundary layer flow past a porous horizontal plate with periodic suction is presented. The fluid in the boundary layer rotates about an axis normal to the plate with a uniform angular velocity. A magnetic field of uniform strength is assumed to be applied normal to the plate. The equations governing the flow and heat transfer are solved by regular perturbation technique assuming the solution to be consist of a mean part and a perturbed part. The expressions for the temperature fields, skin friction at the plate due to primary and secondary velocity fields and the rate of heat transfer from the plate to the fluid in terms of Nusselt number are obtained in non dimensional form. The dimensionless expressions for the amplitude and phases of the fluctuating parts of the skin friction, Nusselt number at the plate are also derived. The skin friction due to primary velocity and skin friction due to secondary velocity at the plate, the amplitude and phase of the fluctuating part of , the rate of heat transfer from the plate to the fluid in terms of Nusselt number and amplitudes and phases of the fluctuating parts of it are demonstrated graphically and the effects of the parameters M (Hartmann number), (rotation parameter)and A (suction parameter)on these fields are discussed.It is seen that M, ,A have significant effect on the flow and heat transfer characteristics.2000 Mathematics subject classification: 76W05