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The present work aims to develop a 3D numerical simulation that describes fresh tomatoes' heat- and mass-transfer characteristics using software COMSOL Multiphysics. Besides, a numerical study of the effect of drying parameters (drying temperature, Velocity of air drying and thickness of the slice) on the moisture content elimination from the tomato slice was realized. Also, an experimental study of the effect of the continuity and the discontinuity of the drying process on the water content vaporization is carried out. In contrast, the numerical simulation developed is validated by comparing the experimental data with the numerical results of the temperature distribution and mass transfer inside the tomato slice. The results show that the numerical simulation is agrees with the experimental tests. In addition, the results show that bacteria contamination appears in the tomato slice when the drying temperature decreases under 50 °C. The discontinuity of the drying process harms the quality of the dried product. Furthermore, the results show that the water evaporation rate in the thin slice was faster compared to the thick slice. Consequently, the drying time was reduced by 39 h when the thickness of the product was decreased from 33 mm to 10 mm. Also, the numerical simulation shows that moisture elimination is faster at higher drying air temperatures and increasing the drying air velocity leads to decrease drying time. The results show that the numerical simulation developed in this paper can accurately simulate the drying process characteristics of the agro-food product, especially Tomato, and that it provides a high spatial resolution of the distribution of water content and temperature inside the slice of tomatoes during the drying process.

In terms of energy efficiency, photovoltaic thermal (PVT) systems have great potential to produce simultaneously heat and electricity. PVT solar air collectors are often used in various applications due to their simple structure and low installation cost. While the overall performance of PVT is closely correlated with its design. In this paper, one proposes to design a novel prototype of PVT air collector, in order to improve the electrical and thermal performances. The presented numerical and Experimental studies are carried out to evaluate the impact of the designed prototype on the PVT efficiency. The essential goal of this work is to identify the optimal geometrical and operational PVT air collector parameters with square tube channel. To achieve this goal, numerical simulation using COMSOL Multiphysics is combined with experimental validation of the PVT system. The objective of the optimization consists on improving the output temperature suitable for drying applications firstly, and cooling PV modules by reducing their temperature in order to improve the electrical characteristics such as power and voltage and thereby the efficiency of the photovoltaic modules. Therfore, the PV panel temperature dropped from 53.37 °C to 42.5 °C when the design varies from PVT-1 to PVT-6. Nevertheless, PVT-5 was retained because it has the most appropriate design which gives the best overall efficiency 58.48%. Finally, it should be remembered that the tests were carried out under the same operating conditions namely, the mass flow rate Qm = 0.0235 kg/s at the inlet of the PVT, the inlet temperature (Tint), the ambient temperature (Ta) and the solar irradiation (G).

PV/T systems are an emerging technology for the simultaneous production of electrical and thermal energy. In this paper, we present an experimental device modified with an arrangement of aluminum square tubes to remove thermal heat from the system and increase its electrical efficiency. A 1D analysis allowed prediction of the heat transfer in the solid components. Moreover, a 3D simulation allowed visualization of the temperature distribution in the prototype. The simulations considered the surrounding temperature, the solar irradiance and the airflow velocity inside the square tubes. The glass temperature, PV cell temperature and the outlet airflow temperature were logged. The study was performed at a low airflow (0.5 m/s) and at a high airflow (2 m/s); for both experiments, the maximum solar irradiance was 800 W/m2 and the heat fluxes were calculated. The time constant was shorter for the experiment at low airflow, because the airflow increased by 63.2% at 5400s. At a high airflow, it took 9100 s to achieve the 63.2% of the maximum increase, and the difference between the outlet temperature and the temperature of the surrounding air was significantly reduced. At 0.5 m/s and 2 m/s the PV cell reached a maximum temperature of 75 °C and 59 °C, respectively. The maximum difference in temperature between the two experiments was 20 °C. The best thermal average efficiency was 42.5%, corresponding to the high airflow experiment. Furthermore, based on the favorable air outlet temperature, at this flow rate, the outlet air could be used for drying in a subsequent process.