The present work deals with the study of the thermal performances of a convective dryer for fruits and vegetables. This dryer, operating with energy generated from the combustion of biomass in a boiler connected to a water/air heat exchanger could be a solution to the problematic of energy related to drying. An experimental and theoretical study is carried out on the temperature profile inside the dryer. For this purpose, 10.3 kg of tomatoes were dried on the experimental setup. The operation lasted about 16 hours and reduced the moisture content from 93.8% to 12% in wet basis. The overall thermal efficiency of the convective dryer during the trial is 10.76%. For the theoretical study, the dryer components (boiler, water/air exchanger and drying chamber) are first modeled individually; the different sub-programs are then coupled to form the convective dryer program. The method of global heat balances combined with the one called "ε-NUT" is used. The set of equations is discretized using the implicit method of finite differences, then solved with the Gauss algorithm in Fortran 90. The theoretical results obtained are in good agreement with those measured.

The use of solar energy is hampered by the intermittency of the resource and the constraints of storing the thermal form of this energy. The processes using this resource are therefore faced with problems of continuity of the process. To remedy this, this work proposes to develop a device for the accumulation of solar thermal energy by a sensitive storage system on a rock bed. A solar thermal energy storage system has been developed and experimentally studied with a view to coupling it to a solar dryer. The thermal performance of the system was evaluated in terms of temporal distribution of bed temperature, total energy stored, total energy discharged, charging efficiency, discharging efficiency. The results obtained indicate that the stratification in the storage system decreases in the afternoon due to the reduction of solar radiation and the output temperature of the solar collector. This contributes to a decrease in the thermal performance of the storage system. The charging efficiency obtained is 76.8%, the discharging efficiency 44.4%. The results also indicate that out of 4.7 MJ of total stored energy almost 89% or 4.17% was recovered during the discharge phase which is interesting for solar dryers.

This paper presents a study of the thermal performance of a solar air collector used to heat the drying air of a fruit and vegetable dryer. The prototype collector could be a viable solution to improve energy efficiency and food security in Burkina Faso and other developing countries, by contributing to the reduction of post-harvest losses and the increase of income for local agricultural producers. The collector is first realized by using black painted cans as air ducts, perforated to increase turbulence, and a glass covering the collection surface. After realization, the collector is connected to the dryer and a measurement campaign is conducted to evaluate the thermal performance of it. The measured parameters are the sunshine and the air temperature by keeping the air speed fixed at 0.3 m/s. The analysis of the results shows an important variation of the air temperature difference going from 0.1°C to 74.4°C, between the inlet and the outlet of the collector for an irradiation which varies between 142 W/m2 and 837 W/m2. The black painted surface of the air ducts as well as the increase in turbulence contributed to improve the efficiency of the collector which varies between 0.94% and 50.68% and allowing to record air temperatures ranging from 27.2°C to 69.2°C inside the dryer. This temperature range is favorable for the drying of most food products.