The objective of this study is it investigates the effect of the microwave pretreatment on drying of banana slices by combined infrared / convection dryer under different power levels and different thickness of banana samples. Three levels of infrared power, namely: 150, 200 and 250 W and three thickness of sample are 2, 4 and 6 mm with air temperature 40 o C and air velocity 1.0 m/s were studied. Drying curves as affected by infrared power, thickness of samples and the microwave pretreatment, experimental data were fitted to some drying models. Specific energy consumption, dryer thermal efficiency, shrinkage of sample thickness and rehydration ratio were also studied. It is clear that the lower thickness sample and the higher infrared power the lower moisture ratio and total drying time at all experiments without microwave and with microwave and it was found that the least drying time was 30 min. at infrared power 250W and sample thickness 2mm with microwave pretreatment. The minimum value of specific energy consumption 1.24 (kw.h/kgwater removed) was recorded at infrared power 250 (W) and thickness of sample 2 (mm) for with assisted the microwave. The highest value of thermal efficiency 56.50 (%) was recorded at infrared power 250 (W) and thickness of sample 2 (mm) for with microwave assisted treatment.

Nowadays there is increasing activity in the development of materials from residual materials. Semistructural materials made from waste materials are usually composites. Current use of these materials is minimal, but future economics can provide these materials with a competitive advantage. Polyurethane foam is an excellent material for various uses. It is made by foaming a liquid mixture of isocyanato -polyols in the presence of a blowing agent. This article contains an experimental study of improving the insulation of rigid polyurethane foam by the means of incorporating various amounts of each cotton stalks and corn stems. Four ratios (0.0, 10, 20, and 30 % by volume) of cotton stalks or corn stems were used with rigid urethane foam. The produced composite mad from rigid urethane foam and cotton stalks or corn stems were tested to measure bulk density, thermal conductivity and thermal resistivity. The results indicated that the thermal conductivity and thermal resistivity affected by the replacement ratios (%). The thermal conductivity was decreased with increasing replacement ratios. On the other hand, the thermal resistivity was increased with increasing replacement ratio (%). The results showed that the thermal properties of rigid urethane foam were improved with adding cotton stalks or corn stems. Corn stems showed the best, lowest, thermal conductivity values than cotton stalks. The lowest thermal conductivity was 0.01692 W/m. o C at corn stems with replacement ratio of 30 (%) as well as, the highest thermal resistivity of 59.09 m. o C/W at the same previous replacement ratio.