Beschreibung:
<jats:title>Abstract</jats:title><jats:sec><jats:label /><jats:p>In this research, the effect of different parameters of a convective hot air dryer on the mass transfer coefficients of thin‐sliced pears in different drying stages is analytically and experimentally investigated. According to the results, in the first stage of drying which begins from the initial moisture content (MC) of 87–57% in this study, the convective heat transfer coefficient, the inlet air temperature and the initial MC of the product had the highest influence on the mass transfer rate of the drying product. In the second drying stage (from 57 to 27% MC), the structure of internal pore of the fruit, the internal MC and the thickness of the cut layers are the most influencing parameters controlling the mass transfer coefficient of the product. In the third region of drying (from MC of 27% to the final MC), the inlet air temperature had the greatest effect on the rate of mass transfer from the product. In this region of drying, increasing the drying temperature from 50 to 60°C at an airflow velocity of 0.5 m/s, yielded increasing the effective diffusion coefficient from 1.19 × 10<jats:sup>−7</jats:sup> to 4.09 × 10<jats:sup>−7</jats:sup> m/s<jats:sup>2</jats:sup>. The results of this study showed that increasing the airflow rate in the third stage of drying reduces the effective mass transfer coefficient. The highest effective diffusion coefficient in the third region of drying for thin‐sliced pears was obtained equal to 6.24 × 10<jats:sup>−7</jats:sup> m/s<jats:sup>2</jats:sup> for drying temperature of 80°C and airflow velocity of 0.5 m/s.</jats:p></jats:sec><jats:sec><jats:title>Practical Applications</jats:title><jats:p>Pears (<jats:italic>Pyrus communis</jats:italic> L.) are bell‐shaped fruits that are in the range of green, yellow, brown, red, or a combination of these colors. This useful fruit is rich in potassium, vitamins, and minerals. There are 30 varieties of pears in the world and they are consumed cooked, compote, or raw. The drying process of fruits and vegetables by reducing the moisture of the product, prevents chemical and biochemical spoilage of the product and increases their shelf life. However, some undesirable physical and chemical changes such as discoloration, texture, and nutritional value may also occur during drying, which reduces consumer acceptance. Drying operations usually take place in the final stages and after other operations and lead to the production of the final product.</jats:p></jats:sec>