Design of drying machine with co-heating and dehumidification and testing of its drying performance on shiitake mushrooms

Objective: In order to improve the mushroom drying efficiency and reduce the power consumption, a new type of co-heating and dehumidification drying machine was designed and built. Methods: The drying machine was a closed system, which took the semiconductor refrigeration piece as the main component, with its hot end as heat source for air pre-heating and its cold end as the cold source for water vapor condensation. On the device, the mushroom drying rate at different drying temperatures （55 and 65 ℃） and sample mass （200 and 400 g） were tested. Results: Nine thin layer mathematical drying models were used to simulate the drying rate, which revealed that the Midilli model had a better predict effect than the others. In addition, it was found that the higher drying temperature resulted in a greater color change and a higher shrinkage rate. The comprehensive energy efficiency ratio of the drying machine was 1.96, and the power consumption of drying mushroom was 81.21 MJ/kg. Conclusion: In the experiment, the indexes such as moisture content and color change of dried mushroom met the national standards, and the energy-saving effect was remarkable compared with the traditional electric heating drying machine.