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In order to solve the problems of time consuming, energy consumption and low simulation accuracy in the hot air-drying system of food drying. Using computational fluid dynamics (CFD) to simulate the drying process of mushrooms can provide a reference for its technology research and development (R&D). The porous media approach was used to model the flow resistance offered by the mushroom. The resistance coefficient and porosity were determined through the experiments. Different air supply ways (wind speed, temperature, fresh air volume, reverse air supply period) were simulated and two optimize ways were suggested according the shortest possible drying time. The simulation results are in good agreement with the experimental results. The air supply way of periodic with reverse (SMPR), which means timed alternate the direction of air flow, or the way of mix in fresh air intermittently can effectively shorten the drying time. Considering comprehensively, the optimal air supply way was the mix in fresh air intermittently with fresh air accounts for 30% or SMPR with the period of 2h under the condition of the hot air temperature of 55°C and wind velocity of 0.6m/s.

In this paper, the commonly used High Efficiency Particulate Air filter (HEPA) material as the research object, through the design of indoor experiment, using pure water, groundwater, and rainwater solution to soak, analysis of unused and abandoned the mesh in different water chemical solution release/adsorption law of anion and metal components, in order to find out its potential impact on the water environment. Results showed that: (1) when the waste HEPA filters were soaked in water solutions, the maximum average release amounts (Qmax¯)$$(\overline {{Q_{max}}} )$$ of four anions were in a order as: SO42−>NO3−>Cl−>F−$${\rm{SO}}_4^{2 - } > {\rm{NO}}_3^ - > {\rm{C}}{{\rm{l}}^ - } > {{\rm{F}}^ - }$$. Pure waters showed the highest (Qmax¯)$$(\overline {{Q_{max}}} )$$ of Cl- and NO3−$${\rm{NO}}_3^ - $$, which were 1.2120 and 0.3387 mg/g, respectively. Groundwater showed the highest (Qmax¯)$$(\overline {{Q_{max}}} )$$ of SO42−>$${\rm{SO}}_4^{2 - } > $$ and F-, which were 6.7329 and 0.0348 mg/g. These indicated that SO42−>$${\rm{SO}}_4^{2 - } > $$ was the major anion pollutant for waste HEPA filters soaked in water solutions, and groundwater and pure water were more susceptible to be contaminated by anions released from waste HEPA filters. (2) the (Qmax¯)$$(\overline {{Q_{max}}} )$$ of three metals released from waste HEPA filters were in a order as Zn> Pb> As, in which, groundwater showed the highest (Qmax¯)$$(\overline {{Q_{max}}} )$$ of Zn (2.21 μg/g), followed by rainwater and pure water. This meant that Zn is the major heavy metal pollutant released from waste HEPA filters into the water environment, and groundwater was more susceptible to be contaminated by metals released from waste HEPA filters. (3) None Zn, Pb, and As were released in these three different solutions for the unused filter, indicating that it has almost no contamination threat to the water environment. This study is expected to further improve the understanding of water environmental pollution prevention and management, and provide a theoretical basis for China’s ecological environment protection.