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The study investigates the drying characteristics of carrots under different coupling forms of airflow and high-voltage electric fields (parallel flow, PF, and cross flow, CF) using heat pump-electrohydrodynamics (EHD) combined drying. The results show that, compared to single heat pump drying, the combined drying under PF mode reduces carrot drying time by 13.33 %–31.58 %, increases effective moisture diffusivity (Deff) by 17.80 %–32.32 %, increases specific moisture extraction rate (SMER) by 12.25 %–34.26 %. While the combined drying under CF mode reduces carrot drying time by 12.5 %–18.18 %, increases Deff by 7.27 %–13.14 %, increases SMER by 4.64 %–12.58 %. The improvements in parameters under the CF mode are weaker than those under the PF mode. Additionally, the β-carotene content under PF mode is consistently higher than under CF mode. Based on the experimental results, the Modified Page model was improved, yielding an updated model MR = aexp(-(kt)^n), with an R2 value of up to 0.9999–1, which provides theoretical guidance for optimizing the heat pump-EHD combined drying process.

The compressor speed, expansion valve opening and drying temperature are critical to the thermal performance improvement and control logic optimization of the closed heat pump drying (CHPD) system. This paper investigates the effects of the three parameters on the thermal performance of the CHPD system by the single factor experiment method. According to the experimental findings, as the compressor speed of the system increased, the heating capacity grew by 11.4%, but the coefficient of performance (COP) declined by 41.3%. As the expansion valve opening of the system increased, the heating capacity and COP grew by 73.5% and 82.9%, respectively. As the drying temperature of the system rose, the heating capacity grew by 3.1%, but the COP dropped by 25.3%. It can be concluded that reducing the compressor speed and drying temperature, and increasing the expansion valve opening could effectively enhance the thermal performance of the CHPD system.

The drying characteristics of yam slices using heat pump-electrohydrodynamics (EHD) combined drying were studied under the conditions of the drying temperatures of 50–60 °C, the voltages of 80–100 kV and the wind speeds of 1∼3 m/s. The results show that compared with the single heat pump drying, the combined drying can effectively reduce the drying temperature by approximately 5 °C. This is relatively friendly to heat sensitive materials and can also improve the running performance of the heat pump system. Furthermore, the sensory score is increased by approximately 21.4% and the specific energy consumption of combined drying at the voltage of 100 kV is reduced by approximately 27.8%. Under the later stage of the combined drying, the wind speed can be reduced to save energy consumption. Through the analysis of model parameters, Page model is more consistent with the variation law of drying experimental data. This paper provides practical guidance for optimizing the process of yam slices using heat pump-EHD combined drying.