The vacuum sublimation-rehydration thawing (VSRT) method, as an innovative approach for thawing, holds promising prospects in the field. To further understand the mechanism of the new vacuum sublimation-rehydration thawing method and optimize its thawing process, fresh pork tenderloin is selected as the research subject, and the effects of rehydration water volume on thawing time, thawing effect, and energy consumption are experimentally investigated and compared with those of the traditional vacuum steam thawing (VST) method. The results showed that the rehydration water volume had an important effect on heat and mass transfer in the rehydration stage, and the thawing performance varied significantly under different rehydration water volumes. When the rehydration water volume entering the unit-volume vacuum chamber was 0.0135 mL/cm³, the thawing efficiency, energy consumption, and thawed product quality simultaneously reached the optimal state. Compared with using the VST method, when using the VSRT method, the thawing time could be shortened by 55% and the thawing loss, total color difference, and system-specific energy consumption could be reduced by 85%, 77%, and 47%, respectively. Moreover, excellent texture parameters could be maintained.

Drying of Lentinus edodes is an effective method to prevent problems such as rotting and browning. During the drying process, the loading density has a significant impact on system performance and drying quality. Based on a newly designed quasi-two-stage enhanced vapor injection heat pump closed drying system, the effects of different loading densities of Lentinus edodes on moisture ratio, drying rate, coefficient of performance of the system (COP_sys), specific moisture extraction rate (SMER), drying capacity per unit energy consumption, and rehydration ratio were experimentally investigated. The results showed that when the drying air supply temperature was 55 ℃ and the circulating air volume was 580 m³/h, the drying rate of Lentinus edodes decreased gradually with the loading density in the drying chamber, from 1.5 kg/m² to 3.0 kg/m². Meanwhile, the average COP_sys, average SMER, drying capacity per unit energy consumption, and rehydration ratio increased first and then decreased. When the loading density was 2.4 kg/m², the average SMER, drying capacity per unit energy consumption, and rehydration ratio reached the maximum values of 0.320 kg/ (kW·h), 0.391 kg/ (kW·h), and 3.6, respectively. When the loading density was 2.4 kg/m², the average COP_sys reached its maximum of 4.22.

A CO₂ heat pump air-conditioning system with single-stage compression secondary throttling and a series gas cooler is proposed to enhance the performance of a CO₂ heat pump system. The heating performances of secondary and conventional throttling systems to achieve identical supply air temperatures under different ambient temperature conditions were compared experimentally, and the cycle characteristics when the cooling performance of the system was optimal at different ambient temperatures were investigated. The results showed that the implementation of a secondary throttling system could significantly reduce the energy consumption of the CO₂ heat pump system, thereby enhancing the system coefficient of performance (COP). Furthermore, the advantages of the secondary throttling system become more pronounced at lower ambient temperatures. Under conditions where the system supply air temperature was 40 ℃ and the ambient temperature was -20 ℃, the power consumption of the secondary throttling system was 256.1 W and 15.4% lower than that of the conventional throttling system, and its COP was 0.67 and 18.3% higher. Under a fresh air environment at -20 ℃, the CO₂ heat pump air conditioning system utilizing the secondary throttling could achieve a heating COP of up to 4.33 when the supply air temperature was 40℃. Under a fresh air environment at 43 ℃, the system could reach a cooling COP of 2.46 when the supply air temperature was 23.6 ℃. Additionally, it was observed that the cooling performance of the system significantly deteriorated when the ambient temperature exceeded 35 ℃.