## 3 Results and Discussion
### Energy Parameters in Different Strategies
The highest value of specific energy consumption (SEC) (51.03 kWh/kg) was in the HA55-IR250, and the lowest (15.42 kWh/kg) value of specific energy consumption was obtained in the IR750 method. The lowest SEC value in the combined methods (HA40-IRS00) was about 42.1% lower than the lowest SEC value in the hot air method (HA70). In a study conducted on sweet potatoes with a convective dryer, the amount of (SEC) was in the range of 15.64-86.37 (kWh/kg) [25]. In another study conducted on apples in an infrared dryer, the amount of (SEC) was in the range of 71.78-110.35 (kWh/kg) [20]. Figure 6 shows the amount of energy efficiency and moisture extraction rate (SMER) in different treatments. The results showed that the maximum energy efficiency was in the IR750 method (10.25%), and the minimum energy efficiency (3.61%) was in the HA55-IR250 method. The highest value of energy efficiency in the combined methods (HA40+IRS00) was about 72.8% higher than the highest value of energy efficiency in the hot air method (HA70). According to the results obtained from the first strategy, the highest efficiency was when using infrared waves with higher radiation intensity. In the second strategy, the energy efficiency decreased compared to that of the other drying strategies. The reason is that the air heating system is used from the beginning to the end of the drying process, which will increase energy consumption. The comparison of energy efficiency between the third and fourth strategies showed that the third strategy (HA+IR) had a more favorable situation in terms of energy efficiency. The reason is that, after the first 60 min, in the second stage until the final moisture, only infrared waves will be used, which have better energy efficiency. Moreover, the results showed that, in the fourth strategy (IR+HA), increasing the radiation intensity in the first stage improves energy efficiency. The reason is that infrared waves with high radiation intensity quickly bring the drying process to its falling phase, and there is considerable moisture evaporation from the apple slices in the  
Figure 5: Specific energy consumption in different strategies. first 60 min. The third strategy (HA+IR) had the highest energy efficiency, with an average of 7.10%, and their average efficiencies were 1.5, 71.22, and 40.72% higher than those of the first, second, and fourth strategies, respectively. In research conducted on the convective drying of apple slices, the energy efficiency was in the range of 2.87-9.11% [30]. According to the results of this research, the specific moisture extraction rate (SMER) was in the range of 0.019-0.054 (kg/kWh), and the highest and lowest values of this parameter were in the IR750 and HA55-IR250 methods, respectively. The results showed that (SMER) was changed according to energy efficiency. In this way, after the infrared drying methods, which had the highest SMER value in the first strategy, the third strategy (HA+IR) had the highest SMER value in combined drying. The average values of SMER in the first, second, third, and fourth strategies were 0.037, 0.022, 0.0385, and 0.027 (kg/kWh), respectively. This parameter in research for convective drying of kiwi was in the range of 0.049-0.15 kg/kWh [32]. The drying efficiency is a main parameter in the construction of any dryer. The results of this research showed that using infrared waves along with hot air by the selection of the appropriate strategy leads to improvement in drying efficiency. The results of this research also showed that the drying efficiency increased with increasing temperature and radiation intensity in most cases, which was due to the reduction in the duration of the drying process. However, sometimes, it had the opposite effect on the drying efficiency due to the hard layer created on the surface (especially in two-step methods). Figure 7 includes the diagram of drying efficiency in the different strategies.