Study on Designing and Manufacturing a Radio-Frequency Generator Used in Drying Technology and Efficiency of a Radio Frequency-Assisted Heat Pump Dryer in Drying of Ganoderma lucidum

Abstract

A radio-frequency (RF) generator applied in drying technology was designed and manufactured for drying Ganoderma lucidum. The drying experiments were conducted by drying method of RF-assisted heat pump in order to inspect the operating parameters of the RF generator and investigate the effects of the input drying parameters on drying rate in the RF-assisted heat pump drying of Ganoderma lucidum. The results have shown that the RF generator achieved the required operating parameters as design such as RF power of 3 kW and operating frequency of 27 MHz. In RF-assisted heat pump drying, increase in RF power and drying air temperature increases the drying rate. Meanwhile, drying air velocity does not significantly affect the drying rate. At RF power of 1.95 kW, the drying time reduces by 9, 17, and 33% in comparison with RF power of 1.3, 0.65, and 0 kW (heat pump drying). At drying air temperature of 50°C, the drying time reduces by 10% and 21% in comparison with drying air temperature of 40 and 45°C. Besides, increasing RF power retains the higher content of polysaccharide in Ganoderma lucidum, and the Ganoderma lucidum samples retain the color better after drying.

Comprehensive assessment of heat pump dryers for drying agricultural products

“…of the radio frequency heat pump dryer. 61 RF-assisted heat pump dryer model lowest specific moisture extraction rates for ambient temperatures of 20°C were 4.4 and 1.4, respectively, and the highest and lowest specific moisture extraction rates for ambient temperatures of −10°C were 2.6 and 1.1, respectively. Furthermore, due to a higher specific moisture extraction rate, the ground source heat pump drying system outperformed the closed air source heat pump drying system.…”

“…Polysaccharide analysis is especially crucial since these macromolecules are responsible for a wide range of physicochemical and sensory phenomena. For drying ganoderma lucidum, radio frequency technology was integrated with a heat pump dryer by Hay et al 61 Results showed that increasing radio frequency power retained more polysaccharide after drying. The polysaccharide content was 7.82, 9.18, 9.31 and 9.47 mg/g, when the radio frequency power was 0, 0.65, 1.3 and 1.95 kW, respectively.…”

“…Recent studies are rare despite the efficiency of this type of heat pump dryer. Radio frequency technology combined with a heat pump dryer for drying Ganoderma lucidum was fabricated by Hay et al 61 Increases in radio frequency power and drying air temperature considerably enhanced the drying rate, according to the findings. Furthermore, the drying rate remained unchanged by the drying air velocity and increasing radio frequency power reduced the drying time.…”

“…Beta-carotenes, vitamin C, phycocyanins, total phenol content, and polysaccharides are among the nutritional parameters frequently assessed in relation to recent studies on heat pump dryers. 34,40,54,61,65,83,84 These bioactive nutrients are highly sensitive to heat that is why they are frequently assessed to assure the quality of dried products. 85 Findings on the nutritional composition of dried biomaterials using heat pump dryers from recently published works are summarized in Table 3.…”

“…Particular attention is therefore paid to the dried products to demonstrate whether the latter has been able to retain all of the properties after drying. Beta‐carotenes, vitamin C, phycocyanins, total phenol content, and polysaccharides are among the nutritional parameters frequently assessed in relation to recent studies on heat pump dryers 34,40,54,61,65,83,84 . These bioactive nutrients are highly sensitive to heat that is why they are frequently assessed to assure the quality of dried products 85 .…”