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The distinctive pharmacological characteristics of Chinese medicinal herbs are rendering them increasingly popular as functional foods. However, fresh herbs are prone to mold and decay. Currently, drying processing is primarily employed to extend the storage time and effectively preserve the bioactive constituents of these herbs. After examining of the recent literatures on drying Chinese medicinal herbs, this paper provides a comprehensive overview of various drying technologies, including shade drying, hot air drying, solar drying, heat pump drying, microwave drying, far-infrared drying, vacuum drying, vacuum freeze drying, radio frequency drying, high voltage electric field drying and some combined techniques. While, an extensive illustration for each drying method principles, advantages/disadvantages, potential improvements and deep investigation of its energetic performance and the influence on the main active components in the drying process, such as polysaccharides, polyphenols, flavonoids, saponins, volatile oils, were summarized. The results showed that the combined drying technology not only had high efficiency and low energy consumption, but also preserved the bioactive medicinal components and sensory quality at the best. This paper provides a theoretical foundation and vast technical support for enhancing the value of Chinese medicinal herbs utilization and drying industry. [ABSTRACT FROM AUTHOR]

The productivity and efficiency of harvesting forage crops depend on the sharpness and quality of the mower blades. Therefore, studying blade wear during Alfalfa harvesting is crucial to sharpening and maintaining blades. This research aims to create mathematical models to predict the wear of mower blades and assess the wear rate of mower blades, fuel consumption, and CO2 emissions during the harvesting operation. Blade wear was measured by the weight loss method and examined by scanning electron microscopy (SEM) before and after the field experiment. The results showed that the weight of the mower blade decreased from 103.82 to 98.39 g after 37.5 working hours. Over time, fuel consumption and operating costs increased due to the wear of blades. Also, CO2 emissions were 17.7 kg h−1 at the beginning of the experiment and increased to 29.5 kg h−1 after 37.5 working hours. Due to wear in the blades, the increase in fuel consumption, cost, and CO2 emissions reached 67% at the end of the experiment. From the obtained mathematical equations, the sharp part of the blade has worn out after 34 ± 3 working hours.Article Highlights: Drum mower blades wear rate is investigated for alfalfa in Egyptian condition. Microscopic and SEM techniques are clearly showed the morphological changes on the mower blades. Wear rate has a significant influence on fuel consumption and CO2 to the environment. A mathematical model is developed to predict blades lifetime. [ABSTRACT FROM AUTHOR]

Flat plate solar air heaters (SAHs) are widely used in many solar thermal applications, to enhance its capability to harvest solar radiation, the solar selective coating should be used. Consequently, a novel solar selective coating with high solar absorptance(α) and low emittance(ε) is fabricated by embedding carbon nanotubes (CNTs) and cupric oxide nanoparticle (CuO) into the black paint. By using UV–Vis and FTIR spectroscopies, the optical properties of several percentages of the CNTs and CuO nanoparticles are studied. Besides, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) are used to study the chemical composition and surface morphology, respectively. The results showed that 4% CNTs/CuO-black paint is the highest solar selective coating with solar absorptance and thermal emittance reaches 0.964 and 0.124, respectively. Energy and Exergy performances of SAH coated with the new selective coating are investigated under four airflow rates. The obtained results show that energy efficiency enhanced by approximately 24.4%. The difference between outlet and inlet temperatures of the air across SAH raises up to 22% based on averaged values. SAH with new coating shows higher exergy efficiency. • Carbon nanotubes and cupric oxide nanoparticles boosted the solar selectivity of the black paint. • Thermal efficiency of solar air heaters enhanced by using 4% CNTs/CuO-black paint. • Exergy efficiency of SAHs coated with 4% CNTs/CuO-black paint have been improved. • SAHs coated with 4% CNTs/CuO-black paint could be suitable for agricultural drying systems. [ABSTRACT FROM AUTHOR]

Enhancements in heat transfer, and consequently the thermohydraulic performance of solar air heaters (SAHs), are necessary to widen and optimize their use in many applications such as solar drying or heating buildings. In this investigation, two techniques were used. A novel solar selective coating combined with broken arc ribs roughness was employed with a SAH and the evaluation of the energetic and exergetic performance was applied under four airflow working conditions compared to a smooth absorber SAH coated with the same coating. The results revealed that the Nusselt number of roughened SAH with the new coating exhibited a notable improvement compared to a smooth absorber SAH and a roughened SAH without a coating. Furthermore, the thermal efficiency increased with the increase in the air flow rate and the maximum rise was 18.8% compared to a smooth SAH. The highest increase in exergy was 51.6% with minimum values of exergy destruction and improvement potentials. In brief, the roughened SAH with 4% CNTs/CuO-black paint under the airflow rate of 0.0244 m3/s (condition C) exhibited the best energetic and exergetic performance. [ABSTRACT FROM AUTHOR]