Bolin H R, Salunkhe D K
Crit Rev Food Sci Nutr. 1982;16(4):327-54. doi: 10.1080/10408398209527339.
Solar driers that are currently being investigated for drying of agricultural products can be divided into two major divisions, depending upon how they transfer the incident solar energy to the product to be dried. These two divisions are direct and indirect drying, with some work also being done on combination drying procedures. In direct solar driers, the product to be dried is usually either inside a tent, greenhouse, or a glass-topped box, where the product to be dried is heated by the direct rays from the sun and the moist air is removed by ambient wind movement. These dryers do accelerate moisture loss rate and the product is usually safe from inclement weather. These dryers usually do not require fans for forced air circulation. With indirect drying, the opposite is true, where most require powered fans for forced air circulation. With this type of dryer, both flatplate and inflated tube solar heat absorbers are used, with each offering certain advantages. Also, combination dryers have been built that utilize both direct and indirect principles. Product evaluation of solar dried foods indicate that in most cases the physical properties, flavor, and vitamin A and C retention were as good as, or better than, conventional dried foods. The economics of the solar systems indicate that most drying procedures are economically feasible for use in small-scale operations only, with the exception of grain drying.
目前正在研究用于农产品干燥的太阳能干燥机可分为两大类，这取决于它们如何将入射太阳能传递给待干燥的产品。这两类是直接干燥和间接干燥，同时也在进行一些组合干燥程序的研究。在直接太阳能干燥机中，待干燥的产品通常位于帐篷、温室或玻璃顶盖的箱子内，待干燥的产品由太阳的直射光线加热，潮湿空气通过周围的风流动排出。这些干燥机确实能加快水分流失速度，而且产品通常能免受恶劣天气影响。这些干燥机通常不需要风扇进行强制空气循环。而间接干燥则相反，大多数间接干燥机需要动力风扇进行强制空气循环。对于这种类型的干燥机，平板式和充气管式太阳能吸热器都有使用，每种都有一定的优点。此外，还制造了利用直接和间接原理的组合干燥机。对太阳能干燥食品的产品评估表明，在大多数情况下，其物理特性、风味以及维生素A和C的保留情况与传统干燥食品一样好，甚至更好。太阳能系统的经济性表明，除了谷物干燥外，大多数干燥程序仅在小规模操作中在经济上可行。
