In the process of making tea, heat is always inseparable. Especially in the drying stage, not only does it remove water, but while evaporating water, complex thermochemical changes occur with the participation of water, which further promotes the color of tea leaves. The formation of aroma and taste. Tea is a plant-based moisture-containing porous material. During the drying process, the internal and external heat and mass transfer conditions and the structural characteristics, biological characteristics, and physical and chemical characteristics of the tea itself interact and interact.
Metal conduction is dry, and the heat is mainly conducted by the iron pan, and the heat transfer is relatively fast. Due to continuous frying, the leaves are dynamically heated, and the leaf temperature changes intermittently and is unstable. The leaf temperature is high when it touches the surface of the pot, and when it is thrown away, the leaf temperature is low, and it is locally heated, causing uneven heating, insufficient conversion of chemical components, and insufficient conversion of bitter anthocyanins; furthermore, the heating intensity is uneven Therefore, the dried taste is still strong and bitter, not mellow.
Hot air drying is based on heat conduction by air, and the heat transfer is faster, and the rise in leaf temperature is gentler than that of frying. During the drying process, hot air is the main medium for heat and mass transfer. During the whole drying process, a large amount of dried materials are brought into contact with uniform hot air with suitable temperature, humidity and flow rate as needed to meet the requirements of the drying curve, so that the heat exchange and moisture exchange can be carried out uniformly and harmoniously during the whole drying process. The temperature and humidity of the hot air during the drying process are the two major factors that determine the drying effect.
Infrared drying is heat transfer in the form of radiation. Infrared drying is in the range of 4-100μm, so it is called far-infrared drying. After the tea absorbs infrared rays, it causes internal molecules to vibrate, and the rapid collision and friction between the molecules quickly transform into heat energy, so that the inside and outside of the tea are evenly heated, but the infrared penetration ability is poor.
The principle of microwave drying is that the microwave generator radiates microwaves to the dried tea, and induces the polar molecules such as tea water to rotate synchronously with the frequency of the microwave, causing the tea to generate frictional heat instantaneously, which causes the surface and the inside of the tea to heat up at the same time. A large number of water molecules overflow from the tea leaves and evaporate, achieving the effect of drying the tea leaves.
The heat pump dehumidification drying adopts a combined drying method. In different drying stages of tea, different drying parameters and drying methods can be used to achieve optimal control of the drying process. Intelligently control the drying process of tea. By establishing a set of control models with higher accuracy, good applicability and strong operability, the production efficiency of drying is improved, and the automatic control of the moisture content of tea can greatly improve the quality and quality of tea. Realize energy saving in the drying process.
As the latest heat pump dehumidification drying method, it has been widely used in seafood, vegetable dehydration, melon seeds, peanuts, fruits and vegetables, meat products, casings, tobacco leaves, leather, mushrooms, wolfberry, dried fruits, mosquito incense, tribute incense, cloth, clothing, Cereals, dried noodles, yuba, fertilizers, medicines, Chinese medicinal materials, paper products, wood, seeds and other industries
