Drying equipment, industrial production and processing of agricultural and sideline products indispensable processing procedures. With the improvement of people’s quality of life, awareness of the protection of the environment has become stronger and more and more non-renewable energy resources (such as natural gas, coal, and petroleum) have become increasingly depleted. The use of high-energy-consumption, high-contamination drying equipment, such as the original fuel and coal, has been severely restricted or even prohibited. Looking for a kind of dry equipment that can replace the old style, and safety, environmental protection, energy-saving drying equipment, it becomes more and more urgent. Heat pump drying equipment came into being in this environment. The history of heat pump drying technology Since the 1970s, the United States, Japan, France, Germany and other countries have conducted research on heat pump drying technology, and the International Energy Center (IEA) has concentrated a large number of research results on heat pump drying technology. China also introduced this technology in the 1980s. The earliest and most widely used is the drying of wood. Since the heat pump drying temperature is close to natural drying, it has gradually been applied to the drying of food and agricultural and sideline products in recent years. In the meantime, good economic benefits have been achieved and the added value of the products has been greatly improved. In particular, the implementation of energy conservation and environmental protection policies by the Chinese government has greatly promoted the development of heat pump drying technology. The materials treated with heat pump drying equipment also expanded from early wood drying to food processing, tea drying, tobacco drying, vegetable dehydration, fish drying, ceramic baking, sterilization and drying of pharmaceuticals and biological products, sludge treatment, Chemical raw materials and fertilizer drying and many other areas. The principle of heat pump dryer Heat pump dryer is the use of inverse Carnot principle, absorb the heat of the air and transfer it to the room, to achieve the temperature of the drying room, with the appropriate equipment to achieve the drying of materials. Heat pump dryer consists of compressor - heat exchanger (inside machine) - throttle - heat sink (external machine) - compressor and other devices constitute a circulatory system. The refrigerant circulates in the system under the action of the compressor. It completes the gaseous pressure raising process (temperature up to 100°C) in the compressor. It enters the internal machine and releases high-temperature heat to heat the air in the drying room. At the same time, it is cooled and turned into a liquid state when it runs to the outside. After that, the liquid rapidly absorbs heat and evaporates again into a gaseous state. At the same time, the temperature drops to -20°C to -30°C, and the air around the heat sink will continuously transfer heat to the refrigerant. The constant circulation of the refrigerant causes the heat in the air to be transported to the air temperature in the heating room in the drying room.
High Precision Machining
High Precision Machining is defined as a process of changing the dimensions or the performance of workpiece with machining facilities.
According to the temperature of the workpiece while in machining, high precision machining can be divided into cold working and hot working. Usually, machining under indoor temperature, and won't change cause chemical change or phisical phase change is named cold working. On the other hand, if under temperature, higher or lower than room temperature, which will lead to chemical changes or phase changes, it will be called as hot working.
For high precision machining, the machining tolerance can be up to 0.0001-0.001mm, the surface finish Ra can be 0.02-0.1um.
Machining precision is to describe the actual geometrical parameter of the part after machining, such as the size, the form, the position, comparing with the theoretical geometry parameter. The difference from these two parameters is the machining tolerance. The number of the difference show the machining accuracy, the bigger, the lower of the machining precision, the smaller, the higher machining precision.
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