Refrigeration is essentially to slow down the movement of molecules in the air, and figuratively speaking, it is to cool the air. The transition from natural sources such as natural ice to artificial refrigeration is the primary stage of refrigeration technology. Nerni 1777. Gerale's experiment of sulfuric acid absorbing water to make ice: 18 10, J.Leslie's sulfuric acid-water absorption ice-making device; 1859, F.Carre made an ammonia absorption refrigerator and applied for a patent in 1860. Monte and Feng? Plate ammonia-water-hydrogen diffusion absorption refrigerator was patented by 1920.
In the mid-20th century, compact refrigerators driven by electric ideas occupied a dominant position in the field of conventional refrigeration. In recent 30 years, absorption refrigeration and heat pump technology have entered a stage of vigorous development. In the 1990s, the research and analysis project of adsorption refrigeration, which was included in the European Joule Plan, brought the research of adsorption refrigeration to a new climax. Working principle of refrigeration unit.
The refrigeration system consists of four basic departments, namely, compressor, condenser, throttling component and evaporator. These four parts are connected into a closed system by copper pipes in a certain order, and a certain amount of refrigerant is filled in the system. Freon is the commonly used refrigerant for air conditioning, and R22 was generally used in the past. Now, some air conditioners have used R407, a new environmentally friendly refrigerant, instead of Freon. The above is the vapor compression refrigeration system. ? Taking refrigeration as an example, the compressor sucks in low-temperature and low-pressure Freon gas from the evaporator, compresses it into high-temperature and high-pressure Freon gas, and then throttles it into low-temperature and low-pressure Freon vapor-liquid two-phase objects through a heat shrinkage valve (capillary). Then the low-temperature and low-pressure Freon liquid absorbs heat from indoor air in the evaporator and becomes low-temperature and low-pressure Freon gas, which is sucked by the compressor. After the indoor air passes through the evaporator, it releases heat and the air temperature drops. If the cycle of contraction-condensation-throttling-evaporation is repeated, the refrigerant will take away the heat of indoor air from time to time, thus reducing the indoor temperature. ? When heating, the moving direction of the refrigerant is changed by switching the four-way valve, so that the outdoor heat exchanger becomes an evaporator to absorb the heat of the outdoor air, and the indoor evaporation becomes a condenser to radiate the heat indoors, thus achieving the purpose of heating.
The working principle of absorption refrigeration absorption refrigeration is a kind of refrigeration mode driven by heat energy, and it also uses refrigerant vaporization to absorb heat to realize refrigeration. Therefore, similar to vapor compression refrigeration, the difference is that the compensation method used to transfer heat from low temperature to high temperature is different. Steam compression refrigeration is compensated by mechanical work, while absorption refrigeration is compensated by thermal energy. At the same time, the working schematic diagrams of absorption refrigerator and vapor compression refrigerator are given. The working medium used in absorption refrigerator is a binary mixture (solution) composed of two substances with different boiling points. Low-boiling substances are refrigerants and high-boiling substances are absorbents. The absorption refrigerator has two cycles-refrigerant cycle and solution cycle. The working pair of absorption refrigeration cycle follows the refrigerant, and the working pair with Freon as refrigerant mainly includes chlorodifluoromethane-dimethylformamide (R22-DMF), chlorodifluoromethane-tetraethylene glycol dimethyl ether (R22-E 18 1), chlorodifluoromethane-dibutyl phthalate (R22-DBP) and so on. It is advantageous to use R22-DMF at high generation temperature and low condensation temperature, and R22-E 18 1 is better for low generation temperature and high condensation temperature, such as solar refrigeration system.
Basic structure and working principle of piston compressor;
Piston compressors are widely used in large and medium-sized cold storage at present. Our bureau installed a 6AW 10 single-stage refrigeration compressor and a 8ASJ 10 double-stage refrigeration compressor, both produced by Dalian Refrigerator Factory. Piston compressor is mainly composed of machine body, crankshaft, connecting rod, piston, intake and exhaust valve group, safety valve, energy regulating mechanism, lubrication system and direct-connected motor. The overall structure of 6AW 10 compressor is as follows: "6" means that the compressor has 6 cylinders (3 exhaust cylinders and 3 suction cylinders), "A" means that the refrigerant is refrigerant, "W" means that the cylinders are arranged like the letter W, and "10" means that the cylinder diameter is 10 cm. The piston stroke of this machine is 100 mm, the rotating speed is 960 rpm, the standard refrigerating capacity is 2,900,000 kj/h, and the motor power is 37 kw/h. This machine can reduce the storage temperature to-300℃. The overall structure of 8 asj10 compressor is: "8" means that the compressor has eight cylinders, and "a" means that the refrigerant is. Among them, 6 cylinders (3 low-pressure suction cylinders and 3 low-pressure exhaust cylinders) are low-pressure stage, and 2 cylinders (1 high-pressure suction cylinder and 1 high-pressure exhaust cylinder) are high-pressure stage. The purpose of this machine is to divide the pressure difference between high and low pressure cylinders, do cascade compression refrigeration, get lower temperature, and reduce the temperature of the warehouse.
The working principle of piston refrigeration compressor is to drive the directly connected crankshaft through the rotation of the motor, and drive the connecting rod, piston and steam valve system to reciprocate up and down in the crankcase cylinder to complete the three processes of steam absorption, compression and discharge, so that the low-pressure refrigerant gas is converted into high-pressure refrigerant gas and discharged into the condenser, forcing refrigerant gas molecules to gather in the container under the action of high pressure to form liquid refrigerant. ? In the refrigeration system, the compressor is the heart of the system, constantly sucking back and outputting refrigerant, which plays a leading and central role. Once the compressor fails and stops working, the whole refrigeration system will be interrupted.
To sum up, the structure of skilled refrigeration equipment and its refrigeration working principle are the basis for doing a good job in refrigeration. We must conscientiously implement the operating rules and strive for perfection. As refrigeration workers, we should first master advanced refrigeration technology, improve professional skills, have a strong sense of professionalism and responsibility, enhance professional ethics, blaze new trails, keep pace with the times, and do a good job in cold storage operation safely, with low consumption and high efficiency.
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