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Refrigeration electrical encyclopedia knowledge introduction

Update:29-06-2021
Summary:

Refrigeration electrical encyclopedia knowledge introdu […]

Refrigeration electrical encyclopedia knowledge introduction

A class of household appliances used for freezing and refrigerating items and making cold beverages. Mainly include refrigerators, freezers, cold drink machines, ice cream machines, ice machines, etc.

Development history

In 1834, American J. Perkins used volatile ether liquid for vaporization and refrigeration in a closed system and obtained a patent. This device consists of a manual compressor, a water-cooled condenser and an evaporator installed in a liquid cooler. In the same year, L.W. Wright successfully developed an ice-making machine using compressed air expansion in the UK. In 1844, the American doctor J. Gorie first used the air compression refrigerator he developed for commercial refrigeration and air conditioning.

In 1855, Frenchman F. Carré successfully designed sulfur dioxide absorption and ammonia absorption refrigerators. Around 1859, he designed an ice machine that used ammonia as a refrigerant and water as an absorbent. In 1890, vapor injection and mechanical vapor compression refrigeration devices were put into practical use, and absorption refrigeration devices began to spread.

In the early stage of mechanical refrigeration, the large equipment, high price and low efficiency restricted the use of mechanical refrigeration. By 1920, a few households had refrigerators. Beginning in 1930, refrigeration devices tended to be miniaturized, with higher benefits, and the use of new and safe refrigerants, and the development of fractional horsepower (less than 1 horsepower) motors, which enabled the rapid development of the refrigeration industry.

Principle of refrigeration

According to the refrigeration method, there are mainly compression refrigeration, absorption refrigeration and thermoelectric refrigeration (also known as semiconductor refrigeration). Compression refrigeration uses a compressor to compress the gaseous refrigerant in a closed system. The refrigerant undergoes condensation, drying and filtration, throttling expansion, and evaporation in the circulating flow to achieve the refrigeration function. It can use electric motors or electromagnetic oscillations as power. Absorption refrigeration uses the continuous diffusion and absorption of ammonia, hydrogen, and water charged into a closed system to achieve the refrigeration function. It can use electricity, gas, kerosene, liquefied petroleum gas, natural gas, solar energy and other energy sources as power. Thermoelectric refrigeration uses the Peltier effect of semiconductor materials to achieve a refrigeration function.

Cold drink machine A refrigeration appliance for making cold drinks. Refrigeration using motor compression refrigeration principle. The compressor performs work on the refrigerant freon charged into the system. The freon undergoes a phase change during the flow process. The liquid refrigerant evaporates in the evaporator and absorbs the heat of the beverage; the gaseous refrigerant in the condenser is replaced by the outside air (or water). ) Cool and liquefy, releasing heat. This keeps circulating to cool down the beverage. The cold drink machine has immersion type, spray type and so on. Jet type is the representative model of cold drink machine (Figure 1).

Refrigeration appliances, which are composed of storage tanks, jet pump components, refrigeration systems, temperature controllers, etc. The jet pump sucks in the beverage from the bottom of the storage tank, sends it to the upper part of the storage tank along the spray pipe, and sprays it on the top surface of the cylindrical heat exchanger to cool the beverage. When the beverage temperature drops to the set temperature, the temperature controller disconnects the circuit and the cold drink machine stops working. The capacity of the jet cooler is generally 15-50l, the beverage cooling temperature is 1-7℃, and the compressor output power is 100-250W.

Ice cream maker A refrigeration appliance for making ice cream. There are divided into with refrigeration system and without refrigeration system. The former is mostly used in the cold drink service industry, and the latter is mostly used in the family. In both cases, ice cream is made in the process of cooling and stirring.

There are two types of ice cream makers without refrigeration system: ① Ice cream makers cooled with crushed ice. There are two metal cylinders inside and outside. The outer wall of the outer cylinder is covered with a thermal insulation layer. The pre-prepared ice cream liquid is placed in the inner cylinder. The annular space between the inner and outer cylinders is manually filled with salt, water and enough crushed materials. For ice cubes, since table salt lowers the freezing point of the solution, the temperature of the brine solution is kept below 0°C, so that there is a good heat exchange between it and the inner cylinder wall. When making ice cream, a micro-motor is used to drive the agitator through a deceleration mechanism, and the ice cream liquid is stirred at a low speed in the inner cylinder. As the heat of the ice cream liquid is continuously absorbed by the cold salt water, the temperature gradually decreases, and finally a soft ice cream composed of ice crystals, air and liquid is formed. ② An ice cream machine cooled in the freezer compartment of the refrigerator. There is only one metal cylinder containing ice cream liquid. The pre-prepared ice cream liquid is placed in the cylinder, and the stirrer is installed. The micro-motor drives the stirrer to stir the ice cream liquid at low speed through the deceleration mechanism, and its heat is continuously absorbed by the freezer compartment evaporator. , The temperature gradually decreases, and when the ice cream liquid freezes to a certain degree of hardness, the spring mechanism installed inside acts to stop the rotation of the micro-motor to make ice cream.

Ice maker A refrigeration appliance for making edible ice cubes. According to the forming method of ice cubes, it can be divided into ice mold forming ice maker (Figure 2), screw feed ice maker and plate ice maker. The ice making capacity of an ice maker is expressed in kilograms of ice making in 24 hours. Generally, a small machine with an ice-making capacity of 40kg or less, a medium-sized machine with an ice-making capacity of 40 to 110kg, and a large machine with an ice-making capacity of 110kg or more. The ice cube weighs about 25g. ①Ice mold into form ice maker. When making ice, the water pump sucks water from the water tank, and sprays the water from bottom to top into the inverted ice mold cavity (evaporator) through the evenly distributed water spray nozzles, so that part of the water is frozen on the ice mold, and the other part of the water is frozen on the ice mold. Reflux into the water. After continuous water spraying and freezing, the thickness of the ice layer in the ice mold gradually increases. When the ice mold is full of ice, the time relay will act to disconnect the compressor and water pump power supply, and the demolding electric heater will be turned on to heat the ice mold to melt the surface of the ice cube frozen in the ice mold and under the action of gravity , Automatically fall into the ice storage tank. Then, the time relay turns off the power supply of the demoulding electric heater according to the preset time, and turns on the power supply of the compressor and the water pump, and starts ice making again. The ice-molded ice machine has small volume and high ice-making efficiency, but the structure of the evaporator and the water supply system are more complicated. ②Screw-feeding ice maker. The evaporator of this ice maker is a spiral cylinder. When the motor drives the deceleration mechanism to slowly rotate the spiral, the purified water provided by the water supply system is also spiraled upward at the same time, and is gradually cooled and frozen during the pushing process. At the top end of the spiral cylinder, the water is frozen into hard ice, and the hard ice is cut into ice cubes through the cutting mechanism. The screw feed type ice maker has a complicated structure, but the ice making efficiency is very high. ③Plate ice type ice maker. The principle of ice making is the same as that of the ice mold forming ice maker. It uses a flat plate evaporator to make plate ice. When the thickness of the ice plate reaches the specified value, the surface of the ice plate is melted by the high temperature and high pressure refrigerant gas discharged from the compressor, and then it slides down into the heating wire cutting grid and is cut into ice cubes. The water-supply ice making system of the plate ice-type ice maker is relatively simple, easy to use and maintain, and the ice cubes made are of high transparency.

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