Refrigeration principle of general refrigerator The function of the compressor is to compress the steam with lower pressure into steam with higher pressure, so that the volume of steam is reduced and the pressure is increased.
The compressor draws in the lower pressure working fluid vapor from the evaporator, causes the pressure to rise, and then sends it to the condenser, which is condensed into a higher pressure liquid in the condenser, and becomes a pressure after being throttled by the throttle valve. After the low liquid is sent to the evaporator, it absorbs heat in the evaporator and evaporates into a lower pressure steam, which is then sent to the inlet of the evaporator to complete the refrigeration cycle.
1. Principle of vapor compression refrigeration The single-stage vapor compression refrigeration system consists of four basic components: refrigeration compressor, condenser, evaporator and throttle valve.
They are connected in turn by pipes to form a closed system. The refrigerant continuously circulates in the system, changes state, and exchanges heat with the outside world.
After the liquid refrigerant absorbs the heat of the cooled object in the evaporator, it is vaporized into low-temperature and low-pressure steam, sucked by the compressor, compressed into high-pressure high-temperature steam, discharged into the condenser, and sent to the cooling medium (water or air in the condenser). The heat is released, condensed into a high-pressure liquid, throttled by a throttle valve to a low-pressure low-temperature refrigerant, and re-entered into the evaporator to absorb heat and vaporize, thereby achieving the purpose of circulating refrigeration. In this way, the refrigerant completes a refrigeration cycle through four basic processes of evaporation, compression, condensation, and throttling in the system.
In refrigeration systems, evaporators, condensers, compressors, and throttle valves are four essential components in refrigeration systems.
Among them, the evaporator is a device that transports cold.
The refrigerant refrigerates by absorbing heat of the object to be cooled therein.
The compressor is the heart and acts to draw, compress, and deliver refrigerant vapor.
The condenser is a device that emits heat, and the heat absorbed in the evaporator is transferred to the cooling medium along with the heat converted by the compressor work.
The throttle valve throttles the refrigerant, simultaneously controls and regulates the amount of refrigerant liquid flowing into the evaporator, and divides the system into two parts: the high pressure side and the low pressure side.
In the actual refrigeration system, in addition to the above four components, there are often some auxiliary equipment, such as solenoid valves, distributors, dryers, collectors, fusible plugs, pressure controllers, etc., which are designed to improve operation. Economical, reliability and security are set.
2. Main components of the refrigeration system The air conditioners can be divided into two types: water-cooled and air-cooled.
According to the purpose of use, it can be divided into two types: single cooling type and cooling type heating type.
No matter which type of structure is formed, it is composed of the following main components:
The main components of the refrigeration system are compressor, condenser, evaporator, expansion valve (or capillary, supercooling control valve), four-way valve, double valve, check valve, solenoid valve, pressure switch, melting plug, output pressure regulating valve , pressure controller, liquid storage tank, heat exchanger, heat collector, filter, dryer, automatic shutter, shut-off valve, liquid injection plug and other components.
The main components of the electrical system are motors (compressors, fans, etc.), operating switches, electromagnetic contactors, interlocking relays, overcurrent relays, thermal overcurrent relays, temperature regulators, humidity regulators, temperature switches (defrost, prevention) Freezing, etc.). Compressor crankcase heater, water shutoff relay, computer board and other components.
The control system consists of several control devices, which are:
Refrigerant controller: expansion valve, capillary tube, etc.
Refrigerant circuit controller: four-way valve, check valve, double valve, solenoid valve.
Refrigerant pressure controller: pressure switch, output pressure regulator, pressure controller.
Motor protector: over current relay, thermal overcurrent relay, temperature relay. temperature regulator:
Temperature level regulator, temperature proportional regulator. Humidity regulator: Humidity level regulator.
Defrost controller: Defrost temperature switch, defrost time relay, various temperature switches.
Cooling water control: water shut-off relay, water volume control valve, water pump, etc.
Alarm control: over temperature alarm, super humidity alarm, under voltage alarm and fire alarm, smoke alarm, etc.
Other controls: indoor fan speed controller, outdoor fan speed controller.
3 Commonly used refrigerants and their properties There are many types of refrigerants. A brief introduction to Freon 12 and 22 is given:
a. Freon 12 (CF2Cl2) code R12 Freon 12 is a colorless, odorless, transparent, almost non-toxic refrigerant.
However, when the content in the air exceeds 80%, it will cause suffocation.
Freon 12 will not burn or explode. When it comes into contact with an open flame or when the temperature reaches 400 °C or higher, it can decompose hydrogen fluoride, hydrogen chloride and phosgene (CoCl2) which are harmful to human body.
R12 is a widely used medium temperature refrigerant suitable for small and medium-sized refrigeration systems, such as refrigerators and freezers.
R12 can dissolve a variety of organic materials, so you can't use ordinary rubber gaskets (rings), usually using neoprene or rubber sheets or seals.
b. Freon 22 (CHF2Cl) code R22 R22 does not burn or explode, its toxicity is slightly larger than R12, although the solubility of water is larger than R12, it may still cause "ice plug" phenomenon in the refrigeration system.
R22 can partially dissolve with the lubricating oil, and its solubility changes with the type and temperature of the lubricating oil. Therefore, the refrigeration system using R22 must have oil returning measures.
The corresponding evaporation temperature of R22 at standard atmospheric pressure is -40.8 °C, the condensation pressure at normal temperature does not exceed 15.68 × 105 Pa, and the refrigeration capacity per unit volume is more than 60% larger than that of R12.
In air conditioning equipment, most choose R22 refrigerant
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