General principles of refrigeration
Role of the general principle of the refrigerator refrigeration compressor is compressed to a higher pressure steam low pressure steam, the volume of steam is reduced, pressure.
The suction pressure of the compressor from the evaporator, the lower the working fluid out of the vapor into the condenser so as to increase the pressure in the high pressure condenser is condensed into liquid by throttling the throttle valve, the pressure becomes representing low liquid into the evaporator, absorbing heat in the evaporator is evaporated into low pressure steam, and then fed to the inlet of the evaporator, thereby completing the refrigeration cycle.
1, vapor compression refrigeration principle
Single-stage vapor compression refrigeration system, the refrigerant compressor, condenser, evaporator and throttle four basic components. Sequentially connecting pipe between them, form a closed system, the refrigerant circulating system constant, a change of state, heat exchange with the outside world.
After the liquid refrigerant absorbs heat of the object to be cooled in the evaporator, the low-temperature low-pressure vaporized into steam, is sucked into the compressor, compressed into a high-temperature high-pressure steam into the condenser, the condenser in the cooling medium (water or air ) heat, high pressure liquid condensed by the throttle valve is throttled to low pressure and temperature refrigerant absorbs heat of vaporization to the evaporator again, the purpose of cooling is reached. Thus, the refrigerant in the system via evaporation, compression, condensation, a throttling process is complete the four basic refrigeration cycle.
In refrigeration systems, evaporator, condenser, compressor and throttle refrigeration systems essential to four pieces, which were cold evaporator device is conveyed. Wherein the refrigerant absorbs heat of the object to be cooled to achieve cooling. Compressor is the heart plays suction, compression, transport refrigerant vapor effect. The condenser is a heat releasing device, the heat absorbed by the evaporator of the compressor work along with the conversion of heat transfer to the cooling medium taken together. Throttle throttling the refrigerant from the antihypertensive effect, while controlling and regulating the number of refrigerant flowing into the evaporator liquid, and the system is divided into the high side and low side of two parts. The actual refrigeration systems, in addition to the above four pieces outside, often have some auxiliary equipment, such as solenoid valves, distributor, dryers, collectors, fusible plug, pressure controllers and other components, which are run in order to improve economy, the reliability and security settings.
2, the main components constituting the cooling system
According to the air conditioner condensation forms can be divided into: two water-cooled and air-cooled, depending on the purpose can be divided into single-cooled two kinds of heating and cooling, regardless of what kind of type of structure, the following are the main components combination.
The main member has a refrigeration system compressor, condenser, evaporator, an expansion valve (or capillary, a subcooling control valve), the four-way valve, double valve, check valves, solenoid valves, pressure switches, fusible plug, the output pressure regulating valve , pressure controller, liquid storage tanks, heat exchangers, collectors, filters, dryers, automatic opening and closing, closing valves, liquid injection plugs and other components.
Electrical system main components are motors (compressors, fans, etc. available), operating switches, magnetic contactors, relays chain, over current relay, thermal over-current relay, temperature controller, humidity controller, temperature switch (defrost, to prevent by freezing, etc.). Compressor crankcase heater, water relays, computer boards, and other components.
Control system composed of a plurality of control devices, which are:
The refrigerant controller: expansion valve, capillary.
Refrigerant loop controllers: four-way valve, check valve, double valve, solenoid valve.
Refrigerant pressure controller: pressure opening and closing, the output pressure regulating valve, pressure controller.
Motor protection: over-current relay, thermal over-current relay, temperature relay. Thermostats:
Temperature-position adjustment, temperature proportional regulator. Humidifiers: humidity-position regulator.
Defrost Controller: defrost temperature switch, defrost relay, various temperature switch.
Cooling water control: without water relays, water control valves, pumps, etc..
Alarm control: over-temperature alarm, over wet alarm, voltage alarm and fire alarm, smoke alarm.
Other Controls: indoor fan speed controller, the outdoor fan speed controllers.
3, commonly used refrigerants and their properties
Many types of refrigerants, Freon 12 and 22 will now make a brief introduction:
a. Freon 12 (CF2Cl2) Code R12 Freon 12 is a colorless, odorless, transparent, almost non-toxic refrigerant, but can cause air content of more than 80% of people choking. Freon 12 will not burn and will not explode when exposed to an open flame or temperature reaches 400 ℃, can decompose harmful hydrogen fluoride, hydrogen chloride and phosgene (CoCl2). R12 is the widely used in the temperature of the refrigerant, for small and medium refrigeration systems, such as refrigerators, freezers and so on. R12 can dissolve many organic, so you can not use the normal rubber gasket (circle), commonly used synthetic chloroprene rubber or nitrile rubber sheet or seals.
b. Freon 22 (CHF2Cl) Code R22 R22 does not burn nor explode, and its toxicity is slightly larger than the R12, although the water solubility greater than R12, but still allows the refrigeration system happen "ice jam" phenomenon. R22 each other with the lubricating oil can be partially dissolved in the solubility depending on the kind and the temperature of the lubricating oil is changed, so the use of R22 refrigerant oil return system must measure.
R22 corresponds to the evaporation temperature at standard atmospheric pressure of -40.8 ℃, condensation pressure at room temperature of not more than 15.68 × 105 Pa, the cooling capacity per unit volume and more than 60% larger than R12. In the air-conditioning equipment, most choose R22 refrigerant.