Related Info
What is the energy efficiency ratio of air conditioning Analysis of common failure causes of totally enclosed refrigeration compressor Don't be afraid if the refrigeration system is clogged. Here are retrieval and cleaning methods Frequently asked questions about refrigeration compressors, do you know these How important is the installation environment of the refrigeration unit It is enough to do these 4 points!What cooling methods do you know Come chat!
1. Steam compression refrigeration
Principle: In the vapor compression refrigeration cycle system, the compressor sucks low-temperature and low-pressure refrigerant vapor from the evaporator, adiabatically compresses the compressor into high-temperature and high-pressure superheated steam, and then presses it into the condenser to cool at a constant pressure. It releases heat to the cooling medium, and then cools to supercooled liquid refrigerant. The liquid refrigerant is adiabatically throttled by an expansion valve (or capillary tube) to become a low-pressure liquid refrigerant, which evaporates and absorbs the heat in the air-conditioning circulating water (air) in the evaporator. In order to cool the circulating water (air) of the air conditioner to achieve the purpose of refrigeration, the low-pressure refrigerant flowing out is sucked into the compressor, and the cycle works in this way.
Steam compression refrigeration
Compressor function:
Compresses the refrigerant vapor from a low-pressure state to a high-pressure state, creating a condition for the refrigerant to liquefy in the condenser at room temperature. Known as the "heart" of the entire device.
Condenser function:
The refrigerant discharged from the compressor is cooled by superheated steam and condensed into a refrigerant liquid, and the heat of the refrigerant in the condenser is discharged to the cooling medium.
Classification: water-cooled condenser, air-cooled condenser, evaporative condenser.
Air-cooled condenser:
Easy to use and install, no need for cooling water and heat to be brought into the atmosphere by extension. However, the heat transfer coefficient is also low, and the weight is relatively large compared to other types. The accumulation of dust on the surface of the fins reduces the heat dissipation capacity and must be cleaned in time.
Evaporator function:
The heat exchange equipment that relies on the evaporation of the refrigerant liquid to absorb the heat of the cooling medium. Its task in the refrigeration system is to output the external cooling capacity.
Classification: full liquid (immersion) evaporator, dry evaporator. Dry evaporator: immersed coil, shell and tube, plate, spray, etc.
Throttle device function:
Cooling and depressurization: After the high-pressure and normal-temperature refrigerant flows through the expansion valve, it becomes a low-pressure and low-temperature refrigerant liquid.
Control refrigerant flow: The expansion valve controls the opening of the valve by sensing the change of refrigerant superheat at the outlet of the evaporator through the temperature sensing package, and adjusts the refrigerant flow into the evaporator so that its flow rate matches the heat load of the evaporator.
Control of superheat: The expansion valve has the function of controlling the superheat of the refrigerant at the outlet of the evaporator, that is, to maintain the full use of the heat transfer area of the evaporator, and to prevent the occurrence of compressor flushing accidents.
Classification: manual throttle valve, thermal expansion valve, capillary tube, electronic expansion valve, float plate, fixed orifice plate, variable orifice plate.
Second, steam absorption refrigeration
Uses refrigerant-absorbent as working fluid, which is called absorption working fluid pair.
Common working fluids: lithium bromide-water (refrigerant is water), ammonia-water (refrigerant is ammonia) -low boiling point working fluid is refrigerant.
Device: Absorption refrigeration device is composed of generator, condenser, evaporator, absorber, circulation pump, throttle valve and other components. The working medium includes refrigerant for preparing cooling capacity and absorbent for absorbing and desorbing refrigerant. Those form the working medium.
Advantages:
A year-round air-conditioned area that needs cold air supply in summer and heating in winter is most suitable for absorption systems.
Quiet operation, can reduce wear to a minimum (except for liquid pump operation), fewer failures and simple maintenance. Does not depend on electricity. Capacity control is easy, only the heat source of the generator needs to be controlled. The system has high safety and no explosion. The system's full load and light load have the same effect. When the load changes, you only need to adjust the generator heat source and water circulation. When the evaporation temperature and pressure decrease, the absorption capacity only decreases to a limited extent, and the operation is stable.
Disadvantages:
When water is used as a refrigerant, a low temperature cannot be obtained (water freezing point is 0 ° C). Improper operation, lithium bromide easily crystallize.
Third, steam jet refrigeration
Principle: High-pressure steam (called working steam) supplied by the boiler enters the main ejector and adiabatically expands in the Laval nozzle. This high-speed steam flow is used to continuously extract steam from the evaporator and keep High vacuum means lower evaporation pressure. The cold water from the refrigeration device enters the evaporator after throttling and decompression, and part of it evaporates and absorbs the heat of the rest of the water to lower its temperature. The cooled water after cooling is output by the pump, and is used repeatedly after supplying the cooling capacity.
4. Adsorption refrigeration
Principle: A certain solid adsorbent has an adsorption effect on a certain refrigerant gas, and the adsorption capacity varies with the temperature of the adsorbent. By periodically cooling and heating the adsorbent, it is alternately adsorbed and desorbed. During desorption, the refrigerant gas is released and condensed into a liquid; during adsorption, the refrigerant liquid evaporates and produces a cooling effect.
Classified by adsorption mechanism: physical adsorption refrigeration, chemical adsorption refrigeration.
Principle: The basic structure of adsorption refrigeration consists of five modules: solar collector, condenser, liquid reservoir, evaporator and valve. The operation mechanism of the adsorption refrigeration system is: during the day, the temperature of the collector increases with the increase of air temperature, the pressure in the refrigerant evaporation collector increases, and the gas enters the condenser and condenses to make a liquid; When the temperature decreases, the adsorbent will absorb the refrigerant vapor, and the pressure in the evaporator will decrease, so more liquid will be vaporized, and the heat will be absorbed during evaporation to cool down.
V. Thermoelectric cooling
Thermoelectric cooling is a cooling method that utilizes the thermoelectric effect (ie, the Peltier effect)-also known as thermoelectric cooling and semiconductor cooling.
Principle: Thermoelectric cooling is a direct conversion of voltage generated by a temperature difference, which means that when electrons in a heated object move from a high temperature zone to a low temperature zone with a temperature gradient, a current phenomenon occurs, and vice versa, when passing direct current, Materials with thermoelectric energy conversion characteristics can produce a cooling function, called thermoelectric refrigeration.
VI. Magnetic refrigeration, acoustic refrigeration
Magnetic refrigeration: Magnetic refrigeration based on the "magnetocaloric effect" (MCE) is a promising alternative to traditional steam cycle refrigeration technology. In materials with this effect, the arrangement and randomization of the magnetic momentum when applying and removing an external magnetic field cause changes in temperature in the material, which can be transmitted to the ambient air.
Acoustic refrigeration: Based on the so-called thermoacoustic effect, the mechanism of thermoacoustic effect can be simply described as adding heat when the sound waves are dense, and exhausting the heat when the sound waves are sparse, the sound waves are strengthened; otherwise, the heat is discharged when the sound waves are dense, and inhaled when the sound waves are thin Heat, the sound waves are weakened. Of course, the actual thermoacoustic theory is much more complicated than this.
7. Other refrigeration related knowledge
Refrigerant classification:
Inorganic compounds: water, ammonia, carbon dioxide;
Halogenated hydrocarbon: Freon;
Hydrocarbons: methane, ethane, propane;
Mixed refrigerant: boiling and non-azeotropic;
Other hydrocarbons: ethylene, propylene.
Cooling capacity: refers to the total amount of heat removed from the enclosed space, room or area per unit time when the refrigeration equipment is performing cooling operation.
Ozone attenuation index ODP: indicates the degree of destruction of the substance to the atmospheric ozone layer. The smaller the better, ODP = 0 is harmless to the atmospheric ozone layer.
Greenhouse effect index GWP: indicates the degree of influence of substances on the greenhouse effect. The smaller the better, GWP = 0 will not cause the atmosphere to warm.
Energy efficiency grade: It means that the energy efficiency grade is a classification method that shows the difference in energy efficiency of household appliances. According to the relevant regulations of national standards, the energy efficiency label in China used to divide the energy efficiency into five grades. Now divided into three levels.
Watt: Symbol: W, the unit of power in the International System of Units. Watt is defined as 1 joule / second (1J / s), which is the rate of energy converted (measured in joules) used or dissipated per second.
BTU: 1Btu is the heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit. 1BTU is approximately equal to 251.99958 calories / 1.055 kJ.
Cold ton: 1 ton of 0 ℃ saturated water in 24 hours to freeze to 0 ℃ ice required cooling capacity. 1 US cold tons = 3024 kcal / hour = 3.517 kW. 1 Japanese cold tons = 3320 kcal / hour = 3.861 kW.
Dry bulb temperature: It is the temperature measured by the thermometer in ordinary air, that is, the temperature we often say in the general weather forecast.
Wet bulb temperature: refers to the air temperature when the water vapor in the air reaches saturation under the same enthalpy value in the air state. On the air enthalpy chart, the air state point is reduced from the air state point along the isenthalpic line to the 100% relative humidity line, corresponding to the point Dry bulb temperature.
Air hazard: It may be that the refrigerator oil is oxidized and becomes black, which generates oil pollution, and reacts with the refrigerant to precipitate water and acid, corroding the refrigeration system. Air will also increase the temperature and pressure of the condensing pressure, reduce the cooling capacity, and reduce the cooling efficiency
Harm of water: At work, due to the lower temperature of the throttling device, the water condenses and ice blockage occurs, making the system unable to work. Moisture will also react with the refrigerant, causing adverse effects.
Hazard of impurities: impurities including dust, metals and metal oxides, etc. These impurities can cause dirty blockages and mechanical circuit failures. At the same time oxide can promote the decomposition of Freon.
In summary, by increasing the vacuum of the refrigeration system, the above part will be reduced to a certain degree, so that the refrigeration system works according to the design requirements
Subscribe to relevant news content?
Subscription
Unsubscription
Recent related posts
Customers frequently viewed
IWAYA DENKI Water Pump 25CJT0752
US$2307.69
Panasonic Servo Motor MHMF022L1V2M
US$653.85
Honeywell Solenoid Valve VE4025B1045
US$334.62
ROTEN Mechanical Seal 8E5K-22-X
US$384.62
DEKEMA Vane Pump 150T-61-L-R
US$596.15
CRYDOM Relay HA4890G
US$144.97
ULVAC Vacuum Pump PMB100DT-MD2A1F1XXXX
Contact Us
Haier Air Conditioner KFR-50LW-81@U1-Hc
US$2422.69
GOLDENBRIDGE Welding Wire JQ.MG50-Ti
US$10.38
