What are the commonly used refrigeration technologies nowadays?

It’s mainly compressed ammonia and compressed Freon

We use liquid ammonia to make ice, and F22 to freeze brine

Lithium bromide absorption chillers can produce low-temperature water

There is also R123 refrigeration water; the main equipment includes centrifugal refrigerators, screw refrigerators, and piston ammonia compressors.

Introduction to the properties of common refrigerants. There are many types of refrigerants, which are also commonly referred to as cooling agents or refrigerant fluids. They serve as the working medium in refrigeration cycles, and heat is transferred through the phase changes of these refrigerants – they absorb heat when vaporizing in the evaporator and release heat when condensing in the condenser. There are over 80 substances that can be used as refrigerants, with ammonia, Freon compounds, water, and a few hydrocarbons being the most commonly used. In September 1987, a specialized international conference was held in Montreal, Canada, where the Montreal Protocol on Substances that Deplete the Ozone Layer was signed. It came into effect on January 1, 1989, imposing restrictions on the production of CFCs such as R11, R12, R113, R114, R115, R502, and R22. In June 1990, the second meeting of the parties to the protocol was held in London, where restrictions were imposed on the production of all CFCs, carbon tetrachloride (CCl4), and methyl chloroform (C2H3CL3). Developed parties among the signatories were required to completely cease the production of these substances by the year 2000, while developing parties could delay this deadline until 2010. In addition, a control schedule for the transitional substance HCFC after 2020 was proposed. R123 and R134a in HCFCs are alternatives to R12 and R22. Thermodynamic requirements for refrigerants 1: The evaporation temperature (boiling point) ts of the refrigerant should be low, under normal atmospheric pressure. This is a very important performance metric. The lower the ts, the lower temperature can be achieved, and at a certain evaporation temperature to, its evaporation pressure Po can be made higher than atmospheric pressure. To prevent air from entering the refrigeration system, making leaks easier to detect. 2 The condensation pressure Pc of the refrigerant at normal temperature should be as low as possible, in order to avoid excessive strength requirements for equipment such as compressors, condensers, and exhaust pipes that operate under high pressure. Furthermore, excessively high condensing pressure can also lead to leakage of the refrigerant and increase the power consumption. 3 For large piston compressors, it is necessary to have as high a cooling capacity per unit volume of refrigerant, qv, as possible, so as to reduce the size of the compressor and the amount of refrigerant that needs to circulate ； For small or micro compressors, the cooling capacity per unit volume can be lower ； For small centrifugal compressors as well, it is required that the refrigerant QV be low, in order to expand the range of applications for such compressors and to avoid the difficulties associated with manufacturing impellers of small size. 4 The critical temperature of the refrigerant should be higher, and the condensation temperature should be lower. The level of the critical temperature determines whether the refrigerant can be liquefied at normal temperatures or in the range of moderate low temperatures. 5 The condensation temperature is the lower limit of the range in which a refrigerant can be used; the lower the condensation temperature, the wider the applicable range of the refrigerant. Refrigerant, Molecular formula, Molecular weight u, Normal evaporation temperature ts(°C), Freezing point tf(°C), Critical temperature tkp(°C), Critical pressure PKP (absolute pressure), Adiabatic index K. Water (R718): H2O, 18.02, +100, ±0, +374.1, 225.6, 1.33. Ammonia (R717): NH3, 17.03, -33.4, -77.7, +132.4, 115.2, 1.31. R11: CFCl3, 137.39, +23.7, -111, +198, 44.6, 1.17. R12: CF2Cl2, 120.92, -29.8, -155, +111.5, 40.86, 1.15. R13: CF3Cl, 104.47, -81.5, -180, +28.8, 39.4. R22: CHF2Cl, 88.48, -40.8, -180, +96, 50.3, 1.19. R115: C2F5Cl, 154.48, -38, -106, +80, 33. Physicochemical requirements: 1. The viscosity of the refrigerant should be as low as possible in order to reduce flow resistance in pipes and enhance the heat transfer efficiency of heat exchange equipment. 2 The thermal conductivity of the refrigerant should be high to improve the efficiency of heat exchange equipment and reduce the heat transfer area. 3 Intermiscibility of refrigerant and oil: The property of a refrigerant to dissolve in lubricating oil should be analyzed from two aspects. If the refrigerant and lubricating oil can mix with each other freely, the advantage is that the lubricating oil can penetrate together with the refrigerant into all the components of the compressor, thereby creating favorable conditions for lubricating the machine ； Moreover, an oil film is not likely to form on the heat exchange surfaces of the evaporator and condenser, thereby preventing heat transfer. Its disadvantage is that it causes an excessive amount of oil to be carried away by the compressor, and it can raise the evaporation temperature in the evaporator. Refrigerants that are partially or slightly soluble in oil have the advantage of requiring less oil to be carried away by the compressor, resulting in a more stable evaporation temperature in the evaporator. Its drawback is that an oil film that is difficult to remove forms on the heat exchange surfaces of the evaporator and condenser, affecting heat transfer. Effects of different categories of soluble refrigerants: 1. Insoluble: NH3, CO2, R13, R14, R15, SO2 – No effect. 2. Slightly soluble (intermingle in the compressor crankcase and condenser, but decompose in the evaporator): R22, R114, R152, R502 – Reduces the viscosity of lubricating oil when dissolved. 3. Completely soluble: R11, R12, R21, R113, hydrocarbons, CH3CI, R500 – Lowers the viscosity and freezing point of lubricating oil, causes paraffins in the oil to settle, and increases the evaporation temperature. 4. Should have a certain water-absorbing capacity to prevent the formation of “ice plugs” in the refrigeration system, which could disrupt normal operation. 5 It should possess chemical stability: it should not burn or explode, and it should not decompose or deteriorate during use. At the same time, the refrigerant itself, or when mixed with oils, water, etc., should not have a significant corrosive effect on metals, and it should cause little swelling of sealing materials. Safety requirements: Since refrigerants may leak during operation, it is required that the working fluid be harmless to human health, non-toxic, and non-irritating.

Screw compressors, with Freon-based cooling being a common method~

The R22 screw-type refrigeration units we use are primarily used for cooling circulating water!

R22 7# wcq1010

1# boblover Generally, common methods for cooling and achieving low temperatures rely on working fluids, and they all fall under mechanical cooling techniques. These include phase-change cooling (such as the use of Freon in air conditioners and refrigerators, or carbon dioxide sublimation for cooling), fluid expansion cooling (which is widely used in air separation processes, such as cooling through compressed air expansion or high-pressure liquid expansion), and thermoelectric cooling (like the USB cooling systems found in computers today, which generate cold energy directly from electrical power). Absorption refrigeration (such as lithium bromide absorption refrigeration) is also common in some devices; less common ones include adsorption refrigeration and steam jet refrigeration. Higher-end cooling methods include hydrogen isotope conversion cooling, optical cooling (such as laser cooling), thermoacoustic cooling (such as ultrasonic cooling), and semiconductor cooling.