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Training Manual for Lithium Bromide Refrigeration Units Compiled by: ************ Company §1 Basic Principles of Refrigeration I. Meaning of refrigeration: Refrigeration refers to the use of certain methods to reduce the temperature of an object or space to a level lower than that of the surrounding environment, and to maintain it within a specified temperature range. The so-called environmental media refer to air or water. II. Methods of achieving cooling: (1) Artificial cooling; (2) Natural cooling (using ice and groundwater). III. Methods of cooling: 1. Cooling by liquid vaporization: (1) Steam compression cooling (screw compressors), which consists of four main components: a compressor, a condenser, a throttling device, and an evaporator. 1: Gas at low temperature and low pressure 2: Gas at high temperature and high pressure 3: Liquid at normal temperature and normal pressure 4: Liquid at low temperature and low pressure (2) Absorption refrigeration A. Ammonia absorption refrigerator B. Lithium bromide absorption refrigerator. Absorption refrigerators do not have compressors, but their generator and absorber serve the function of a compressor, and are referred to as “heat compressors”. (3) Steam jet refrigeration (4) Absorption refrigeration. 2. Air expansion refrigeration. 3. Thermoelectric refrigeration, also known as temperature difference refrigeration, is a type of refrigeration that makes use of the thermoelectric effect. 4. Eddy current tube refrigeration 5. Thermal storage air conditioning IV. Commonly used refrigeration equipment 1. Electric refrigerators using positive displacement compressors (1) Piston refrigerators (2) Screw refrigerators 2. Electric refrigerators using dynamic compressors – Centrifugal refrigerators 3. Lithium bromide absorption refrigerators V. Comparison between lithium bromide refrigerators and electric refrigerators 1. Characteristics of lithium bromide absorption refrigerators: Low power consumption, which helps alleviate power shortages ； The refrigerant is water, and the absorbent solution is a lithium bromide solution ； It is harmless to environmental safety, and allows for full utilization of steam and natural gas ； Few moving parts and few wear-prone components, making maintenance convenient; low vibration and low noise levels ； Microcomputer-based intelligent control ； Working principle: The lithium bromide solution is heated to concentrate it, and the absorption effect is utilized to cause the refrigerant to evaporate at low temperatures under vacuum. 2. Characteristics of electric refrigerators: high power consumption, electricity shortages in summer ； The refrigerants are Freon and ammonia; R22 destroys the ozone layer and causes environmental problems, and its use has been banned or restricted in some cases (R22 will be banned by 2020) ； Many moving parts and wear-prone components, along with high vibration and noise levels ； Some have also achieved automated control. §2 Properties of lithium bromide aqueous solutions I. Properties of water: Water is an easily available substance; it is non-toxic, does not burn or explode, has a high latent heat of vaporization, and a large specific volume. II. Physical properties of lithium bromide: 1. It is a colorless granular crystal with a salty taste; its properties are similar to those of table salt, and it is non-toxic. 2. High melting point. 549℃3, High boiling point. 1265℃4. High water absorption. 5. It has stable properties and does not deteriorate or decompose in the atmosphere. III. Physical properties of lithium bromide aqueous solution: 1. It is a colorless liquid with a salty taste and is non-toxic. 2. The solubility of lithium bromide in water decreases as the temperature drops. 3. The water vapor partial pressure of the lithium bromide solution is very low. 4. The density of lithium bromide solution is greater than that of water. 5. The lithium bromide solution has a low density and specific heat. 6. The lithium bromide solution has a high viscosity. 7. The lithium bromide solution has high surface tension. (It does not absorb water vapor easily; a surfactant is required.) 8. Lithium bromide solution is corrosive to metals. (Addition of corrosion inhibitor: lithium molybdate) IV. Surfactants: To improve heat exchange efficiency, surfactants are often added to lithium bromide solutions. Common surfactants are isooctanol or n-octanol. At normal pressure, octanol is a colorless liquid with an irritating odor, and it has very low solubility in solutions. Tests show that the cooling capacity increases by about 10% after adding octanol. Adding 0.1-0.3% (V%) of octanol to a typical engine mixture is sufficient to achieve the desired effect. Mechanism of action: (1) Improves the absorption efficiency of the absorber by reducing the surface tension of the solution, thereby enhancing the solution’s ability to absorb water vapor. (2) The transition of water vapor from film condensation to droplet condensation improved the condensing efficiency of the condenser. Properties of octanol: (1) It is practically insoluble in lithium bromide solution. (2) It is volatile and may be carried out of the device along with non-condensable gases during vacuum pumping. The more times pumping is performed, the greater the amount of octanol that is removed from the device. When there is no odor of octanol in the gas discharged by the vacuum pump, or when the odor is very faint, replenishment should be carried out. V. Corrosion and Anti-corrosion 1. Reasons for corrosion of metals by lithium bromide solution: Iron and copper, in the presence of oxygen within lithium bromide solution, undergo chemical reactions with this solution and get corroded, while hydrogen is also produced. 2. Factors affecting the corrosion of metals by lithium bromide solutions (1) Presence of oxygen: The presence of oxygen is the main factor that causes lithium bromide solutions to corrode metals. (2) Temperature tests on the solution showed that when the temperature is below 165°C, the temperature of the solution has little effect on metal corrosion ； When the temperature is above 165°C, the corrosion of carbon steel and red copper by the solution increases sharply. (The temperature parameter for the high-temperature regenerator is: