Moisture Effect On The Integrity Of The System Cooling
Moisture combines in varying degrees with the most commonly used refrigerants. This mixture reacts with lubricating oil and other materials in the system, to produce highly corrosive compounds. As a result of chemical reactions often leads to pitting and other damage to the valves, seals, bearing journals, cylinder walls and other polished surfaces in the system. It can also degrade the lubricant oils, sludge that may stick together valves, hammer oil passages, evaluation of the bearing surface and produce other effects which reduce the life of the system. Moisture, corrosion often worsens electrical insulation located on the motor windings of hermetic compressors in the end, causing a short circuit between windings and other reasonable compressor components of the dome.
Moisture in the refrigeration system can exist in solution with refrigerant or free water. When the amount of moisture in the system exceeds the amount that the refrigerant can hold in solution, die excess will free up water.
Free water can freeze in ice crystals inside the dispenser and in the evaporator tubes systems that operate below the freezing point of water. This reaction is called freeze-up. The ability of the refrigerant to hold moisture in the solution decreases as its temperature decreases. Thus, the content of moisture, low temperatures, the system must be maintained at very low levels, to prevent the freezing. Freeze-ups can occur air conditioning or other systems where the evaporator temperature remains above the freezing point of water.
When the hang occurs, the formation of ice in crater measuring device temporarily stops die flow of the liquid refrigerant. Consequendy, the effect of cooling inside the evaporator stops, and its temperature increases. When the die temperature of the evaporator exceeds the die temperature of melting ice, melting of refrigerant flow is restored. In such circumstances, die refrigeration space experience, raising the temperature of the refrigerant flow, cycled by thawing and freezing ice hole in the metering device. This action has a negative impact on stored food products, reducing their quality and shelf life.
Refrigerants differ widi respect of the amount of moisture in the soil, they can hold in solution and die effects, which absorbed moisture on system components. Right hydrocarbon refrigerants absorb a minimum of moisture. Consequently, any humidity in systems using diese refrigerants die in the form of free water, making her presence known through freeze-ups. With diis moisture must be removed immediately, to save die of a system of operational, moisture, corrosion is generally not a problem in these applications. On the contrary, ammonia has a high affinity to water. It can absorb the moisture in such large quantities that free water is rare in diese systems. For this reason, ammonia systems can be successfully exploited, even with a relatively large amounts of moisture are present in the system.
Freeze-ups also an indication that the moisture content in the system at a level that will allow corrosion to occur. However, the lack of freeze-ups does not mean that the moisture level in the system does not cause corrosion. Some refrigerants you can spend enough moisture in the decision that the corrosion occurs without the presence of free water. Although these systems are not affected by the hang of reaction is called hydrolysis occurs. Hydrolysis die a name given to any chemical reaction with the participation of water as one of the reacting substances. Hydrolysis can change the acidity of the system and molecules of both reagents can share and recombine to form new substances. In ammonia systems, hydrolysis produces ammonia water, strong alkalis, that the attacks of non-ferrous metals (copper, brass, copper alloys). Conversely, most halocar-Bon refrigerants nydrolyze only slighdy, forming a small number of acids and other aggressive substances. As a rule, these connections do not cause corrosion in the systems when the humidity is maintained below the level that causes a hang, if the high quality lubricating oils and discharge temperature is kept low enough. High temperature refrigeration systems with the evaporator temperature is about 40 F (4.4C) subject to higher levels of corrosion, because a relatively large amount of moisture may remain undetected in these systems for longer periods of time.
Absolutely moisture-free cooling system is difficult to achieve. Therefore, a good refrigeration practices require that the moisture content in the system will be maintained below the level that produces harmful reactions in the system. This level is not clearly defined and varies depending on the nature of refrigerant, the quality of lubricating oils and operating system temperatures, in particular, compressors discharge temperature. Devices called filter-driers are installed in systems to absorb moisture remaining in the system after he was evacuated and charged. Sight glass, having an absorbent material in the view port is also used to indicate when moisture is present in the system. This material will change color in the presence of moisture, giving warning that service is required before significant damage caused to die...