Cascade staging - Cascade staging

Technical information Industrial Cascade Compressor Staging

Cascade Intermediate Compressor

Cascade scene consists of several separate cooling systems that use different refrigerants and closed the heat exchangers to achieve low temperatures and reasonable condensing pressure. Cascade phased system design varies from direct setting of the system in various aspects. Cascade system has a separate (isolated) refrigeration circuits. While the refrigerant used in the direct setting of the system is the same through each compressor, cascade systems usually include different refrigerants in each of the stages to maximize the efficiency of the entire process. Metering devices used in cascade systems usually capillaries. Therefore, no receiver tanks employed and the refrigerant is critical. Interface between each stage consists of a tube-in-tube heat exchanger called a cascade of capacitor, which serves as the bottom of the condenser and the evaporator to the next higher stage.

Low refrigerant boiling point, such as methane, ethane, ethylene, R-23, R-508b is used in low stage of the cascade system. These refrigerants ultra high pressure at a normal ambient temperature.

Therefore, they should be condensed at low temperatures to reduce the level of compression and the associated inefficiencies. The lowest stage is the usual naked tube or plate evaporator is located in the conditioned space. At lower stages of the condenser is to cascade capacitor consisting of a tube-heat exchanger, through which the high evaporation temperature of the refrigerant from the lowest scale transfers its heat to the low temperature of liquid refrigerant in the following, the higher level of compression. The second stage of the cascade evaporator, as a rule, includes R-22, R-134a, R-404a, R-717 or propane.

To avoid excessively high pressure in the system, from developing in the low temperature stage during periods when the compressor is off, fade-out of the ship included in the low side of the pipelines. This expansion tank is designed so that the system volume is sufficiently large to accommodate all of the refrigerant is in vapor state acceptable to the saturation pressure. As long as any liquid is present in the system, refrigerant pressure depends on its temperature. When the compressor cycles off or the unit is turned off, the low side pressure starts to rise. Hie evaporation of the coolant expands in scope fade-out of the ship. Once all of the refrigerant was transformed into the vapor state, any further increase in temperature causes a small increase in pressure in accordance with Charles law. This additional low-side volume is low side of the pipeline, which is typically filled with its refrigerant vapor in the scene, so it does not affect the operation of the system during operation of the compressor. Recall that the same pressure fade-out principle is used widi gas, pressure limiting the expansion of the valve stem.

The disadvantage of the cascade setting overlap refrigerant temperature that occurs in the cascade of the capacitor. This reduces the load on the thermal efficiency of the system, which is below the comparable direct setting of the system. However, cascade interim makes it possible to use high-density, high-pressure refrigerants with lower stages, which usually leads to a significant reduction in the volume necessary for low levels. The use of high pressure refrigerants also simplifies the construction of low-stage evaporator, because higher pressure loss of refrigerant from the evaporator can be resolved without unnecessary loss in the system capacity and efficiency. In addition, because of refrigerants die in several stages (not mix and each stage is a separate system within himself, oil return is carried out in the individual stages in the same manner as any single-stage system of working die under the same conditions...

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