Exactly matching the refrigeration load with the capacity of refrigeration compressors is referred to as. Jul 14 PM Solution. Questions Courses. What is the difference between an even and an uneven parallel compressor system?
Exactly matching Exactly matching the refrigeration load with the capacity of refrigeration compressors is referred to as A. Jul 14 PM. Expert's Answer Solution. Feedback :. Next Previous. Related Questions. A two-stage compression refrigeration system with an adiabatic liquid-vapor separation unit as shown in Fig.
P11—60 uses refrigeranta as the working fluid. What type of a system are most centrifugal compressors used on? How can oil be delivered to internal moving compressor parts? What is the purpose of a crankcase heater on a compressor? Initially the refrigerant is compressed adiabatically in the compressor. This allows the low temperature and low pressure refrigerant to be converted to high pressure and high temperature refrigerant. After compression high pressure and high temperature fluid is allowed to move into condenser.
Condenser plays the role of removal of heat from the refrigerant at high pressure. The heat removed from the refrigerant theoretically neither affects pressure nor temperature. Thereby in theory condensation is isobaric constant pressure as well as isothermal constant temperature. Throttling or expansion process allows decrease in pressure and temperature of the refrigeration after passing from throttling valve. Evaporator is actually the output section of the refrigerator or air-conditioning system.
It is the component that accounts for the refrigeration effect produced by the cooling system. Evaporator allows the absorption of heat through the surrounding as the refrigerant moves through the refrigerant coils. The process is called evaporation. Theoretically evaporation is isothermal as there is no change in the temperature of refrigerator. Refrigerant boils during its movement through the evaporation coils.
A typical rack refrigeration system schematics and flow diagram is provided below. The principle followed is same as that of any refrigeration system. However the only major difference is in the configuration and number of components.
The rack refrigeration system specifically provided in the diagram is remote type refrigeration system. Remote refrigeration is a subtype of rack refrigeration system that has compressor and condensers at different locations. In other words in this type of refrigeration system compressor and condenser are not combined together in a single unit. All the compressors are contained in a single room called the machine room while the condensers are fixated on roof tops for sufficient air flow to remove the heat from the condenser coils.
A compressor rack consists of multiple compressors that may or may not be operating at the same time. These multiple compressors may refrigerate different cases that are operating at different temperatures. Using multiple parallel compressors in the rack are very useful. As they allow variable operation of refrigeration depending on how much cooling power is required. This is different from single compressor systems in which there are only two option.
Either it is operating and we have the percent cooling power or it is not operating in which case we have 0 percent cooling power. Now this rack will be able to run at 4 capacities i. Hence in the above case by use of three compressors in the rack it would provide cooling operation at 0 percent, Using multiple parallel compressors with uneven compressor values is even better as it allows more diverse configuration of compressors.
Now this rack will be able to provide 7 capacities i. Hence in the above case of multiple uneven compressor rack using three compressors, it would provide cooling operation at 0 percent, Thereby we will get maximum variation of cooling power when using uneven multiple compressor rack. This is especially important in the scenario when food is transported on a truck or other delivery vehicle and it is somewhat warm in the beginning.
However with the passage of time as the desired cooling temperature is maintained the cooling power is reduced for an efficient operation. The cooling power is adjusted by the use of microprocessor controllers. They accurately adjust the operation of compressors depending on the requirement of the cooling power. The cooling power is adjusted by the data received by pressure and temperature sensors recorded throughout the system.
The most critical data is the pressure at delivery end of compressor and the temperature in the evaporator. Refrigerant pipes are carried in trenches underneath the floor or overhead using hangers. Proper insulation is necessary to prevent electrolytic action i. Water is developed in the refrigerant coils during the operation of refrigeration. Thereby it must be removed periodically. For that purpose liquid line dryers are used to remove water from the system.
They are replaced periodically depending on the operation as a preventive measure. The compressor usually reciprocating type consists of several mechanically moving parts. Thereby just like an automobile engine it requires consistent lubrication.
The oil separator plays the role of separating oil in the discharge gas and returning it to the crankcase. Subcoolers allow the decrease in temperature of liquid refrigerant below the saturation temperature.
This is done to decrease the amount of flash gas through the expansion device located before the refrigerated case. Massive amount of refrigerant travel from the compressor room to the individual refrigerated cases.
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