subject: Refrigeration Plant Various Components And Their Functions [print this page] A refrigeration plant consists of four major components compressor, condenser, expansion valve and evaporation system that function together to cool the articles in a plant and maintain them at a temperature lower than the ambient temperature. Read on to know the role of various components of refrigeration system.
Main components of a refrigeration plant are:
* Compressor
* Condenser
* Expansion Valve
* Evaporation System
Compressor
Role of the compressor is to suck vapor from the evaporator and push it into the condenser. There are several types of compressors like piston, centrifugal scroll and screw, and most popular among these is piston compressor. It covers a large capacity range, right from single cylinder models for household refrigerators up to 8 to 12 cylinder models for industrial applications.
In small applications, hermetic compressor is used. This model has compressor and motor built together, enclosed in welded steel casing and connected by a common shaft, making it a compact and portable unit.
For medium-sized plants, larger sizes of hermetic compressors in either piston or scroll versions are usually used. Such applications are chillers, general commercial refrigeration and air condition.
For larger applications, semi-hermetic compressor is more popular. Its design helps avoid the shaft glands, which is important as it is hard to replace shaft glands. However, all ammonia compressors and HFC compressors are designed to be open compressors. Semi-hermetic design cant be used on ammonia plants as the refrigerant attacks motor windings.
Condenser
Job of the condenser is to remove the heat that equals to the sum of heat produced by compression and absorbed in the evaporator. The system consists of a condensing coil, water distribution tubes, fans and deflection plates. The warm refrigerant vapor reaches to the top of the condensing coil where it condenses and runs from the bottom of the coil as liquid. Water distribution tubes along with the nozzles are put over the condensing coil so that water is spread over and runs down the coil. The fans make air flow strongly across the condensing coil and falling drops of water, resulting in absorption of evaporating heat from the refrigerant vapor. When it is not possible to use water for condensing process, air-cooled condenser is used.
Expansion Valve
Expansion valve ensures an adequate pressure differential between the high and low pressure sides of the system. It is placed to allow high pressure liquid refrigerant be gradually exposed to low pressure, where it boils and evaporates in the process. The valve controls the amount of refrigerant flow into the evaporator thereby putting tabs on superheating. If the load inside the evaporator is higher the valve increases flow of the refrigerant and when the load reduces, it brings down the flow.
Evaporation Systems
Evaporators are used in different versions, depending on the requirements. Earlier refrigerators were fitted with plain tubes, but now finned elements or ribbed tubes are preferred. Forced air circulation is used in the new models for increased evaporator performance. It is done by increasing air velocity.
In a plant, the refrigerant compressor unit can be installed in any room with an outlet to fresh air. The plant must be dimensioned in accordance with the largest load it will be subjected to. However, facilities must exist in the plat for altering yield to accommodate smaller loads. This functionality is made possible by automatic controls.
