Parts of refrigeration cycle

Introduction and Parts of refrigeration cycle 

Before I talking in detail about the refrigeration cycle , we must review some physical lows which all of refrigeration cycles depends on it , its only five laws : 

Laws of refrigeration cycle 

1- Fluids absorb heat when it converted from liquid to gas and giving heat when it converted from gas to liquid . 

2- Fluid can switsh to another phase at the same temperature degree and pressure . 

3- Heat transfer only from the high temperature body to the lower one . 

4- Metal parts of condenser and evaporator must be have a good connecting to heat . 

5- Thermal energy and other form of energy can switch to another one .

Basic refrigeration cycle 

As I say the basic idea is to absorb heat which happen by converting liquid to gas or on another word evaporating liquid and after that we pump the gas by using compressor and at this point the temperature and pressure of the refrigerant raise, so we getting this raise .. out by the condenser which convert the gas to liquid by losing the heat . 

So the main parts of the refrigeration cycle will be : 

1- Compressor 

2- Condenser 

3- Expansion valve 

4- Evaporator

1] Compressor

Types of Compressors 

There are a number of different types of compressors used for refrigeration and air conditioning. Like pumps, all "heat pumps" can first be categorized as either positive displacement or non-positive displacement (centrifugal). Positive displacement compressors have chambers which decrease in volume during compression, while non-positive displacement compressors have fixed-volume chambers. This video explains visually: 

Beyond this distinction, each type differs based on its specific mechanism for fluid compression. The five main types of compressors are piston, rotary, screw, scroll, and centrifugal.

Piston Compressors

Piston compressors, also called reciprocating compressors, use a piston and cylinder arrangement to provide compressive force - like combustion engines or piston pumps. The reciprocating motion of the piston due to external power compresses the refrigerant inside the cylinder. Piston compressors have a low initial cost and a simple, easy to install design. They have a large power output range and can reach extremely high pressures. However, they have high maintenance costs, potential vibrational issues, and are not typically designed to run continuously at full capacity.

     

                  

 Rotary Compressors

Rotary compressors have two rotating elements, like gears, between which the refrigerant is compressed. These compressors are very efficient because the actions of taking in refrigerant and compressing refrigerant occur simultaneously. They have very few moving parts, low rotational speeds, low initial and maintenance costs, and are forgiving in dirty environments. However, they are limited to smaller volumes of the gas and produce less pressure than other types of compressors.

                                 Rotary vane compressor

Screw Compressors

Screw compressors use a pair of helical rotors or screws which mesh together to compress the refrigerant between them. They can produce high pressure for a small quantity of gas and consume less power than reciprocating compressors. They have low to medium initial and maintenance costs and few moving parts. However, they have difficulty in dirty environments, high rotational speeds, and shorter life expectancies than other designs.

                                             Screw compressor 

Scroll Compressors

Scroll compressors use two offset spiral disks nested together to compress the refrigerant. The upper disk is stationary while the lower disk moves in orbital fashion. Scroll compressors are quiet, smooth-operating units with few moving parts and the highest efficiency ratio of all compressor types. They also are more flexible for handling refrigerants in the liquid. However, as fully hermetic designs, scroll compressors cannot be easily repaired. They also typically cannot rotate in both directions. Scroll compressors are commonly used in automobile air conditioning systems and commercial chillers.

                                            Rotary vane compressor 

Centrifugal Compressors 

Centrifugal compressors use the rotating action of an impeller wheel to exert centrifugal force on refrigerant inside a round chamber (volute). Unlike other designs, centrifugal compressors do not operate on the positive displacement principle, but have fixed volume chambers. They are well suited to compressing large volumes of refrigerant to relatively low pressures. The compressive force generated by an impeller wheel is small, so systems that use centrifugal compressors usually employ two or more stages (impellers wheels) in series to generate high compressive forces. Centrifugal compressors are desirable for their simple design, few moving parts, and energy efficiency when operating multiple stages.

                                                             Centrifugal compressor