Year: 2020

Sep 17

Refrigerants and its Types

Any substance that absorbs heat through expansion or vaporization may be termed a refrigerant. In broad sense, refrigerant is also applied to secondary cooling medium as brine solution or cold water. As commonly interpreted, however, refrigerant includes only those working medium which passes through cycle of evaporation, recovery, compression and liquefaction. Thus circulating cold mediums, ice and solid carbon dioxide are not primary refrigerants. The primary refrigerants directly take part in refrigeration system whereas secondary refrigerants are first cooled with the help of primary refrigerant and are further used for cooling purposes.

Fig: Refrigerants (https://primefeed.in/wp-content/uploads/2020/08/HVAC-Refrigerant.jpg)

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Sep 15

Working Principle of Expansion Devices and its Types

Expansion devises are used in between evaporator and condenser in refrigeration system. These devices meters and regulates the flow of liquid refrigerant to an evaporator. The expansion device have following specific functions.
1. To reduce the pressure of liquid refrigerant coming from condenser.
2. To maintain desired pressure difference between high pressure and low pressure side of the system.
3. Capacity expansion devices are used to maintain the desired rate of flow and pressure drop across the system.
4. To control the flow of refrigerant according to variation of load on the evaporator. Read more

Sep 14

Working Principle of Condenser and its Types

High side equipment: The pressure of the refrigerant in the condenser is very little that at the compressor discharge. The pressure at compressor discharge is higher than at any other part of the system. Hence the condenser and other equipment in the system between compressor discharge and expansion valve are referred to as high side equipment.

Low side valve equipment: Since the refrigerant in the evaporator is at low pressure compared to that in the condenser, the evaporator and auxiliaries between the expansion valve and the compressor intake are often referred to as low side equipment. Read more

Sep 12

Working Principle of Evaporator and its Types

The function of evaporator is to absorb heat from surrounding location or medium which is to be cooled by means of refrigerant. The refrigerant either boils as it flows through a pipe, tube or other type of space so that liquid is continuously wetting all the inside surface or it boils in a shell around submerged tubes through which the fluid to be cooling is flowing. Various methods are used for evaporators, depending upon the refrigerant to be used and evaporator application, but iron, steel and copper predominate. Read more

Sep 11

Working Principle of Compressor and its Types

Basically, compressor in refrigeration system have following main function
1. Remove low temperature and low pressure refrigerant vapors from cooling coil through suction line.
2. Compress refrigerant vapors by increasing the pressure and temperature resulting in an increase of boiling point of refrigerant.
3. Discharge the refrigerant vapors of high temperature and pressure to condenser through discharge line.
Compression of refrigerant gas may be accomplished by any one of several different means such as positive displacement (reciprocating, rotary, gear types) and centrifugal (centrifugal compressor). The common type of compressors in use are
1. Reciprocating compressor
2. Rotary compressor
3. Centrifugal compressor
4. Screw compressor
5. Scroll compressor Read more

Sep 08

Introduction to Vapor Absorption Refrigeration System (VARS)

The compressor in vapor absorption system consumes a lot of energy. To avoid this, vapor absorption refrigeration system has been developed. The absorption system uses heat energy supplied by a flame or some other source of heat.

Michel Faraday experiment on liquefaction of gas:

vapor absorption refrigeration system is based on the principle of experiment developed by Michel Faraday. He sealed in a bent test tube a compound of silver chloride (a white powder) and dry ammonia gas which have been absorbed by the powder. He heated the end of tube containing the powder and at the same time, cooled the opposite end of the tube with water. Ammonia vapor was released during the application of heat and was condensed to cool end of the tube. When the flame under the powder was extinguished, vapor that had not been liquefied was reabsorbed by the powder reducing the pressure on liquid ammonia. The liquid ammonia begins to boil, change back to vapor and was reabsorbed by the powder. The end of tube containing boiling liquid was intensely cold. The evaporating ammonia having drawn heat from the nearest substance, the test tube itself. Read more

Sep 07

Introduction to Vapor Compressor Refrigeration System (VCRS)

Refrigeration can be defined as the process of transferring heat from low temperature region to high temperature region. In other words, it is the process of cooling the substance. This can be achieved only if heat is removed from that substance.

Principle of refrigeration: Principle of refrigeration is based on second law of thermodynamics. It states that heat doesn’t flow from low temperature body to high temperature body without the help of external work. In refrigeration process, since heat has to be transferred from low temperature body to high temperature body some external work has to be done according to second law of thermodynamics as shown below (fig 2.) Here, the external work is done by compressor, condenser etc. The machine which works under this principle and serves the purpose of refrigeration is called refrigerator. Read more