Refrigeration:- The process of removing heat from a space or substance to reduce its temperature and transferring that heat to some another space or substance i.e. air or water.or
This is the technique by which we keep the temperature of the given space by lower then surroundings. We used to remove heat from the substance to be cooled and transfer this heat to air, water or other cooling medium.
To remove the heat from the given space we used to evaporate a volatile liquid by lower its pressure
During this process the liquid become vapour by taking heat from the system making it cool.
Unit of Refrigeration:- It may be define as
Heat added to 1 ton of ice at 32° F to convert it into water of 32° F in 24 hours is known as Ton of Refrigeration or TR.Or
Heat removed from 1 ton of water at 32° F to convert it into ice of 32° F in 24 hours is known as Ton of Refrigeration of TR.
1 TR = 12000 BTU/hour (British thermal unit) = 3024.2 kcal/hour
Heat added to convert 32° F ice into water of 32° F= (weight of water X latent heat of water, Ice) / time
= (2000 lbs X 144 Btu/lbs) / 24
= 12000 BTU/hr
Refrigeration Cycle:- It is combination of the process which took place in a refrigeration system during removing heat from a given space and adding it to other place/cooling medium which can be air or water.
There are following type of refrigeration cycle:-
1. Vapour Compression Cycle
2. Vapour Absorption Cycle
1. Vapour Compression Cycle:- In this type of systems we compress the vapour refrigeration after evaporator. The main parts of this cycle are as follows:-
· Compressor
· Condenser
· Receiver
· Expansion Valve
· Evaporator
Vapour compression systems there are mainly four processes as follow: -
i). Compression:- it is the process of vapour compression cycle in which we increase the pressure of the vapour refrigerant by the means of compressing it. This work is done by a Compressor.
‘Low pressure, low temperature, super heated vapour refrigerant’ enters into compressor from suction line. Here the pressure and the temperature of the vapour refrigerant is increased by compressing the vapour particles. When the vapour refrigerant leaves the compressor from discharge line it is ‘High pressure, high temperature and more super heated vapours’.
ii). Condensing process:- It is the process of vapour compression cycle in which we condensate the vapor refrigerant into liquid stage by the means of heat transfer to a cooling medium. This work is done by a Condenser.
To convert a gas from vapor state to liquid state we have to increase its pressure (This is done in
Compression process, during compression process heat is also added in the vapor refrigerant) and remove heat from this high pressure gas (this is done in Condensing process).
‘High pressure, high temperature and more super heated vapors’ from compressor enter into condenser. Here the heat from this vapor refrigerant is removed by a cooling medium air or water.
When the refrigerant leaves condenser it is ‘high pressure, high temperature, and sub cooled liquid.
Liquid receiver:- This is a liquid storage tank in which refrigerant in liquid stage is stored.
Refrigerant leaving condenser is collected here and sent to evaporator as par the requirement.
In small unit such as domestic refrigerator and air-conditioning there is no receiver is used.
iii). Pressure reducing process:- It is the process of vapour compression cycle in which we reduce the pressure of liquid refrigerant by the means of passing the liquid refrigerant through a small hole/orifice. This work is done by an Expansion Valve.
Liquid refrigerant from receiver enters into expansion valve as ‘High pressure, high temperature and sub cooled liquid’ and passes through a small hole/orifice causing the pressure drop. When the liquid from a small orifice comes out and comes in a contact with a bigger space, the pressure drop become more causing refrigerant to be evaporate at very low temp in evaporator. When the liquid refrigerant exits from expansion valve it is in the state of ‘Low pressure, low temperature saturated liquid’.
iv). Vaporizing process:- It is the process of vapour compression cycle in which we get cooling effect by the means of evaporating liquid refrigerant. This work is done by the Evaporator.
‘Low pressure, low temperature, saturated liquid’ enters into evaporator and get heating from the surroundings (space to be cooled) causing surrounding to become cool by the evaporation process.
Object in the surrounding gives their heat to this liquid refrigerant so that the refrigerant gets evaporates and produces cooling. Refrigerant leaves the evaporator in the state of ‘low pressure, low temperature saturated vapour’.
As this refrigerant passes the suction line it gets more heat from high temperature surrounding and become 'low temperature, low pressure, and super heated vapour’.
This is the technique by which we keep the temperature of the given space by lower then surroundings. We used to remove heat from the substance to be cooled and transfer this heat to air, water or other cooling medium.
To remove the heat from the given space we used to evaporate a volatile liquid by lower its pressure
During this process the liquid become vapour by taking heat from the system making it cool.
Unit of Refrigeration:- It may be define as
Heat added to 1 ton of ice at 32° F to convert it into water of 32° F in 24 hours is known as Ton of Refrigeration or TR.Or
Heat removed from 1 ton of water at 32° F to convert it into ice of 32° F in 24 hours is known as Ton of Refrigeration of TR.
1 TR = 12000 BTU/hour (British thermal unit) = 3024.2 kcal/hour
Heat added to convert 32° F ice into water of 32° F= (weight of water X latent heat of water, Ice) / time
= (2000 lbs X 144 Btu/lbs) / 24
= 12000 BTU/hr
Refrigeration Cycle:- It is combination of the process which took place in a refrigeration system during removing heat from a given space and adding it to other place/cooling medium which can be air or water.
There are following type of refrigeration cycle:-
1. Vapour Compression Cycle
2. Vapour Absorption Cycle
1. Vapour Compression Cycle:- In this type of systems we compress the vapour refrigeration after evaporator. The main parts of this cycle are as follows:-
· Compressor
· Condenser
· Receiver
· Expansion Valve
· Evaporator
 |
| Vapour Compression Refrigeration Cycle |
Vapour compression systems there are mainly four processes as follow: -
i). Compression:- it is the process of vapour compression cycle in which we increase the pressure of the vapour refrigerant by the means of compressing it. This work is done by a Compressor.
‘Low pressure, low temperature, super heated vapour refrigerant’ enters into compressor from suction line. Here the pressure and the temperature of the vapour refrigerant is increased by compressing the vapour particles. When the vapour refrigerant leaves the compressor from discharge line it is ‘High pressure, high temperature and more super heated vapours’.
ii). Condensing process:- It is the process of vapour compression cycle in which we condensate the vapor refrigerant into liquid stage by the means of heat transfer to a cooling medium. This work is done by a Condenser.
To convert a gas from vapor state to liquid state we have to increase its pressure (This is done in
Compression process, during compression process heat is also added in the vapor refrigerant) and remove heat from this high pressure gas (this is done in Condensing process).
‘High pressure, high temperature and more super heated vapors’ from compressor enter into condenser. Here the heat from this vapor refrigerant is removed by a cooling medium air or water.
When the refrigerant leaves condenser it is ‘high pressure, high temperature, and sub cooled liquid.
Liquid receiver:- This is a liquid storage tank in which refrigerant in liquid stage is stored.
Refrigerant leaving condenser is collected here and sent to evaporator as par the requirement.
In small unit such as domestic refrigerator and air-conditioning there is no receiver is used.
iii). Pressure reducing process:- It is the process of vapour compression cycle in which we reduce the pressure of liquid refrigerant by the means of passing the liquid refrigerant through a small hole/orifice. This work is done by an Expansion Valve.
Liquid refrigerant from receiver enters into expansion valve as ‘High pressure, high temperature and sub cooled liquid’ and passes through a small hole/orifice causing the pressure drop. When the liquid from a small orifice comes out and comes in a contact with a bigger space, the pressure drop become more causing refrigerant to be evaporate at very low temp in evaporator. When the liquid refrigerant exits from expansion valve it is in the state of ‘Low pressure, low temperature saturated liquid’.
iv). Vaporizing process:- It is the process of vapour compression cycle in which we get cooling effect by the means of evaporating liquid refrigerant. This work is done by the Evaporator.
‘Low pressure, low temperature, saturated liquid’ enters into evaporator and get heating from the surroundings (space to be cooled) causing surrounding to become cool by the evaporation process.
Object in the surrounding gives their heat to this liquid refrigerant so that the refrigerant gets evaporates and produces cooling. Refrigerant leaves the evaporator in the state of ‘low pressure, low temperature saturated vapour’.
As this refrigerant passes the suction line it gets more heat from high temperature surrounding and become 'low temperature, low pressure, and super heated vapour’.
