17-04-2014, 01:05 PM
Introduction to refrigeration
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Definition and Scope of Refrigeration
Literally, the word “refrigerate” is to make or keep cool or cold; to preserve (food, biologicals, etc) by keeping cold and freezing, as in Webster’s New World Dictionary.
According to ASRE (American Society of Refrigeration Engineering), refrigeration is defined as the science of providing and maintaining temperatures below that of surroundings.
Refrigeration may also be defined as the artificial withdrawal of heat, producing in a substance or within a space a temperature lower than that which would exist under the natural influence of surroundings.
Refrigeration and Heat Pump
The places, where surroundings are at temperatures lower than the required condition, have to be heated up.
The similar machinery as refrigerator which performs the heating process is called a heat pump. The main difference between the refrigeration system and heat pump system can be physically conceived of from the fact that in the former there is pumping of heat out of the system into the surrounding as against pumping of a heat from surrounding into the system in the latter case.
Thus a refrigeration system can be used as a heat pump, just by reversing the direction of operation as shown in Fig.1-2.
Refrigeration and Air Conditioning
The definition of comfort air conditioning is “the process of treating air to control simultaneously its temperature, humidity, cleanliness, and distribution to meet the comfort requirements of the occupants of the conditioned space”
Refrigeration can offer cooling, dehumidifying, and also heating (by heat pump) for air conditioning. Refrigeration has also many other applications other than air conditioning, as shown in Fig.1-3.
Comfort air conditioning
Comfort air conditioning applies not only in domestic, office, and commercial building, but also in automobile, train, ship, and airplane. Comfort air conditioning is one of the largest applications of refrigeration.
There are mainly three kinds of air conditioners (AC) for domestic, office, and commercial building: window air conditioner, split system air conditioner and central air conditioning system. The last one is also called “Chilled-water and Cooling-tower AC Unit” .
Air liquefaction and separation
Air consists primarily of 78% nitrogen and 21% oxygen, and also some rare gases, such as Ar, Ne, He.
Liquid air is used commercially for freezing other substances and especially as an intermediate step in the production of nitrogen, oxygen, and argon and the other inert gases.
The air liquefaction and air separation approach is based on the application of refrigeration.
Firstly, air is pressurized in a compressor, and after going through heat-exchangers it is expanded in the expansion machine or on a throttle valve.
As a result the temperature falls down and the air turns into a liquid.
[attachment=61486]
Definition and Scope of Refrigeration
Literally, the word “refrigerate” is to make or keep cool or cold; to preserve (food, biologicals, etc) by keeping cold and freezing, as in Webster’s New World Dictionary.
According to ASRE (American Society of Refrigeration Engineering), refrigeration is defined as the science of providing and maintaining temperatures below that of surroundings.
Refrigeration may also be defined as the artificial withdrawal of heat, producing in a substance or within a space a temperature lower than that which would exist under the natural influence of surroundings.
Refrigeration and Heat Pump
The places, where surroundings are at temperatures lower than the required condition, have to be heated up.
The similar machinery as refrigerator which performs the heating process is called a heat pump. The main difference between the refrigeration system and heat pump system can be physically conceived of from the fact that in the former there is pumping of heat out of the system into the surrounding as against pumping of a heat from surrounding into the system in the latter case.
Thus a refrigeration system can be used as a heat pump, just by reversing the direction of operation as shown in Fig.1-2.
Refrigeration and Air Conditioning
The definition of comfort air conditioning is “the process of treating air to control simultaneously its temperature, humidity, cleanliness, and distribution to meet the comfort requirements of the occupants of the conditioned space”
Refrigeration can offer cooling, dehumidifying, and also heating (by heat pump) for air conditioning. Refrigeration has also many other applications other than air conditioning, as shown in Fig.1-3.
Comfort air conditioning
Comfort air conditioning applies not only in domestic, office, and commercial building, but also in automobile, train, ship, and airplane. Comfort air conditioning is one of the largest applications of refrigeration.
There are mainly three kinds of air conditioners (AC) for domestic, office, and commercial building: window air conditioner, split system air conditioner and central air conditioning system. The last one is also called “Chilled-water and Cooling-tower AC Unit” .
Air liquefaction and separation
Air consists primarily of 78% nitrogen and 21% oxygen, and also some rare gases, such as Ar, Ne, He.
Liquid air is used commercially for freezing other substances and especially as an intermediate step in the production of nitrogen, oxygen, and argon and the other inert gases.
The air liquefaction and air separation approach is based on the application of refrigeration.
Firstly, air is pressurized in a compressor, and after going through heat-exchangers it is expanded in the expansion machine or on a throttle valve.
As a result the temperature falls down and the air turns into a liquid.