REFRIGERATION & AIR CONDITIONING

REFRIGERATION & AIR CONDITIONING

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REFRIGERATION & AIR CONDITIONING

ABSTRACT: Refrigeration is very essential for humans and industrial utilities so it has wast applications and demand in existence In commerce and manufacturing, there are many uses for refrigeration. Refrigeration is used to liquefy gases like oxygen, nitrogen, propane and methane for example. In compressed air purification, it is used to condense water vapor from compressed air to reduce its moisture content.

In oil refineries, chemical plants, and petrochemical plants, refrigeration is used to maintain certain processes at their required low temperatures (for example, in the alkylation of butanes and butane to produce a high octane gasoline component). Metal workers use refrigeration to temper steel and cutlery. In transporting temperaturesensitive foodstuffs and other materials by trucks, trains, airplanes and sea-going vessels, refrigeration is a necessity. ` Refrigeration air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dewpoint) evaporator coil condenses water vapor from the processed air, (much like an ice-cold drink will condense water on the outside of a glass), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity.

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REFRIGERATION & AIR CONDITIONING

Main overview Here in the refrigeration system heat is to be extracted from the body which has to be cooled. The rejection of heat from low level to high level can only performed by the law of thermo dynamics Refrigeration air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dew point) evaporator coil condenses water vapor from the processed air, (much like an ice-cold drink will condense water on the outside of a glass), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space.

Types of refrigeration: 

Vapor compression refrigeration (vcr)



Vapor absorption refrigeration (var)



Vapor compression refrigeration (vcr):

The working fluid in this is Freon 12, it readily evaporates and condenses. it boils at a temperature of -20c,1.54kg/cm2 .when the volatile vapor evaporates ,it absorbs the latent heat for the purpose from its surroundings. Vapor compression refrigeration system works on the principle of abstracting latent heat of vapor required by the refrigerant from the surrounding which are required to be cooled.

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REFRIGERATION & AIR CONDITIONING

The vapor-compression cycle is used in most household refrigerators as well as in many large commercial and industrial refrigeration systems. Figure 1 provides a schematic diagram of the components of a typical vapor-compression refrigeration system.

Figure 1: Vapor compression refrigeration

The thermodynamics of the cycle can be analyzed on a diagram[10][11] as shown in Figure 2. In this cycle, a circulating refrigerant such as Freon enters the compressor as a vapor. From point 1 to point 2, the vapor is compressed at constant entropy and exits the compressor superheated. From point 2 to point 3 and on to point 4, the superheated vapor travels through the condenser which first cools and removes the superheat and then condenses the vapor into a liquid by removing additional heat at constant pressure and temperature. Between points 4 and 5, the liquid refrigerant goes through the expansion valve (also called a throttle valve) where its pressure abruptly decreases, causing flash evaporation and auto-refrigeration of, typically, less than half of the liquid.

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REFRIGERATION & AIR CONDITIONING

There are four main components in a refrigeration system: •

The Compressor

•

The Condensing Coil

•

The Evaporator

•

The Metering Device

The refrigeration cycle commences from the evaporator. The refrigerant in evaporator absorbs heat from cold body and converts low pressure liquid to low pressure vapor as soon as the vapor formed the compressor sucks this vapor from evaporator and increases its pressure.

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REFRIGERATION & AIR CONDITIONING

The Compressor:

•

The compressor is the heart of the system. The compressor does just what it’s

name is. It compresses the low pressure refrigerant vapor from the evaporator and compresses it into a high pressure vapor. •

The inlet to the compressor is called the “Suction Line”. It brings the low

pressure vapor into the compressor. •

After the compressor compresses the refrigerant into a high pressure Vapor, it

removes it to the outlet called the “Discharge Line”.

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REFRIGERATION & AIR CONDITIONING

Compressor motor: The compressor motor is an induction motor which is a capacitor start and capacitor run. This is used for compressing the refrigeration On compression vapor gets heated up so that its temperature is higher than surroundings the compressor discharges liquid vapor to the condenser. The cooling medium in the condenser extracts heat from the heated vapor refrigerant and converts it to liquid refrigerant. Now the liquid moves to throttle valve.

The Condensing Coil: •

The “Discharge Line” leaves the compressor and runs to the inlet of the

condenser. •

Because the refrigerant was compressed, it is a hot high pressure vapor (as

pressure goes up – temperature goes up). •

The hot vapor enters the condenser and starts to flow through the tubes.

•

Cool air is blown across the out side of the finned tubes of the condenser (usually

by a fan or water with a pump). •

Since the air is cooler than the refrigerant, heat jumps from the tubing to the

cooler air (energy goes from hot to cold – “latent heat”). •

As the heat is removed from the refrigerant, it reaches it’s “saturated temperature”

and starts to “flash” (change states), into a high pressure liquid.

•

The high pressure liquid leaves the condenser through the “liquid line” and travels

to the “metering device”. Sometimes running through a filter dryer first, to remove any dirt or foreign particles.

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REFRIGERATION & AIR CONDITIONING

The Evaporator: •

The evaporator is where the heat is removed from your house , business or

refrigeration box. •

Low pressure liquid leaves the metering device and enters the evaporator.

•

Usually, a fan will move warm air from the conditioned space across the

evaporator finned coils. •

The cooler refrigerant in the evaporator tubes, absorb the warm room air. The

change of temperature causes the refrigerant to “flash” or “boil”, and changes from a low pressure liquid to a low pressure cold vapor. •

The low pressure vapor is pulled into the compressor and the cycle starts over.

•

The amount of heat added to the liquid to make it saturated and change states is

called “Super Heat”. •

One way to charge a system with refrigerant is by super heat.

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REFRIGERATION & AIR CONDITIONING

The Metering Device:

The above shown figure is throttle valve which is used for regulating the flow of refrigerant. If the load on the evaporator changes, the valve can respond to the change and increase or decrease the flow accordingly

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REFRIGERATION & AIR CONDITIONING

 Vapor absorption refrigeration (var):

The absorption cycle is similar to the compression cycle, except for the method of raising the pressure of the refrigerant vapor. In the absorption system, the compressor is replaced by an absorber which dissolves the refrigerant in a suitable liquid, a liquid pump which raises the pressure and a generator which, on heat addition, drives off the refrigerant vapor from the high-pressure liquid. Some work is required by the liquid pump but, for a given quantity of refrigerant, it is much smaller than needed by the compressor in the vapor compression cycle. In an absorption refrigerator, a suitable combination of refrigerant and absorbent is used. The most common combinations are ammonia (refrigerant) and water (absorbent), and water (refrigerant) and lithium bromide (absorbent).

Figure 2: Temperature–Entropy diagram That results in a mixture of liquid and vapor at a lower temperature and pressure as shown at point 5. The cold liquid-vapor mixture then travels through the evaporator coil or tubes and is completely vaporized by cooling the warm air (from the space being refrigerated) being blown by a fan across the evaporator coil or tubes. The resulting 28

REFRIGERATION & AIR CONDITIONING

refrigerant vapor returns to the compressor inlet at point 1 to complete the thermodynamic cycle.

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REFRIGERATION & AIR CONDITIONING

INNERVIEW OF AIR CONDITIONER

Figure 2. Minimal air conditioning. The part of the system in the room, on the left, pulls air first over a cool surface and then over a warming surface. The part of the system on the right recalculates the cooling fluid. The fluid passes from the reservoir through a valve into the lower pressure within the cooling unit in the room. There the liquid boils, removing heat from the air. The boiling point is fixed by the constant pressure set by valve A. The vapor is then compressed and condensed back into a liquid which collects in the reservoir ready for another cycle.

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REFRIGERATION & AIR CONDITIONING

APPLICATIONS: Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat and humidity loads and external weather conditions. Although often in the comfort range, it is the needs of the process that determine conditions, not human preference. Process applications include these: 

Aircraft air conditioning. Although nominally aimed at providing comfort for

passengers and cooling of equipment, aircraft air conditioning presents a special challenge because of the changing density associated with changes in altitude, humidity and temperature of the outside air[ 

Data centers



Textile factories



Physical testing facilities



Plants and farm growing areas



Nuclear facilities



Chemical and biological laboratories



Mines



Industrial environments



Food cooking and processing areas

DISADVANTAGES: The only disadvantage is that it emits colure flora carbons which are atmosphere pollutants

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REFRIGERATION & AIR CONDITIONING

CONCLUSION: Refrigeration & air conditioning is more essential for the humans and future extension So these are widely used by the world in many household and industrial applications like Refrigeration air conditioners etc. it is the efficient one in cooling biological samples in medical applications

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