jahangirabad institute of technology

Refrigeration and Air Conditioning

NME:604Unit5

Presented byMr Naphis AhmadAssistant professorJETGI Barabanki

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INTRODUCTION

Air conditioning is the process of altering the properties of air to more favorable conditions.

The control of these conditions may be desirable to maintain the health and comfort of the occupants.

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TYPE OF AIR-CONDITIONING1) Window air-conditioning system2) Split air-conditioning system3) Central air-conditioning system4) Package air-conditioning system

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Split Air-Conditioning SystemThe split air conditioner comprises of two parts: the outdoor unit and the

indoor unit.

The outdoor unit, fitted outside the room, houses components like the compressor, condenser and expansion valve.

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Windows Air-conditioning System Window air conditioners are one of the most commonly used and cheapest

type of air conditioners. Window air-conditioner units are reliable and simple-to-install solution to

keep a room cool while avoiding the costly construction of a central air system.

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Central Air-Conditioning System

The central air conditioning plants or the systems are used when large buildings, hotels, theaters, airports, shopping malls etc. are to be air conditioned completely.

The window and split air conditioners are used for single rooms or small office spaces. Further, these small units cannot satisfactorily cool the large halls, auditoriums, receptions areas etc.

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Packaged Air-Conditioning SystemThe window and split air conditioners are usually used for the small air

conditioning capacities up to 5 tons.

The packaged air conditioners are used for the cooling capacities in between these two extremes.

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Circuit Diagramwinter Air conditioning system

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The main components

the main components of refrigeration system:The CompressorThe Condensing CoilThe Metering DeviceThe Evaporator

Thermal expansion Valves

A very common type of metering

device is called a TX Valve

(Thermostatic Expansion Valve). This

valve has the capability of controlling

the refrigerant flow. 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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The EvaporatorThe evaporator is where the heat is removed from your house , business or refrigeration box.

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.

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Main Features of Cooling Towers

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• Frame and casing: support exterior enclosures• Fill: facilitate heat transfer by maximizing water / air contact

• Splash fill• Film fill

• Cold water basin: receives water at bottom of tower

Components of a cooling tower

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• Drift eliminators: capture droplets in air stream• Air inlet: entry point of air• Louvers: equalize air flow into the fill and retain water within tower• Nozzles: spray water to wet the fill• Fans: deliver air flow in the tower

Components of a cooling tower

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• Hot air moves through tower• Fresh cool air is drawn into the tower from bottom• No fan required• Concrete tower <200 m• Used for large heat duties

Types of Cooling Towers

Natural Draft Cooling Towers

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Natural Draft Cooling Towers

Cross flow Counter flow

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• Large fans to force air through circulated water• Water falls over fill surfaces: maximum heat transfer• Cooling rates depend on many parameters• Large range of capacities• Can be grouped, e.g. 8-cell tower

Mechanical Draft Cooling Towers

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Three types• Forced draft• Induced draft cross flow• Induced draft counter flow

Mechanical Draft Cooling Towers

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• Air blown through tower by centrifugal fan at air inlet

• Advantages: suited for high air resistance & fans are relatively quiet

• Disadvantages: recirculation due to high air-entry and low air-exit velocities

Forced Draft Cooling Towers

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• Two types• Cross flow• Counter flow

• Advantage: less recirculation than forced draft towers• Disadvantage: fans and motor drive mechanism require

weather-proofinh

Induced Draft Cooling Towers

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• Hot water enters at the top• Air enters at bottom and exits at top• Uses forced and induced draft fans

Induced Draft Counter Flow CT