Building Services - Air Conditioning

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Basics of Refrigration.

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BASIC REFRIGERATION PRINCIPLES

AIR CONDITIONING
Building Services III

PRINCIPLE OF REFRIGERATION
Refrigeration is governed by the second law of thermodynamics that heat cannot flow from a cold body to a hot body unless an
external force acts on it.

EXTERNAL INPUT

COLD BODY

Heat

REFRIGERATOR

Heat

HOT BODY

TYPES OF REFRIGERATION SYSTEMS
• Ice refrigeration System
• Air Refrigeration System
• Vapor Refrigeration system

REFRIGERANT
Refrigerant is a substance in vapor or liquid form used as a working fluid in refrigerators, through which heat is transferred from
a cold body to the hot body.
Any substance capable of absorbing heat from another substance can be used as a refrigerant.

Some properties of a refrigerant are :
• Low freezing and boiling point
• High latent heat of vaporization
• Non-corrosive
• Be easy to liquefy
• Low specific volume
Examples.
• Air
• Ammonia
• Fluorinated carbons

VAPOUR REFRIGERATION CYCLE
Vapour compression cycle is an improved type of air refrigeration cycle in which a suitable
working substance, termed as refrigerant, is used.

VAPOUR REFRIGERATION CYCLE
The refrigerant used, does not leave the system, but is circulated throughout the system
alternately condensing and evaporating.
In evaporating, the refrigerant absorbs its latent heat from the solution which is used for
circulating it around the cold chamber and in condensing; it gives out its latent heat
to the circulating water of the cooler.

VAPOUR REFRIGERATION CYCLE
Components: COMPRESSER

VAPOUR REFRIGERATION CYCLE
Components: CONDENSER

VAPOUR REFRIGERATION CYCLE
Components: RECEIVER

VAPOUR REFRIGERATION CYCLE
Components: REFRIGERANT CONTROL DEVICE or THROTTLE VALVE or
EXPANSION VALVE

VAPOUR REFRIGERATION CYCLE
Components: EVAPORATOR

ELECTRIC MOTOR
Electric motors are used in refrigeration systems for running compressors, fans and
pumps. The electric motors are generally divided into two categories:
• Less than 1 HP capacity
• More than 1 HP capacity

AIR HANDLING UNIT
An air handler, or air handling unit (often
abbreviated to AHU), is a device used to
condition and circulate air as part of a
heating, ventilating, and air-conditioning
(HVAC) system.
Usually, an air handler is a large metal
box containing a blower, heating and/or
cooling elements, filter racks or
chambers, sound attenuators, and
dampers. Air handlers usually connect to
ductwork that distributes the conditioned
air through the building, and returns it to
the AHU. Sometimes AHUs discharge
(supply) and admit (return) air directly to
and from the space served, without

COOLING TOWERS
A cooling tower is a heat rejection device, which extracts waste heat to the atmosphere
though the cooling of a water stream to a lower temperature
The heat from the water stream transferred to the air stream raises the air's temperature
and its relative humidity to 100%.
Evaporative heat rejection devices such as cooling towers are commonly used to provide
significantly lower water temperatures than achievable with "air cooled" or "dry" heat
rejection devices, like the radiator in a car, thereby achieving more cost-effective and
energy efficient operation of systems in need of cooling.

Resources
• A TEXTBOOK ON BUILDING SERVICES, R.UDAYAKUMAR

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