Refrigeration and Air-conditioning

(Aeronautical Engineering, 8ANU2)

1.0 Introduction

Dr. Brajesh Tripathi

 1.0 Introduction
Introduction:
• Brief history and need of refrigeration and air conditioning,

• Methods of producing cooling,

• Ton of refrigeration,

• Coefficient of performance,

• Types and application of refrigeration and air condensing systems.

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 Introduction and General Terms
• Refrigeration is the removal of heat from a material or space, so that it’s
temperature is lower than that of it’s surroundings.
• When refrigerant absorbs the unwanted heat, this raises the refrigerant’s
temperature (“Saturation Temperature”) so that it changes from a liquid to a gas
it evaporates.
• The system then uses condensation to release the heat and change the
refrigerant back into a liquid. This is called “Latent Heat”.
• This cycle is based on the physical principle, that a liquid extracts heat from the
surrounding area as it expands (boils) into a gas.
• To accomplish this, the refrigerant is pumped through a closed-looped pipe
system.
• The closed-looped pipe system stops the refrigerant from becoming
contaminated and controls its stream.
• The refrigerant will be both a vapor and a liquid in the loop creating refrigeration
effect.
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 Introduction and General Terms
• “Saturation Temperature” – can be defined as the temperature of a liquid, vapor, or a
solid, where if any heat is added or removed, a change of state takes place.
• A change of state transfers a large amount of energy.

• At saturation temperature, materials are sensitive to additions or removal of heat.

• Water is an example of how saturation property of a material, can transfer a large

amount of heat.

• Refrigerants use the same principles as ice. For any given pressure, refrigerants have a
saturation temperature.

• If the pressure is low, the saturation temperature is low. If pressure is high, saturation
temperature is high.

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 Introduction and General Terms
“Latent Heat”- The heat required to change a liquid to a gas (or the heat that
must be removed from a gas to condense it to a liquid), without any change
in temperature.
• Heat is a form of energy that is transferred from one object to another
object.

• Heat Is a form of energy transferred by a difference in temperature.

• Heat transfer can occur, when there is a temperature difference between

two or more objects. Heat will only flow from a warm object to a colder
object.

• The heat transfer is greatest, when there is a large temperature

difference between two objects.
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 History of Refrigeration and…………
• The history of air conditioner started in the early days with the need to
preserve foods. Foods that are kept at room temperature spoil easily due
to the growth of bacteria.
• At temperature below 4°C (40°F), the growth of bacteria is reduced rapidly.
As a result of the development in food refrigeration, other applications that
follows include air conditioning, humidity control and manufacturing
processes.
• The discovery of the principles of the absorption type of refrigeration in
1824 showed that liquefied ammonia could chill air when it is allowed to
evaporate. Ice was created using compressor technology in the year 1842
by a physician named John Gorrie.
• The commercially available of air conditioning applications started based
on the need to cool air for industrial processes than for personal comfort.
The first electrical air conditioning was invented by Willis Haviland Carrier
in the year 1902. He was also known as the Father of Modern Air
Conditioning.
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 History of Refrigeration and…………
• His invention was designed to improve the manufacturing process of a printing
plant. By controlling the temperature and humidity of the plant, the processes
were made more efficient as the paper size and the ink alignment were
consistently maintained.
• The Carrier Air Conditioning Company of America was established by him to meet
the demand of better productivity in the workplace. Today, Carrier Corporation is
the biggest air conditioner manufacturer and marketing corporation in the world
in central air conditioning.
• The discovery of Freon in 1928 by Thomas Midgley, Jr., a safer refrigerant to
humans compared to the toxic and flammable gases such as ammonia, propane
and methyl chloride sparks the invention of air conditioning systems for
residential, industrial and commercial applications.
• Unfortunately, the use of CFC and HCFC refrigerants are causing the depletion of
ozone layer in our atmosphere that is causing harmful rays to penetrate our
earth. Newer ozone friendly refrigerants have been developed to replace
refrigerants such as R-11, R-12 and R-22 to name a few. Non-ozone depletion
refrigerant such as R-410a has been used in newer air conditioning systems.
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 History of Refrigeration and…………
• 1820 Ice was first artificially made as an experiment.
• 1824 Michael Faraday discovered the principles for the absorption type of refrigeration.
• 1834 Jacob Perkins invented the first artificial ice manufacturing machine which led to
our modern compression systems.
• 1902 Willis Haviland Carrier invented the first air conditioner to control the temperature
and humidity of a printing company, marking the first time effort taken to control the
temperature of the surroundings. This starts the history of air conditioning.
• 1906 Stuart W. Cramer come out with the term "Air Conditioning." which was later
adopted by Carrier.
• 1913 The first international refrigeration expo is held in Chicago.
• 1928 The discovery of Freon refrigerant by Thomas Midgley, Jr.
• 1930 The White House is air-conditioned.
• 1946 The demand for room air conditioners began to increase with more than 30,000
units produced on this year.
• 1953 Room air conditioners sale started commercially and achieved its milestone.
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 History of Refrigeration and…………
• 1953 The Refrigeration Equipment Manufacturers Association and The Air-Conditioning
and Refrigerating Machinery Association are formed.
• 1957 The first rotary compressor was developed hence making air conditioning units
smaller and more efficient compared to the reciprocating type.
• 1977 Heat Pumps equipment developed that allows cooling and heating cycle using the
same machine that can be used to provide cooling during summer and heating during
winter.
• 1987 Montreal Protocol signed to protect the earth's ozone layer is signed in Montreal,
Canada. The Protocol establishes international cooperation on the phase out of ozone
depleting substances, including the chlorofluorocarbon(CFC) refrigerants used in HVAC
equipment.
• 1990 Microprocessor control systems are used in all areas of refrigeration and air
conditioning due to the readily available semiconductor technology.
• 1992 The R-22 Alternative Refrigeration Evaluation Program (AREP) starts to find
alternative refrigerants to R-502 and R-22.
• 1995 Chloroflourocarbon (CFC) manufacturing in the USA ends on December 31.
• 1997 Kyoto Protocol signed to protect the earth's climate by reducing greenhouse gases
that cause climate change. AED, UD, RTU Kota 9
 Need of refrigeration and air conditioning
• Industrial air conditioning has been used for drying, humidity control, and dust
and smoke abatement. Its most familiar function is to provide a comfortable
working environment, to increase the comfort and productivity of personnel in
offices, commercial buildings, aircraft a/c and industrial plants.
• Air conditioning is the process of treating and distributing air to control
temperature, humidity, and air quality in selected areas.
• Refrigeration is the process of lowering the temperature of a substance below
that of its surroundings and includes production of chilled water for air
conditioning or process applications.
• Refrigeration systems are also used to provide chilled antifreeze solutions (brines)
at temperatures below the freezing point of water. Brines are used in ice making
and cold storage, in addition to a variety of chemical process applications.
• Chilled water may be used in air washers, either in closed coils or as spray water.
Chilled water may also be used for closed systems and for individual spray water
systems.
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 Methods of producing cooling
• For temperature and humidity control, air is moved over chilled or heated coils
and/or a spray of water at a controlled temperature.
• Direct water sprays also remove dust and odors. Other air cleaning systems may
include mechanical separation, adhesion, screening, filtration, or static attraction,
depending on the type of air contaminants encountered and the required air
quality.
• Many methods are used to produce and distribute chilled air. In central air
conditioning systems, air is passed over coils chilled by water, by brine, or by
direct expansion of a volatile refrigerant. The chilled air is then distributed
through ductwork.
• The water systems associated with air conditioning can be classified into three
general categories: open recirculating cooling, air washers, and closed or open
chilled water systems. In water treatment applications, open recirculating cooling
systems are similar to open chilled water systems.

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 Methods of producing cooling
• The basic mechanical components of an air conditioning system are the air and
water distribution systems, a refrigeration machine, and a heat rejection system.
Refrigeration for air conditioning is usually provided by either absorption or
compression cycles.
• Absorption refrigeration uses low-pressure steam or high-temperature hot water
as the energy source, water as the refrigerant, and lithium bromide or lithium
chloride as the absorbent.
• Compression refrigeration systems generally utilize a halocarbon compound or
ammonia as the refrigerant.
• An internal combustion engine, turbine, or electric motor supplies the power to
drive a centrifugal or positive displacement compressor.
• Refrigeration, or cooling, occurs when the liquid refrigerant absorbs heat by
evaporation, generally at low temperature and pressure. When the refrigerant
condenses, it releases heat to any available cooling medium, usually water or air.

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 Ton of refrigeration, coefficient of
performance
• Tons of refrigeration (TR): One ton of refrigeration is the amount of cooling obtained by one ton
of ice melting in one day: 3024 kCal/h, 12,000 Btu/h or 3.516 thermal kW.
• Net Refrigerating Capacity: A quantity defined as the mass flow rate of the evaporator water
multiplied by the difference in enthalpy of water entering and leaving the cooler, expressed in
kCal/h, tons of Refrigeration.
• kW/ton rating: Commonly referred to as efficiency, but actually power input to compressor
motor divided by tons of cooling produced, or kilowatts per ton (kW/ton). Lower kW/ton
indicates higher efficiency.
• Coefficient of Performance (COP): Chiller efficiency measured in Btu output (cooling) divided by
Btu input (electric power).
• Energy Efficiency Ratio (EER): Performance of smaller chillers and rooftop units is frequently
measured in EER rather than kW/ton. EER is calculated by dividing a chiller's cooling capacity (in
Btu/h) by its power input (in watts) at full-load conditions. The higher the EER, the more efficient
the unit. AED, UD, RTU Kota 13
Ton of refrigeration, coefficient of
performance

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 Types and application of refrigeration and air
conditioning systems
Air-Conditioning Systems
• Air Conditioning (for comfort / machine), Split air conditioners, Fan coil units in a
larger system, Air handling units in a larger system, evaporative cooling.
Refrigeration Systems
• Comfort air conditioning (20° – 25° C),
• Chilled water system (8° – 10° C),
• Brine system (sub-zero applications),
• Two principle types of refrigeration plants found in industrial use are: Vapour
Compression Refrigeration (VCR) and Vapour Absorption Refrigeration (VAR). VCR
uses mechanical energy as the driving force for refrigeration, while VAR uses
thermal energy as the driving force for refrigeration.

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 Refrigeration and Air-conditioning
(Aeronautical Engineering, 8ANU2)

1.0 Introduction……..ends

Next ………2.0 Refrigerants