This document discusses refrigeration and air conditioning. It describes how refrigeration cools products or spaces below the surrounding temperature, while air conditioning controls temperature, moisture, cleanliness, odor, and air circulation for occupants or processes. Common applications are listed such as room air conditioners, refrigerators, evaporative coolers, and commercial refrigeration/air conditioning. The document then focuses on evaporative cooling systems, automotive air conditioners, refrigerants used, and criteria for selecting refrigerants including thermodynamic properties, environmental impact, and safety.
2. The Process of achieving and maintaining the
temperature below that of the surroundings, the aim
being to cool some product or space to required
temperature.
It refers to the treatment of air so as to
simultaneously control its temperature, moisture
content , cleanliness, odour and circulation as
required by occupant, a process or product in the
space.
Refrigeration
Air conditioning
3. • Domestic Air Conditioners
• Domestic Refrigerator
• Automotive Air Conditioners
• Evaporative Coolers
• Water Coolers
• Commercial Refrigeration- Diary, Cold
Storage, Ice plant
• Commercial Air Conditioning – Multiplex,
Hospitals
Applications
10. • ∈ =
(𝑡0− 𝑡 𝑠)
𝑡0− 𝑡0 ,𝑤𝑏𝑡
• Where,
• 𝑡0 = Initial Temperature of air
• 𝑡 𝑠 = Temperature of supply (product) air
• 𝑡0 ,𝑤𝑏𝑡 = Wet bulb temperature of initial atm.
air
Effectiveness of Direct Evaporative Cooling
System
18. Condenser
• The Condenser is designed to radiate heat.
• Its location is usually in front of the radiator.
• As hot compressed gasses are introduced into the top of the
Condenser, they’re cooled off. As the gas cools, it condenses and
exits the bottom of the Condenser as a high pressure liquid.
21. • Located inside the vehicle
• Evaporator serves as the heat absorption
component
• Refrigerant enters the bottom of the Evaporator
as a low pressure liquid
• The warm air passing through the Evaporator
fins causes the refrigerant to boil (refrigerants
have very low boiling points). As the refrigerant
begins to boil, it can absorb large amounts of
heat.
Evaporator
27. Provide Refrigeration by undergoing phase change
process in the evaporator
• Used for transporting thermal energy from one
location to other
• Do not undergo phase change
• E.g.: Solutions of water and ethylene glycol,
Propylene glycol or calcium chloride
Primary Refrigerants
Secondary Refrigerants (brines)
29. • Thermodynamic and Thermo-physical
properties
• Environmental and Safety properties
• Economics
Refrigerant Selection Criteria
30. • Suction Pressure: At a given evaporator
temperature, Saturation pressure should be
above atmospheric for prevention of air or
moisture ingress into the system and ease of
leak detection. Smaller compressor
displacement.
• Discharge Pressure: At a given condenser
temperature, discharge pressure should be as
small as possible to allow light-weight
construction of compressor, condenser
Thermodynamic and thermo-physical
properties
31. • Pressure Ratio: Should be as small as possible for
high volumetric efficiency and low power
consumption
• Latent heat of vaporization: Should be as large as
possible so that required mass flow rate per unit
cooling capacity will be small.
• Liquid specific heat: Should be small so that degree
of subcooling will be large
• Vapour specific heat: Should be large so that the
degree of superheating will be small
Thermodynamic and thermo-physical properties
32. • Thermal conductivity: Should be high for higher
heat transfer coefficients
• Viscosity: Should be small for smaller frictional
pressure drops
Thermodynamic and thermo-physical
properties
33. • Ozone Depletion Potential (ODP): According to
Montreal protocol, the ODP of refrigerants
should be zero. ODP depends mainly on the
presence of chlorine or bromine in the
molecules.
• R11, R12 – Non zero ODP- Phase out
• Global warming potential (GWP):Refrigerant
should have as low as GWP.
• R134a – Zero ODP but high value of GWP
Environmental and safety properties
34. • Total equivalent warming index (TEWI):TEWI considers
both direct (due to release into atmosphere) and indirect
(through energy consumption) contributions of
refrigerants to global warming. It should be low
• Toxicity: Refrigerants used in a refrigeration system
should be non toxic.
• Flammability
Environmental and safety properties
