basic civil and mechanical engin

1. UNIT - V
REFRIGERATION ,AIR CONDITIONING
AND PUMPS

2. SYLLABUS

3. I - REFRIGERATION
• The American society of Refrigeration
Engineers defines “Refrigeration as the
process of removing heat continuously from a
body to reduce its temperature lower than
that of its surrounding atmosphere and
maintain it by continuously absorbing the
heat.”

4. • Refrigerator :
– It is an equipment used for producing and maintaining
the temperature in a closed space below the
surrounding atmospheric temperature.
• Refrigerant :
– Refrigerant is the working fluid in the refrigerator. It
has low boiling temperature so it evaporates at low
temperature than normal atmospheric temperature
and absorbs the heat from the surroundings.
– The refrigerant continuously absorbs the heat from
the space inside the refrigerator to keep it cool at a
temperature less than the atmospheric temperature.
Finally it rejects the heat to the atmosphere. The
space inside the refrigerator is called Refrigeration
space. The principle of refrigeration is simple it uses
the evaporation of a fluid to absorb heat.

5. • Refrigerator :
– EXAMPLE :
– You might have experienced that when you put water
on your skin , it makes you feel cool. As the water
evaporates , it absorbs the heat from the body and
creates the cool feeling. Such that when you rub
alcohol or petrol in your skin you feel even cooler. The
reason is that petrol or alcohol evaporates at a lower
temperature.
– Similary the refrigerant evaporates i.e., changes from
liquid to vapour state at a very low temperature.
Therefore it creates freezing temperature inside the
refrigerated space. All substance has the ability to
absorb heat but the refrigerant absorbs heat quickly
and in large quantities.
• Second law of thermodynamics :
– It states that “Heat flows from a system at a lower
temperature to a system at a higher temperature
with the aid of external work”

6. Properties of refrigerant :
• Low boiling point
• Low freezing point
• High latent heat of evaporation
• High coefficient of performance
• Low viscosity
• Low specific volume
• Non- explosive
• Resistance to electricity
• Good chemical stability
• Odourless and colourless
• Inflammable
• Non toxic
• Non corrosiveness

7. commonly used refrigerants :
• Ammonia (NH3) :
– It has high latent heat so produces high refrigeration effect.
– It has low specific volume.
– It is used in ice manufacturing and cold storage plants
– It is toxic and inflammable, thus not used in domestic refrigerators and air conditioners
• Freon -12 :
– It is colourless, odorless and non – irritative to human body.
– It non toxic , non – inflammable , non – corrosive to metals and non- explosive.
– It does not affect the stored food products.
– It is used in domestic refrigerators , water coolers and air conditioners etc
• Freon – 22 :
– It is superior to freon – 12 in many aspects
– It is colourless, odorless and non – irritative to human body
– It non toxic , non – inflammable , non – corrosive to metals and non- explosive.
– It does not affect the stored food products.
– It is used in food freezing and air conditioners in large capacity plants.
• Carbondioxide (CO2)
– It is colourless, odorless, non toxic , non – inflammable , non – corrosive and non- explosive
– It is used in marine refrigerators.
• Sulphur di- oxide (SO2)
– It reacts with water to form sulphuric acid, which is corrosive to metals
– It was used in small tonnage of refrigerators in the earlier years
• Air
– It is used in air craft where C.O.P ie., efficiency of operation is secondary.

8. Terminology
• Refrigerating effect :
– Refrigeration effect is defined as the rate at which the heat is removed from
the space to be cooled in a cycle. It is expressed in KJ/ second or KW.
• Ton of refrigeration :
– It is also called as capacity of refrigerator , it is defined as the rate at which
heat can be absorbed from the cold body. It expressed in Ton of refrigeration.
• Unit of refrigeration :
– Unit of refrigeration is expressed in terms of Ton of refrigeration. A Ton of
refrigeration is the amount of heat absorbed to produce 1 tonne of ice at 0⁰C
within 24 hours when the initial condition of water is also at 0⁰C. The value of
1 tonne of refrigeration is 3.5 KJ/second or 3.5 KW in S.I Units. Air conditioners
are also specified by the same unit TR
• Co-efficient of performance : (C.O.P)
– The performance of the refrigeration system is measured by the co- efficient
of performance (C.O.P). it is defined as the ratio of amount of heat removed in
a system to the external work done upon the working medium to achieve the
heat removal.
– There fore , C.O.P = Q/W
Q – heat removed from the refrigerator in KW
W – work done upon the working medium in KW

9. Types of Refrigeration System
1. Vapour compression refrigeration system
2. Vapour absorption refrigeration system

10. Vapour compression refrigeration system

11. Vapour compression refrigeration system

12. Vapour absorption refrigeration system

13. LAYOUT OF TYPICAL DOMESTIC REFRIGERATOR:

14. AIR CONDITIONING

21. PUMPS

22. PUMPS
• Definition :
• A hydraulic pump is a mechanical device which converts mechanical energy in to
hydraulic energy.
• Here the hydraulic energy refers to the potential and kinetic energy of a liquid.
• USES OF PUMP:
• The two broad application of pump are given below:
• Pump is used to transport liquid in fluid transport systems
– Transport of water from water reservoir (well or river)to house/industries
using pipe lines
– Transport of petroleum oil/gas from one country to another through oil/gas
pipe lines.
• Pump is used to develop pressure in fluid power system
– Manufacturing industry(hydraulic operated m/c’s)
– Automobile industry( hydraulic breaks, power steering etc)
– Agricultural industry(hydraulic driven farm equipments)
– Naval industries(cargo handling ,winches etc)
– Aviation and aerospace industry(landing gears,missilelauncing)
– Mechatronics field(spindle drives , feed drives,auto tool clamping and work
clamping)
– Material handling field(lift trucks,elevators,trucks& rams)
– Construction field(earth moving equipments)
– And many more industrial applications

23. CLASSIFICATION OF PUMPS:
• According to the design and principle of operation ,pumps can be broadly
classified in to
– Positive displacement pump, and
– Non-positive displacement pumps.

24. CLASSIFICATION OF PUMPS:
• Positive displacement pumps :
– Positive displacement pumps are those which uses the
reciprocating motion exerted on the fluid and move the
fluid from lower pressure to higher pressure.
– The main principle involved in these types of pump is
conversion of mechanical energy in to pressure energy
by exerting thrust on the fluui through reciprocating
motion.
– (eg : reciprocating pumps)
• Non-positive displacement pumps:
– It is other wise called as roto dynamic pumps.
– Roto dynamic pumps are those which uses centrifugal
force acting on the fluid and move the fluid from lower
pressure to higher pressure
– The main principle involved in this type of pumps are
conversion of mechanical energy in to pressure
energyby the application of centrifugal force of the fluid.
– Eg : centrifugal pump

25. SPECIFACTION OF PUMP:
• Horse power
• Flow rate
• Outlet pressure head
• Inlet suction head

26. CENTRIFUGAL PUMP
• Centrifugal pump are the devices which
convert the mechanical energy in to hydraulic
energy by means of centrifugal force acting
on the fluid acting on the liquid

27. Classification of centrifugal pump:
• Based on the shape and type of casing
– Volute or spiral
– Vortex or whirl pool
– Volute casing with guide blades
• Based on the working head
– Low head(upto 15m)
– Medium head (15m to 40m)
– High head (over 40m)
• Based on the relative direction of flow through impellers
– Radial flow
– Axial flow
– Mixed flow
• Based on number of stages
– Single stage
– Multistage

28. CENTRIFUGAL PUMP

29. CASINGS
• VOLUTE CASING
• VORTEX CASING
• VOLUTE CASING WITH GUIDE BALDES

30. MULTISTAGE CENTRIFUGAL PUMP
Multistage pump for high head
Multistage pump for larger
delivery

31. RECIPROCATING PUMP ( SINGLE ACTING)

32. RECIPROCATING PUMP ( DOUBLE ACTING)