Different Refrigeration Equipments

1. REFRIGERATION
EQUIPMENTS
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

2. GENERAL VAPOUR COMPRESSION
REFRIGERATION SYSTEM
3,5
3,5
3,5
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

3. REFRIGERANT COMPRESSORS
 A refrigerant compressor is a device used to
compress the vapour refrigerant from the
evaporator and to raise its pressure so that the
corresponding saturation temperature is higher
than that of the cooling medium . The purpose of
the compressor in a refrigeration system is to raise
the pressure of the refrigerant vapor from
evaporator pressure to condensing pressure.
 It also continuously circulates the refrigerant
through the system.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

4. CLASSIFICATION OF COMPRESSORS
 According to number of stages -
1) Single Stage
2) Double Stage
 According to location of prime mover –
1) Semi-Hermetic Compressors ( Motor and
Compressor in separate housings )
2) Hermetic Compressors (Motor and Compressor in
same housings )
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

5. CLASSIFICATION OF COMPRESSORS
 According to method of Compression -
1) Reciprocating Compressors
2) Rotary Compressors
3) Centrifugal Compressors
 According to number of working strokes –
1) Single Acting Compressors
2) Double Acting Compressors
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

6. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

7. RECIPROCATING COMPRESSOR
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

8. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

9. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

10. GENERAL VIEW OF A RECIPROCATING
COMPRESSOR
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11. SCROLL COMPRESSORS
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12. WORKING POSITIONS
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13. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

14. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

15. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

16. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

17. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

18. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

19. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

20. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

21. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

22. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

23. HERMETIC COMPRESSORS
 Compressor and motor operate on same shaft
 They eliminate the use of crankshaft seal , as
used in ordinary compressors
 Can operate on reciprocating and rotary
principle
 Used widely for small capacity systems such as
domestic refrigerators, home freezers and
window air conditioners
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

24. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

25. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

26. MULTISTAGE COMPRESSION
 The requirement of higher pressure of the
vapour refrigerant will increase the size of a
single stage compressor.
 The alternative is to employ a Compressor
having higher pressure ratio or compress the
refrigerant in two or three stages.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

27. TWO STAGE RECIPROCATING COMPRESSOR
WITH INTERCOOLER
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

28. ADVANTAGES OF MULTI-STAGE COMPRESSION
1.Improved Volumetric Efficiency
2.Size of both compressors may be adjusted to
suit the volume and pressure
3.Reduces leak loss
4.More uniform Torque
5.Effective lubrication
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

29. CONDENSERS
 Condenser is an important device used in the
high pressure side of a refrigeration system.
 Its function is to remove heat of the hot vapour
refrigerant discharged from the compressor.
 Heat from hot vapour refrigerant in a
condenser is removed first by transferring it to
the walls of condenser tubes and then from the
tubes to condensing or cooling medium
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

30. CLASSIFICATION OF CONDENSERS
 Air Cooled Condensers
 Water cooled Condensers
 Evaporative Condensers
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

31. AIR COOLED CONDENSERS
 Removal of heat is done by air
 Steel or copper tubing is employed
 Steel tubing is employed for Ammonia
Refrigerating systems
 They may have two or more rows of tubings
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

32. TYPES OF AIR COOLED CONDENSERS
 Natural Convection type –
1.Air comes in contact with warm condenser
tubes
2.It absorbs heat from the refrigerant and thus
the temperature of air increases.
3.The warm air being lighter rises up and the cold
air from below rises to take away the heat from
the condenser.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

33. TYPES OF AIR COOLED CONDENSERS
 Forced Convection type –
A Fan is used to force the air over the
condenser coils to increase its heat transfer
capacity.
Types – Base Mounted Air cooled Condensers
Remote Air cooled Condensers
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

34. AIR COOLED CONDENSERS
FORCED CONVECTION
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

35. AIR COOLED CONDENSERS
NATURAL CONVECTION
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

36. WATER COOLED CONDENSERS
 Water is used as a condensing medium
 Preferred when adequate supply of water is
available
 The water cooled condensers may use either of
the following two water systems –
1. Waste water systems
2. Recirculated water system
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

37. TYPES OF WATER COOLED CONDENSERS
 Tube-in-tube condensers (Double Pipe)
 Shell and coil condensers
 Shell and tube condensers
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

38. TUBE IN TUBE CONDENSERS
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39. TUBE IN TUBE CONDENSERS
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40. SHELL AND COIL CONDENSERS
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

41. Shell and Coil
Condenser
Shell Hot discharge gas from
compressor
Subcooled liquid from condenser
Cool water in
Warm water out
Water coil Droplets of condensed refrigerant
Bottom of shell acts as a
receiver
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

42. SHELL AND COIL CONDENSERS
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

43. SHELL AND TUBE CONDENSERS
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

44. EVAPORATIVE CONDENSERS
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

45. FACTORS AFFECTING CONDENSING CAPACITY
 Construction Material
Different materials have different heat transfer rates.
 Amount of Contact
Contact between condenser surface and condensing
medium
 Temperature Difference
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

46. COMPARISON BETWEEN AIR COOLED
CONDENSERS AND WATER COOLED
CONDENSERS
AIR COOLED CONDENSER WATER COOLED CONDENSER
1.Construction is very Simple, so Initial
cost is less
1.Construction is complicated,so Initial
cost is high
2.No handling problem 2.Difficult to handle
3.Do not require piping arrangement 3.Requires pipes to carry water
4.No disposal problem 4.Problem of disposal unless a
recirculation system is used.
5.No corrosion,so fouling effect is low 5.Fouling effects are high
6.Low heat transfer capacity due to low
thermal conductivity of air
6.High heat transfer capacity due to high
thermal conductivity of water
7.Used for low capacity plants (5 TR) 7.Used for high capacity plants
8.Distribution of air is not uniform 8.Uniform distribution of water
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

47. EXPANSION DEVICES
 An expansion device is another basic
component of a refrigeration system. The basic
functions of an expansion device used in
refrigeration systems are to:
 1. Reduce pressure from condenser pressure
to evaporator pressure, and
 2. Regulate the refrigerant flow from the high-
pressure liquid line into the evaporator at a rate
equal to the evaporation rate in the evaporator
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

48. CLASSIFICATION OF EXPANSION DEVICES
1. Fixed Opening type
Flow Area remains fixed
2. Variable Opening type
Area changes with changing mass
flow rates
There are basically seven types of Expansion
devices -
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

49. CLASSIFICATION OF EXPANSION DEVICES
1. Hand(Manual) Expansion Valves
2. Capillary Tubes
3. Orifice
4. Constant pressure or Automatic Expansion Valve (AEV)
5. Thermostatic Expansion Valve (TEV)
6.Float Type Expansion Valve
a) High side Float Valve
b) Low side Float Valve
7. Electronic Expansion Valve
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

50. CAPILLARY TUBE
 A capillary tube is a long, narrow tube of
constant diameter. The word “capillary” is a
misnomer since surface tension is not
important in refrigeration application of
capillary tubes. Typical tube diameters of
refrigerant capillary tubes range from 0.5 mm
to 3 mm and the length ranges from 1.0 m to 6
m.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

51. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

52. The pressure reduction in a capillary tube occurs due
to the following two factors:
 1. The refrigerant has to overcome the frictional
resistance offered by tube walls. This leads to some
pressure drop, and
 2. The liquid refrigerant flashes (evaporates) into
mixture of liquid and vapour as its pressure reduces.
The density of vapour is less than that of the liquid.
Hence, the average density of refrigerant decreases
as it flows in the tube. The mass flow rate and tube
diameter (hence area) being constant, the velocity of
refrigerant increases since m = ρVA. The increase in
velocity or acceleration of the refrigerant also requires
pressure drop
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

53. AUTOMATIC EXPANSION VALVE (AEV)
 An Automatic Expansion Valve (AEV) also known as a constant
pressure expansion valve acts in such a manner so as to
maintain a constant pressure and thereby a constant
temperature in the evaporator.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

54. APPLICATIONS OF AEV
The automatic expansion valves are used wherever
constant temperature is required, for example, milk
chilling units and water coolers where freezing is
disastrous. In air-conditioning systems it is used when
humidity control is by DX coil temperature. Automatic
expansion valves are simple in design and are
economical. These are also used in home freezers
and small commercial refrigeration systems where
hermetic compressors are used. Normally the usage is
limited to systems of less than 10 TR capacities with
critical charge.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

55. THERMOSTATIC EXPANSION VALVE (TEV)
Thermostatic expansion valve is the most
versatile expansion valve and is most
commonly used in refrigeration systems. A
thermostatic expansion valve maintains a
constant degree of superheat at the exit of
evaporator; hence it is most effective for dry
evaporators in preventing the slugging of the
compressors since it does not allow the liquid
refrigerant to enter the compressor
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

56. S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

57. FLOAT VALVE
Float type expansion valves are normally used with
flooded evaporators in large capacity refrigeration
systems. A float type valve opens or closes depending
upon the liquid level as sensed by a buoyant member,
called as float.
The float could take the form of a hollow metal or
plastic ball, a hollow cylinder or a pan. Thus the float
valve always maintains a constant liquid level in a
chamber called as float chamber. Depending upon the
location of the float chamber, a float type expansion
valve can be either a low-side float valve or a high-side
float valve.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

58. LOW SIDE FLOAT VALVES
 A low-side float valve maintains a constant liquid level
in a flooded evaporator or a float chamber attached to
the evaporator. When the load on the system
increases, more amount of refrigerant evaporates
from the evaporator.
 As a result, the refrigerant liquid level in the
evaporator or the low-side float chamber drops
momentarily. The float then moves in such a way that
the valve opening is increased and more amount of
refrigerant flows into the evaporator to take care of
the increased load and the liquid level is restored.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

59. LOW SIDE FLOAT VALVES
 The reverse process occurs when the load falls,
i.e., the float reduces the opening of the valve
and less amount of refrigerant flows into the
evaporator to match the reduced load.
 These valves are normally used in large
capacity systems and normally a by-pass line
with a hand-operated expansion is installed to
ensure system operation in the event of float
failure.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

60. HIGH SIDE FLOAT VALVES
 A high-side float valve maintains the liquid level
constant in a float chamber that is connected to the
condenser on the high pressure side. When the load
increases, more amount of refrigerant evaporates and
condenses. As a result, the liquid level in the float
chamber rises momentarily. The float then opens the
valve more to allow a higher amount of refrigerant flow
to cater to the increased load, as a result the liquid
level drops back to the original level. The reverse
happens when the load drops.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

61. HIGH SIDE FLOAT VALVES
 Since a high-side float valve allows only a fixed
amount of refrigerant on the high pressure
side, the bulk of the refrigerant is stored in the
low-pressure side (evaporator). Hence there is
a possibility of flooding of evaporator followed
by compressor slugging. However, unlike low
side float valves, a high-side float valve can be
used with both flooded as well as direct
expansion type evaporators.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

62. HIGH SIDE FLOAT VALVES
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63. ELECTRONIC TYPE EXPANSION VALVE
in
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64. EVAPORATORS
 An evaporator, like condenser is also a heat
exchanger. In an evaporator, the refrigerant
boils or evaporates and in doing so absorbs
heat from the substance being refrigerated.
The name evaporator refers to the evaporation
process occurring in the heat exchanger.
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

65. CLASSIFICATION OF EVAPORATORS
 Forced Convection
 Natural Convection
 Dry and Flooded Evaporators
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon

66. FLOODED TYPE EVAPORATOR
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67. SHELL AND TUBE EVAPORATOR
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68. SHELL AND COIL EVAPORATOR
S.A.Wani, Department of Mechanical Engg., P.V.P.I.T.Budhgaon