Construction and working of various compressors Description of air & water cooled condensor, Comparison & application. Evaporative Condenser Expansion Devices Evaporators and chillers – Bare tube plate surface Capacity and their application, Chillers and their application.

1. Equipment Selection
(Refrigeration & Air Conditioning)
1
Mr. KONAL SINGHMr. KONAL SINGH
Director and Founder of
ProBotiZ Group, NagpurProBotiZ Group, Nagpur
(W) - Probotizgroup.com (M) - 8862098889, 9423632068 (E) - probotizinfo@gmail.com

2. Syllabus
• Construction and working of various
compressors
• Description of air & water cooled condensor,
Comparison & application. Evaporative
Condenser
• Expansion Devices
• Evaporators and chillers – Bare tube plate
surface Capacity and their application, Chillers
and their application.
2

3. Learning Objective
• Details of various Compressors, Condensors
Evaporators, Expansion valve their types and
Classifications

4. Classification of compressor

5. Reciprocating compressor
Reciprocating compressors
consist of a piston moving
back and forth in a cylinder,
with suction and discharge
valves to achieve suction
and compression of the
refrigerant vapor..
The suction side of the
compressor is connected to
the exit of the evaporator,
while the discharge side of
is connected to the

6. Reciprocating compressor
• The suction (inlet) and the discharge (outlet)
valves open and close due to pressure
differences between the cylinder and inlet or
outlet manifolds respectively.
• The pressure in the inlet manifold is equal to or
slightly less than the evaporator pressure.
Similarly the pressure in the outlet manifold is
equal to or slightly greater than the condenser
pressure.
• The valves used are of reed or plate type, which
are either floating or clamped.

7. Multiple vane type compressors
This type of compressor
does not require suction or
discharge valves, check
valves are used on
discharge side to prevent
reverse rotation during off-
time due to pressure
difference.

8. Multiple vane type compressors
• In these compressors, sealing is required
between the vanes and cylinder, between the
vanes and the slots on the rotor and between
the rotor and the end plate. However, since
pressure difference across each slot is only a
fraction of the total pressure difference, the
sealing is not as critical as in fixed vane type
compressor.

9. Rotary Screw Compressor

10. Rotary Screw Compressor
• The twin-screw type compressor consists of two
mating helically grooved rotors, one male and
the other female .
• The male rotor has lobes, while the female rotor
has flutes , flow is mainly in the axial direction.
Suction and compression take place as the
rotors unmesh and mesh. When one lobe-gully
combination begins to unmesh the opposite
lobe-gully combination begins to mesh.
• Discharge takes place at a point decided by the
designed built-in volume ratio

11. Rotary Screw Compressor
• As the rotor normally rotates at high speeds,
screw compressors can handle fairly large
amounts of refrigerant flow rates compared to
other positive displacement type compressors.
Screw compressors are available in the capacity
range of 70 to 4600 kW.

12. Scroll Compressor

13. Scroll Compressor
• Large suction and discharge ports reduce pressure
losses during suction and discharge
• Physical separation of suction and compression
reduce heat transfer to suction gas, leading to high
volumetric efficiency
• Volumetric efficiency is also high due to very low
re-expansion losses and continuous flow over a
wide range of operating conditions
• High compression efficiency, low noise and
vibration compared to reciprocating compressors
• Compact with minimum number of moving parts

14. rotary vane type compressors

15. Rotary vane type compressor
• Rotary vane type compressors have low mass-to-
displacement ratio, which in combination with
compact size makes them ideal for transport
applications.
• Both single-stage compressors with the cooling
capacity in the range of 2 to 40 kW are available
commercially. The cooling capacity is normally
controlled either by compressor speed regulation or
suction gas throttling. Currently, these compressors
are available for a wide range of refrigerants.

16. Classification

17. Evaporative Condenser

18. Evaporative Condenser
• steam flows through a set of gilled piping which is
bent backwards and forwards and placed in a
vertical place.
• Cooling water is sprayed from the top over the
pipes. As it drips from one pipe to the other, it
forms a thin film over the pipes.
• evaporates the water film resulting in condensing of
the steam flowing through the pipes.
• This condenser is very suitable when water is
expensive or a small quantity of pure water is
available.

19. Shell and Tube condenser

20. Shell and Tube condenser
• In these condensers the refrigerant flows through
the shell while water flows through the tubes in
single to four passes.
• The condensed refrigerant collects at the bottom
of the shell. The coldest water contacts the liquid
refrigerant so that some subcooling can also be
obtained.
• The liquid refrigerant is drained from the bottom
to the receiver.
• The shell also acts as a receiver. Further the
refrigerant also rejects heat to the surroundings

21. Central Flow type Condenser

22. Central Flow type Condenser
• Suction pipe of the air pump is located at the
centre of the tube nest. The condensate then
leaves at the bottom
• where the condensate extraction pump is
placed. In this type, the steam comes into close
contact with the whole periphery of the tubes. In
the inverted type, the air suction pump is at the
top.
• The steam flows upwards and then the
condensate returns to the bottom of the
• condenser by flowing near the outer surface.

23. Flooded type Evaporator

24. Flooded type Evaporator
• The refrigerant enters a surge drum through a
float type expansion valve. The compressor
directly draws the flash vapour formed during
expansion.
• This vapour does not take part in refrigeration The
liquid refrigerant enters the evaporator from the
bottom of the surge drum. This boils inside the
tubes as heat is absorbed.
• The mixture of liquid and vapour bubbles rises up
along the evaporator tubes. The vapour is
separated as it enters the surge drum.

25. Finned Evaporator

26. Finned Evaporator
• Various fin arrangements are use ,tubes with
individual spiral straight fins or crimpled fins
welded to it are used in some applications like
ammonia. Plate fins accommodating a number
of rows are used
• The liquid refrigerant enters from top through a
thermostatic expansion valve . This arrangement
makes the oil return to compressor better rather
than feeding refrigerant from the bottom of the
coil. When evaporator is close to the
compressor, a direct expansion coil is used

27. Finned Evaporator
• since the refrigerant lines are short, refrigerant
leakage will be less and pressure drop is small.
• If the air-cooling is required away from the
compressor, it is preferable to chill water and
pump it to air-cooling coil to reduce the
possibility of refrigerant leakage and excessive
refrigerant pressure drop, which reduces the
COP.

28. Automatic Expansion Valve

29. Automatic Expansion Valve
• 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.
force along with the force due to follow-up spring Ffs
controls the location of the needle with respect to the
orifice and thereby controls the orifice opening.
• When the compressor is started after the off-cycle
period, the evaporator pressure as a result the
needle stand moves downwards (away from the
needle stand) and the valve opens.

30. Automatic Expansion Valve
• When the refrigerant starts to enter the
evaporator, the evaporator pressure does not
decrease at the same fast rate as at starting
time. Thus, the movement of the needle stand
will slow down as the refrigerant starts entering.
As the needle moves downwards, the
adjustment spring elongates, therefore the force
decreases.
• The constant is sum of force due to spring force
and the atmospheric pressure, hence it depends
upon position of adjustment spring. This will be
the equilibrium position.
• Then onwards, the valve acts in such a manner
that the evaporator pressure remains constant

31. Summary
From this Chapter you all understand the…
• Components of VCRS
• Construction and working of various
compressors
• Description of air & water cooled condensor,
Comparison & application. Evaporative
Condenser
• Expansion Devices
• Evaporators and chillers – Bare tube plate
surface Capacity and their application, Chillers
and their application.
31

32. Referances
• Books: Khurmi and Gupta
• Book: Arrora and Domkundwar