In this presentation, we delve into the fundamentals of condensers, exploring their various types and the principles governing their operation. From basic definitions to complex numerical analyses, this slide deck offers a comprehensive overview for students, engineers, and enthusiasts alike.

1. Welcome To
Heating, Ventilation, Air Conditioning
and Refrigeration Engineering
• Topic : Thermal Design of Refrigeration System
Components
Condenser
Cooling Tower
R.S. KOLHE
ME (HEAT POWER)
BE (MECHANICAL)

2. Thermal Design of Refrigeration System
Components
• Compressor : Characteristic curves of reciprocating & Centrifugal
compressors, sizing of reciprocating compressor
• Evaporator : Standards & Codes, Performance analysis of Dx
evaporator,
• Condenser: Standards & Codes, air-cooled condenser, shell & tube
condenser and evaporative condenser.
• Expansion Devices : Standards & Codes, Operating Characteristics,
Liquid Charge in the Sensing Bulb , Hunting of Thermostatic Expansion
Valve
• Cooling Tower: Types & design of cooling towers, cooling tower
thermal performance, tower Efficiency.

3. Introduction:
• The 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.
• The hot vapour refrigerant consists of the heat absorbed by the
evaporator and the heat of compression added by the mechanical energy
of the compressor motor.
• The heat from the hot vapour refrigerant in a condenser is removed first
by transferring it to the walls of the condenser tubes and then from the
tubes tothe condensing or cooling medium.
• The cooling medium may be air or water or a combination of the two.

4. Working of a Condenser

5. Factors Affecting the Condenser Capacity
• Material. Since the different materials have different abilities of heat
transfer, therefore the size of a condenser of a given capacity can be
varied by selecting the right material. It may noted that higher the ability
of a material to transfer heat, the smaller will be the size of condenser
• Amount of contact. The condenser capacity may be varied by controlling
the amount contact between the condenser surface and the condensing
medium. This can be done by varying the surface area of the condenser
and the rate of flow of the condensing medium over condenser surface.
• Temperature difference. The heat transfer capacity of a condenser
greatly depends upon the temperature difference between the
condensing medium and the vapour refrigerant. As temperature
difference increases, the heat transfer rate increases and therefore the
condenser capacity increases.

6. Heat Rejection Factor
• The load on the condenser per unit of refrigeration capacity is known
heat rejection factor.
• The load on the condenser (Qc) is given by

7. Classification of Condensers
• According to the condensing medium used, the condensers are
classified into the following three groups :
1. Air-cooled condensers,
2. Water-cooled condensers, and
3. Evaporative condensers.

8. Air-Cooled Condensers
• An air-cooled condenser is one in
which the removal of heat is done by
air. It consists steel or copper tubing
through which the refrigerant flows.
• The size of tube usually ranges from
6 mm to 18 mm outside diameter,
depending upon the size of
condenser. Generally copper tubes
are used because of its excellent heat
transfer ability.
• The condensers with steel tubes are
used in ammonia refrigerating
systems.

9. Types of Air-Cooled Condensers
• Natural convection air-cooled condensers.
• In natural convection air-cooled condenser, the heat
transfer from the condenser coils to the air is by natural
convection.
• As the air comes in contact with the warm condenser
tubes, it absorbs heat from the refrigerant and thus the
temperature of air increases. The warm air, being lighter,
rises up and the cold air from below rises to take away
the heat from the condenser.
• This cycle continues in natural convection air-cooled
condensers.
• Since the rate of heat transfer in natural convection
condenser is slower, therefore they require a larger
surface area as compared to forced convection
condensers.
• The natural convection air-cooled condensers are used
only in small-capacity applications such as domestic
refrigerators, freezers, water coolers and room air-
conditioners.
1. Natural convection air-cooled condensers
2. Forced convection air-cooled condensers

10. Forced convection air-cooled condensers
• In forced convection air-cooled
condensers. the fan (either
propeller or centrifugal) is used
to force the air over the
condenser coils to increase its
heat transfer capacity.
• The forced convection
condensers may be divided into
the following two groups:
• (a) Base mounted air-cooled
condensers, and
• (b) Remote air-cooled
condensers.

11. • The base mounted air-cooled condensers, using propeller fans, are
mounted on the same base of compressor, motor, receiver and other
controls. The entire arrangement is called as condensing unit.
• ln small units, the compressor is belt-driven from the motor and the fan
requires to force the air through the condenser is mounted on the shaft of
the motor. The use of this type of compressor for indoor units is limited up
to 3 kW capacity motor only. These condensing units are used on packaged
refrigeration systems of 10 tonnes or less.
• The remote air-cooled condensers are used on systems above 10 tonnes
and are available to 125 tonnes. The systems above 125 tonnes usually
have two or more condensers. These condensers may be horizontal or
vertical. They can be located either outside or inside the building

12. Water-Cooled Condensers
• A water-cooled condenser is one in which water is used as the
condensing medium.
• They always preferred where an adequate supply of clear inexpensive
water and means of water disposal available. These condensers are
commonly used in commercial and industrial refrigerating units.
• water-cooled condensers may use either of the following two water
systems :
1. Waste water system, or 2. Recirculated water system.

13. Water-cooled condenser using waste
water system.
Water-cooled condenser with recirculating
water system.

14. Types of Water-Cooled Condensers
1. Tube-in-tube or double-tube condensers
2. Shell and coil condensers
3. Shell and tube condensers.

15. Tube-in-tube or double-tube condensers
The tube-in-tube or double-tube condenser
consists of a water tube inside a large refrigerant
tube.
• In this type of condenser, the hot vapour
refrigerant enters at the top of the condenser.
• The water absorbs the heat from the
refrigerant and the condensed liquid
refrigerant flows at the bottom.
• Since the refrigerant tubes are exposed to
ambient air, therefore some of the heat is also
absorbed by ambient air by natural convection.
• Counter flow system.
• Parallel flow system.

16. Shell and coil condensers.
• A shell and coil condenser, consists of one or more water
coils enclosed in a welded steel shell.
• The shell and coil condenser may be either vertical or
horizontal.
• In this type of condenser, the hot vapour refrigerant enters
at the top of the shell and surrounds the water coils.
• As the vapour condenses, it drops to the bottom of the
shell which often serves as a receiver.
• Most vertical type shell and coil condensers use counter-
flow water system as it is more efficient than parallel-flow
water system.
• Since the water coils are enclosed in a welded steel shell,
therefore the mechanical cleaning of these coils is not
possible. The coils are cleaned with chemicals. The shell
and coil condensers are used for units up to 50 tonnes
capacity.

17. Shell and tube condensers
• The shell and tube condenser consists of a cylindrical
steel shell containing a number of straight water tubes.
The tubes are expanded into grooves in the tube sheet
holes to form a vapour tight fit. The tube sheets are
welded to the shell at both the ends.
• The removable water boxes are bolted to the tube
sheet at each end to facilitate cleaning of the
condenser. The intermediate supports are provided in
the shell to avoid sagging of the tubes.
• In this type of condenser, the hot vapour refrigerant
enters at the top of the shell and condenses as it comes
in contact with water tubes.
• The condensed liquid refrigerant drops to the bottom of
the shell which often serves as a receiver.

19. Evaporative Condensers
• The evaporative condensers, uses both air and
water as condensing mediums to condense the
hot vapour refrigerant to liquid refrigerant.
• These condensers perform the combined
functions of a water-cooled condenser and a
cooling tower.
• In its operation, the water is pumped from the
sump to a spray header and sprayed through
nozzles over the condenser coils through which
hot vapour refrigerant from the compressor is
passing.
• The heat transfers from the refrigerant through
the condensing tube walls and into the water. At
the same time, a fan draws air from the bottom
side of the condenser and discharged out at the
top of the condenser

20. Cooling Tower
• A cooling tower is an enclosed tower like structure through which atmospheric
air circulates cool large quantities of warm water by direct contact.
• A spray pond consists of a piping and spray nozzle arrangement suspended
over an outdoor open reservoir or pond. It can also cool large quantities of
warm water.
• The cooling towers and spray ponds, used for refrigeration and air-conditioning
systems, cool the warm water pumped from the water-cooled condensers.
• Then the warm water can be used again and again to cool the condenser.
• The principle of cooling the water in cooling towers and spray ponds is similar
to that of evaporative condensers, i.e. the warm water is cooled by means of
evaporation.

21. Capacity of Cooling Towers and Spray Ponds
The amount of evaporation of water, in turn, depends upon the
following factors :
1 The amount of water surface exposed to the air
2. The length of the exposure time
3. The velocity of air passing over the water droplets formed in cooling
towers, and
4. The wet bulb temperature of the atmospheric air

22. Types of Cooling Towers
• The cooling towers are mainly divided, according to their method of
air circulation, into the following two groups :
1. Natural draft cooling towers, and
2. Mechanical draft cooling towers.
• In natural draft cooling towers, the air circulates through the tower by
natural convection whereas in Mechanical draft cooling towers the air
is forced through the tower by mean fans blowers.

23. Natural Draft Cooling Towers
Atmospheric natural draft (spray type)
cooling towers:
• The atmospheric natural draft (spray
type) cooling tower, consists of a box-
shaped structure with louvers.
• The louvers allow the atmospheric air to
pass through the tower, but slant down
towards the inside of the tower to retain
water in it.
• The framework and louvers are usually
made of steel. The size of the cooling
tower depends upon the capacity of the
unit.
• The atmospheric natural draft (spray
type) cooling towers should be located in
the open space or on the roof of a
building where the air can blow freely
through them.

24. Natural Draft Cooling Tower.
• In this type of cooling tower, warm water
from the condenser is pumped to a spray
header provided at the top of a tower.
• It is sprayed down into the tower through
the nozzles . Since the heat transfer from
water from air is dependent upon the
surface of water exposed to the air stream,
therefore spray nozzle having finer spray
pattern is essential for good performance of
the cooling tower.
• It may be noted that the finer spray
exposes more water surface to air. However,
if the spray is too fine, too much water is
blown away.
• The water spray blown away by the air is
called drift.
• The drift increases water loss in the tower,
but does not affect the cooling action

25. Atmospheric Natural draft (splash deck type) cooling tower.
• The atmospheric natural draft (splash deck
type) cooling tower, is similar to a spray type
cooling tower except that it contains decking
(also called fill) made. from redwood hollow
tiles, ceramic, metal sheets or plastic.
• Many splash deck towers do not employ
nozzles.
• The water splashes on the decking from the
holes in the bottom of a water box on the top
of a tower, as shown in Fig.
• The objective of decking is to increase the rate
of heat transfer, by exposing a large amount of
wetted surface to the air.
• The decking also helps to break up the water
into small droplets and slows down the fall of
water to the bottom of tower.
• This type of cooling tower is 20 to 30 per cent
more efficient than the spray type for the same
size and same quantity

26. Mechanical Draft Cooling Towers
• The mechanical draft cooling towers are similar to atmospheric natural draft cooling towers
except that the fans are used to force the air through them.
• These towers may use either propeller or centrifugal fans.
• Advantages
1. The mechanical draft cooling towers are smaller in size than natural draft cooling tower of
the same capacity, because the large volume of forced air increases the cooling capacity.
2. The cooling capacity of mechanical draft cooling towers can be controlled by the amount
of forced air.
3. The mechanical draft cooling towers can be located inside the building because they do not
depend upon atmospheric air.
Disadvantages
1. The mechanical draft cooling towers require additional power to operate the fans.
2. The maintenance of fans, motors and controls increases the operating cost.
The mechanical draft cooling towers may be either forced draft
or induced draft

27. Forced Draft Cooling Towers
• In the forced draft cooling tower, a fan
forces the air through the tower.
• In its operation, the warm water from the
condenser is sprayed at the top of the
tower through the spray nozzles.
• The air is forced upward through the tower
by the propeller fan provided on the side
near the bottom of the tower as shown in
the figure.
• The condenser warm water is cooled by
means of evaporation .
• The effectiveness of the cooling tower may
be improved by increasing the height of the
tower, area of water surface exposed to air
or the velocity of air.
• The air velocities from 75 to 120 m/min is
recommende with a flow of 90 to 120 m3 I
min per tonne of refrigeration capacity

28. Forced Draft Cooling Towers

29. Induced Draft Cooling Towers
In the induced draft cooling tower, the fan sucks the air through the tower. The induced
draft cooling towers are similar to forced draft cooling towers except that the fans are
located at the top instead of at the bottom and draw the air upward through the tower.

30. Moist air is heated from 20oC to 65oC by hot water whose temperature
changes from 95oC to 75oC. Determine the true mean temperature
difference if the heat exchanger is of the following type: (a) pure
counterflow, (b) pure parallel flow, (c) average temperature difference

32. EXAMPLE 2: Determine the length of tubes in a two-pass 10 TR shell-and-
tube R22 water cooled condenser with 52 tubes arranged in thirteen
columns as shown in Figure . The heat rejection ratio is 1.2747. The
condensing temperature is 45oC. The water inlet and outlet temperatures
are 30oC and 35oC respectively. The tube inner and outer diameters are 14.0
and 16.0 mm respectively. The average properties of the refrigerant and
water are as follows:

39. References
1) REFRIGERATION AND AIR CONDITIONING BY R.S.KHURMI

40. Have a Good Day
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