types of expansion devices ,evaporators and condensers

1. ASSSIGNMENT-1
NAME-BHASKAR KANDPAL
ROLLNO-170620141
SUBJECT-RAC(REFRIGERTION AND AIR CONDITIONING))
BATCH AND BRANCH-BTECH AND MECHANICAL
SUBMITTED TO
MANDEEP KAUR MAM

2. CONTENT.
1. CONDENSER & ITS CLASSIFICATIONS.(4-19)
2. EXPANSION DEVICES & ITS TYPES.(20-42)
3. EVAPORATOR & ITS TYPES.(43-59)

3. CONDENSERS
&
ITS TYPES

4. CONDENSER
It is a device used in the high pressure side of a
referigeration system.
FUNCTION
1.The purpose of the condenser in the refrigeration system is to remove
heat from the refrigerant vapor leaving the compressor (or generator in
case of absorption system) so that the refrigerant will condense to its
liquid state.
2. This liquid refrigerant will then be able to achieve the refrigerating effect
in the evaporator.

5. Working of a Condenser
1.First of all,the superheated vapour is
cooled to saturation temperature (called
desuperheating)corresponding to the
pressure of the refrigerant.This is shown by
line 2-3 is fig(b).The desuperheating
occurs in the discharge line and in the first
few coils of the condenser.
2.Now the saturated vpour refrigerant gives
up its latent heat and is condensed to a
saturated liquid refrigernt.This process,
called condensation,is shown y the line 3-4.
3.The temperature of the liquid refrigerant
is reduced below its saturation
temperature(i.e. subcooled) in order to
increase the refrigeration effect. This
process is shown by the line 4-5.

6. Classification of Condensers
 1. Air-cooled Condensers
a. Natural convection air-cooled condensers
b. Forced convection air-cooled condensers
 2. Water-Cooled Condensers
a. Tube-in-tube or double-tube condensers
b. Shell and coil condensers
c. Shell and tube condensers
 3. Evaporative Condensers

7. Air Cooled Condensers.
The Condenser uses air as cooling medium to
condense refrigerant is called as Air Cooled
Condenser.
Air is used as fluid for cooling purpose i.e.
refrigerant rejects heat to air flowing over a
condenser.
Further Classifications:
A. Natural Convection Type:
 The finned type condensers are mounted either below
the refrigerator at an angle or on the backside of the
refrigerator.
 In case, it is mounted below, then the warm air rises
up and to assist it an air envelope is formed by
providing a jacket on backside of the refrigerator.
The fin spacing is kept large to minimize the effect of
fouling by dust and to allow air to flow freely with
little resistance.

8.  A thin wires are welded to the serpentine/helical tube coil. The wires act
like fins for increased heat transfer area.
Wire-and-tube type condenser commonly used in domestic
refrigerators. Hence these condensers are used for small capacity
refrigeration systems like household refrigerators and freezers.
ADVANTAGES: No fan used to air flow.
DISADVANTAGES: Natural convection is a slow process.
APPLICATION:Domestic refrigerator , Air conditioner.

9. Air Cooled Condensers
B. Forced Convection Type:
In forced convection type
condensers, the circulation of air over
the condenser surface is maintained by
using a fan or a blower.
 These condensers are normally uses fins
on air- side for good heat transfer. The
fins can be either plate type or annular
type.
 Forced convection type condensers
are commonly used in window,air
conditioners, water coolers &
pacakged air conditioning plants.

10. ADVANTAGES
Increases heat transfer capacity.
DISADVANTAGES
Require high power fan to force the air.
It is power consuming as well as noisy.
APPLICATION
Condensing of steam in large power plant.

11. ADVANTAGES & DISADVANTAGES
OF AIR COOLED CONDENSERS
ADVANTGES
1. Air cooled condensers are
simple in operation.
2. They are smaller in size.
3. Required maintenance of air
cooled condensers is low.
4. Cleaning process is easy
5. Installation cost is
comparatively less.
6. Design of air cooled condensers
are less complex.
7. This type of condensers is more
flexible to use.
DISADVANTAGES
1. Air cooled condensers required
more power to run.
2. It is not suitable for long
duration period.
3. The cooling effect is not so
high.
4. It does not supply the required
cooling in a short time.

12. APPLICATIONS
1. Biomass power plants.
2. Gas-fired power plants.
3. Waste incineration plants.
4. Oil-fired power plants.

13. A. Double Type Tube-or In-Tube type:
 Double pipe condensers are normally used
up to 10 TR capacity.
 The cold water flows through the inner
tube.Refrigerant flows through the annulus
in counter flow.
 Headers are used at both the ends to make
the length of the condenser small and
reduce pressure drop.
 The refrigerant in the annulus rejects a
part of its heat to the surroundings by free
convection and radiation.
 The heat transfer coefficient is usually low
because of poor liquid refrigerant
drainage if the tubes are long.
Water Cooled Condensers
It uses water as a cooling medium it may be
recirculated or fresh water depends upon availability.

14. B. Shell and coil type
 These condensers are used in systems
up to 50 TR capacity.
 The water flows through multiple coils,
which may have fins to increase the
heat transfer coefficient. The refrigerant
flows through the shell.
In smaller capacity condensers,
refrigerant flows through coils while
water flows through the shell.
When water flows through the coils,
cleaning is done by circulating suitable
chemicals through the coils.
Water Cooled Condensers

15. Water Cooled Condenser.
C. Shell-and-tube type:
 Used in systems from 2 TR upto
thousands of TR capacity.
 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 liquid refrigerant is drained from
the bottom to the receiver.

16.  A vent connecting the receiver to the condenser for smooth drainage of
liquid refrigerant.
 The most common type is horizontal shell type.
 Vertical shell-and-tube type condensers are usually used with ammonia
in large capacity systems so that cleaning of the tubes is possible from
top while the plant is running.

17. ADVANTAGES & DISADVANTAGES
OF WATER COOLED CONDENSERS
ADVANTGES
1. Water cooled condensers have a
high rate of heat transfer.
2. Overall operation is less
expensive.
3. Water cooled condensers are
used for large capacity plants.
4. It produces less noise.
5. The size of the compressor is
less.
6. Water cooled condensers can
operate at low condensing
temperature.
DISADVANTAGES
1. Installations cost is more.
2. It required more maintenance.
3. Operating the water-cooled
conde.nser is not easy.
4. It is not so flexible to use
everywhere.
5.It required an additional
recirculation system for used
water.
6.Water cooled condenser parts
undergo to corrosion effect.

18. Evaporative Condenser

19.  The heat transfer coefficient for evaporative cooling is very large and
can be operated at low condensing temperatures (about 11 to 13 K
above the wet bulb temperature of air).
 The role of air is primarily to increase the rate of evaporation of water.
 The required air flow rates are in the range of 350 to 500 m /h per TR
of refrigeration capacity

20. ADVANTAGES & DISADVANTAGES
OF EVAPORATIVE CONDENSERS
ADVANTGES
1. Simple in design.
2. Low initial cost.
3. Low quantity cooling water
required.
4. Small capacity cooling water
pump.
5. Low operating cost.
DISADVANTAGES
1. Vacuum maintained is less.
2. Due to less vacuum work done
per kg of steam is less.
3. Not suitable for medium and
large power plant.
4. Needs regular maintenance.
5.This types of condenser can be
used only for medium sized
refrigeration plant.

21. Expansion Device
&
Its Types

22. Expansion valve is the term usually used in industry for any device
that meters or regulates the flow of liquid refrigerant to an evaporator the
expansion device performs the following functions :
•To reduce the pressure of liquid refrigerant coming from the condenser.
•To maintain the desire pressure difference between the high pressure and
low pressure sides of the system.
•Capacity expansion devices are used to maintain the desired rate of flow and
the pressure drop two the system.
•To control the flow of refrigerant according to variation of load on the
evaporator.
Expansion device
It also known as metering device or throttling device is an important
device that divides the high pressure side and the low pressure side of a
refrigeration system.

23.  TYPES OF EXPANSION DEVICES
1. CapillaryTubes
2. Hand(manual) operated expansion valve.
3. Constant pressure or Automatic ExpansionValve(AEV)
4. Thermostatic ExpansionValve(TEV
5. Float type ExpansionValve
a) High Side FloatValve
b) Low Side FloatValve

24. Capillary tube
A capillary tube is a long, narrow
tube diameter. of constant.
The refrigerant has to overcome
the frictional resistance offered by
tube walls.This leads to some
pressure drop.

25. Working
1.Controls refrigerant flow by the pressure drop across it
2.Diameter and length of the tube determine flow at a given
pressure.
3.Does not maintain evaporator pressure or superheat .
4.Used when the load is relatively constant.
5.No moving parts to wear out.
6.Capillary tube systems are critically charged.
7.All refrigerant in the system circulates at all times when the
system is running.
8.Capillary tube sometimes fastened to the suction line for heat
exchange.
9.Responds very slowly to system load changes.

26.  Advantages and disadvantages :-
o It is inexpensive.
o It does not have any moving parts hence it does not require
maintenance .
o It cannot adjust itself to changing flow conditions in response to daily
and seasonal variation in ambient temperature and load.
o It is susceptible o clogging because of narrow bore of the tube.
o It cant operated efficicency at other condition.

27. HAND OPERATED EXPANSION VALVE
 A manual valve expansion is that it makes
no automatic adjustments in accordance
with changes in system of coolingload.
 It must be opened or closed manually each
time you change the load on the system.
Equipment operator must be on hand at
each change of the load on the system.
When automatic control isrequired.
 They are called as Throttle vlves.

28. Working
•
•
Hand operated valve illustrates the main means by which the refrigerant is
measured through all adjustable devices of the account. This manual
valve. The speed of the refrigerant flow through the valve is determined by
three things: the size of the valve orifice or opening, pressure difference
through the hole, and as far valve is open. Zoom in on any of these three
factors, the increase in the flow, while the decline in any will reduce the
flow.
To illustrate how this metering device matches the capacity to boot the
system, let's assume that we have air conditioning for cooling small
amount area which is being used air-cooled condenser. He uses hand-
expansion valve as the measuring device. When the thermal load on the
air conditioning system is low (say 50% of the rated load), valve manually
adjusted up to half of the window. This setting allows the refrigerant to
enter the evaporator at a rate that produces slightly superheated gas from
the evaporator.

29.  It is a device which work automatically.
 When the evaporator pressure drops, the valve opens.
 The spring pressure pushes to open the valve.
 The evaporator pressure pshes to close the valve.
 Turning the adjustment screw int the valve increases the
spring pressure.
Automatic Expansion Valve

30.  Automatic expansion valve
 This works in response to the pressure changes in the evaporator due
to increase in load( pressure increase) or due to decrease in load
(pressure decreases).
 This valve maintains a constant pressure throughout the varying
load on the evaporator controlling the quantity of refrigerant
flowing into Evaporator.
 The automatic expansion valve opens and closes to either increaseor
decrease the amount of refrigerant feeding into the evaporator in
response to the pressure of the refrigerant in the evaporator.

32.  Application of automatic expansion
valve:-
 The automatic expansion valves are used wherever constant
temperature is required, for example, milk chilling units and
water coolers .
 These are also used in home freezers and small commercial
refrigeration systems where hermetic compressors are used.

33. Thermostatic Expansion Valve.
• Thermostatic expansion valve controls
the flow of refrigerant through the
evaporator I such a way that the quality
of the vapour leaving the evaporator will
always in superheated condition.
• Its operation is used for maintaining a
constant degree of superheat at the
evaporator outlet.

34. • Maintain a constant evaporator superheat.
• If the evaporator superheat is high, the
valve will open.
• Superheat ensures that noliquid refrigerant
leaves the evaporator.
• Low superheat increases the net refrigerant
effect.

35. Thermostatic expansion valve

36.  Advantages and disadvantages
 It provides excellent control of refrigeration capacity as the supply of
refrigerant to the evaporator matches the demand.
 It ensures that the evaporator operates efficiently by preventing
starving under high load conditions .
 It protects the compressor from slugging by ensuring a minimum
degree of superheat under all conditions of load, if properly selected
 The feeler bulb must always be in good thermal
contact with the refrigerant tube.
 TEV cannot be used since very small extent of superheating.

37.  Float type expansion valves
 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.
 It is actuated by a float that is immeresed in the liquid
refrigerant.
 Both low side float and high side float are used to control the
flow of liquid refrigerant.

38.  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 or decreases.

40. Working
• The low-pressure float valve controls the liquid level, & is
normally mounted in a chamber parallel to the liquid/vapour
separator.
• For thermosiphon systems, this modifies the effect of the
force of gravity, which drives the refrigerant into the
evaporator. If the level of refrigerant in the separator
increases, the valve will close and vice versa. Balance is
maintained when the refrigerant flow into the evaporator is
equal to the vapour flow from the evaporator.
• For forced circulation systems, the circulation pump will
control the degree of evaporation.

41. High-side float valves
In the this type float chamber is placed on the
high pressure side between the condenser
and the evaporator.
The refrigerant condensed in the condenser
moves to the float valve. As the level of the
refrigerant rises the float ball moves up and
opens the float valve that allows for the
passage of the refrigerant through needle
valve.
The level of the refrigerant coming from the
condenser reduces when there is less load on
the plant. When the level of the refrigerant
drops down thus reducing the flow of the
refrigerant through it.

43. Working
• Floats on the high pressure liquid and the needle forms a
construction.
• The float chamber is in open connection with the condenser,
and the condensed refrigerant enters the chamber
continuously. When the liquid level increases, the needle
opens the flow to the evaporator.

44. EVAPORATOR.
&
ITS TYPES

45. Evaporation
 Evaporation is a unit operation that consists of the
elimination of water of a fluid food by means of vaporization
or boiling
 Evaporation is theremoval of solvent asavapor froma
solution orslurry.
 Evaporation is used forconcentration of aqueous solutions,
it involves removal of water from solution by boiling the
liquor in suitable vessel called evaporator and withdrawing
thevapor

46. Evaporator
Vaporout
Feed in
Steam in
(Saturatedvapor)
Condensateout
(Saturated
Liquid)
Productout
Vapor
Separator
HeatExchanger
Vaccum fornon
condensable
Condensor
unit
CoolantIn
Coolantout

47. FACTORS AFFECTING THE HEAT TRANSFER
CAPACITY OF AN EVAPORATOR
 MATERIAL
 TEMPERATURE DIFFERENCE
 VELOCITY OF REFRIGERENT
 THICKNESS OF THE EVAPORATOR COIL WALL
 CONTACT OF SURFACE AREA

48. APPLICATIONS
EVAPORATORS ARE USED IN WIDE RANGE OF PROCESS
INDUSTRIES, PAPER AND PULP ONDUSTRIES, WINERY,
 BEVERGARES, FOOD PRESERVATION, ICE PLANTS,
CHEMICAL, POLYMERS AND RESINS, INORGANIC SALTS,
ACIDES AND VERITY OF OTHER MATERIALS

49. TYPES OF EVAPORATORS
 According to type of construction
1. Bare tube coil evaporator
2. Finned tube evaporator
3. Plate evaporator
4. Shell and tube evaporator
5. Shell and coil evaporator
6. Tube in tube evaporator
 According to the manner in which liquid refrigerant is fed
1. Flooded evaporator
2. Dry expansion evaporator

50.  According to the mode of heat transfer
1. Natural convection evaporator
2. Forced convection evaporator
 According to operating condition
1. Frosting evaporator
2. Non-frosting evaporator
3. Defrosting evaporator

51. Bare tube coil evaporator
•Prime surface evaporator.
•Easy to clean and defrost.
•Surface contact area is less.
•Limited applications.
FINNED TUBE EVAPORATOR
•Over the bare tube metal fins
are fastened.
•Shape, size, spacing can be
adapted for better rate of heat
transfer.
•Extended surface evaporators.

52. PLATE EVAPORATOR
•The bare coils are either welded
on the plate or between the two
plates which are welded together
•Used in household refrigerators,
beverage cooler, ice cream
cabinets
SHELL AND TUBE EVAPORATOR
•Contraction is same as shell and tube
type of condenser
•Available in flooded as well as dry
expansion type
•Baffle plates are provided for good
turbulence of liquid
•Capacity 2TR to 250TR

53. SHELL AND COIL EVAPORATOR
•Generally dry expansion
evaporators for chilling water
•Used for small capacity
2TR to 10TR
•Restricted to operate above 5
degree calicoes to prevent
freezing problems
TUBE IN TUBE EVAPORATOR
•Double tube evaporator
•Refrigerant can flow in outer pipe and
liquid to be cooled can flow in inner
pipe
•The flow of refrigerant can be
parallel or counter

54. • A flooded evaporator is completely filled with
liquid refrigerant, and the level of the refrigerant is
maintained in an accumulator by a float-valve.
• Evaporators are connected in parallel to the
accumulator.
• One pipe from the bottom of the vessel supplies
liquid refrigerant.
• The return pipe containing liquid refrigerant and
vapour enters the vessel near the top.
• The liquid pipe containing liquid refrigerant and
vapour enters the vessel near the top.
 

56. • The disadvantage of the flooded evaporator is
that it requires a considerable charge of
refrigerant and is bulky.
• The main advantage is that the inside of the
pipes are completely wetted with refrigerant
and this produces a very high rate of heat
transfer.
• 

57.  Dry expansion evaporators are so called because
liquid refrigerant enters the evaporator by an
expansion valve and vaporizes by the time it
reaches the end of the evaporator coil.
 There is always at least 20% vapor present within
the evaporator pipe work.
 The amount of liquid present in dry expansion
evaporators will depend upon the fixture load.
 At light load conditions, the amount of liquid will
be small, and in high load conditions, the amount
of liquid will be large.
 The larger the wetted surface, the greater the
efficiency.

59. •Low velocity and min. hydration is
require
•Velocity of air depends upon temp.
difference
•Circulation of air around coil
depends upon its size shape and
location
•The coil should occupy 2/3rd of width
of the path & 3/4th the length of the
box
FORCED CONVECTION
EVAPORATORS
•Air is forced over refrigerant coils
•Fins are provided to increase heat
transfer rate
•More efficient than natural
convection evaporators
•Require less cooling surface and high
evaporator pressure can be used which
save power input to the compressor

60. NON-FROSTING EVAPORATORS
•Operates above 0°C therefore
frost does not forms on
evaporators
•Temp. close to cooling 0.6°C to 1°C
•RH from 75-80 % in the cabinet
•This keeps the food fresh & stops
shrinking in weight
FROSTING EVAPORATORS
•Operates below 0°C
•The frost forms on the evaporator
comes from the moisture of the air
•Cooling efficiency is decreases
until the ice and frost is removed

61. DEFROSTING EVAPORATORS
•Frost creates on the coils on the
coils when the compressor is
running & melts after the
compressor shuts off
•Temp. of about -7°C to -6°C
•It also keeps high RH of about
90% to 95%

62. THANKYOU
MAM