Presentation on expansion devices.Mechanical Engineering,Refrigration and air conditioning topic.. JOIN US FOR MORE..!

1. SEMINAR PRESENTATION
ON
EXPANSION DEVICES
SUBMITTED
By- NAME

2.  CONTENT:-
 INTRODUCTION
 TYPE OF EXPANSION DEVICE
 DESCRIPTION
 FUNCTION IN REFRIGERATION CYCLE
 ADVANTAGES AND DISADVANTAGES
 APPLICATION AND FUNCTION OF EXPANSION DEVICES
 CONCLUSION

3.  INTRODUCTION :-
The basic functions of an expansion device used in refrigeration systems
are……..
 Reduce pressure from condenser pressure to evaporator pressure.
 The control functions which may involve the supply of liquid to the
evaporator at the rate at which it is evaporated.This determines the
efficiency with which evaporator surface is utilized.
 It controls the mass floe rate of refrigerant according to the load on the
evaporator.
 Decrease the pressure and temperature of flowing refrigerant .

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

5. Description
 Not use one flow control, or metering, of the
refrigerant is accomplished by use of a
temperature sensing bulb, filled with a similar gas
as in the system, that causes the valve to open
against the spring pressure in the valve body as
the temperature on the bulb increases. As the
suction line temperature decreases, so does the
pressure in the bulb and therefore on the spring
causing the valve to close. An air conditioning
system with a TX valve is often more efficient
than other designs that do

6. Function in Refrigeration Cycle
 Expansion valves are flow-restricting devices that
cause a pressure drop of the working fluid. The
valve needle remains open during steady state
operation. The size of the opening or the position
of the needle is related to the pressure and
temperature of the evaporator. There are three
main parts of the expansion valve that regulate
the position of the needle. A sensor bulb, at the
end of the evaporator, monitors the temperature
change of the evaporator. This change in
temperature creates a change in pressure on the
diaphragm……FOR EX..-
 if the temperature in the evaporator increases,
the pressure in the diaphragm increases causing
the needle to lower

7.  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 increase or
decrease the amount of refrigerant feeding into the evaporator in
response to the pressure of the refrigerant in the evaporator.

9.  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.

10.  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.

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

12.  Thermostatic Expansion Valve
(TEV) :-
• 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.

14.  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

15.  Electronic Type Expansion Valve :-
 An electronic expansion valve consists of an orifice and a needle in front
it.
 The needle moves up and down in response to magnitude of current in
the heating element. If the refrigerant will superheat the resistance
offered by heat element will be less so it increases the mass flow rate of
refrigerant. If less then it will decrease the mass flow rate of refrigerant.

17.  An expansion valve is used to control the superheat of the refrigerant
exiting the evaporator and is designed to maintain a set superheat in
normal operating conditions.
 It reduces the high pressure liquid refrigerant to low pressure liquid
refrigerant .
 It control the flow of refrigerant according to the load .
 Expansion devices available to suit many different domestic,
commercial and light industrial refrigeration and air conditioning
applications.
 Advantages and function of expansion
devices :-

18.  Hand operated expansion valve :-
 A manual valve expansion is that it makes no automatic adjustments
in accordance with changes in system of cooling load.
 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 is required,.

20.  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.
 Float type expansion valves :-

21.  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.

23.  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.

25. Thank you for
your attention…!!!