Different types of expansion device used in refrigerator - tharmal II - 116010319119

Thermal engineering - 2

1. Different types of Expansion Device used in
refrigerator
Guide By:
Mr Y. A. Sakpal Prepared By:
Patel Satish
116010319119
A. Y. Dadabhai Technical Institute
Department of
Mechanical Engineering
THERMAL ENGINEERING - II (3351902)

2. A. Y. DADABHAI TECHNICAL INSTITUTEA. Y. DADABHAI TECHNICAL INSTITUTE
CERTIFICATE
This is to certify that Mr. Patel Satish M. of A.Y. Dadabhai Technical Institute form Mechanical
Engineering Department, Enrollment No. 116010319119 Studies in 5
th
semester has satisfactorily
complete term work in the term ending in October-November 2016, in partial fulfillment of
requirement for the diploma mechanical engineering of the Gujarat Technological university (GTU)
__________________
Guide

3. 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

4. Expansion device used in refrigeration system between
condenser and evaporator.

5. •Hand operated valve
•low-side float
•High-side float
•Automatic expansion valve
•Thermostatic expansion valve
•Electronic expansion valve
•Capillary tube
•Solenoid valve
Types of Expansion Device

6. Hand operated valve

7. 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.

8. low-side float

9. Working
•The low-pressure float valve controls the liquid level, and is
normally mounted in a chamber parallel to the liquid/vapour
separator.
•For thermo siphon 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.

10. High-side float

11. Working
•Floats on the high-pressure liquid and the needle forms a
constriction
•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.

12. Automatic expansion valve

13.  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 pushes to close the
valve
Turning the adjustment screw into the valve
increases the spring pressure
Automatic Expansion Valve:

14. The pressure P1 in element acts to open the valve.
The evaporator pressure P2 of the power element
tending to close the valve.
The pressore P3 of superheat spring also assist in
closing action.
Now, if the power element P1 is greater than the
combined pressureof P2 & P3, the valve will open.
Operation of Automatic expansion valve:

15. To maintain a constant pressure and temperature.
Make sure the evaporator is fully charging the refrigerant.
Used in an Refrigerator to change the pressure of the
refrigerant.
Reduces the high pressure in the liquid line to low
pressure in the evaporator.
Functions of Automatic exp. valve :

16. Diaphragm
Needle and Seat
Spring
Liquid refrigerant from
condenser or receiver
Saturated refrigerant to the
evaporator
Evaporator pressure
Spring pressure

17. Thermostatic expansion valve

18. THERMOSTATIC EXPANSION VALVE (TXV)
•Maintains a constant evaporator superheat
•If the evaporator superheat is high, the valve
will open
•Superheat ensures that no liquid refrigerant
leaves the evaporator
•Low superheat increases the net refrigerant
effect

19. Thermostatic
Expansion Valve
Evaporator
Direction of Refrigerant
Flow
Liquid Line
Transmission Line
Thermal Bulb

20. TXV COMPONENTS
•Valve body
•Diaphragm
•Needle and seat
•Spring
•Adjustment and packing gland
•Sensing bulb and transmission tube

21. Electronic expansion valve

22. Working
•Uses a small motor to control the valve port
•Valve port controls evaporator superheat
•Temperature sensor sends a signal to the controller
•The controller sends a signal to the motor
•The motor turns a fraction of a rotation for each controller
signal

23. Capillary tube

24. •Fixed restriction type device.
•Simple and no moving part.
•Low cost
•Pressure drop developed due to:
1.Friction
2.Acceleration

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

26. Solenoid Valve

27. Working
•When the solenoid coil is electrically energized, it produces a
magnetic field that attracts iron and many of its alloys.
•An iron armature or plunger is drawn up into the core of the
solenoid.
•A stem and pin or poppet attached to this plunger opens the valve
port.
•When the solenoid valve is de-energized, the plunger falls, and the
poppet closes the valve port.