1. Refrigeration Components
CHAPTER
Refrigeration Components 14
Instructor Name: (Your Name)

2. Learning Objectives
Describe the purpose of the compressor, condenser, metering valve, and evaporator.
Explain the construction of the compressor, condenser, metering valve, and evaporator.
Illustrate the operation of service valves and Schrader valves.
Describe the purpose and construction of a vibrasorber.

3. Learning Objectives (continued)
Demonstrate the operation of a thermostatic expansion valve.
Explain the superheat setting of the TXV.
Describe the mounting location of a sensing bulb.
Determine the superheat setting of the TXV.
Explain the purpose of the distributor.
Describe the purpose of the receiver tank.

4. Learning Objectives (continued)
Compare the drier materials and explain the purpose of the filter dryer.
Describe the purpose and operation of the heat exchanger
Describe the purpose and operation of the accumulator.
Explain the purpose of pressure regulating devices.
Describe the purpose and operation of the different types of refrigerant safety valves.

5. The Four Basic Component
The Compressor
The Condenser
The Metering Device
The Evaporator
Refrigerant, the fifth basic component

6. Four Cylinder Compressor

7. The Compressor
Pumps refrigerant through the system
Pressurizes the vapor refrigerant
Raises the temperature of the refrigerant
Draws a very low suction pressure
High discharge and low suction pressures help control the boiling of the refrigerant

8. Compressor Operation
Refrigerant passes through suction throttling valve (if equipped) into compressor crankcase.
Piston moves down cylinder, refrigerant is drawn in through suction reed valve.
Piston moves upward, refrigerant compresses to 50:1 ratio.
Compressed vapor exits through the discharge valve plate to discharge manifold.

9. Compressor Cycle

10. Service Valves
Located on compressor suction and discharge ports
Allows service manifold connection
Can isolate the compressor for service or repairs
Back seated- isolates service port
Mid seat- opens service ports
Front seat- isolates compressor from system

11. Service Valves

12. CAUTION
Care must be taken to NEVER front seat the discharge service valve while the compressor is operating. Even thought the high pressure cut-out switch might be positioned below the valve, it would not operate fast enough to prevent major damage to the compressor and prevent possible personal injury.

13. Schrader Service Valves

14. Vibrasorbers Flexible suction and discharge lines
Positioned at the compressor
Prevent engine and compressor vibrations from reaching the copper piping of the refrigerant system
There are two types of vibrasorbers
Typical discharge vibrasorbers are made up of bellows shaped stainless steel center and a covering of braided stainless steel wire
Typical suction vibrasorber made up of reinforced fabric covered hoses, often using replaceable mechanical fittings

15. Vibrasorbers

16. Condenser
Located outside of controlled space
Releases heat from controlled space to outside air
Consists of copper tubing running through aluminum cooling fins
Refrigerant changes state from a high pressure hot vapor to high pressure cooler liquid

17. Condenser

18. Receiver Tank
Acts as storage tank for refrigerant
Usually contains one or two sight glasses
Usually have inlet and outlet service valve
Refrigerant can be isolated between receiver and compressor for downstream service

19. Receiver Tank

20. Filter Dryer
Filters and dries refrigerant
Located in liquid line between receiver outlet and TXV
May be between compressor and condenser
May be between evaporator and compressor
Three different materials commonly used
Silica Gel
Activated Alumina
Molecular Sieve

21. Filter Dryer

22. Moisture Indicator

23. Heat Exchanger
Located in liquid line between receiver and TXV or outlet of evaporator
Two important functions:
Subcools liquid refrigerant before TXV
Evaporates any liquid refrigerant before it reaches the compressor

24. Heat Exchanger

25. Thermal Expansion Valve
Division between high and low side of system
Modulates the flow of refrigerant to the evaporator
Monitors evaporator outlet temperature
Internal or external equalization

26. Thermal Expansion Valve

27. Thermal Expansion Valve Operation
Sensing bulb pressure applied to one side of the diaphragm tries to open valve against spring pressure.
Evaporator outlet or compressor suction pressure applied to the opposite side of the diaphragm helps to make the valve responsive to compressor suction pressure.
Spring pressure, which is applied to the needle assembly and diaphragm on the evaporator side, constantly tries to close the valve.

28. Determining Superheat
Determine the suction pressure at the compressor suction service valve.
Using a refrigerant pressure temperature chart, determine the saturation temperature at the observed pressure.
Measure the temperature of the suction gas at the evaporator outlet.
Subtract the saturated temperature read from the chart in Step 2 from the temperature measured in Step 3. The difference between the two is the superheat of the suction gas returning to the compressor.

29. TXV Sensing Bulb
TXV sensing bulb regulates the flow of refrigerant to the evaporator
Bulb is normally filled with same refrigerant used in the system
Charge can be vapor or liquid
Some are designed to control the maximum opening pressure of the TXV to prevent compressor slugging
Sensing bulb must have good mechanical connection with the evaporator outlet

30. TXV Sensing Bulb (continued)
Sensing bulb must be positioned on the suction line so it can monitor actual vapor or line temperature, follow manufacturers recommendations
If mounted at 6 o’clock, refrigerant oil can provided insulation from true vapor temperature
If mounted at 12 o’clock bulb would be in direct contact with line possibly causing incorrect sensing of vapor temperature

31. Distributor Tube
Distributor and header are located between the TXV outlet and evaporator inlet
Divides the refrigerant flow into several routes to the evaporator for greater efficiency
Equipped with a passage so that during the heating and defrost cycle, hot gas is pumped into the evaporator, bypassing the TXV

32. Evaporator Receives boiling refrigerant from the distributor
As refrigerant boils it absorbs heat through the cooling fins which cools the air as it passes through them
Refrigerant boils because of the pressure of the refrigerant is significantly lowered by the TXV
Moist air can freeze on the fins reducing efficiency, a defrost cycle is needed to prevent this
Most evaporators are constructed of copper tubing swedged into aluminum fins.
Tubing configuration and number of tubes determine the BTU rating of evaporator

33. Evaporator

34. Accumulator
Separates liquid refrigerant from vaporous refrigerant before entering the compressor
When system is operating intermittently or as heat pump, large quantities of liquid refrigerant can pass through suction line and enter the compressor
Liquid refrigerant can cause broken pistons, bent connecting rods, broken valves, blown head gaskets, and damaged bearings
Accumulator normally has the capacity to hold the entire refrigerant charge to prevent compressor damage

35. Accumulator

36. Accumulator Operation
Liquid and vapor enter accumulator and drop to the bottom
Vapor returns through “U” shaped tube to compressor
As vapor passes “U” tube it picks up liquid refrigerant and oil through metering hole in bottom of “U” tube
To prevent to much liquid refrigerant from returning to compressor an anti-siphon hole is placed at the top of the “U” tube
To aid in the evaporation process of the accumulator a device to heat the shell of the may be added

37. Evaporator Pressure Regulator
Evaporator pressure regulator controls evaporator pressure regardless of compressor suction pressure
The pressure setting is that which is equal to 30 to 32 degrees Fahrenheit inside the evaporator coil
Oil by pass line between the base of the evaporator to the compressor suction is required
This type of valve not used in many application because many cargos require the evaporator to reach very low pressures in order to obtain low box temperatures

38. Suction Pressure Regulator
Designed to limit crankcase suction pressure during heat and defrost cycle or startup
During startup when evaporator and crankcase pressures are high, valve is closed
When the crankcase internal suction pressure is below the set point of the valve, it begins to open and lower evaporator pressure
As the pressure of the evaporator is lowered the valve setting, it opens still more

39. Suction Pressure Regulator (continued)
During defrost/heat cycle high pressure vapor is pumped from compressor to the distributor and evaporator, suction pressure rises.
High pressure overcomes spring pressure in the valve and closes the inlet cutting off inlet flow of refrigerant
The restriction caused by the valve provides needed restriction for compressor to pump against during heat/defrost cycle

40. Suction Pressure Regulator (continued)
This process causes compressor to pump high-pressure (temperature) refrigerant to evaporator for heating/defrost cycle
Suction pressure regulators do not totally restrict refrigerant flow, they do not require oil bypass line
These valves are adjustable by increasing or decrease spring pressure

41. Pressure Regulating Devices

42. Safety Valves
Most refrigeration units with more than 1 pound of refrigerant are equipped with a pressure relieving safety device
Prevent possible explosion by relieving pressure caused by fire, coil blockage, or overheating of unit
2 types currently used, spring loaded and fusible metal plug
Spring loaded type has spring loaded piston that excessive refrigerant pressure must overcome and vent through an exhaust port passage

43. Safety Valves (continued)
Piston type may have slight refrigerant leak after venting but should reseal itself
Fusible metal plug work on temperature only, usually 200 to 22 degree Fahrenheit or about 415 to 450 psi
The core material is designed to melt away, allowing refrigerant to escape
Once a fusible plug releases pressure they must be replaced

44. Safety Valves
Fusible Plug
Spring-loaded Piston

45. Summary
There are four main components used in a refrigeration system
There are many other components that improve the efficiency of the system but not necessary
From the compressor superheated refrigerant passes service valves through the vibrasorber
Vibrasorbers isolates system from vibration caused by engine and compressor

46. Summary (continued)
Refrigerant then enters the condenser and gives up heat to ambient air
Refrigerant cools in the condenser and condenses from gas to liquid
Liquid refrigerant then enters the receiver where it is stored until needed
Refrigerant leaves receiver and passes through the filter dryer which removes moisture and contaminants
Refrigerant enters the heat exchanger which further removes heat from liquid refrigerant

47. Summary (continued)
Refrigerant enters TXV and is metered to the distributor and then evaporator
TXV balances inlet flow to outlet temperature and pressure of refrigerant so it all has time to change state from liquid to a gas before exiting evaporator
Refrigerant then enters the accumulator if system is equipped
Accumulator separates vapor to prevent liquid from entering the compressor

48. Summary (continued)
Refrigerant flows from accumulator through suction line, through suction vibrasorber, through suction service valve, then through suction pressure regulator if equipped
Regulator controls the load placed on the engine or electric motor
Refrigerant flows out suction pressure regulator into suction side of compressor
The refrigerant is then compressed and starts the journey again