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CHAPTER. Refrigeration Components. 14. Instructor Name: (Your Name ). Learning Objectives. Describe the purpose of the compressor, condenser, metering valve, and evaporator. Explain the construction of the compressor, condenser, metering valve, and evaporator. - PowerPoint PPT Presentation
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Copyright © 2014 Delmar, Cengage Learning
Refrigeration Components
Instructor Name: (Your Name)
14CHAPTER
Copyright © 2014 Delmar, Cengage Learning
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.
Copyright © 2014 Delmar, Cengage Learning
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.
Copyright © 2014 Delmar, Cengage Learning
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.
Copyright © 2014 Delmar, Cengage Learning
The Four Basic Component
The Compressor The Condenser The Metering Device The Evaporator Refrigerant, the fifth basic component
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Four Cylinder Compressor
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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
Copyright © 2014 Delmar, Cengage Learning
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.
Copyright © 2014 Delmar, Cengage Learning
Compressor Cycle
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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
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Service Valves
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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.
Copyright © 2014 Delmar, Cengage Learning
Schrader Service Valves
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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
Copyright © 2014 Delmar, Cengage Learning
Vibrasorbers
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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
Copyright © 2014 Delmar, Cengage Learning
Condenser
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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
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Receiver Tank
Copyright © 2014 Delmar, Cengage Learning
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
1. Silica Gel2. Activated Alumina3. Molecular Sieve
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Filter Dryer
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Moisture Indicator
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Heat Exchanger
Located in liquid line between receiver and TXV or outlet of evaporator
Two important functions:1. Subcools liquid refrigerant before TXV2. Evaporates any liquid refrigerant before it
reaches the compressor
Copyright © 2014 Delmar, Cengage Learning
Heat Exchanger
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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
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Thermal Expansion Valve
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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.
Copyright © 2014 Delmar, Cengage Learning
Determining Superheat1. Determine the suction pressure at the compressor
suction service valve.2. Using a refrigerant pressure temperature chart,
determine the saturation temperature at the observed pressure.
3. Measure the temperature of the suction gas at the evaporator outlet.
4. 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.
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
Evaporator
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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
Copyright © 2014 Delmar, Cengage Learning
Accumulator
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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
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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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
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Pressure Regulating Devices
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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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
Safety Valves
Spring-loaded Piston
Fusible Plug
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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
Copyright © 2014 Delmar, Cengage Learning
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