Refrigeration Components - PowerPoint Presentation

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Refrigeration Components

Instructor Name: (Your Name)

14

CHAPTERSlide2

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.Slide3

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.Slide4

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.Slide5

The Four Basic Component

The CompressorThe CondenserThe Metering Device

The EvaporatorRefrigerant, the fifth basic componentSlide6

Four Cylinder CompressorSlide7

The Compressor

Pumps refrigerant through the systemPressurizes the vapor refrigerantRaises the temperature of the refrigerant

Draws a very low suction pressureHigh discharge and low suction pressures help control the boiling of the refrigerantSlide8

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.Slide9

Compressor CycleSlide10

Service Valves

Located on compressor suction and discharge portsAllows service manifold connectionCan isolate the compressor for service or repairs

Back seated- isolates service portMid seat- opens service portsFront seat- isolates compressor from systemSlide11

Service ValvesSlide12

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.Slide13

Schrader Service ValvesSlide14

Vibrasorbers

Flexible suction and discharge linesPositioned at the compressorPrevent engine and compressor vibrations from reaching the copper piping of the refrigerant systemThere are two types of vibrasorbers

Typical discharge vibrasorbers are made up of bellows shaped stainless steel center and a covering of braided stainless steel wireTypical suction vibrasorber made up of reinforced fabric covered hoses, often using replaceable mechanical fittingsSlide15

VibrasorbersSlide16

Condenser

Located outside of controlled spaceReleases heat from controlled space to outside airConsists of copper tubing running through aluminum cooling fins

Refrigerant changes state from a high pressure hot vapor to high pressure cooler liquidSlide17

Condenser Slide18

Receiver Tank

Acts as storage tank for refrigerantUsually contains one or two sight glassesUsually have inlet and outlet service valve

Refrigerant can be isolated between receiver and compressor for downstream serviceSlide19

Receiver TankSlide20

Filter Dryer

Filters and dries refrigerantLocated in liquid line between receiver outlet and TXV

May be between compressor and condenserMay be between evaporator and compressorThree different materials commonly used

Silica Gel

Activated AluminaMolecular SieveSlide21

Filter DryerSlide22

Moisture IndicatorSlide23

Heat Exchanger

Located in liquid line between receiver and TXV or outlet of evaporatorTwo

important functions:

Subcools liquid refrigerant before TXVEvaporates any liquid refrigerant before it reaches the compressorSlide24

Heat ExchangerSlide25

Thermal Expansion Valve

Division between high and low side of systemModulates the flow of refrigerant to the evaporator

Monitors evaporator outlet temperatureInternal or external equalizationSlide26

Thermal Expansion ValveSlide27

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.Slide28

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.Slide29

TXV Sensing Bulb

TXV sensing bulb regulates the flow of refrigerant to the evaporatorBulb is normally filled with same refrigerant used in the systemCharge can be vapor or liquid

Some are designed to control the maximum opening pressure of the TXV to prevent compressor sluggingSensing bulb must have good mechanical connection with the evaporator outletSlide30

TXV Sensing Bulb (

continued)Sensing bulb must be positioned on the suction line so it can monitor actual vapor or line temperature, follow manufacturers recommendationsIf 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 temperatureSlide31

Distributor Tube

Distributor and header are located between the TXV outlet and evaporator inletDivides the refrigerant flow into several routes to the evaporator for greater efficiencyEquipped with a passage so that during the heating and defrost cycle, hot gas is pumped into the evaporator, bypassing the TXVSlide32

Evaporator

Receives boiling refrigerant from the distributorAs 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 TXVMoist 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 evaporatorSlide33

EvaporatorSlide34

Accumulator

Separates liquid refrigerant from vaporous refrigerant before entering the compressorWhen 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 bearingsAccumulator normally has the capacity to hold the entire refrigerant charge to prevent compressor damageSlide35

AccumulatorSlide36

Accumulator Operation

Liquid and vapor enter accumulator and drop to the bottomVapor returns through “U” shaped tube to compressorAs 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 addedSlide37

Evaporator Pressure Regulator

Evaporator pressure regulator controls evaporator pressure regardless of compressor suction pressureThe 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 requiredThis 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 temperaturesSlide38

Suction Pressure Regulator

Designed to limit crankcase suction pressure during heat and defrost cycle or startupDuring 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 pressureAs the pressure of the evaporator is lowered the valve setting, it opens still moreSlide39

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 cycleSlide40

Suction Pressure Regulator (continued)

This process causes compressor to pump high-pressure (temperature) refrigerant to evaporator for heating/defrost cycleSuction pressure regulators do not totally restrict refrigerant flow, they do not require oil bypass line

These valves are adjustable by increasing or decrease spring pressureSlide41

Pressure Regulating DevicesSlide42

Safety Valves

Most refrigeration units with more than 1 pound of refrigerant are equipped with a pressure relieving safety devicePrevent possible explosion by relieving pressure caused by fire, coil blockage, or overheating of unit

2 types currently used, spring loaded and fusible metal plugSpring loaded type has spring loaded piston that excessive refrigerant pressure must overcome and vent through an exhaust port passageSlide43

Safety Valves (continued)

Piston type may have slight refrigerant leak after venting but should reseal itselfFusible 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 escapeOnce a fusible plug releases pressure they must be replacedSlide44

Safety Valves

Spring-loaded Piston

Fusible PlugSlide45

Summary

There are four main components used in a refrigeration systemThere are many other components that improve the efficiency of the system but not necessaryFrom the compressor superheated refrigerant passes service valves through the vibrasorber

Vibrasorbers isolates system from vibration caused by engine and compressorSlide46

Summary (continued)

Refrigerant then enters the condenser and gives up heat to ambient airRefrigerant cools in the condenser and condenses from gas to liquid

Liquid refrigerant then enters the receiver where it is stored until neededRefrigerant leaves receiver and passes through the filter dryer which removes moisture and contaminants

Refrigerant enters the heat exchanger which further removes heat from liquid refrigerantSlide47

Summary (continued)

Refrigerant enters TXV and is metered to the distributor and then evaporatorTXV 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 equippedAccumulator separates vapor to prevent liquid from entering the compressorSlide48

Summary (continued)

Refrigerant flows from accumulator through suction line, through suction vibrasorber, through suction service valve, then through suction pressure regulator if equippedRegulator controls the load placed on the engine or electric motor

Refrigerant flows out suction pressure regulator into suction side of compressorThe refrigerant is then compressed and starts the journey again