Refrigeration Components

CHAPTER

14

Refrigeration

Components

Instructor Name: (Your Name)

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.


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.


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.


The Four Basic Component



The Compressor



The Condenser



The Metering Device



The Evaporator



Refrigerant, the fifth basic component


Four Cylinder Compressor


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


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.


Compressor Cycle


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


Service Valves


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.


Schrader Service Valves


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


Vibrasorbers


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


Condenser


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


Receiver Tank


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 Gel

2. Activated Alumina

3. Molecular Sieve


Filter Dryer


Moisture Indicator


Heat Exchanger



Located in liquid line between receiver and

TXV or outlet of evaporator



Two important functions:

1. Subcools liquid refrigerant before TXV

2. Evaporates any liquid refrigerant before it reaches the compressor


Heat Exchanger


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


Thermal Expansion Valve


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.


Determining Superheat

1. 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.


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


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


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


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


Evaporator


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


Accumulator


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


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


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



(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



(continued)



This process causes compressor to pump highpressure (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


Pressure Regulating Devices


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


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


Safety Valves

Spring-loaded Piston

Fusible Plug


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


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





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





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


Refrigeration Components

Refrigeration

Components

CAUTION

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CAUTION

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