Compressor

Front 1

How to find cylinder displacement

Back 1

Bore × stroke × # of cylinders

Bore = diameter (3.14× r2)

Front 2

CFM of a cylinder

Back 2

CFM = displacement × RPM

Front 3

Tons capacity

Back 3

Tons = (cfm ÷ spv) × btu/lb

Front 4

Clearance volumn = ?

Back 4

Amount of gas remaining in cylinder after discharging.

Front 5

Compression ratio = ?

Back 5

CR = absolute discharge pressure ÷ absolute suction pressure

Front 6

How much oil can a compressor lose on start up

Back 6

5% -7% can be lost oil moving with the refrigerant

Front 7

Discharge temp should not exceed what temperature?

Back 7

225° F

Front 8

Why do screw compressor have low discharge temps?

Back 8

Because of the large amounts of oil needed for lubrication

Front 9

True or false ..

Scroll compressor will have a discharge check valve.

Back 9

True

Front 10

Heart of the Refrigeration system is?

Back 10

The compressor

Front 11

State of the gas before compression and after

Back 11

Before(suction): low temp - low pressure vapor

After(discharge): high temp - high pressure vapor

Front 12

What is an open drive compressor?

Back 12

Is driven by a mechanical power source that is separate from the compressor

Front 13

Shaft seal

Back 13

Create a leak proof seal between the shaft and the case where the shaft emerges.

Front 14

Shaft seal must be able to ?

Back 14

- with stand the varying pressures inside the case

- must allow the shaft to rotate without excessive drag

- common failure point

Front 15

Name the 2 elements of a shaft seal

Back 15

1) element turns with the shaft

2) other element is stationary and is mounted to the compressor case with a leak proof gasket.

Front 16

What is a direct drive compressor?

What is the speed?

Back 16

Is driven by a coupling connecting the shaft of an electric motor directly to the compressor shaft.

Compressor turns the same speed as the motor

Front 17

What is a Belt driven compressor ? What is the speed ?

Back 17

Belt connects a pulley on the drive motor to a pulley on the compressor.

Speed is determined by the pulley sizes of both the motor and compressor.

Front 18

Semi hermetic compressor

Back 18

Combines motor and compressor inside a multipart shell that is bolted together.

- is serviceable.

- motor and compressor are arranged horizontally.

- they are often air cooled and have cooling fins on exterior housing to increase surface area.

Front 19

5 basic types of compressors & compression ratio

Back 19

1- reciprocating ( 20:1 )

2- rotary (5:1)

3- scroll (20:1)

4- screw (20:1)

5- centrifugal (3:1)

Front 20

Reciprocating compressor are classified by?

Back 20

- number of cylinders

- crankshaft type

- construction type ( open drive, belt driven, hermetic)

- cylinder arrangement

Front 21

Components of a reciprocating compressor?

Back 21

- crankshaft

- connecting rods

- pistons

- cylinders

- intake and exhaust valve (reed valve)

Front 22

Crankshaft types

Back 22

1) eccentric

2) crank throw - most common

3) scotch yoke- small high speed compressors.

Front 23

Connecting rods ?

Back 23

Connects a piston to a crankshaft.

Often have a split lower end where it connects to the crankshaft. Is called a journal.

Front 24

Pistons?

Back 24

Is part of the compressor that actually compresses the gas.

Front 25

Pistons compression ring purpose.

Back 25

- top ring is the compressor ring. Primary purpose is to prevent the pressurized Refrigerant from blowing past the piston in to the crank case

Front 26

Pistons oil ring purpose.

Back 26

Is the lower ring, is designed to help lubricate the cylinder wall while simultaneously preventing excess lubrication from entering the cylinder.

Front 27

Piston pins

Back 27

Are metal cylinders that connect the pistons to the connecting rods.

Front 28

Cylinders are?

Back 28

Cylinders are the bores in the cylinder block within which the pistons move up and down.

Front 29

Compressor valves do what?

Back 29

They regulate the flow of the refrigerant in to and out of the cylinder.

2 main types, Reed valves & poppet valves

Front 30

Reed valves ?

Back 30

Are the simplest of the valve design. They are strips of of spring steel that bend to open the valve passage and spring back to their flat shape to close the valve.

Intake valve is on the piston side

Exhaust valve is on the cylinder head side.

Front 31

Poppet valves?

Back 31

Are used in large compressors. They are very sturdy but slow.

Suitable for low speed compressors.

Front 32

Cylinder head ...

Back 32

Serves as a pressure plate sealing the top of the cylinders so the refrigerant can be compressed.

Supports and holds valves & valves plate in position.

Intake and exhaust valves are part of the cylinder head.

Front 33

Rotary compressor.....

Back 33

Is a compressor in which vapor compression takes place in a space between the cylinder wall and sides of an off-center rotor that spins inside the cylinder.

Check valve usually placed in the discharge line.

Small refrigerated appliances.

High volumetric efficiency

Front 34

2 types of rotary compressors.

Back 34

1) rotating vane rotary compressor

2) stationary blade rotary compressor.

Front 35

Rotating vane compressor uses a....

Back 35

Uses a off center rotor to turn vanes(blades) that create pockets between the rotor and cylinder wall.

Maybe spring loaded or vanes are pulled outward by centrifugal force of the spinning shaft.

Front 36

3 Advantages of a rotating vane compressor

Back 36

1- provide a large opening into the suction line

2- provide a large inlet port

3- have a very small clearance space.

Front 37

Stationary blade (divided block)

Back 37

-Blade is mounted in the block housing.

- blade is spring loaded and pressed against the rotor as it rotates

Front 38

Scroll compressors ...

Back 38

Produce vapor compression between the walls of a fixed scroll and an orbiting scroll.

Front 39

Screw compressors ....

Back 39

-Use a pair of special helical rotors to compress refrigerant vapor.

- 2 rotors, one Male other female.

- Male rotor has 4 lobe

- female rotor has 6 interlobe spaces and drives the male rotor.

- vapor enters from one end, discharges at opposite end

Front 40

Screw compressors provide a ...

Back 40

Provide a continuous, steady pressure rather than a pulsating, pumping pressure like that of a reciprocating compressor.

- very little vibration

- unloaders reduce loads for easier starting.

Front 41

Centrifugal compressors ...

Back 41

Is a compressor consisting of a rotor-operator impeller with a radial blades inside a volute casing.

- non positive displacement.

- centrifugal force throws the vapor outwards.

Front 42

Lubrication splash system

Back 42

Splash system, crankcase is filled with oil up to the bottomed of the main bearings or to the middle of the crankshaft bearings, so the oil covers half of the main bearings.

Each crank revolution, the crank throw or eccentric dips in to the oil. It splashes the oil around the inside of the compressor.

Some connecting rods have little dips or scoops attached.

Front 43

Lubrication pressure system

Back 43

Use a small oil pump to force oil on the main bearings, lower connecting rods bearing and sometimes the pistons.

Provides a better protection than a splash system.

Front 44

Crank case heater ...

Back 44

Is a devise that warms the compressor crankcase to evaporate any liquid refrigerant trapped in the oil.

Keeps crankcase up to 30°F warmer than system temp.

Front 45

Net Oil pressure should be

Back 45

30 - 40 psi

Front 46

Max discharge Temp

Back 46

225F - 275F

Front 47

Max discharge Temp

Back 47

225F - 275F

Front 48

Max suction temp

Back 48

65F - 95F