Powerpoint notes pg. 1+2

Question 1

Compressors are essentially ______ pumps

Answer 1

vapour

Question 2

What can damage the compressor?

Answer 2

too much liquid

Question 3

Vapour comes in as _____ temp, _____ pressure and leaves as _____ temp, _____ pressure

Answer 3

low, low,

high, high

Question 4

How does a compressor raise temperature and pressure?

Answer 4

by decreasing volume and compressing

Question 5

In a reciprocating compressor, the refrigerant vapour enters the cylinder when the pressure in the cylinder is _____ that of the suction line

Answer 5

below

Question 6

In a reciprocating compressor, refrigerant vapour is discharged from the cylinder when pressure in the cylinder is ______ than the discharge line

Answer 6

greater

Question 7

what term describes the space 1lb of gas occupies at a certain temperature and pressure?

Answer 7

specific volume

Question 8

Increase in pressure means ________ in specific volume

Answer 8

decrease

Question 9

______ _____rate is based on the density number in lbs in a cubic foot of gas

Answer 9

mass flow

Question 10

________ _____ _____ is determined by the compressor type and design

Answer 10

volumetric flow rate

Question 11

A compressor that delivers a constant volume of gas under a constant speed is called

Answer 11

positive displacement

Question 12

How is capacity measured?

Answer 12

but/hr

Question 13

capacity increases as mass flow rate increases resulting from a decrease in _______ _______

Answer 13

specific volume

Question 14

capacity increases as specific volume decreases resulting from an increase in ____\_____

Answer 14

sst/pressure

Question 15

Capacity increases as volumetric flow rate increases resulting from an increase in ____ _________

Answer 15

comp. displacement

Question 16

Capacity increases as compression ratios decreases resulting from a decrease in _______ _______

Answer 16

specific volume

Question 17

What are the main parts of a reciprocating compressor?

Answer 17

crankshaft
crank throw
eccentric
piston
connecting rods 
cylinder

Question 18

Mass flow rate =

Answer 18

Volumetric flow rate/specific volume

Question 19

name two types of reciprocating compressor crankshafts

Answer 19

crank throw and eccentric

Question 20

What is the purpose of the shaft seal?

Answer 20

keeps refrigerant in and air out

Question 21

What type of compressor is the centrifugal?

Answer 21

non-positive displacement compressor

Question 22

Reciprocating compressors have pistons that when moving down pull air __ through the intake and when moving up push high pressure air ___ the exhaust valve

Answer 22

in, out

Question 23

Three types of valves in a reciprocating compressor

Answer 23

Reed valve, ring valve, discuss valve

Question 24

Methods of cooling for reciprocating compressors?

Answer 24

Air cooled, water cooled, refrigerant vapour cooled

Question 25

How do Hermetic reciprocating compressors look?

Answer 25

round and covered

Question 26

how do reciprocating semi-hermetic compressors look?

Answer 26

bolts everywhere

Question 27

Hermetic cooling method of cooling?

Answer 27

primary method of vapour

Question 28

Semi-hermetic primary method of cooling?

Answer 28

vapour/air/water

Question 29

Open drives primary methods of cooling?

Answer 29

air/water/oil

Question 30

Oil pressure in a refrigeration compressor is the difference between ______ pressure and ___ _____ pressure

Answer 30

crankcase pressure and oil pump pressure

Question 31

Net oil pressure =

Answer 31

oil pump discharge pressure - oil pump inlet pressure/crankcase pressure

Question 32

On what side of the compressor is the oil pump located?

Answer 32

low side

Question 33

Since the oil pump is on the low side of the compressor, the crankcase is the _ starting point for the oil pump

Answer 33

0

Question 34

Most systems operate at the design load less than ___ percent of the time due to variations in lighting, occupancy, ambient temp

Answer 34

20

Question 35

operating below design load is to rebalance at a lower ______ temp and pressure

Answer 35

evaporator

Question 36

lower evap pressure means lower suction pressure and this lower pressure means less _________ _______

Answer 36

compressor capacity

Question 37

operating at lower evap temp could result in:

Answer 37

frosted coils, poor oil return, poor humidity control, and short cycling

Question 38

Capacity control methods ; (3)

Answer 38

on/off, speed control, multiple compressors

Question 39

Name three types of mechanical unloaders? (Capacity control method)

Answer 39

cylinder bypass suction cutoff hydraulic

Question 40

what are mechanical unloaders operated by? (3)

Answer 40

pressure, electrically, or hydraulics

Question 41

what are mechanical unloaders controlled by?

Answer 41

temperature or suction pressure

Question 42

(Capacity control method) Refrigerant hot gas bypass to ______ line and ________ inlet

Answer 42

suction line | evaporator inlet

Question 43

Rotary compressors capacity control?

Answer 43

speed control on/off

Question 44

Rotary compressors are _______ shaped

Answer 44

cylinder

Question 45

Scroll compressors have ___ % less moving parts, and are ___% more efficient

Answer 45

70% less | 20% more

Question 46

scroll compressors have one fixed ____ and one vibrating against it

Answer 46

scroll

Question 47

three structural type of compressors

Answer 47

hermetic , semi hermetic , open drive

Question 48

how does a scroll compressor compress the vapour?

Answer 48

volume decreases as vapour flows from the outside of the scroll toward the middle

Question 49

positive displacement uses a decrease in _______ in order to compress

Answer 49

volume

Question 50

diffuser slows down the refrigerant and converts _______ energy into _______ pressure

Answer 50

kinetic energy static pressure

Question 51

what creates the pressure differential?

Answer 51

speeding up and slowing down