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Flashcards in cooling systems Deck (68):
1

4 functions of the engine cooling system

remove excess engine heat from combustion process
regulate engine temp
remove heat from other sources. engine oil coolers, hyd cooler, torque converter and coolant to air after cooler
allow for fast engine warm up

2

1/3 rule of cooling systems

33% of heat from burning fuel used for power
33% is absorbed and radiated by cooling system
33% is radiated to atmosphere by exhaust

3

3 methods of heat transfer

convection
conduction
radiation

4

convection

movement of liquid or gas from hot area to cool area

5

radiation

heat dissipation through vibration of molecular structure

6

conduction

heat transferred from one molecule to another within an object

7

examples of good heat conductors

copper ,aluminium, cast iron ,steel

8

examples of poor heat conductors

glass , wood , air

9

liquids will boil at higher altitude because

there is less pressure acting on the surface of the liquid

10

pressure in a cooling system will allow the coolant to

exceed the normal boiling point

11

1psi of pressure will raise the boiling point

3 F

12

increased pressure will also improve

heat transfer and reduce aeration and cavitation

13

advantage of air cooled systems

.lighter engine weight
.reduced system maintenance
.reduced complexity
.elimination of coolant leaks cavitation corrosion and antifreeze agents

14

disadvantage of air cooled systems

louder operation
temp may be affected by ambient temp

15

cooling fins on air cooled engines

offer increased cooling surface area

16

engine drive fan or cooling blower

may be controlled by heat sensing device

17

shrouds,metal shields and baffles

direct air past cooling fins in a determined direction and velocity to maintain even engine temp

18

integral flywheel cooling fan

operates at the same speed as the engine cannot be changed

19

dirt and dust build up on cooling fins

dissipate the engines ability to reduce heat

20

advantages of liquid cooled engine

.cooling is more uniform
.reduced noise
.controlled engine temp allows bearing to have tighter clearance
.reduced distortion of components due to even heating

21

engine coolant must

absorb and carry away excess heat generated by the engine
must not allow corrosion to form in cooling passages
must remain a liquid during engine operation in cold climates

22

scale and rust deposits will

act as an insulator

23

1" thick cast surface with 1/16 thick deposit of scale is equal to

4" thick cast in heat transferability

24

antifreeze products are manufactured with

petroleum products and should be considered toxic

25

three methods for glycol testing

anti-freeze hydrometer
litmus paper
refractometer

26

when operating engines in moderately cold temp

50/50 anti-freeze to water should be used

27

coolant with more than 60% antifreeze can cause

gelling of the coolant
reduced heat transfer ability
higher boiling point

28

corrosion inhibitors often referred to as

SCA supplemental coolant additives

29

coolant filters

remove sludge and rust from cooling system to help prevent small cooling passages from being plugged and causing hot spots

30

small zinc plate in some filters is used for

to focus electrolytic action on the plate and not on cylinder liner walls or rad cores

31

down flow radiator

consist of a top tank central cooling core and bottom tank

32

horizontal flow tank

have two side tanks and a central cooling core

33

central cooling core construction

one piece or multi piece construction composed of individual cooling pipes that are finned to improve heat transfer

34

single pass process rad

coolant enters in one direction and leaves the rad core in one cycle

35

low flow or multi path rad

coolant remains in rad longer
first flows in one direction then in the opposite direction through a separate cooling section until it leaves the rad

36

radiator core

main heat exchanger used in the engine cooling system

37

de-aeration tubes

remove small air bubbles from coolant during operation

38

materials used for rad tank

copper brass cast iron cast aluminium plastic/fiberglass sheet steel

39

two types of rad core design

tube and fin
honeycomb

40

rad tank design depends on

application, cost, cooling efficiency

41

surge tank operation

acts as a remote reservoir
used when temp and pressure changes
has pressure cap to allow it to breath when coolant expands and contracts
has sight glass to check coolant level hot or cold

42

when checking coolant at the rad

must be done when coolant is cold and on level ground

43

advantages of coolant recovery tank

greater positive head pressure to coolant pressure
space for vapor to condense back to liquid
minimizes aeration by keeping rad full
reduces corrosion and rust

44

pressure caps protect the cooling system from

dangerously high pressures
vacuum from cooling coolant

45

coolant that is full of air bubbles

wont be able to cool an engine as well because air is a shit insulator

46

thermostats

regulates engine coolant temp and allows for faster engine warm up
normally located near the top of cylinder head

47

three types of thermostats

bypass
partial blocking
full blocking

48

bypass thermostats

allows about 25% of coolant to circulate through rad when cold
will lengthen time required to warm up engine

49

partial blocking thermostats

allows about 10% of coolant to circulate through to rad

50

full blocking thermostat

allows no coolant to pass through to rad
allows for faster engine warm up

51

thermostat operation

is a heat sensitive valve that opens gradually when coolant heats up allowing for regulation of engine temp

52

coolant bypass operation cold

when coolant is cold and thermostat is closed bypass tube will allow coolant to re circulate in engine and will cause faster warm up

53

coolant bypass operation warm

when engine has reached operating temp bypass tube will be fully closed allowing flow of coolant through rad

54

cooling shutter systems

will open and close with engine temp
when closed no air will flow over rad fins
full open allows for full flow of air over fins

55

shutter operation

controlled by a shutterstat
when temp rises shutterstat opens allowing air pressure , vacuum , or engine oil pressure to overcoming spring force holding shutters closed

56

cooling fans

often connected to water pump assembly
if water pump is gear driven then fan will be belt driven at a separate location

57

fan shrouds

ensure air is pushed or pulled through rad core
prevent air from recirculating around fan tips
shrouds should cover 1/3 to 2/3 of fan pitch

58

fan blade spacing

reduces fan noise and maintains balance

59

push type fans

prevent debris build up from plugging rad core
forces air from engine compartment through rad core

60

reversible fan type

fan blades can be manually changed from push to pull type

61

fan guards

must be around fan at all times to protect personnel and rad core

62

thermostatic fans

operate only when they need to
prevent parasitic load on engine

63

general temp for thermostats to open

185'F

64

general temp for shutters to open

190-195'F

65

general temp for fans to begin operation

200'F

66

fans can create a parasitic load on engines of between

9 to 40 horsepower

67

water pump

creates a positive circulation of coolant through the engine at all times
can be gear or pulley driven

68

localized over heating could be the cause of

scale and corrosion build up causing reduced pump flow