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Cooling systems > cooling systems > Flashcards

cooling systems Flashcards

1
Q

4 functions of the engine cooling system

A

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

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2
Q

1/3 rule of cooling systems

A

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

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3
Q

3 methods of heat transfer

A

convection
conduction
radiation

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4
Q

convection

A

movement of liquid or gas from hot area to cool area

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5
Q

radiation

A

heat dissipation through vibration of molecular structure

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6
Q

conduction

A

heat transferred from one molecule to another within an object

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7
Q

examples of good heat conductors

A

copper ,aluminium, cast iron ,steel

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8
Q

examples of poor heat conductors

A

glass , wood , air

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9
Q

liquids will boil at higher altitude because

A

there is less pressure acting on the surface of the liquid

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10
Q

pressure in a cooling system will allow the coolant to

A

exceed the normal boiling point

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11
Q

1psi of pressure will raise the boiling point

A

3 F

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12
Q

increased pressure will also improve

A

heat transfer and reduce aeration and cavitation

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13
Q

advantage of air cooled systems

A

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

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14
Q

disadvantage of air cooled systems

A

louder operation

temp may be affected by ambient temp

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15
Q

cooling fins on air cooled engines

A

offer increased cooling surface area

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16
Q

engine drive fan or cooling blower

A

may be controlled by heat sensing device

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17
Q

shrouds,metal shields and baffles

A

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

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18
Q

integral flywheel cooling fan

A

operates at the same speed as the engine cannot be changed

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19
Q

dirt and dust build up on cooling fins

A

dissipate the engines ability to reduce heat

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20
Q

advantages of liquid cooled engine

A

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

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21
Q

engine coolant must

A

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

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22
Q

scale and rust deposits will

A

act as an insulator

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23
Q

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

A

4” thick cast in heat transferability

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24
Q

antifreeze products are manufactured with

A

petroleum products and should be considered toxic

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25
Q

three methods for glycol testing

A

anti-freeze hydrometer
litmus paper
refractometer

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26
Q

when operating engines in moderately cold temp

A

50/50 anti-freeze to water should be used

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27
Q

coolant with more than 60% antifreeze can cause

A

gelling of the coolant
reduced heat transfer ability
higher boiling point

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28
Q

corrosion inhibitors often referred to as

A

SCA supplemental coolant additives

29
Q

coolant filters

A

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

30
Q

small zinc plate in some filters is used for

A

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

31
Q

down flow radiator

A

consist of a top tank central cooling core and bottom tank

32
Q

horizontal flow tank

A

have two side tanks and a central cooling core

33
Q

central cooling core construction

A

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

34
Q

single pass process rad

A

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

35
Q

low flow or multi path rad

A

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
Q

radiator core

A

main heat exchanger used in the engine cooling system

37
Q

de-aeration tubes

A

remove small air bubbles from coolant during operation

38
Q

materials used for rad tank

A

copper brass cast iron cast aluminium plastic/fiberglass sheet steel

39
Q

two types of rad core design

A

tube and fin

honeycomb

40
Q

rad tank design depends on

A

application, cost, cooling efficiency

41
Q

surge tank operation

A

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
Q

when checking coolant at the rad

A

must be done when coolant is cold and on level ground

43
Q

advantages of coolant recovery tank

A

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
Q

pressure caps protect the cooling system from

A

dangerously high pressures

vacuum from cooling coolant

45
Q

coolant that is full of air bubbles

A

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

46
Q

thermostats

A

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

47
Q

three types of thermostats

A

bypass
partial blocking
full blocking

48
Q

bypass thermostats

A

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

49
Q

partial blocking thermostats

A

allows about 10% of coolant to circulate through to rad

50
Q

full blocking thermostat

A

allows no coolant to pass through to rad

allows for faster engine warm up

51
Q

thermostat operation

A

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

52
Q

coolant bypass operation cold

A

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
Q

coolant bypass operation warm

A

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

54
Q

cooling shutter systems

A

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
Q

shutter operation

A

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
Q

cooling fans

A

often connected to water pump assembly

if water pump is gear driven then fan will be belt driven at a separate location

57
Q

fan shrouds

A

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
Q

fan blade spacing

A

reduces fan noise and maintains balance

59
Q

push type fans

A

prevent debris build up from plugging rad core

forces air from engine compartment through rad core

60
Q

reversible fan type

A

fan blades can be manually changed from push to pull type

61
Q

fan guards

A

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

62
Q

thermostatic fans

A

operate only when they need to

prevent parasitic load on engine

63
Q

general temp for thermostats to open

A

185’F

64
Q

general temp for shutters to open

A

190-195’F

65
Q

general temp for fans to begin operation

A

200’F

66
Q

fans can create a parasitic load on engines of between

A

9 to 40 horsepower

67
Q

water pump

A

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

68
Q

localized over heating could be the cause of

A

scale and corrosion build up causing reduced pump flow

Cooling systems (5 decks)

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