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cooling systems Flashcards

(68 cards)

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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
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

Cooling systems (5 decks)

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