Heating and Cooling Systems

Question 1

Engine Cooling in Cars

Answer 1

A petrol vehicle typically converts only 12-30% of the chemical energy stored in its fuel into kinetic energy in the wheels. The remaining energy is converted into other forms, primarily heat. To prevent damage to the engine, the excess heat must be removed through a car’s cooling system.

Question 2

Car cooling system contains

Answer 2

Pump
Thermostat
Radiator
Fan

Question 3

Pump

Answer 3

Pump pushes coolant around engine

Question 4

Thermostat

Answer 4

Thermostat releases coolant into radiator once it reaches a high temp

Question 5

Radiator

Answer 5

Set of tubes surrounded by thin pieces of metal called radiator fans. Heat from coolant is transferred to fins which transfer it to the air moving past them.

Question 6

Fan

Answer 6

Pulls air through radiator as required to increase rate of cooling

Question 7

Heat Pumps

Answer 7

Heat usually flows from hot objects to cold objects. Heat pumps allow the opposite: the movement of energy from a cold place to a warmer place.

Question 8

Heat Pump steps

Answer 8

1. compressor pressurises gas called refrigerant, driving up the temp
2. refrigerant travels through tubes called condenser where it releases heat to surroundings and condenses into liquid
3. refrigerant depressurised by expansion valve so it cools down
4. refridgerant goes through evaporator where it absorbs heat from surroundings and turns into gas, re-enters compressor and repeats cycle

Question 9

Refrigerator (Heat pump)

Answer 9

the condenser is on the back, surrounded by radiator fins
evaporator inside fridge absorbs heat from contents in fridge
fridges come w adjustable thermostats that turn off compressor at a set temperature

Question 10

Air Conditioning (heat pump)

Answer 10

the condenser is outside, where fins and a fan assist with heat transfer to the air
the evaporator is inside, where it absorbs heat from the air
cooled air is blown into the room by another fan

Question 11

Evaporate Air Conditioning

Answer 11

air is forced through a wet filter pad
heat from the air is absorbed as the water in the pad evaporates
the cooled air is forced into the room by a fan

Question 12

Heat Pump Steps

Answer 12

Compressor (pressurise vapour) -> condensor (release heat to surrounding, condense into liquid) -> expansion valve (liquid cool down) -> evaporator (absorb heat from outside, turn into gas again)

Question 13

Gay Lussacs Law

Answer 13

Pressure proportional to temperature

Question 14

Refrigerator Steps

Answer 14

An evaporator, through which the low-pressure, low-temperature refrigerant absorbs heat from a heat sink (e.g., a freezer compartment or a space to be refrigerated) and changes from a two-phase mixture to a saturated or superheated vapour.
A compressor, which is used to increase the pressure and temperature of the refrigerant vapour by consuming work.
A condenser, through which heat is rejected to a heat source (e.g. kitchen or outdoor air). At the exit of the condenser, the refrigerant is typically a two-phase mixture or a liquid.
An expansion valve, which is used to reduce the pressure and temperature of the refrigerant in order to achieve a liquid-vapour mixture of desirable quality at the exit of the expansion valve.

Question 15

What does an evaporator do

Answer 15

Absorb heat

Question 16

What does a condenser do

Answer 16

Release heat