Heating and Cooling Systems

Question 1

Engine cooling in cars

Answer 1

Petrol vehicle is only 12-30% efficient.

Car cooling system consists of

Pump: pushes coolant around engine
Thermostat: releases coolant into radiator once it reaches high temp
Radiator: Set of tubes surrounded by thin pieces of metal called radiator fins.
Fan: Pulls air through radiator to increase rate of cooling

Question 2

Heat Pumps

Answer 2

Heat pumps move energy from cold place to a hotter place

Compressor: Pressurises refrigerant gas, increasing temp
Condenser: refrigerant travels through set of tubes called condenser, releasing heat to surroundings, condensing to liquid
Expansion valve: Depressurises refrigerant, cooling it down
Evaporator: Refrigerant goes through evaporator and absorbs heat from surroundings, turning into gas and process repeats.

Question 3

Refrigerator

Answer 3

Use heat pumps

Condenser is on back surrounded by radiator fins (like car)
Evaporator is inside fridge, absorbing heat from refrigerator contents

Equipped with adjustable thermostat, turns off compressor at certain temp

Question 4

Air Conditioning

Answer 4

Refrigerative air conditioners also rely on heat pumps

Condenser is outside

Evaporator is inside, absorbing heat from air

Cooled air is blown into room

Question 5

Evaporative air cooling

Answer 5

Cool room by using cooling effect of evaporating water

Air is forced through wet filter pad
Heat from air is absorbed as water in pad evaporates
Cooled air is forced into room by fan

Question 6

Passive Solar House Design (Position of building)

Answer 6

Longest side of building should face north (in southern hemisphere)
Have a lot of windows on this side to allow winter sun in
Have large eaves to block sun

Question 7

Passive Solar House Design (Position of rooms)

Answer 7

put rooms used in day in the north end of house to make most of winter sun.

Bedrooms put on southern end where they will stay cool during summer

Question 8

Passive Solar House Design (Insulation)

Answer 8

Double glazed windows: 2 panels of glass with pocket of air in between

Double bricked walls work same as double glazed

Fibreglass insulation same effect

Question 9

Passive solar house design (shade)

Answer 9

Trees are sources of shade that can prevent sunlight entering house

Deciduous trees better as they lose leaves in winter

Question 10

Passive solar house design (thermal mass)

Answer 10

Materials with high thermal mass are useful as they absorb lots of heat before releasing it slowly

In winter materials absorb heat during day and release at night keeping house warm.