Engineer-in-Residence ProgramHeat

John Hazel, P.Eng.

What is Heat ?

Transfer of energy between things Measured in Joules, Watts or Calories Temperature is the average energy of things

William Thompson

(Lord Kelvin)James Joule

Heat Transfer

Heat in a Car Engine

Fluid heated by engine

Fluid heats core (conduction)

Fan cools fluid (convection)

Some fluid used to transfer heat to car heater

Specific Heat Capacity

The amount of energy required to increase 1 kg of something by 1 degree

Specific Heat Capacityitem C

(J/kg.K)Item C (J/kg.K)

Water 4190 Glass 750

Flesh 3500 Stainless steel 510

Wax 2500 Iron 448

Wood (oak) 2390 Nickel 439

Petroleum 2140 Copper 385

Air 1000 Brass 370

Aluminum 900 Gold 130

What Makes the Best Pot Handle ?

Insulation

Effects of Heat on MaterialsWhen things get hot they expand since they have more energy

New Volume = Old volume X Temperature change x Coefficient of Expansion

Item Coeff of exp

Aluminum .000007

Steel 3.6

Copper 4.2

Protecting Bridges Some bridges can get several feet longer on a hot day If it has nowhere to go, it will buckle and crack due to

thermal stresses

How Cold?

• The colder things are, the less energy they have

• Absolute zero is 0 K or -273.15 C

• Strange things happen to matter at absolute zero:

• superconductors

• superfluidity