Modes of Heat Transfer

Question 1

Conduction

Answer 1

Heat transfer by direct contact

• Hot Packs
• Cold Packs

Heat is conducted from hot to cold

Question 2

Convection

Answer 2

Heat transfer as a result of direct contact between a circulating medium and another material of a different temperature

• Fluidotherapy
• Whirlpool
• Blood circulation

Question 3

Conversion

Answer 3

Heat transfer by conversion of a nonthermal form of energy into heat

• Ultrasound
• Diathermy

Does not depend on heat of thermal agent

Question 4

Radiation

Answer 4

Direct transfer of energy from a material with a higher temperature to one with a lower temperature without the need for an intervening medium

• infared lamps

Question 5

Evaporation

Answer 5

Absorption of energy as a result of conversion of a material from a liquid to a gas

• perspiration
• alcohol
• vapo-coolant sprays

Question 6

Specific Heat

Answer 6

Amount of energy required to reaise the temperature of a substance by a given amount of degrees

• amount of calories to raise 1g of material one degree C

Examples

• Water = 4.19
• Air = 1.01
• Human body = 3.56
• Skin = 3.77
• Muscle = 3.75
• Fat =2.30
• Bone = 1.59

Question 7

Thermal Conductivity

Answer 7

Measure of the efficiency of a material or tissue to conduct heat

• Silver = 1.01
• Aluminum = 0.50
• Ice = 0.005
• Water at 20^o C = 0.0014
• Bone = 0.0011
• Fat = 0.0005
• Air at 0 degrees celcius = 0.000057