Explain why the heat flow for a home is different in the winter vs. the summer.

When heat energy flows in any heat engine from a high-temperature place to a low-temperature place, part of this energy is transformed into work output.

24.5 Heat Engines and the Second Law

Thermal energy (or heat) is converted to mechanical energy out (work).

waste heat is exhausted.

Heat Engine PhysicsA steam turbine engine demonstrates the role of temperature difference between heat reservoir and sink.

24.5 Heat Engines and the Second Law

Heat Engine PhysicsA steam turbine engine demonstrates the role of temperature difference between heat reservoir and sink.

Pressure does work on the turbine, causing it to turn

Thermal energy transferred to water reaches heat of vaporization—phase change of liquid to gas. Expanding gas increases pressure inside pipe

Original heat of vaporization is released when energy is transferred to the turbine. Gas condenses into liquid.

• 22. How do natural systems tend to proceed?

Natural systems tend to proceed toward a state of greater disorder.

The universe trends from a higher state to a lower state of organization.

Examples: Air flows from high to low pressureHeat flows from hot to cold

24.6 Order Tends to Disorder

According to the second law of thermodynamics, in the long run, the entropy of a system always increases for natural processes.

24.7 Entropy

Entropy is the measure of the amount of disorder in a system. Disorder increases; entropy increases.

24.7 Entropy

This run-down house demonstrates entropy. Without continual maintenance, the house will eventually fall apart.

24.7 Entropy

Heat Transfer Processes

Starter 4

• Solve problems 26-28 found on pg. 426.• Specific Heat Table is on pg. 413• For problem 26, see specific heat of iron found

in problem 25.

Fuel Sources for Heating

• Wood• Coal• Oil• Natural Gas (methane)

Methane

CH4

Burn a fuel

Heat a fluid

Circulate a heated fluid

radiator

Water-filled pipes

Burn a fuel

Heat a fluid

Circulate a heated fluid

Convection, Conduction or Radiation?

1. Stick in campfire2. Hot air balloon rising3. Hot concrete surface

at pool 4. Lizard sunning itself on

a rock5. Pan of soup warming

on the stove6. Foot on cold tile floor

• Conduction• Convection• Radiation

• Radiation

• Convection

• Conduction