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

## Presentation on theme: "Explain why the heat flow for a home is different in the winter vs. the summer."— Presentation transcript:

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 Physics A steam turbine engine demonstrates the role of temperature difference between heat reservoir and sink. 24.5 Heat Engines and the Second Law

Heat Engine Physics A 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 pressure Heat 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 CH 4

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 campfire 2.Hot air balloon rising 3.Hot concrete surface at pool 4.Lizard sunning itself on a rock 5.Pan of soup warming on the stove 6.Foot on cold tile floor Conduction Convection Radiation Convection Conduction

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