Thermodynamics Chapter 6 Review Notes

Thermodynamics Chapter 6 Review Notes - Thermodynamics...

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Thermodynamics Chapter 6 Review Notes - The second Law of Thermodynamics 6.1 Introduction to the Second Law - energy always flows from high potential to low potential - energy has a quality not just a quantitl - the second law is used to calculate the theoretical limits of a process 6.2 Thermal Energy Reservoirs Thermal Energy Reservoir – a body with a relatively large ehat capacity (Mass * Specific heat) that can absorb finite amounts of heat without undergoin any change in temperature. -rivers, oceans, and the atmospheres are good examples of thermal energy reservoirs Two Phase System – can absorb and realease large amounts of energy while remaining at a constant temperature. - the guidelines for a reservoir require that it have sufficient mass or volume that the temperature is not changed by whatever is being dumped into it. Source – a Reservoir that supplies energy in the form of heat Sink – A reservoir that absorbs energy in the form of heat - these are often refered to as heat reservoirs - thermal pollution takes place where large amounts of energy are dumped 6.3 Heat Engines Heat Engine – any device that is used to convert heat to work Characteristics of heat engines: 1. They must receive heat from a high temperature source. 2. They convert part of the heat into work 3. They Reject the remaining waste heat to a low temperature sink 4. They operate on a cycle Working Fluid – the fluid or medium that heat is transferred to and from in a cycle. - the best example of a heat engine is a steam powered powerplant o Q in = heat supplied by furnace o Q out = Heat lost in heat sink o W out = Work delivered b the system as it expands in a turbine o W in = work required to compres the water back to boiling pressure o out in out net in out out net Q Q W W W W - = - = , ,
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Thermal Effeciency - This is the measure of performance of the heat engine - The Q out is never equal to zero - in out in out net th Q Q Q W - = = = = 1 Input Heat Total output Net work efficiency Thermal , η - Q h =The magnitude of the heat transfer between the cyclic device and the high
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Thermodynamics Chapter 6 Review Notes - Thermodynamics...

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