Section 2.5: Applications of Thermodynamics
Thermodynamics principles are widely applied in engineering, physics, chemistry, and everyday life. Some key applications include heat engines, refrigerators, power plants, and biological systems.
- Heat Engines: Devices that convert heat into work, governed by the first and second laws. Efficiency is limited by the Carnot cycle: \[ \eta = 1 - \frac{T_C}{T_H} \] where \(T_H\) = temperature of the hot reservoir, \(T_C\) = temperature of the cold reservoir.
- Refrigerators and Heat Pumps: Transfer heat from cold to hot regions using external work. Coefficient of performance (COP): \[ \text{COP} = \frac{Q_C}{W} \] where \(Q_C\) = heat removed from the cold reservoir, \(W\) = work input.
- Natural Processes: Explains phenomena such as spontaneous heat flow, phase changes, and energy distribution in living organisms.
Example: Carnot Engine Efficiency
A Carnot engine operates between 500 K and 300 K. Determine its maximum possible efficiency.
\[ \eta = 1 - \frac{T_C}{T_H} = 1 - \frac{300}{500} = 0.4 \text{ or } 40\% \]
Practice Problems
- A refrigerator removes 200 J of heat from the cold compartment while consuming 50 J of work. Determine its COP.
- Explain why no engine can be 100% efficient according to the second law of thermodynamics.
- Describe a real-world application of thermodynamics in biology.
- Calculate the efficiency of a Carnot engine operating between 600 K and 400 K.
- State how thermodynamic principles are used in designing power plants.