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Chapter 4: 4.9 (page 129)
Estimate the maximum possible COP of a household air conditioner. Use any reasonable values for the reservoir temperatures.
COP=21
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Derive equation for the efficiency of the Otto cycle.
In table 4.1, why does the entropy of water increase with increasing temperature, while the entropy of steam decreases with increasing temperature?
The amount of work done by each stroke of an automobile engine is controlled by the amount of fuel injected into the cylinder: the more fuel, the higher the temperature and pressure at points 3 and 4 in the cycle. But according to equation 4.10, the efficiency of the cycle depends only on the compression ratio (which is always the same for any particular engine), not on the amount of fuel consumed. Do you think this conclusion still holds when various other effects such as friction are taken into account? Would you expect a real engine to be most efficient when operating at high power or at low power? Explain.
Calculate the efficiency of a Rankine cycle that is modified from the parameters used in the text in each of the following three ways (one at a time), and comment briefly on the results: (a) reduce the maximum temperature to ; (b)reduce the maximum pressure to 100 bars; (c)reduce the minimum temperature to .
Explain why a rectangular cycle, as considered in Problems and , cannot be used (in reverse) for refrigeration.
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