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As compared to air standard cycle, in actual working, the effect of variations in specific heats is to:
- a)Increase maximum pressure and maximum temperature
- b)Reduce maximum pressure and maximum temperature
- c)Increase maximum pressure and decrease maximum temperature
- d)Decrease maximum pressure and increase maximum temperature
Correct answer is option 'B'. Can you explain this answer?
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As compared to air standard cycle, in actual working, the effect of va...
Effect of variations in specific heats on actual working of cycles
Introduction:
The air standard cycle assumes that the working fluid, air, behaves as an ideal gas with constant specific heats during the entire cycle. However, in actual working, the specific heats of the working fluid vary due to several factors. This has an effect on the performance of the cycle.
Effect of variations in specific heats:
The effect of variations in specific heats on the actual working of cycles can be summarized as follows:
1. Reduction in maximum pressure:
When the specific heat at constant pressure, cp, of the working fluid is higher than that at constant volume, cv, the expansion process during the power stroke of the engine is less adiabatic and more isobaric. This results in a lower temperature drop and hence a lower pressure ratio. Therefore, the maximum pressure achieved in the cycle is reduced.
2. Reduction in maximum temperature:
When the specific heat at constant volume, cv, of the working fluid is higher than that at constant pressure, cp, the compression process during the intake stroke of the engine is less adiabatic and more isochoric. This results in a higher temperature rise and hence a lower temperature ratio. Therefore, the maximum temperature achieved in the cycle is reduced.
3. Reduction in thermal efficiency:
The actual thermal efficiency of the cycle is reduced due to the variations in specific heats. This is because the specific heats affect the amount of heat added or rejected during the cycle. A higher specific heat at constant volume, cv, results in a lower amount of heat added during the combustion process, while a higher specific heat at constant pressure, cp, results in a higher amount of heat rejected during the exhaust process.
Conclusion:
Therefore, the effect of variations in specific heats is to reduce the maximum pressure and maximum temperature achieved in the cycle, as well as the thermal efficiency. These effects are more pronounced at higher compression ratios and higher operating temperatures.
Introduction:
The air standard cycle assumes that the working fluid, air, behaves as an ideal gas with constant specific heats during the entire cycle. However, in actual working, the specific heats of the working fluid vary due to several factors. This has an effect on the performance of the cycle.
Effect of variations in specific heats:
The effect of variations in specific heats on the actual working of cycles can be summarized as follows:
1. Reduction in maximum pressure:
When the specific heat at constant pressure, cp, of the working fluid is higher than that at constant volume, cv, the expansion process during the power stroke of the engine is less adiabatic and more isobaric. This results in a lower temperature drop and hence a lower pressure ratio. Therefore, the maximum pressure achieved in the cycle is reduced.
2. Reduction in maximum temperature:
When the specific heat at constant volume, cv, of the working fluid is higher than that at constant pressure, cp, the compression process during the intake stroke of the engine is less adiabatic and more isochoric. This results in a higher temperature rise and hence a lower temperature ratio. Therefore, the maximum temperature achieved in the cycle is reduced.
3. Reduction in thermal efficiency:
The actual thermal efficiency of the cycle is reduced due to the variations in specific heats. This is because the specific heats affect the amount of heat added or rejected during the cycle. A higher specific heat at constant volume, cv, results in a lower amount of heat added during the combustion process, while a higher specific heat at constant pressure, cp, results in a higher amount of heat rejected during the exhaust process.
Conclusion:
Therefore, the effect of variations in specific heats is to reduce the maximum pressure and maximum temperature achieved in the cycle, as well as the thermal efficiency. These effects are more pronounced at higher compression ratios and higher operating temperatures.
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As compared to air standard cycle, in actual working, the effect of variations in specific heats is to:a)Increase maximum pressure and maximum temperatureb)Reduce maximum pressure and maximum temperaturec)Increase maximum pressure and decrease maximum temperatured)Decrease maximum pressure and increase maximum temperatureCorrect answer is option 'B'. Can you explain this answer?
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