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Which is the wrong assumption for calculation of air standard efficiency?
- a)All processes are reversible
- b)Specific heat remains constant at all temperatures
- c)No account of the mechanism of heat transfer is considered
- d)Gases dissociate at higher temperatures
Correct answer is option 'D'. Can you explain this answer?
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Verified Answer
Which is the wrong assumption for calculation of air standard efficien...
To simplify analysis, the following assumptions are made for calculation of air standard efficiency:
1. The working fluid is air, which continuously circulates in a closed loop and always behaves as an ideal gas.
2. All the processes that make up the cycle are internally reversible.
3. The combustion process is replaced by a heat - addition process from an external source.
4. The exhaust process is replaced by a heat - rejection process that restores the working fluid to its initial state.
Most Upvoted Answer
Which is the wrong assumption for calculation of air standard efficien...
The wrong assumption for calculation of air standard efficiency is:
Option D: Gases dissociate at higher temperatures
Explanation:
The air standard efficiency is a measure of the efficiency of an internal combustion engine or gas turbine. It is calculated by assuming a theoretical air standard cycle, which consists of a series of idealized processes.
The given assumption in option D, that gases dissociate at higher temperatures, is incorrect because it goes against the assumption of the air standard cycle. The air standard cycle assumes that all processes are ideal and reversible, which means that there is no dissociation of gases.
Assumptions for Calculation of Air Standard Efficiency:
1. All processes are reversible: The air standard cycle assumes that all processes, such as compression, combustion, and expansion, are reversible. This assumption allows for the determination of the maximum possible efficiency of the engine.
2. Specific heat remains constant at all temperatures: Another assumption made in the air standard cycle is that the specific heat of the working fluid, which is typically air, remains constant at all temperatures. This assumption simplifies the calculations and allows for the use of specific heat values at ambient conditions.
3. No account of the mechanism of heat transfer is considered: The air standard cycle assumes that the heat transfer in the engine is perfect and there are no losses or inefficiencies. It neglects the actual mechanism of heat transfer and assumes that all heat addition and rejection occur at constant temperature.
4. Gases do not dissociate at higher temperatures: The correct assumption for the air standard cycle is that gases do not dissociate at higher temperatures. This assumption allows for the use of specific heat values and thermodynamic properties of the working fluid without considering the dissociation of molecules.
Conclusion:
The wrong assumption for the calculation of air standard efficiency is option D, which states that gases dissociate at higher temperatures. This assumption contradicts the ideal and reversible nature of the air standard cycle and the assumption of constant specific heat at all temperatures.
Option D: Gases dissociate at higher temperatures
Explanation:
The air standard efficiency is a measure of the efficiency of an internal combustion engine or gas turbine. It is calculated by assuming a theoretical air standard cycle, which consists of a series of idealized processes.
The given assumption in option D, that gases dissociate at higher temperatures, is incorrect because it goes against the assumption of the air standard cycle. The air standard cycle assumes that all processes are ideal and reversible, which means that there is no dissociation of gases.
Assumptions for Calculation of Air Standard Efficiency:
1. All processes are reversible: The air standard cycle assumes that all processes, such as compression, combustion, and expansion, are reversible. This assumption allows for the determination of the maximum possible efficiency of the engine.
2. Specific heat remains constant at all temperatures: Another assumption made in the air standard cycle is that the specific heat of the working fluid, which is typically air, remains constant at all temperatures. This assumption simplifies the calculations and allows for the use of specific heat values at ambient conditions.
3. No account of the mechanism of heat transfer is considered: The air standard cycle assumes that the heat transfer in the engine is perfect and there are no losses or inefficiencies. It neglects the actual mechanism of heat transfer and assumes that all heat addition and rejection occur at constant temperature.
4. Gases do not dissociate at higher temperatures: The correct assumption for the air standard cycle is that gases do not dissociate at higher temperatures. This assumption allows for the use of specific heat values and thermodynamic properties of the working fluid without considering the dissociation of molecules.
Conclusion:
The wrong assumption for the calculation of air standard efficiency is option D, which states that gases dissociate at higher temperatures. This assumption contradicts the ideal and reversible nature of the air standard cycle and the assumption of constant specific heat at all temperatures.
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Which is the wrong assumption for calculation of air standard efficiency?a)All processes are reversibleb)Specific heat remains constant at all temperaturesc)No account of the mechanism of heat transfer is consideredd)Gases dissociate at higher temperaturesCorrect answer is option 'D'. Can you explain this answer?
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