Thermal engineering (fuels): identify the incorrect statement about fuels Options compare properties of liquid and solid fuels and desirable fuel characteristics. Choose the single incorrect statement from the list.
Mechanical Engineering
Thermodynamics
Difficulty: Easy
Choose an option
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AThe liquid fuels consist mainly of hydrocarbons.
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BLiquid fuels generally have higher calorific value than solid fuels.
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CSolid fuels have higher calorific value than liquid fuels.
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DA good fuel should ignite easily (low ignition temperature) for reliable starting.
Answer
Correct Answer: Solid fuels have higher calorific value than liquid fuels.
Explanation
Concept/Approach
- Typical gross calorific values: gasoline/petrol ≈ 44–46 MJ/kg; diesel ≈ 42–46 MJ/kg; coal ≈ 24–35 MJ/kg. Thus, liquids are usually higher than common solids.
- Fuels are predominantly hydrocarbons.
- For many practical uses a fuel that lights readily (not excessively high ignition temperature) is desirable; some texts say “moderate to low” ignition temperature.
Why C is incorrectStatement C reverses the usual trend: solid fuels typically have a lower calorific value than liquid fuels.
Final AnswerSolid fuels have higher calorific value than liquid fuels.