Boiler performance statements: identify the incorrect statement among the following. Context: Factor of evaporation (FE), equivalent evaporation, and boiler efficiency are standard boiler performance terms. Select the statement that is wrong.
Mechanical Engineering
Steam Boilers and Engines
Difficulty: Medium
Choose an option
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AThe factor of evaporation for all boilers is always greater than unity.
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BThe amount of water evaporated in kg per kg of fuel burnt can be expressed as equivalent evaporation from and at 100°C.
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CThe ratio of heat actually used in producing the steam to the heat liberated in the furnace is called boiler efficiency.
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DNone of the above
Answer
Correct Answer: The factor of evaporation for all boilers is always greater than unity.
Explanation
Concept check
- Factor of evaporation (FE) adjusts actual evaporation to an equivalent basis (from and at 100°C). It is not necessarily always > 1. FE can be less than, equal to, or greater than 1 depending on feedwater temperature and final steam state.
- Equivalent evaporation expresses evaporation on the standard basis “from and at 100°C”. It may be reported per hour or per kg of fuel (i.e., equivalent evaporation per kg fuel).
- Boiler efficiency is correctly defined as useful heat to steam / heat released in the furnace.
ThereforeOption A is wrong because FE is not always greater than unity.