How much efficiency can be gained by using an economizer?

Study for the Massachusetts 3rd Class Engineer Exam. Access flashcards and multiple choice questions with hints and explanations. Prepare for success on your exam!

Using an economizer in a boiler system enhances efficiency by recovering waste heat from the flue gases and using it to preheat the feed water. This process leads to a better thermal efficiency of the overall system.

The correct choice indicates that you can gain an efficiency improvement of approximately 1% for each 10-degree rise in feed water temperature. Preheating the feed water reduces the amount of fuel needed to achieve the desired steam temperature, contributing to more efficient operation.

Understanding the mechanics behind this means recognizing that lower feed water temperatures require more energy to heat up in the boiler. By using an economizer, this energy is already partially supplied through recovered heat, leading to that 1% efficiency increase per 10-degree rise.

In contrast, the other options suggest higher percentages of efficiency gain, which can be misleading and excessive according to standard operational expectations. A 2% or higher gain per 10 degrees is generally unrealistic for typical economizer applications, which underscores why the stated 1% figure is a widely accepted estimate in practical scenarios. This highlights the advantages of economizers while maintaining realistic expectations for efficiency improvements.

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