Question 15Steam Plants - Assistant Engineer

The correct answer is B) the specific weight of the flue gases. A mechanical carbon dioxide recorder operates by detecting the difference between the specific weight of the air and the specific weight of the flue gases. This difference in specific weight is used to determine the carbon dioxide content of the flue gases, which is a critical measurement for ensuring proper combustion efficiency. The other answer choices are incorrect because they do not accurately describe the operating principle of a mechanical carbon dioxide recorder. The soot content (A), color (C), and temperature (D) of the flue gases are not directly measured by this type of instrument.