The thermal efficiency of a boiler with a stack temperature of 750°F and a furnace temperature of 3200°F is what percent?

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Study for the Washington DC 1st Class Boiler Test. Prepare with comprehensive questions, each with explanations and insights. Equip yourself thoroughly for success!

Multiple Choice

The thermal efficiency of a boiler with a stack temperature of 750°F and a furnace temperature of 3200°F is what percent?

Explanation:
A quick way to estimate boiler thermal efficiency uses the ratio of the stack temperature to the furnace temperature to gauge heat loss. The idea is that the furnace temperature represents the maximum usable heat, while the heat leaving as flue gas at the stack is lost energy. So the efficiency is approximately 1 minus the fraction lost in the stack: efficiency ≈ 1 − (T_stack / T_furnace). Plugging in the numbers: 750°F divided by 3200°F equals about 0.234. Subtracting from 1 gives 0.765, or roughly 76.5%—the closest option is 75%. This is a rough estimate used for quick checks; actual efficiency depends on other losses and fuel properties.

A quick way to estimate boiler thermal efficiency uses the ratio of the stack temperature to the furnace temperature to gauge heat loss. The idea is that the furnace temperature represents the maximum usable heat, while the heat leaving as flue gas at the stack is lost energy. So the efficiency is approximately 1 minus the fraction lost in the stack: efficiency ≈ 1 − (T_stack / T_furnace).

Plugging in the numbers: 750°F divided by 3200°F equals about 0.234. Subtracting from 1 gives 0.765, or roughly 76.5%—the closest option is 75%.

This is a rough estimate used for quick checks; actual efficiency depends on other losses and fuel properties.

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