Definition check — evaporative capacity of a boiler Is the statement correct? “The evaporative capacity of a boiler is defined as the evaporation of 15.653 kg of water per hour from and at 100°C.”

Introduction:
Boiler performance is characterized by several related terms: evaporative capacity, equivalent evaporation, and boiler horsepower. Confusing these leads to wrong sizing and comparisons. This question asks you to validate a specific numeric definition attributed to evaporative capacity.

Given Data / Assumptions:

• Standard engineering definitions used in steam engineering texts.
• Reference condition “from and at 100°C” for equivalence calculations.

Concept / Approach:
Evaporative capacity is the mass of water the boiler can evaporate per unit time (e.g., kg/h) under stated conditions. It has no fixed universal value. The number 15.653 kg/h corresponds to the historical definition of one boiler horsepower (BHP): 34.5 lb/h ≈ 15.653 kg/h of steam evaporated from and at 100°C per boiler horsepower. Thus, 15.653 kg/h is a unit conversion constant for BHP, not the definition of evaporative capacity itself.

Step-by-Step Solution:

Verification / Alternative check:
Equivalent evaporation and boiler horsepower relations: 1 BHP = 34.5 lb/h ≈ 15.653 kg/h from and at 100°C. Large boilers have capacities many orders higher, confirming that evaporative capacity is not tied to this fixed number.

Why Other Options Are Wrong:

• Yes / qualified “correct” options: conflate a unit definition (BHP) with the general parameter.
• Economiser or SI caveats: irrelevant to the definition.

Common Pitfalls:
Mixing up evaporative capacity with equivalent evaporation; believing 15.653 kg/h is a universal constant rather than a per-horsepower yardstick.

Final Answer: