Boiler Capacity Comparison — Reference Conditions To fairly compare the steaming capacity of different boilers, the conventional reference for equivalent evaporation uses feedwater and pressure taken as:

Introduction / Context:
Boilers operate at widely varying pressures and feedwater temperatures. To compare capacities, engineers convert the actual duty to an equivalent amount of evaporation “from and at 100°C” — a universally accepted reference basis that normalizes performance across plants and seasons.

Given Data / Assumptions:

• Equivalent evaporation is defined using saturated water at 100°C and atmospheric pressure as the reference state.
• Latent heat at 100°C is about 2257 kJ/kg.
• Comparison is independent of actual working pressure/temperature.

Concept / Approach:
Equivalent evaporation answers the question: “How many kilograms of water would this boiler evaporate per unit time if it were simply producing dry saturated steam at 100°C from water at 100°C?” Thus, the conventional reference conditions are 100°C and normal atmospheric pressure (approximately 1.013 bar), which fix the latent heat used as the denominator in the factor of evaporation.

Step-by-Step Solution:
Identify the reference: water and steam at 100°C under atmospheric pressure.Use latent heat h_fg ≈ 2257 kJ/kg as the comparison basis.Therefore, choose 100°C and normal atmospheric pressure as the standard reference.

Verification / Alternative check:
If a boiler actually produces dry saturated steam at 100°C from 100°C water, then equivalent evaporation equals actual evaporation (factor of evaporation = 1), confirming the chosen reference.

Why Other Options Are Wrong:
50°C entries: do not match the “from and at 100°C” standard basis.100°C at 1.1 bar: not the conventional atmospheric reference; 1.1 bar changes the latent heat.

Common Pitfalls:
Confusing equivalent evaporation with evaporation ratio; the former is a standardized energy-based conversion.

Final Answer:
100° C and normal atmospheric pressure