In furnace heat-transfer calculations, the Lobo and Evans method is primarily applied to estimate which of the following quantities?

Introduction / Context:
The Lobo and Evans method is a classic furnace engineering approach used in fired-heater design and performance checks. Understanding what it specifically calculates helps separate furnace-radiation analysis from unrelated heat-transfer or mass-transfer problems.

Given Data / Assumptions:

• Industrial fired heater or furnace with distinct radiant and convective sections.
• Radiant-section tubes absorb heat mainly by thermal radiation from hot gases and flames.
• The method offers a systematic way to estimate radiant heat absorption.

Concept / Approach:
In the radiant section, radiation dominates. The Lobo and Evans method relates furnace geometry, gas emissive power, tube surface characteristics, and view factors to compute the heat absorbed by the tubes. It is not a mass-transfer method and not focused on external forced convection (like reboilers) or vacuum-condensation duties, which involve different mechanisms and correlations.

Step-by-Step Solution:
Identify problem domain: fired-heater radiant section.Recall method purpose: estimate radiant heat absorbed by process tubes.Select the matching choice accordingly.

Verification / Alternative check:
Heater design texts list the Lobo and Evans method alongside other radiant-section design procedures (e.g., Hottel-type or zone methods), all explicitly targeting radiant heat absorption, not convective reboilers or condensers.

Why Other Options Are Wrong:
Forced convection in a reboiler / Vacuum condensers: Different equipment and governing correlations.Mass transfer coefficient: Outside the heat-radiation focus of the method.

Common Pitfalls:

• Mixing up furnace radiant calculations with convection-dominated exchangers.
• Confusing named methods across heat and mass transfer contexts.

Final Answer:
heat absorption in radiant section of a furnace.