Identify the situation where heat transfer occurs simultaneously by conduction, convection, and radiation in thermal systems.

Introduction / Context:
Engineers must recognize dominant heat-transfer modes to design efficient equipment. In many real systems, more than one mode operates simultaneously. Boiler furnaces are a classic example where conduction, convection, and radiation all play significant roles.

Given Data / Assumptions:

• Combustion gases at very high temperature are present.
• Metal enclosures, refractory linings, and boiler tubes exist.
• Flowing gas sweeps over heated surfaces.

Concept / Approach:
Radiation dominates heat transfer from the luminous flame and hot gas to furnace walls and tube banks. Convection accompanies the gas motion over the tubes. Conduction transmits absorbed heat through tube walls to the working fluid (water/steam). Recognizing all three modes is essential for accurate thermal calculations and material selection.

Step-by-Step Solution:

Verification / Alternative check:
Heat-flux measurements show radiation fractions are high near burners, while convective contributions increase downstream; metal wall temperature gradients confirm conduction through solids.

Why Other Options Are Wrong:

Melting ice: mainly convection in liquid and conduction within the solid; radiation is negligible without hot radiative surroundings.Surface condenser: dominant condensation convection with conduction through tubes; radiation is negligible at low temperatures.“No process involves all three”: contradicted by furnace practice and textbooks.

Common Pitfalls:
Underestimating radiation at high temperatures or ignoring conduction through metal walls when focusing on fluid-side coefficients only.

Final Answer:

Boiler furnaces in steam power plants