In a heat-balance visualization for industrial heating processes, what is the name of the diagram where the width of each band is proportional to the quantity of heat flowing through that item?

Introduction / Context:
Engineers use graphical tools to communicate energy flows and losses in furnaces, heaters, and plant utilities. The most recognizable visualization is the diagram where flow thickness represents magnitude, enabling quick identification of major heat sinks and inefficiencies.

Given Data / Assumptions:

• We are representing a heat balance for a furnace or heating process.
• Each stream (useful absorption, stack loss, wall loss, leakage) is shown with a proportional band.
• The intent is intuitive comparison, not detailed time histories.

Concept / Approach:
A Sankey diagram scales the width of each arrow/band with the flow quantity (here, heat). This instantly highlights dominant terms such as radiant absorption vs. stack losses. In energy audits, Sankey diagrams often accompany KPIs to prioritize improvement projects (e.g., air preheating or insulation upgrades).

Step-by-Step Solution:
Match description: band width proportional to heat quantity.Recognize the canonical name: Sankey diagram.Select the corresponding option.

Verification / Alternative check:
Heat and mass balance visualizations in textbooks and audit reports consistently label such proportional-flow diagrams as Sankey diagrams, regardless of the domain (energy, material, money).

Why Other Options Are Wrong:
Ostwald/Cox charts: These are not the standard names for proportional-flow energy diagrams.None of these: Incorrect because “Sankey diagram” is the well-established term.

Common Pitfalls:

• Confusing Sankey with ordinary block flow or schematic piping diagrams.
• Assuming uniform line widths convey quantities; they do not.

Final Answer:
Sankey diagram