Furnace heat accounting visualisation: Which diagram is conventionally used to present a furnace heat balance in a clear, proportional, and diagrammatic form?

Introduction / Context:
Energy management in furnaces requires a concise visual of where input heat goes: to the stock, to walls, to flue gases, and to losses. Engineers commonly use a specific flow-proportional diagram to depict this distribution when auditing or optimizing furnace performance.

Given Data / Assumptions:

• The question asks for a “diagrammatic heat balance,” i.e., a plot where arrow widths scale with heat quantities.
• We focus on standard industrial practice in thermal systems.

Concept / Approach:
A Sankey diagram shows energy or mass flows with arrows whose widths are proportional to flow magnitudes. For furnaces, this directly communicates how much heat is used productively and how much is lost via flue gas, wall losses, openings, and radiation, enabling quick identification of improvement opportunities.

Step-by-Step Solution:
Identify the diagram type that scales arrow thickness with quantity: the Sankey diagram.Relate to furnace use: input fuel energy splits into useful heating and various losses; Sankey captures this.Select the correct option accordingly.

Verification / Alternative check:
Energy audit literature consistently illustrates furnace and boiler heat balances using Sankey diagrams because they intuitively display proportional flows and losses.

Why Other Options Are Wrong:
Cox/Ostwald charts: not standard for heat balance flow visualization.Mollier (h-s) chart: used for steam/water thermodynamic properties, not for heat balance depiction.None of these: incorrect because Sankey diagram is precisely the established tool.

Common Pitfalls:
Confusing property charts (state diagrams) with flow accounting charts; the former describe thermodynamic states, while Sankey diagrams portray energy distribution.

Final Answer:
Sankey diagram