Sankey Diagram – Sankey Chart – Sankey Graph – Sankey diagrams are a type of a flow diagram where width of an arrow is proportionate to flow quantity. Sankey diagrams are often used to show energy flows. The below example shows energy loss in the combustion engine. Sankey Diagram Diagram - Chart - diagrams and charts with labels. This diagram depicts Sankey Diagram and explains the details of Sankey Diagram.