In the following graph, the vertical axis represents the heat to be removed and the horizontal axis represents the airflow; both axes are logarithmic.
Power Dissipation vs. Airflow for Various Temperature Increases.
The sloping lines define the temperature rise in o C.To use the graph, find the sloping line that represents the permitted temperature rise.
Then, find the point on this line that corresponds to the heat to be removed.
The horizontal position of this point shows the airflow required.