Convection

Synthetic Course: written to test the Site template, from no Professor's material

Summary

A surface hands heat to the fluid around it

A surface warmer than the fluid flowing past it loses heat at a rate set by Newton’s law of cooling:

\dot{Q} = h A \left(T_s - T_\infty\right)

The heat transfer coefficient $h$ grows with the flow: still air gives a small $h$ , a fan or a pumped liquid a larger one. As a resistance, convection is $R = \frac{1}{h A}$ , so it adds in series with the wall it sits on.

Practice

1. A plate with a face of $A = 2\ \text{m}^2$ sits at $T_s = 80\ ^\circ\text{C}$ in air at $T_\infty = 20\ ^\circ\text{C}$ , with $h = 25\ \text{W/(m}^2\text{·K)}$ . Find the heat it loses, in kW.