Convection heat transfer rate, as described by Newton's cooling law, does not include a term for relative velocity between the fluid and solid surface, yet faster airflow over a hot surface intuitively seems to enhance cooling. In scenarios of very fast convection, the fluid temperature approaches that of the solid, indicating that heat transfer does not depend on velocity, while slow convection results in proportional heat transfer to velocity. The discussion clarifies that convection does depend on relative velocity, particularly affecting the heat transfer coefficient, which is often treated as a constant in basic heat transfer courses. Empirical formulas for heat transfer coefficients, influenced by parameters like Reynolds number, are derived from experimental data rather than theoretical assumptions. Understanding these principles helps in accurately applying convection laws in various fluid scenarios.
