Chapter 1.11, Problem 97RP

It is well known that cold air feels much colder in windy weather than what the thermometer reading indicates because of the “chilling effect” of the wind. This effect is due to the increase in the convection heat transfer coefficient with increasing air velocities. The equivalent wind chill temperature in °F is given by [ASHRAE, Handbook of Fundamentals (Atlanta, GA, 1993), p. 8.15]

$\begin{array}{l}{T}_{\text{equiv}}=91.4-\left(91.4-T_{\text{ambient}}\right)\\ \times \left(0.475-0.0203V+0.304\sqrt{V}\right)\end{array}$

where V is the wind velocity in mi/h and T_ambient is the ambient air temperature in °F in calm air, which is taken to be air with light winds at speeds up to 4 mi/h. The constant 91.4°F in the given equation is the mean skin temperature of a resting person in a comfortable environment. Windy air at temperature T_ambient and velocity V will feel as cold as the calm air at temperature T_equiv. Using proper conversion factors, obtain an equivalent relation in SI units where V is the wind velocity in km/h and T_ambient, is the ambient air temperature in °C.

$\begin{array}{l}Answer:T_{\text{equiv}}=33.0-\left(33.0-T_{\text{ambient}}\right)\\ \times \left(0.475-0.0126V+0.240\sqrt{V}\right)\end{array}$