Question

The approximate rate equation for convective heat transfer between a surface and adjacent fluid is calculated by:

• A. Newton’s law of Cooling
• B. Kirchhoff’s law
• C. Newton’s first law
• D. Wein’s displacement law

Hint:

While called a "law," Newton's Law of Cooling is actually a defining equation for the convection coefficient $h$, which is not a property of the fluid but depends on the flow conditions and geometry.

Answer 1

The Correct Option is A

Concept: Convection involves the transfer of heat between a solid surface and a moving fluid.

• The rate of heat transfer depends on the surface area and the temperature difference.

• A proportionality constant $h$ (convective heat transfer coefficient) is used.

Step 1: Defining the Heat Transfer Equation.
The rate of convective heat transfer ($Q$) is given by: $Q = h \cdot A \cdot (T_s - T_f)$ Where $A$ is area, $T_s$ is surface temperature, and $T_f$ is fluid temperature.

Step 2: Identifying the Law.
This linear relationship between heat loss and temperature difference is known as Newton's Law of Cooling.

Step 3: Ruling out other options.
Kirchhoff's law and Wein's law relate to thermal radiation. Newton's first law relates to classical mechanics (inertia). Final Answer: (A)