The heat transfer coefficient is a measure of the effectiveness of heat transfer between a solid surface and a fluid flowing over or around it. It accounts for the combined effects of convection and thermal conductivity in transferring heat energy across the interface. The SI unit of heat transfer coefficient ($h$) is the Watt per square meter-kelvin (W/(m²·K)). The heat transfer coefficient ($h$) can be calculated using,

Where:

• $q$ is the rate of heat transfer,
• $h$ is the heat transfer coefficient,
• $A$ is the surface area of heat transfer,
• $\Delta T$ is the temperature difference between the fluid and the surface.