The convective coefficient is a measure of the heat transfer rate between a solid surface and a fluid flowing over it. In the case of forced convection, the fluid flow is caused by an external force such as a pump or a fan. The convective coefficient depends on various factors including the properties of the fluid, the velocity of the fluid, and the nature of the surface.

The convective coefficient of air and superheated steam in the case of forced convection is typically in the range of 30-300 W/m^2K. This means that for every square meter of surface area, there is a heat transfer rate of 30-300 watts for every degree Kelvin temperature difference between the surface and the fluid.

The convective coefficient for forced convection is generally higher than that for natural convection (where the fluid flow is caused by density differences due to temperature variations). This is because forced convection involves a higher fluid velocity, which enhances the heat transfer rate.

The convective coefficient can vary depending on the specific conditions of the flow and the surface. For example, the convective coefficient for air might be higher than that for superheated steam due to the differences in the properties of the two fluids. Similarly, the convective coefficient can vary depending on the surface roughness and the presence of any obstructions that might disrupt the flow.

It is important to note that the given range of 30-300 W/m^2K is a general guideline and may not be applicable to all situations. The convective coefficient can be determined experimentally or estimated using correlations based on empirical data. These correlations take into account the fluid and surface properties, as well as the flow conditions, to provide a more accurate estimate of the convective coefficient.

Overall, the convective coefficient of air and superheated steam in the case of forced convection is typically in the range of 30-300 W/m^2K, indicating a moderate to high heat transfer rate between the surface and the fluid.