Why is the heat transfer coefficient of superheated steam lower than that of saturated steam?
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It has been said that steam with high superheat is used less often, as its heat transfer coefficient is much lower than that of saturated steam. Does that hero know why?
The superheated steam is cooled; it’s heat exchange between gases, so of course the temperature drops. And saturated vapor undergoes condensation, so of course it’s high.
Superheated steam is generally used for transportation, as this results in fewer losses, since there is no phase change when superheated steam turns into saturated steam
When superheated steam turns into saturated steam, there is no phase change – it is merely a change in temperature; this is what is referred to as sensible heat. On the other hand, when saturated steam turns into water, a phase change occurs, and latent heat of vaporization is released.
When superheated steam transfers heat, its temperature drops; this is a case of single-phase flow convective heat transfer, and the heat transfer coefficient is low. However, steam is often superheated during pipeline transportation, which reduces the heat loss during transport. Moreover, as it overheats, the pressure increases and the speed speeds up.