For the boiling curve and the table data in the figures belo

For the boiling curve and the table data in the figures below: What is happening as the heater power is increased from point C to point D?

Solution

When, Texcess is increased past point C, the heat flux decreases. This is because a large fraction of the heater surface is covered by a vapor film, which acts as an insulation due to the low thermal conductivity of the vapor relative to that of the liquid. Liquids take too much heat and they form huge amount of vapor that cause the formation of vapor blanket or vapor cover. Thus the surrounding liquids find it hard to get into the heater surface. That’s why we see the significant heat flux drop. Here the heat transfer rate decreases.

Liquids take too much heat and they form huge amount of vapor that cause the formation of vapor blanket or vapor cover. Thus the surrounding liquids find it hard to get into the heater surface. That’s why we see the significant heat flux drop. Here the heat transfer rate decreases.