Boiling is classified as pool boiling or flow boiling, depending on the presence of bulk fluid motion.
Pool Boiling and Flow Boiling
- Boiling is called pool boiling in the absence of bulk fluid flow and flow boiling (or forced convection boiling) in the presence of it. In flow boiling, the fluid is forced to move in a heated pipe or over a surface by external means such as a pump or from height. Therefore, flow boiling is always accompanied by other convection effects.
Sub-cooled Boiling and Saturated Boiling
Boiling is said to be sub cooled (or local) when the temperature of the main body of the liquid is below the saturation temperature Tsat (i.e., the bulk of the liquid is sub cooled) and saturated (or bulk) when the temperature of the liquid is equal to Tsat (i.e., the bulk of the liquid is satu
Void fraction in a Gas-Liquid Flow
The fraction of the channel volume that is occupied by the gas phase.
The fraction of the channel cross-sectional area that is occupied by the gas phase.
Quality Profile :- Vapour Quality is the percentage of mass in a saturated mixture that is vapour i.e. saturated vapour has a “quality” of 100%, and saturated liquid has a “quality” of 0%.
This type of boiling take place in Nuclear reactors and Aerospace Engines.
Flow boiling is also used in the cooling of Electronic Circuit Boards using Micro channels.
All the refrigeration cycles are based on flow boiling.
Cooling systems in various industries comprise of Flow boiling.