It is known that, several boiling phases exists in regimes of boiling out of which interface evaporation exists up to excess temperature of 5 degree Celsius and nucleate boiling from 5 to 50 degree Celsius. The critical heat flux is attained here. Apart from this reason, is there anything to consider nucleate boiling phase in design of thermal equipment?
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Thank you İbrahim Halil Yılmaz , Md Washim Akram and Saad Najeeb Shehab for your responses.
Nucleate boiling is necessarily considered while going for boiling heat transfer. The peak heat flux is attained in this.
All the heat transfer equipment are designed in nucleate boiling phase only. In this phase, we can get maximum heat flux.
Dear Ibrahim Halil Yilmaz and Saad Nazzeb,
All thermal equipments are designed in nucleate boiling conditions only where the excess temperature ranges between 5 to 50 degree Celsius and maximum heat flux attained is 1MW/m2. However, heating beyond excess temperature above 50 degree Celsius may lead to decrease and then reach maximum heat flux of 1MW/m2 in film boiling regime according to boiling regime curve. Hence it is unnecessary to heat beyond excess temperature of 50 degree Celsius and is also waste of spending energy. It is also not true that getting more heat flux in film boiling regime is possible.
Owing to the technically problematic situations, in order to design or operate thermal equipment, they are done in nucleate boiling phase only not in film boiling.
Nucleate boiling is a phase where excess temperature (difference of surface to saturation) falls in between 5 degree Celsius to 50 degree Celsius. This is where, maximum heat flux is obtained. Hence all thermal equipments are designed in this phase only.
Nucleate boiling is considered and used for thermal equipments since all the equations and conditions are specified. The condition of design generally falls in this range of temperature.
All the thermal equipment considered for boiling heat transfer falls in the range of nucleate boiling phase only. Hence nucleate boiling concept is used in calculating boiling heat transfer.
Nucleate boiling phase is the one used to solve boiling heat transfer problems since number of equations are developed and the equipment are used to run in this range of excess temperature.
In boiling heat transfer, nucleate boiling phase is most essential and important in thermal equipment. This covers the entire range of operational features in evaluation of heat flux.
Nucleate boiling phase shows the way to proceed in evaluating various heat transfer parameters especially heat flux. All the heat transfer equipments operated also will be safe in this phase of operation.
Nucleate boiling phase is used only in heat transfer equipment design for evaluating boiling heat flux. The heat transfer equipment are made safe to operate in this region.
One has to consider this nucleate boiling phase for evaluation of boiling heat transfer since this gives the correct approach and has relevance.
Nucleate boiling phase is most suitable and reliable for boiling heat transfer equipment.
Nucleate boiling phase is in sense actual in evaluation of boiling heat transfer of thermal equipment.
Nucleate boiling is the one mostly and essentially considered in evaluating boiling heat transfer. This is the only phase all the boiling heat transfer equipment makes eligible to operate.
The characterization of the bubble size, growth and dependency in the environment conditions can be best studied and analyzed in nucleate boiling phase. Hence this has become much important.
In boiling phase, one can definitely define the stages of interface evaporation, nucleate boiling and film boiling. Nucleate boiling gives increase in heat flux to peak which is burnout point. Hence all the thermal equipments are designed and operated under nucleate boiling phase.
All the thermal equipments are designed under nucleate boiling phase since maximum heat flux can be attained with raise in excess temperature from 5 to 50 degree centigrade only. The equations can also be derived easily, are available and be used.
In evaluation of boiling heat transfer, nucleate boiling phase is considered, since in a small excess superheat (5 -50 degree Celsius), maximum heat flux is ontained. This is also advisable to run the thermal equipment in this region.
Out of interface evaporation, nucleate boiling and film boiling phases existing in boiling heat transfer, for designing thermal equipment, nucleate boiling phase is given prime importance, since with a small excess superheat, this region this gives peak wall heat flux.
All thermal and heat transfer equipment are designed and run in nucleate boiling phase, since the lowest excess temperature required to get or reach peak heat flux is attained in this region and the equations are also developed.
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