Here is an example. A long cylindrical sample 20 mm in diameter made of AISI 52100 steel is heated to 850oC and then intensively quenched by forsed water flow. What is minimum water flow which prevents transient nucleate boiling process?
We have developed such criteria, however we would like to compare sesults of calculations with the other methods of calculations to be sure that received data are absolutely correct.
Do you know who else is dealing with such problem?
According to our calculations, water flow should be more than 7.5 m/s. In this case convective heat transfer coefficient is 31500 W/m2K which provides direct convection during quenching. Calculations were made for cylindrical sample 20 mm in diameter which was cooled in the tube 40 mm in diameter by forsed water flow.
The generalized answer to your question would be: Provide a single-phase convective heat transfer coefficient sufficiently high to cause a temperature gradient in the boundary layer sufficiently high that the vapor bubble-tip temperature is too low to allow the bubble to escape the cavity from which it grows. (In other words: keep the metal surface temperature below the so-called 'Onset of Nucleate Boiling'-criterion.) Details of how this is calculated may be found in e.g. Collier: Convective Boiling and Condensation, and other textbooks on boiling heat transfer.
Yes, I agree. We have developed our own approach and we'll compare results of our calculations with the other methods you recommended. Thanks, Prof. Erling !
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Heat Transfer