To use all functions of this page, please activate cookies in your browser.

my.chemeurope.com

With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.

- My watch list
- My saved searches
- My saved topics
- My newsletter

## Critical heat flux
## Additional recommended knowledgeNOTE: the ## DescriptionWhen a liquid coolant undergoes a change in phase due to the absorption of heat from a heated solid surface, a higher transfer rate occurs. The more efficient heat transfer from the heated surface (in the form of heat of vaporization plus sensible heat) and the motions of the bubbles (bubble-driven turbulence and convection) leads to rapid mixing of the fluid. Therefore, The use of boiling is limited by a condition called Consequently, the occurrence of CHF is accompanied by an inordinate increase in the surface temperature for a surface-heat-flux-controlled system. Otherwise, an inordinate decrease of the heat transfer rate occurs for a surface-temperature-controlled system. This can be explained with Newton's law of cooling:
where ## UseThe understanding of CHF phenomenon and an accurate prediction of the CHF condition are important for safe and economic design of many heat transfer units including nuclear reactors, fossil fuel boilers, fusion reactors, electronic chips, etc. Therefore, the phenomenon has been investigated extensively over the world since Nukiyama (1934) first characterized it. In particular, a large amount of significant work has been done during the last four decades with the development of water cooled nuclear reactors. Now many aspects of the phenomenon are well understood and several reliable prediction models are available for conditions of common interests. A number of different terms are used to denote the CHF condition: departure from nucleate boiling (DNB), liquid film dryout (LFD), annular film dryout (AFD), dryout (DO), burnout (BO), boiling crisis (BC), boiling transition (BT), etc. DNB, LFD and AFD represent specific mechanisms which will be introduced later. DO means the disappearance of liquid on the heat transfer which properly describes the CHF condition; however, it is usually used to indicate the liquid film dryout from annular flow. BO, BC and BT are phenomenon-oriented names and are used as general terms. The CHF condition (or simply the CHF) is the most widely used today, though it may mislead one to think as if there exists a criticality in the heat flux. The terms denoting the value of heat flux at the CHF occurrence are CHF, dryout heat flux, burnout heat flux, maximum heat flux, DNB heat flux, etc. The term peak pool boiling heat flux is also used to denote the CHF in pool boiling. |

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Critical_heat_flux". A list of authors is available in Wikipedia. |