{"id":14414,"date":"2017-05-22T10:27:02","date_gmt":"2017-05-22T10:27:02","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=14414"},"modified":"2022-10-24T07:27:35","modified_gmt":"2022-10-24T07:27:35","slug":"internal-flow","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/fluid-dynamics\/internal-flow\/","title":{"rendered":"Internal Flow"},"content":{"rendered":"
In fluid dynamics, internal flow is a flow for which a surface confines<\/strong> the fluid. Detailed knowledge of the behavior of internal flow regimes is important in engineering because circular pipes can withstand high pressures and hence are used to convey liquids. Non-circular ducts are used to transport low-pressure gases, such as air in cooling and heating systems. The internal flow configuration is a convenient geometry for heating and cooling fluids used in energy conversion technologies such as nuclear power plants<\/a>.<\/div><\/div>\n

For the internal flow regime, an entrance region<\/strong> is typical. In this region, a nearly inviscid upstream flow converges and enters the tube. The hydrodynamic entrance length<\/strong> is introduced to characterize this region and is approximately equal to:<\/p>\n

\"hydrodynamic<\/a><\/p>\n

\"Internal<\/a>
Source: White Frank M., Fluid Mechanics, McGraw-Hill Education, 7th edition, February, 2010, ISBN: 978-0077422417<\/figcaption><\/figure>\n

The maximum hydrodynamic entrance length, at ReD,crit<\/sub>\u00a0= 2300<\/strong> (laminar flow<\/strong>), is Le<\/sub> = 138d, where D\u00a0is the diameter of the pipe. This is the longest development length possible. In turbulent flow<\/strong>, the boundary layers grow faster, and Le<\/sub>\u00a0is relatively shorter. For any given problem, Le<\/sub>\u00a0\/ D<\/strong> has to be checked<\/strong> to see if Le<\/sub> is negligible compared to the pipe length. The entrance effects may be neglected at a finite distance from the entrance because the boundary layers merge and the inviscid core disappears. The tube flow is then fully developed<\/strong>.<\/p>\n

<\/span> Classification of Flow Regimes<\/div>
From a practical engineering point of view, the flow regime can be categorized according to several criteria<\/strong>.<\/p>\n

All fluid flow<\/strong> is classified into one of two broad categories or regimes. These two flow regimes are:<\/p>\n