View source for Baffle (heat transfer)

{{Short description|Fluid-flow-directing vane or panel}}
[[Image:U-tube_heat_exchanger.svg|right|350px]]
[[File:Agitated vessel.svg|thumb|right|350px|Cross-sectional diagram of [[Continuous stirred-tank reactor|stirred tank reactor]]]]
'''Baffles''' are flow-directing or obstructing vanes or panels used to direct a flow of liquid or gas. It is used in some household stoves<ref>{{cite web |url=https://www.hansforsman.se/product.html/baffelplat-wamsler-k144s |access-date=22 July 2021|title=Baffelplåt till WAMSLER K144S }}</ref> and in some [[industrial process]] vessels (tanks), such as [[shell and tube heat exchanger]]s, [[chemical reactor]]s, and [[static mixer]]s.
Baffles are an integral part of the shell and tube heat exchanger design. A baffle is designed to support tube bundles and direct the flow of [[fluid]]s for maximum efficiency.  Baffle design and tolerances for heat exchangers are discussed in the standards of the [[Tubular Exchanger Manufacturers Association]] (TEMA).
==Use of baffles==
The main roles of a baffle in a shell and tube heat exchanger are to:
* Hold tubes in position (preventing sagging), both in production and operation
* Prevent the effects of [[steam starvation]], which is increased with both fluid  velocity and the length of the exchanger
* Direct shell-side fluid flow along the tube field. This increases fluid  velocity and the effective [[heat transfer]] co-efficient of the exchanger
In a static mixer, baffles are used to minimize the tangential component of velocity which causes vortex formation, and thus promotes [[Mixing (process engineering)|mixing]].<ref>''SPE/ANTEC 1999 Proceedings'' edited by SPE Staff pp. 163–164</ref>
In a chemical reactor, baffles are often attached to the interior walls to promote mixing<ref>''Chemical reactor modeling: multiphase reactive flows'' by Hugo A. Jakobsen,
published in 2008 by Springer-Verlag in Berlin Heidelberg, pp. 681–683
</ref> and thus increase [[heat transfer]] and possibly [[Reaction rate|chemical reaction rate]]s.
In a household stoves like Handölkassetten and similar stoves a baffle is used to prevent the gas from going directly up in the chimney and possibly causing a chimney fire and direct the gas towards the front of the oven before it continues upwards into the chimney.<ref>{{cite web |url=https://www.utsidan.se/forum/threads/taeltkamin-rund-el-rektangulaer.48168/page-2 |access-date=22 July 2021|title=Tältkamin rund el rektangulär |date=20 February 2008 }}</ref> In this case the baffle helps increase the efficiency of the stove as more heat leaves the gas before it exits.
*The baffles prevent the rotational flow without affecting radial or longitudinal flow. The tank is provided with baffles which prevent swirling and vortex formation. Except in very large tanks, four(4) baffles are placed.
==Types of baffles==
Implementation of baffles is decided on the basis of size, cost and their ability to lend support to the tube bundles and direct flow:
* Longitudinal Flow Baffles (used in a two-pass shell)
* Impingement Baffles (used for protecting bundle when entrance velocity is high)
* Orifice Baffles
* Single segmental
* Double segmental
* Support/Blanking baffles
* Deresonating (detuning) baffles used to reduce tube vibration(Anish Apw)
==Installation of baffles==
As mentioned, baffles deal with the concern of support and fluid direction in heat exchangers. In this way it is vital that they are spaced correctly at installation. The minimum baffle spacing is the greater of 50.8&nbsp;mm or one fifth of the inner shell diameter. The maximum baffle spacing is dependent on material and size of tubes.  The [[Tubular Exchanger Manufacturers Association]]<ref>[http://www.tema.org/ Tubular Exchanger Manufacturers Association, Inc.]</ref> sets out guidelines. There are also segments with a "no tubes in window" design that affects the acceptable spacing within the design. An important design consideration is that no recirculation zones or dead spots form – both of which are counterproductive to effective heat transfer.
==References==
<references/>
* (Editors) Perry, R.H. and Green, D.W. (Oct, 2007) ''Perry's Chemical Engineers' Handbook'' (8th ed.) McGraw-Hill {{ISBN|0-07-142294-3}}
*  Wolverine Tube Inc, (2008) ''Heat Transfer Data Book'' Available [https://web.archive.org/web/20090106162547/http://www.wlv.com/products/databook/ch1_4.pdf]
* Professor J. Kavanagh (2009) ''Heat Transfer Lectures 4&5'' Usyd Chemical Engineering Department
[[Category:Heat exchangers]]