INTERACTION EFFECTS OF HYDRODYNAMICALLY FULLY DEVELOPED PRIMARY FLOW AND SECONDARY FLOW IN THE THERMAL ENTRANCE REGION OF ANNULAR DUCT
Main Article Content
Abstract
Experiments have been conducted to study the local and average heat transfer by mixed
convection for hydrodynamically fully developed, thermally developing and fully developed
laminar upward air flow in an inclined annulus with adiabatic inner cast iron tube and uniform
heated outer aluminum tube with an aspect ratio ( Ω = 0.72) and (L/Dh≈40) for both calming and
test sections). A wide range of Reynolds number from 859 to 2024 has been covered, and heat
flux has been varied from 159 W/m2 to 812 W/m2 (these values of heat flux and Reynolds
number gave Richardson number range from 0.03 to 0.٣٨), with angles of annulus inclination
φ =0o (horizontal position), φ =60o (inclined position), and φ =90o (vertical position). The hydrodynamically fully developed condition has been achieved by using aluminum annulus
(calming section) has the same dimensions as test section and has connected with it by Teflon
piece. The average Nusselt numbers have been correlated with the product of (Richardson
number and Reynolds number) and compared with available literature and showed satisfactory
agreement. The temperature and local Nusselt number profiles results have revealed that the
secondary flows created by natural convection have a significant effect on the heat transfer
process.
Article Details
Section
How to Cite
References
[Bergles A.E.and Simonds,R.R.] "Combined forced and free convection for laminar flow in a horizontal tube with
uniform heat flux". Int . J. Heat mass transfer Vol. 3, No. 14, PP-1989-2000 (1971).
[Holman J. P.] "Experimental Method for Engineers", McGraw-Hill, Tokyo, Japan, 4th Edition (1984).
[Holland F.A. , M.moores R.M., Wastor F.A and wilkingson J. K ] "heat transfer" Heinemann Educational Books, Loondon,(1970).
[Gada A. Sadiq] "Developing laminar mixed convection heat transfer through concentric annuli with adiabatic inner cylinder " M.SC. thesis, University of Baghdad , College of Engineering, Mars (2009).
[Ihsan Y. Hussain and Akeel A. Mohammed] "Laminar combined convection in the fully developed region of concentric inclined annulus with uniformly heated inner cylinder ",the 6th engineering conference, university of Baghdad, collge of
engineering. Vol.3: Mechanical and Nuclear Engineering, PP.19-35, 5-7 April (2009).
[Incropera F.P. and Dewitt D.P.] Fundamentals of Heat and Mass Transfer, fifth ed.,John Wiley and Sons Inc. , (2003).
[Kaviany M.] " Laminar combined convection in a horizontal annulus subjected to constant heat flux inner wall and adiabatic outer wall", J. Heat Transfer, Vol. 108, pp. 392-397, May, 1986.
[Kotake S. and Hattori N] "Combined forced and free convection heat transfer for fully developed laminar flow in
horizontal annuli" Int. J. Heat Mass transfer. Vol.28,No.11,PP.2113-2120, (1985).
[Nieckele A. O. and Patankar S. V] "Laminar mixed convection in a concentric annulus with horizontal axis "J. heat
transfer, Vol.107, PP.902-909, November, (1985).