@Article{hmt.7.22,
AUTHOR = {Amnart Boonloi, Withada Jedsadaratanachai},
TITLE = {NUMERICAL INVESTIGATIONS ON HEAT TRANSFER AND FLOW  STRUCTURE IN A CIRCULAR TUBE WITH VARIOUS SHAPES OF  WINGLET VORTEX GENERATORS},
JOURNAL = {Frontiers in Heat and Mass Transfer},
VOLUME = {7},
YEAR = {2016},
NUMBER = {1},
PAGES = {1--16},
URL = {http://www.techscience.com/fhmt/v7n1/54680},
ISSN = {2151-8629},
ABSTRACT = {The numerical investigations on flow structure, heat transfer characteristic and thermal performance in a circular tube heat exchanger with various 
shapes of winglet vortex generators are reported. The rectangular winglet vortex generators (<i>RWVG</i>), delta winglet vortex generators (<i>DWVG</i>) and 
curve winglet vortex generators (<i>CWVG</i>) are inserted in the middle of the test tube on both downstream and upstream arrangements. The effects of 
blockage ratios; <i>BR</i> = 0.1 – 0.3, with single pitch ratio (<i>PR</i> = 1) and flow attack angle (α = 30o) on thermal performance are studied for the Reynolds 
numbers; <i>Re</i> = 100 – 2000. The numerical results are presented in terms of flow and heat transfer patterns; tangential velocity vectors, temperature 
distributions, local Nusselt number distributions, and compared with the smooth tube. As the results, it is found that the use of the winglets performs 
higher heat transfer rate, friction factor and thermal performance higher than the smooth tube for all cases. The rise of <i>BR</i> and <i>Re</i> leads to enhance on 
both the heat transfer rate and friction loss due to the stronger vortex flow. The <i>RWVG</i> provides the highest heat transfer rate and friction loss, while 
the <i>DWVG</i> gives the reversed result. The downstream arrangement produces higher heat transfer rate than the upstream. In addition, the thermal 
enhancement factor is found to be maximum at <i>BR</i> = 0.2, <i>Re</i> = 1000, for <i>RWVG</i> with pointing downstream around 2.52.},
DOI = {10.5098/hmt.7.22}
}