Augmentation of Heat Transfer by Creation of Streamwise Longitudinal Vortices Using Vortex Generators

Abstract

This paper summarizes the current state of the art related to improvement of the heat exchanger surfaces using streamwise longitudinal vortices. Primarily, the improvements related to fin-tube cross-flow heat exchangers and the plate-fin heat exchangers have been addressed. Protrusions in certain forms, such as delta wings or winglet pairs, act as vortex generators, which can enhance the rate of heat transfer from the heat-exchanger surfaces that may be flat or louvered. The strategically placed vortex generators create longitudinal vortices, which disrupt the growth of the thermal boundary layer, promote mixing between fluid layers, and hence lead to augmentation in heat transfer. The flow fields are dominated by swirling motion associated with modest pressure penalty. Heat transfer is augmented substantially for all the proposed configurations of the longitudinal vortex generators, such as delta wings, rectangular winglet pairs, and delta winglet pairs, with varying degree of pressure penalty. Both computational and experimental investigations on flow and heat transfer in the heat exchanger passages with built-in vortex generators are revisited and summarized.

Performance enhancement of a louvered fin heat exchanger by using delta winglet vortex generators

“…Heat exchanger performance can also be improved by introduction and/or exploitation of secondary flows, which result in a smaller pressure drop penalty [11]. A typical example of this secondary flow enhancement is the use of longitudinal vortex generators [12,13]. These protrusions from the heat transfer surface generate longitudinal vortices which cause an intense mixing of the downstream flow and thin the thermal boundary layers.…”

Effect of perforated concave delta winglet vortex generators on heat transfer augmentation of fluid flow inside a rectangular channel: An experimental study

“…Their work informed that the use of delta winglet VG increases the effectiveness of heat transfer by 16.6% of that without using VG. The improvement of heat transfer using a longitudinal vortex generator (LVG) has been studied by Gautam Biswas et al [8]. Zdanski et al studied the effects of delta winglet VG on convection heat transfer in the arrangement of in-line tubes [9].…”

Classification and Separation of Granules in Vortex Granulators

“…The results of calculations are confi rmed by experimental investigations performed on a prototype of a suspended-layer vortex granulator. The optimum design of the work space of a suspended-layer vortex granulator as a function of the required fractional composition of the granulated product may be determined on the basis of results of theoretical and experimental investigations.Swirling of fl ows is one of the most effi cient methods of intensifying heat and mass exchange processes in chemical engineering [1][2][3].Through the use of vortex fl ows, it becomes possible to achieve stabilization of the hydrodynamic conditions in an apparatus and to equalize the temperature inside the apparatus.The introduction of suspended-layer vortex granulators into the technology employed in producing mineral fertilizers, granules with special properties, or multilayer granules has made it possible to raise the specifi c output of granulation plants and increase the degree of monodispersivity of the fi nished product, and to also realize production effi ciency [4].The creation of multifunctional apparatuses that can achieve several processes in a single work cycle (for example, granulation and cooling, granulation and drying, granulation and classifi cation) [5] represents a promising direction in the development of the technology of granulation.Granulators with constant cross-sectional area do not fully assure realization of processes of classifi cation and separation in view of the fact that in these types of apparatuses the ascending (fl ow) component of the total velocity of the gas fl ow is constant and equal to the working rate of suspension of particles of a given dimension (polydispersed system of narrow fractional composition). The value of the working rate of suspension for suspended-layer apparatuses is given by…”

“…Swirling of fl ows is one of the most effi cient methods of intensifying heat and mass exchange processes in chemical engineering [1][2][3].…”