%0 Journal Article
%T Enhancement of Heat Transfer by Ultrasound: Review and Recent Advances
%A Mathieu Legay
%A Nicolas Gondrexon
%A St¨¦phane Le Person
%A Primius Boldo
%A Andr¨¦ Bontemps
%J International Journal of Chemical Engineering
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/670108
%X This paper summarizes some applications of ultrasonic vibrations regarding heat transfer enhancement techniques. Research literature is reviewed, with special attention to examples for which ultrasonic technology was used alongside a conventional heat transfer process in order to enhance it. In several industrial applications, the use of ultrasound is often a way to increase productivity in the process itself, but also to take advantage of various subsequent phenomena. The relevant example brought forward here concerns heat exchangers, where it was found that ultrasound not only increases heat transfer rates, but might also be a solution to fouling reduction. 1. Introduction In engineering applications, ultrasound is helpfully used to improve systems efficiencies. Intensifying chemical reactions, drying, welding, and cleaning are among the various possible applications of ultrasonic waves [1]. An analogous observation can be made for heat transfer processes, which are omnipresent in the industry: cooling applications, heat exchangers, temperature control, and so forth. It is somewhat logical and natural to wonder what could be the influence of ultrasound upon heat transfer systems. Strangely, it has not been a research topic deeply investigated until recently. It appears that researches undertaken in the past concerned basic systems, usually with a single fluid, such as heating rods or walls in a volume of water subjected to ultrasonic vibrations. The tendency goes toward systems getting more complicated (e.g., cooling of tiny components, vibrating structures for heat exchangers) and models becoming more accurate with powerful numerical simulations for example. The objectives of this paper are to provide scientific and historical backgrounds to the future studies concerning heat transfer enhancement by ultrasonic vibrations and to bring forward the evolution of this domain with several examples of applications. The first part describes an overview of ultrasound, induced phenomena, and how they positively influence heat transfer processes. Then, examples drawn from various fields of interest are analysed (thermal engineering, food industry, experimental and numerical simulations). Emphasis is made on the best improvements and results obtained. Finally, recent adaptation of ultrasonic technologies to heat exchanger devices is discussed thoroughly, with examples drawn from new patents and current laboratory work. 2. Generalities about Ultrasound 2.1. Standard Classification by Power, Frequency, and Use Acoustic waves of which frequencies are higher than
%U http://www.hindawi.com/journals/ijce/2011/670108/