Enhanced heat transfer and power dissipation in oscillatory-flow tubes with circular-orifice baffles: a numerical study

The present study is investigated the causes of enhanced heat transfer during the melting process of solid-liquid PCM (Phase Change Material) using an ultrasonic vibration. Paraffin (noctadecane) was selected as a PCM and experimental studies were performed as following. Heat transfer coefficient and enhancement ratio of heat transfer was measured, acoustic streaming induced by ultrasonic waves observed using a PIV (Particle Image Velocimetry) and thermally oscillating flow phenomenon observed using an infrared thermal camera during the melting process. For the numerical study, a coupled FE-BEM (Finite Element-Boundary Element Method) was applied to investigate acoustic pressure occurred by acoustic streaming in a medium. And then, the profiles of pressure variation compared with the enhancement ratio of heat transfer. The results of this study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming and thermally oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. Also, as the acoustic pressure occurred by acoustic streaming increases, the higher enhancement ratio of heat transfer is obtained.

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NUMERICAL STUDY OF OSCILLATORY FLOW AND HEAT TRANSFER IN A LOADED THERMOACOUSTIC STACK

Numerical Heat Transfer Part A Applications ◽

10.1080/104077899275362 ◽

1999 ◽

Vol 35 (1) ◽

pp. 49-65 ◽

Cited By ~ 31

Author(s):

Aniruddha S. Worlikar

Keyword(s):

Heat Transfer ◽

Oscillatory Flow ◽

Numerical Study ◽

Flow And Heat Transfer

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Enhanced heat transfer during oscillatory flow in annular channels

Heat Transfer-Asian Research ◽

10.1002/htj.20094 ◽

2005 ◽

Vol 35 (1) ◽

pp. 61-74

Author(s):

Yuichi Ohno ◽

Gaku Tanaka ◽

Makoto Hishida

Keyword(s):

Heat Transfer ◽

Oscillatory Flow ◽

Enhanced Heat Transfer ◽

Annular Channels

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A Numerical Study on the Temperature Field of Oscillatory Flow Reactor with Conic Ring Baffles

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.455-456.121 ◽

2012 ◽

Vol 455-456 ◽

pp. 121-126 ◽

Cited By ~ 1

Author(s):

Peng Wu ◽

Jia Wu ◽

Wei Li

Keyword(s):

Heat Transfer ◽

Temperature Field ◽

Oscillatory Flow ◽

Flow Reactor ◽

Numerical Study ◽

Maximum Temperature ◽

Vortex Interaction ◽

3 Dimensional ◽

Bias Flow ◽

Experimental Researches

In published papers, the experimental researches have been carried out on heat transfer in Oscillatory Flow Reac-tors (OFRs) with annular baffles in both batch and continuous modes. It’s found that even with low net flow rates (or without net flow) the heat transfer properties of OFR can match turbu-lent pipe flow. But there’s no paper shows the micro-structure of temperature field in OFRs to illustrate the heat transfer mechan-ism. In this paper, we report our 3-dimensional numerical simu-lation results of heat transfer of OFR with novel conic ring baf-fles which is particularly suitable for liquid-solid systems. The temperature field of conic baffled OFR was obtained by using the commercial CFD package CFX11.0. It’s found that in “soft” mix-ing region the maximum temperature gradient lies approximate-ly in the middle of each cell, i.e. between the two pairs of vortices. It can be speculated that the convection caused by the intense vortex interaction leads to heat transfer essentially. When it’s global mixing, severe bias flow occurs. The temperature field becomes more chaotic and the heat convection is caused by more disordered vortex interaction.

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