EHD enhanced heat transfer in a vertical annulus B Walter Grassi T , Daniele Testi, Mario Saputelli LOTHAR (LOw gravity and THermal Advanced Research laboratory), Department of Energetics bL. Poggi Q, University of Pisa, via Diotisalvi 2, 56126 Pisa, Italy Available online 17 March 2005 Abstract The preliminary experimental results of the effect of an electrostatic field on turbulent aided mixed convection in a short vertical annulus are reported herein. A dielectric liquid (FC-72 by 3M) is used as working fluid. The local heat transfer improvement is obtained by inserting appropriate points on the inner surface of the annulus, generally acting as the positive electrode, while the surrounding pipe is grounded. A high voltage (up to 22 kV) is established between the two surfaces. The heat exchange revealed to be highly enhanced by this technique, thus providing encouraging indications for practical applications. D 2005 Elsevier Ltd. All rights reserved. Keywords: EHD; Enhanced heat transfer; Vertical annulus 1. Introduction The material presented herein represents the very beginning of a broader research work aimed at performing a feasibility study of an EHD (electrohydrodynamic) enhanced high efficiency compact heat exchanger for space applications. In particular we, at first, confined our interest to the rather weak flow typical of a cold plate. Before starting a very systematic investigation, we checked the existence of the foreseen effects and their real extent in terms of heat transfer enhancement. As this initial step provided us with very encouraging indications, we decided to immediately communicate them. In the meantime we started performing a very detailed experimental campaign, as required by the complexity of the involved matter and by the high potentiality of this technique. With the above aim in mind, we will not 0735-1933/$ - see front matter D 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.icheatmasstransfer.2004.10.011 B Communicated by J.W. Rose and A. Briggs. T Corresponding author. E-mail addresses: w.grassi@ing.unipi.it (W. Grassi)8 d.testi@ing.unipi.it (D. Testi). International Communications in Heat and Mass Transfer 32 (2005) 748 – 757 www.elsevier.com/locate/ichmt