Title: Experimental study on CuO nanoparticles in distilled water and its effect on heat transfer

Authors: Ramakrishna N. Hegde; Srikantha S. Rao; Ranapratap P. Reddy

Addresses: National Institute of Technology, MF 4/10, Block D, Nandini Layout, Bangalore, Karnataka State, 560096, India; Department of Mechanical Engineering, Ramaiah Institute of Technology, MSR Nagar, Bangalore, 560054, India. ' Department of Mechanical Engineering, National Institute of Technology, Surathkal, 575025, India. ' Reva Institute of Technology, Yelahanka, Bangalore, 560064, India

Abstract: The pool boiling characteristics of dilute dispersions of CuO nanoparticles in water were studied using a 36 gauge NiCr wire at atmospheric pressure. Significant enhancement in critical heat flux (CHF) can be achieved at modest nanoparticle concentrations (< 0.1% by volume) without facing any problem of agglomeration and fouling. During experimentation and subsequent inspection, formation of a porous layer of nanoparticles on the heater surface was observed. Boiling of nanofluid resulted in nanoparticle deposition smoothing the surface at lower concentration. To substantiate the nanoparticle deposition and its effect on critical heat flux, investigation was done by measuring the surface roughness and SEM images of the wire surface. While SEM images revealed particle coating, measurement of surface roughness indicated surface modification. Formation of the porous layer on the heater surface as revelled by SEM images provided an excellent location for nucleation sites and subsequent bubble formation. Flow visualisation of the CuO nanofluid (0.1 g/l) up to critical heat flux gave an idea of bubble growth. The experimental results showed the evidence of nanoparticle deposition on the wire surface enhancing critical heat flux.

Keywords: CuO nanofluids; nanoparticle deposition; critical heat flux; CHF; pool boiling; flow visualisation; nanoparticles; nanotechnology; cupric oxide; surface roughness; surface quality; distilled water; heat transfer; nucleation; bubble formation; NiCr wire; nickel chromium wire.

DOI: 10.1504/IJNP.2012.044495

International Journal of Nanoparticles, 2012 Vol.5 No.1, pp.16 - 36

Received: 09 Nov 2010
Accepted: 22 Mar 2011
Published online: 20 Aug 2014 *

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