Exceptional heat transfer performance induced by intrinsic flow oscillations during subcooled flow boiling over a copper mesh surface

Abstract

An experimental investigation of subcooled flow boiling heat transfer in an orthogonal macro channel (dh = 16 mm) is undertaken. An extraordinary heat transfer performance is observed when a single copper wire mesh screen covers the heating surface of the channel. Experiments are performed with deionized water, at a mass flux range of 100–410 kg/m2s and a heat flux range of 50–850 kW/m2. A series of highly subcooled flow boiling experiments demonstrates the existence of regions of heat transfer enhancement, compared to a smooth reference surface. The addition of the mesh layer triggers a self-sustained flow instability accompanied by intense pressure oscillations which allows for remarkably thermally steady state conditions to take place. While in several heat transfer studies, the appearance of pressure oscillations has been attributed with heat transfer deterioration, in the current study we observe that a self-sustained oscillatory flow leads altogether to heat transfer enhancement, baring close resemblance to the well-known microbubble emission boiling flow phenomenology and heat transfer. Aspects of temperature, pressure and flow regimes are presented and discussed accordingly.