Regular Article

Nanofluid Al₂O₃–H₂O evaporation: energy and deposition patterns^★

¹ Key Lab of Refrigeration Technology, Tianjin Univ. of Commerce, 300134 Tianjin, PR China
² LMT/ENS-Cachan/CNRS/Paris-Saclay Univ., 61 av du Présdent Wilson, 94235 Cachan, France

^* e-mail: lbtjcu@tjcu.edu.cn

Received: 6 March 2018
Received in final form: 28 June 2018
Accepted: 11 July 2018
Published online: 18 October 2018

Abstract

This study experimentally investigated the deposition patterns of Al₂O₃–H₂O nanofluid droplets with mass concentration of 0.05%, 0.2%, 1% and 3% after evaporating on transparent glass substrate with temperature of 30 °C, 40 °C, 50 °C and 60 °C, obtaining three typical kinds of patterns: the peripheral ring, the thin uniform layer with a thicker ring at the periphery and the concentric circular respectively. With the increase of concentration, the uniform pattern embedded in the peripheral ring changes into a concentric circular pattern gradually. The flow velocities corresponding to the three typical forces were solved and the results are 10⁻³ < V_ma/V_{rad − a} < 10⁻² and 10⁻²⁸ < V_DLVO+/V_{rad − a} < 10⁻⁵ (Marangoni, V_ma, the integral mean value of the entire radius V_{rad − a} and the velocity caused by DLVO force V_DLDO+). This indicated that the radial flow played a dominant role in the formation of the deposition pattern.