Molecular dynamic simulation to study the effects of roughness elements with cone geometry on the boiling flow inside a microchannel

M Zarringhalam and H Ahmadi-Danesh-Ashtiani and D Toghraie and R Fazaeli, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 141, 1-8 (2019).

DOI: 10.1016/j.ijheatmasstransfer.2019.06.064

Present work studies effects of presence of surface roughness elements with cone geometry on the boiling flow behavior of Argon fluid inside microchannels which are affected by different boundary wall temperatures using molecular dynamic simulation method. Firstly, microchannel is simulated with smooth surfaces under boundary wall temperatures of 84 K, 96 K, 108 K, 114 K and 133 K to prepare boiling condition for Argon atoms. Microchannel surfaces are roughened by cone shape of roughness elements and mentioned temperatures are applied on the roughened microchannel walls to be comparable with smooth one. Also, an external driving force of 0.002 eV/A is applied on the Argon atoms at the entrance of both rough and smooth microchannels for all cases of wall temperatures. Statistical approach is employed to compare results of both microchannels. It is reported that adding roughness elements on the smooth surfaces of microchannel can extend contact surfaces of energy transfer which empowers boiling process of fluid flow. Presence of cone geometry of roughness elements causes fluid flow velocity reduction as much as 0.5-1.5%. Also, it is observed that roughness elements results in enhancement of temperature profiles of fluid. Moreover, it is found that role of roughness element in low time steps is stronger than high time step. Therefore, evolution of boiling process can reduce consequences of roughness on the flow behavior. Finally, due to ignorable consequences of roughness element on the boiling flow behavior, it is concluded that preparing very smooth surfaces is not economical for practical application such as medical micro probes to destroy abnormal or diseased tissues. (C) 2019 Elsevier Ltd. All rights reserved.

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