Numerical investigation of critical heat flux in subcooled flow boiling of nanofluids K. DolatiAsl 1 • Y. Bakhshan 1 • E. Abedini 1 • S. Niazi 1 Received: 26 April 2019 / Accepted: 19 July 2019 Ó Akade ´miai Kiado ´, Budapest, Hungary 2019 Abstract Nanofluid flow boiling and critical heat flux (CHF) are interesting topics for many researchers and have industrial application for preventing potential damages. On this basis, numerous experimental studies have been performed on the determination of CHF; however, due to the weakness of the existing correlations for this purpose, an accurate numerical study on CHF is yet needed to be reported. In the present study, the subcooled flow boiling of nanofluid has been simulated to predict CHF. For estimating the nucleation site density (NSD), a correlation is used, into which the liquid properties, flow characteristics and surface properties contribute. The studies were performed at different concentrations of alumina nanoparticles. The simulation results indicated error percentages below 10% in CHF estimation, confirming the reliability of the results. No significant difference was observed between the CHF values calculated in the simulation studies considering constant thermal properties for the nanoparticles, as compared to those obtained with variable thermal properties for the nanoparticles. Taking the tube in a horizontal position, rather than the vertical position, increased the CHF value. However, the increase in CHF was negligible. Keywords Simulation  Flow boiling  Critical heat flux  Nanofluid List of symbols A b The portion of wall surface covered by nucleating bubble (-) A i Interfacial area (-) C d Drag coefficient (-) C L Lift coefficient (-) C P Heat capacity (J kg -1 K -1 ) C wl Wall lubrication coefficient (-) d np Nanoparticle diameter (m) D b Bubble diameter (m) d bw Bubble departure diameter (m) F ~ D Interfacial drag force (N) F ~ Disp Turbulent force (N) F ~ L Interfacial lift force (N) F ~ wl Interfacial wall lubrication force (N) F v Correction factor (velocity) (-) F ~ vm Virtual mass force (N) F sub Correction factor (subcooling) (-) G Mass flux (kg s -1 m -2 ) h Heat transfer coefficient (-) h fg Latent heat of vaporization (J kg -1 ) Ja Jacob number (-) k Thermal conductivity (W m -1 K -1 ) K Correlation (-) M Molecular weight of the base fluid (kg mol -1 ) N Avogadro number = 6.022 9 10 23 (mol -1 ) N w Active site density scale (m -2 ) p Pressure (Pa) Pr Prandtl number (-) q Heat flux (W m 2 ) q e Evaporation heat flux (W m 2 ) q c Convective heat flux (W m 2 ) q q Quenching heat flux (W m 2 ) R Gas constant based on a molecular weight (J kg -1 K -1 ) & E. Abedini abedini@hormozgan.ac.ir K. DolatiAsl kianoush.dolati@gmail.com Y. Bakhshan bakhshan@hormozgan.ac.ir S. Niazi s.niazi@hormozgan.ac.ir 1 Department of Mechanical Engineering, University of Hormozgan, Bandar Abbas, Iran 123 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-019-08616-8