Transient heat transfer performance of stainless steel structured surfaces combined with air-water spray evaporative cooling at high temperature scenarios

Abstract

The objective of the study is to enhance heat transfer performance of stainless steel structured surfaces with different geometries at different initial sample temperature (Ts) under air-water spray having constant spray parameters. Square fin, straight fin and pyramid fin (2 geometries each) are machined on stainless steel blocks. A smooth reference surface (FL) is used as base line. Commercial inverse heat conduction solver INTEMP is used to estimate the time-varying surface heat flux and surface temperature. Burnout heat flux (qb) and critical heat flux (qc) showed significant increase for wide square fin (Sq-W) sample at all tested sample temperatures with respect to smooth reference surface. The highest cooling rate of 166 °C/sec was achieved with Sq-W sample for Ts= 900 °C. In addition, heat transfer coefficient, h increases gradually with decreasing surface super heat (ΔT). A sharp increase in heat transfer coefficient is observed when cooling process enter into nucleate boiling regime. Wide square fin structured surface showed h-curve sharp increase in nucleate boiling regime earlier than other tested samples. Boiling Number (Bo) for pyramid narrow fin (Py-N) and square wide fin (Sq-W) is higher than smooth flat surface (FL).