Investigation of dissolved salts on heat transfer for aluminum alloy 2024 during spray quenching

摘要

An experiment was performed to investigate the influence of four dissolved salts (NaCl, CaCl2, Na2SO4 and MgSO4) on heat transfer. Concentration of all salts varied from 0.01 M to 0.4 M. And deionized water (DI water) was used as the solvent. The aluminum alloy 2024 thin sheets were heated to 495 degrees C and quenched by two spray nozzles with a constant range of volumetric flux. Time-temperature curves were smoothed by B-spline approximation with a smoothing parameter of 10(-4). The results indicate that only MgSO4 solution increases both nucleate boiling and transition boiling heat flux. Solution of CaCl2 has the greatest influence on nucleate boiling heat transfer, followed by Na2SO4 compared with the minimum influence of NaCl. These effects are attributed to the surface tension gradient, transition concentration and vapor pressure for different salts. The largest heat flux enhancement is observed at concentration of 0.2 M for solutions of NaCl, CaCl2 and MgSO4 in contrast to 0.06 M for Na2SO4. (C) 2016 Elsevier Ltd. All rights reserved.