Experimental study on the characteristics of CHF and pressure fluctuations of surfactant solution flow boiling

The critical heat flux (CHF) and presure fluctuation characteristics of surfactant solution flow boiling were studied experimentally and compared to that of pure water. The tested fluid was an aqueous solution of cetyltrimethyl ammonium chloride (CTAC) with addition of sodium salicylate (NaSal) at the same mass concentration. Tests were performed in a flow channel with 6.0 × 3.5 mm cross-section over flow rate range of 192-406 ml/min, at 80 °C inlet temperature and 101.3 kPa outlet pressure. The present experimental results show that, the CTAC/NaSal solutions behave an increased CHF: the value of CHF kept nearly constant at a level about 1.26 times of that of pure water when the solution concentration was beyond 100 ppm (ppm: part per million). And the CTAC/NaSal solution had stronger pressure fluctuations than water. Visualization of the flow boiling process shows that bubbles in CTAC/NaSal solution have smaller diameters and larger population density than that in water, which may be the reason of higher CHF for surfactant solution case. And the bubbles in CTAC/NaSal solution existed for a longer time than in water, which was about ten times of the bubbles in water. These bubbles increased flow velocity and enhanced disturbances, which may be another reason of flow boiling heat transfer enhancement and stronger pressure fluctuations.