Transient CHF enhancement in High Pressure Pool Boiling on Rough Surface

Publication date: Available online 26 March 2018 Source:Chemical Engineering and Processing - Process Intensification Author(s): Avdhoot Walunj, A. Sathyabhama Experimental investigation of transient pool boiling heat transfer (PBHT) to saturated water from thick, non-lumped 20 mm diameter copper sample is carried at 1 bar, 5 bar and 10 bar pressure. The time constant (γ) of exponential heat supply is varied from 1 to 6. The unidirectional scratches are made on the surface to obtain wide range of surface roughness varying from Ra  = 0.106 μm to Ra  = 4.03 μm. The effect of surface roughness, pressure and time constant on transient critical heat flux (CHF) is extensively studied. Transient CHF enhancement for Ra  = 4.03 μm when γ = 1 is found to be 98.88%, 76.55% and 53.21% at pressures P = 1 bar, P = 5 bar and P = 10 bar, respectively, however it is found to be lower by 9.38%, 21.40% and 9.73%, compared to steady state CHF enhancement for Ra  = 4.03 μm, at respective pressures. The Gorenflo correlation is modified by including the additional parameter γ and it predicts the present transient HTC values with mean absolute error (MAE) of 14.91%. The CHF model is developed by considering the effect of capillary wicking in the narrow unidirectional scratches and the bubble angle. This model predicts the present transient CHF values with MAE of 11.89%. Graphical abstract

Source: Chemical Engineering and Processing: Process Intensification - March 27, 2018 Category: Chemistry Source Type: research