Effect of heat transfer enhancement on pyrolysis coking process for n-decane at supercritical pressure in corrugated cooling channels

Abstract

The safety of engine cooling systems is compromised by hydrocarbon fuel pyrolytic coking. In this study, a numerical model based on a dynamic grid technique was developed at a supercritical pressure of 4 MPa, the model comprised a detailed chemical kinetic model of n-decane and an empirical pyrolytic coking kinetic model. The chemical kinetic model included 16 species and 26 elementary reactions. The flow and heat transfer in smooth and corrugated channels of length 500 mm, mass flow rate 1.5 g/s, inlet temperature 300 K, and wall heat flux 1.3 MW/m2 were studied after 20 min of transient coking. Compared with that in the smooth channel, the temperature of the corrugated external wall decreased by a maximum of 160K, and the amount of coke decreased by 51.89%. The convective heat transfer and Nusselt coefficients for the corrugated channel increased by a maximum of 36.3% and 42.4%, respectively. The pressure drop in the cooling channel changed after pyrolytic coking. The change in the pressure drop after 20 min of pyrolytic coking in the smooth channel was 9.89%, whereas it was only 4.39% in the corrugated channel. This indicates that the coking in the corrugated channel had a smaller effect on the flow distribution.