Analysis of the effect of pyrolytic coking on the flow and heat transfer performance of n-decane in cooling channels at supercritical pressure

Abstract

• Coking deposition of n -decane on the inner surface of the cooling channel was simulated. • This model is capable of making reasonably accurate predictions in pyrolytic coking. • The effects of pyrolytic coking on flow, heat transfer, and pyrolysis performance were investigated. The formation and deposition of coke in cooling channels is the main factor that limits the application of regenerative cooling. To study the effects of coking deposition on regenerative cooling performance under heavy-cracking conditions, we established a two-dimensional axisymmetric numerical model based on the dynamic mesh model. A detailed pyrolytic chemical reaction model, which contains 16 species and 26 step reactions, and a modified coking deposition kinetic model are incorporated in the numerical model. The numerical model is validated by comparing the temperature, mass fraction, and coking thickness between simulation and experimental results. The transient numerical simulation of n -decane flow, heat transfer, pyrolysis, and pyrolytic coking within 20min was carried out. The results reveal that coking deposition has a significant effect on the flow and heat transfer performance of the cooling channel, while having minimal effect on the pyrolytic performance. The conductive heat transfer resistance will be greater than the convection when the coking layer thickness is more than 110 µm. The research methodology adopted in this study can be used to estimate and manage coke deposition in the regenerative cooling systems, and the quantitative results obtained can provide guidance for the design of cooling channels under heavy-cracking conditions.