Surface coke deposition influences on flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts

Surface coke deposition influences on the flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts were experimentally investigated at supercritical pressures, to research the active cooling technology of new flying vehicles. The SS304 test tubes had a 4 mm inner diameter and a 6 mm outer diameter. The twist ratios of the two types of twisted-tapes are 6.31 and 12.63. The experimental system pressure, outlet temperature, and mass flow rate were fixed at 3 MPa, 893.15 K, and 1.20 g.s(-1), respectively. The results indicated that the twisted-tape insert mixed the fluid, washed coke deposited on the inner wall, and improved the heat transfer. With the insertion of a twisted-tape, the maximum value of the pressure drop of the test section decreased more than 85%, the total amount of coke decreased more than 93%, and the wall temperature were significantly decreased. At the same axis position, the difference between the top and bottom wall temperatures decreased and the heat transfer coefficient improved compared with a plain tube. A well-predicted correlation of the Nusselt number was proposed.

Automated summary

This experiment investigated the influence of surface coke deposition on the flow and heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts under supercritical pressures. The results showed that the use of twisted-tape inserts improved heat transfer, reduced coke deposition, and proposed a well-predicted correlation of the Nusselt number.