Experimental investigation on convective heat transfer of hydrocarbon fuel in circular tubes with twisted-tape inserts

The convective heat transfer of a kerosene-type hydrocarbon fuel was experimentally investigated in electrically heated horizontal circular tubes with twisted-tape (TT) inserts, in the fuel bulk temperature range of 288.0 similar to 873.0 K, at supercritical pressures. The effects of the system pressure, heat flux, buoyancy, thermal acceleration and twist ratio were investigated with a wide range of supercritical conditions. The sharp variation in the thermal properties with respect to temperature was the key factor influencing the heat transfer. Normal heat transfer, heat-transfer enhancement and heat-transfer deterioration occurred in the dimensionless position. The difference between the top and bottom wall temperatures in plain and TT tubes was investigated. Gr/Re-2 was calculated and used to predict the buoyancy effects, and K-v was calculated to examine the thermal acceleration effects. The inner wall temperature and heat-transfer coefficients were compared for plain and TT tubes. The circular tube with TT inserts was shown to enhance heat transfer. Finally, a well-predicted empirical correlation of the Nusselt number was proposed for horizontal flow heat transfer in TT tubes. (C) 2019 Elsevier Ltd. All rights reserved.