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

Abstract 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 ~ 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/Re2 was calculated and used to predict the buoyancy effects, and Kv 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.