Experimental investigation on convective heat transfer of hydrocarbon fuel in transverse corrugated tubes.

• Heat transfer of supercritical pressure hydrocarbon fuel in horizontal flow was studied. • The first use of transverse corrugated tubes to enhance the convective heat transfer of hydrocarbon fuel. • Effects of experimental parameters on convective heat transfer characteristics were discussed. • Sharp variation of thermophysical properties near pseudo-temperature was the key factor to influence heat transfer. To improve the heat transfer performance of regenerative fuel cooling technology and CCA (Cooled Cooling Air) technology, the convective heat transfer characteristics of hydrocarbon fuel in transverse corrugated tubes under supercritical pressures were experimentally studied. The length, outer and inner diameter of the test tubes were 200 mm, 3 mm, and 2 mm, respectively, and the corrugation depth was 0.4 mm. The corrugation pitches of different transverse corrugated tubes were 30, 40, and 50 mm, respectively. The effects of heat flux, system pressure, mass flow rate, inlet temperature, buoyancy, and corrugation pitch are summarized. Experimental results indicated that the secondary flow and backflow are generated behind the concave corrugation, which can destroy the fluid boundary layer, make the fluid mixing more uniform, reduce the temperature gradient of the boundary layer, and enhance heat transfer. An average HTC (heat transfer coefficient) was increased by 35–51% compared with the plain tube. In addition, a ratio of Gr (Grashof number) to the square of Re (Reynolds number) was used as the criterion for evaluating the effect of buoyancy force. Gr ⋅ Re −2 near the corrugation was much smaller than in other locations. [ABSTRACT FROM AUTHOR]