| Summary: | This work numerically studied the heat transfer and flow characteristics of supercritical R134a in horizontal pipes equipped with DDIR, considering variations in the rotation angle of DDIR. The aim is to improve the effects of the DDIR configuration on the heat transfer of supercritical flow. After validation with experimental data, the AKN model was employed to examine the effects of four sets of rotation angles (0°, 30°, 45°, and 60°) on the axial and circumferential heat transfer characteristics of DDIR horizontal tubes under the influence of strong (<i>q</i><sub>1</sub>/<i>G</i><sub>1</sub> = 0.1 kJ/kg) and medium (<i>q</i><sub>2</sub>/<i>G</i><sub>2</sub> = 0.056 kJ/kg) buoyancy. Results show that variations in the rotation angle do not induce significant alterations in the flow field, thus exerting minimal influence on the axial heat transfer characteristics. Meanwhile, the rotation angle determines the relative positioning of the circumferential inner wall temperatures and heat flux distribution, although the magnitude of this effect remains inconspicuous. The rotational angle parameter can be reasonably neglected in the future design and installation of heat exchangers.
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