Heat transfer characteristics of carbon dioxide cross flow over tube bundles at supercritical pressures

Supercritical carbon dioxide is preferable for the working fluids for various industries and power cycles due to the advantages of environmental protection, compactness, high energy conversion efficiency and safety. Cross flow over tube bundles is a basic flow pattern for the heat transfer equipments. However, the investigations of supercritical fluid cross flow and heat transfer over tube bundles are rarely seen. The heat transfer characteristics of carbon dioxide cross flow over inline and staggered tube bundles at supercritical pressures were numerically investigated. The transverse and stream wise pitches have different influences on the heat transfer in inline and staggered tube bundles. The transverse and stream wise tube pitch almost have no influence on the heat transfer in inline tube bundle. The heat transfer in staggered tube bundles with larger transverse tube pitches and smaller stream wise pitches is better than that in tube bundles with smaller transverse pitches and larger stream wise pitches. The Zukauskas correlation, which is based on experimental data of heat transfer of subcritical in-compressible fluid cross flow over tube bundles, cannot be applicable to the pseudo critical region. New correlations are proposed for pseudo critical carbon dioxide cross flow over inline and staggered tube bundles with cooling or heating conditions. The new correlations agree well with the numerical results. The maximum difference is below 25%.