Table 7.5 illustrates the operation of a typical heat-recovery exchanger for supercritical water gasification. The data are taken from a large operating near­supercritical gasification plant. The fluid-to-wall heat-transfer coefficient in clean supercritical water in the tube may be calculated by the correlation of Yamagata et al. (1972):

Nu = 0.0135Re»a85Pr»a8 (7.14)

Based on Yamagata’s experiments with isobutane, Hsu (1979) found that the Sieder-Tate equation, as follows, is in better agreement:

Heat transfer in SCWG may vary because of solids in the fluid. Thus, applica­bility of these equations to SCWG is uncertain. Information on this aspect of heat transfer is presently unavailable.