A computer program named ORRIBLE was written to predict the flow and temperature distribution for steady single-phase flow through a bundle of 19 heated rods spaced by helical wire wraps in a hexagonal duct. Any combination of flow subchannels can be blocked at the inlet. The section can have an uriheated entrance length followed by a heated section and an unheated exit length. In the heated section, the linear heat rate of each of the rods can be individually specified. Turbulent interaction, sweeping crossflow due to the wire wrap, and transverse thermal conduction are considered. An approximate relationship for pres sure-diversion crossflow in terms of local axial mass velocities is used to eliminate pressure as a variable. Hence, the computational procedure does not require iterative techniques.