b
Figure 11. Nusselt number and friction coefficient at the downstream section of 1.2 ” elbow relative to their values at x/D (fully redeveloped flow). (a) velocity = 1.2 m s-1 (b) velocity = 5.2 m s-1. Solution: 2300 ppm ETHOQUAD T13 + 2000 ppm NaSal in a molar ratio to surfactant of 2.5:1. Source: [10].