The tube of Problem 10.58 is modified by milling sharp-cornered grooves around its periphery, as in Figure 10.15. The 2-mm-deep grooves are each 2 mm wide with a pitch of S = 4 mm. Estimate the minimum condensation and heat transfer rates per unit length that would be expected for the modified tube. How much is the performance enhanced relative to the original tube of Problem 10.58?

Data From Problem 10.58

A horizontal tube of 50-mm outer diameter, with a surface temperature of 34°C, is exposed to steam at 0.2 bar. Estimate the condensation rate and heat transfer rate per unit length of the tube.