Single-phase heat transfer, friction, and fouling characteristics of three-dimensional cone roughness in tube flow

This paper reports heat transfer and friction characteristics of three tubes having a conical, three-dimensional roughness on the inner tube surface with water flow in the tube. The TC3 truncated cone tube has twice the cone area density as TC2 and provides a Nusselt number 3.74 times that of a plain tube. The h-value is 36% higher than TC2, but it has it has nearly 60% higher pressure drop. The three-dimensional roughness offers potential for considerably higher heat transfer enhancement (e.g., 50% higher) than is given by helical ridged tubes, such as the Turbo-B type. The two truncated cone tubes provide 14–20% higher h-value than the commercial Wolverine Turbo BIII tube. Further, they have both have approximately 5% higher efficiency index than Turbo BIII. Accelerated particular fouling data are also provided for 3-D tube TC3, and for helical-ribbed tubes. The results show that although the 3-D tube provided the highest heat transfer coefficient, relative to a plain tube (h/hp), it also had the highest asymptotic fouling resistance, relative to a plain tube (Rf∗/RP∗). Significant long-term fouling would not be expected in applications using relatively clean water.