A Correlation for Laminar Hydrodynamic Entry Length Solutions for Circular and Noncircular Ducts

Abstract

Laminar hydrodynamic entry length solutions for circular and noncircular ducts are essential in proper design of compact heat exchangers and other heat transfer and fluid flow devices. A closed form equation has been proposed to present these solutions for the circular tube, parallel plates, rectangular, equilateral triangular, and concentric annular ducts. The necessary constants are evaluated and it is shown that the proposed correlation predicts the apparent friction factors within ± 2.4 percent.