Bypass Flow Across a Bend for Chemical Injection into Microirrigation Systems

Abstract

The hydraulic characteristics of a bypass injector for chemical injection into microirrigation systems were evaluated. Bypass injectors operate on the basis of the pressure differential generated between the inner and outer walls at the midpoint of a bend. A general equation to determine the pressure head differential across a bend is presented along with the bypass and main flow discharge relationship. Bypass flow depends not only on the available pressure differential across the bend, but also on the bypass tubing size and length. An equation to predict the bypass flow as a function of the bend geometric characteristics and the available pressure differential is proposed. An equation for head loss caused by the entrance and exit of fluid through the by-pass inlet and outlet was developed. Bypass flow rates were increased up to 2.5 times by using crested nipples. The effect of size, shape, and length of the crests on bypass flow rate was also measured.