Alexandria Engineering Journal (Jul 2022)
Economic pipe diameter of laterals in small tube irrigation system
Abstract
Small tube irrigation is a new type of micro-irrigation that the emitters were replaced by small tubes. The small tubes of 4 mm diameter were connected to the laterals through the flow stabilizer or directly to the laterals. The discharge formulations and total heads of the system have been driven from the basic formulas of friction losses and other minor losses of the laterals. Based on hydraulic analysis of laterals, the cost function of lateral and pump, the operation cost and the objective function of lateral diameter optimization technique was established. In the study, a typical irrigation system of fruit tree was taken as an example, in which the length of lateral pipe was 100 m, and assuming that the small tube flow range is 10–40L/h, lateral diameter ranges 12–25 mm, and the field slope ranges −20%∼20%. The results showed that the minimum total cost was obtained with a lateral diameter of 13.6 mm at 10 L/h flow rate, for the flow rate of 20L/h, the minimum cost is obtained at the diameter of 13.6 mm for down-slopes and 17.2 for flat land and up-slopes, and for the flow rate of 30L/h and 40L/h the minimum cost is obtained at 17.2 mm diameter for any slopes.
