Sensitivity of thin-walled drip tape emitter discharge to water temperature. Appl. Engr in Agric

ABSTRACT. One of the primary goals in the design of microirrigation systems is to have a hydraulic balance to ensure uniform emitter discharge. However, while most design processes focus on pressure distributions and changes associated with friction and elevation differences, elevated water temperatures will change the physical properties of the water and may change the physical properties of some emitters. Laboratory studies were conducted to measure the effects of water operating temperature on the sensitivity and discharge rate of emitters from thin-walled drip tape (collapsible emitting hose) products. Two different product types (Robert’s Ro-Drip, RD; and T-Tape, TT,) each with two wall thicknesses, were evaluated. The RD product included wall thicknesses of 0.20 mm (8 mil, RD-08) and 0.38 mm (15 mil, RD-15), whereas the TT product included wall thicknesses of 0.25 mm (10 mil, TT-10) and 0.38 mm (15 mil, TT-15). Additional characterization tests included a standard operating pressure/emitter discharge rate test and a tubing tensile stress (elongation) test. All tests were conducted in accordance with ASAE Standard S553, “Collapsible Emitting Hose (Drip Tape) — Specifications and Performance Testing.” Increases in water operating temperature from 21C to 50C resulted in an 18%, 44%, and 97 % increase in emitter discharge from the RD-08 product at operating pressures of 55, 69, and 83 kPa, respectively. Emitter discharge rate changes in the RD-15 product were not as great (10 to 12 % increase) for similar water temperature changes. Effects of water temperature on the discharge rate from the TT products were quite different from the RD products. Emitter discharge rate increased slightly(<5%) with water temperature at 55 kPa, but decreased by up to 7 % at 83 kPa. TDR values (also referred to as