Local head loss caused in connections used in micro-irrigation systems

Abstract

Information about local head loss caused by connections employed in micro-irrigation systems is hard to be found in literature. The objective of this research was to experimentally determine the local head losses in connections commonly used in micro-irrigation and propose mathematical models using the theorem of Buckingham. The methodology of tests was based on international standards. The tests were carried out under controlled inlet pressure, at 150 kPa, and five to ten units of each connection model were tested. The curves relating flow and head losses were drawn based on 15 flow conditions, obtained under increase and decrease of flow rate. For each condition, 30 points were collected resulting in a sample size of 900 points in each test. For each connection model evaluated, the following information was obtained: curves of local head loss as a function of flow rate and of local head loss coefficient (KL). The obtained values of KL ranged from 2.72 to 24.16, which become constant for Reynolds number higher than 10,000. The sensitivity of the coefficient related to a ratio of the internal sections in the connections was also verified. The flow exponents presented values close to the one applied by the Darcy-Weisbach equation (m = 2). The models developed for the connections presented a satisfactory performance.

Performance of models to determine flow rate using orifice plates

“…Here, it was obtained by plotting the reference flow rates as a function of the theoretical flow rates (Method 2). The same principle is often used to approximate the minor loss coefficient (K L ) in fittings and accessories used in irrigation systems (Bombardelli et al, 2019;Sobenko et al, 2020;Vilaça et al, 2017). Normally, K L exhibits a wide variation as a function of the Reynolds number, and a suitable approximation is obtained by assuming K L to be equal to the angular coefficient of a zero-intercept straight line, which plots the local head losses as a function of the kinetic head.…”

Discharge sensitivity of collapsible drip tapes to water temperature

“…derivative controller (PID), which aimed to ensure accuracy and stability for the control of test pressures (Bombardelli et al, 2019;Rocha et al, 2017). A pressure transmitter was used; it had a measurement range of 0 to 500 kPa, resolution of 0.1 kPa, and expanded measurement uncertainty of 0.1% in relation to the full scale (FS).…”

Analyzing the Energy Efficiency of Fan Systems by Using the Dimensional Analysis (DA) Method

“…In [17,18] it is shown how the head loss in microirrigation systems may be modeled. The proposed method can also be used in analyzing systems working with two-phase (air-water) flows.…”