Assessment of pressure drop across discs in irrigation filters: New experimental and calculation methodology

The pressure drop across the discs in disc filters for irrigation systems is a key parameter for assessing hydraulic performance and suggesting design improvements to allow energy savings. However, to date, no clear procedure or method has been reported for obtaining this information. Therefore, an experimental apparatus was developed to test four types of discs from two different manufacturers. This device allowed the measurement of the pressure drop across the discs alone, without any additional element that could mask it. The effects of the disc pack height, compression, and filtration grade were investigated. Furthermore, the discs were imaged using an ultra-high resolution field emission scanning electron microscope to characterise the groove dimensions. These data were employed to calculate the pressure drop using a proposed analytical model based on the Darcy-Weisbach and minor loss equations, assuming two limiting cases for the grooves: open and closed conduits, alongside an additional bound-interpolated weighted model (BIW model) that combined both cases. The results showed an inverse relationship between the groove cross-sectional area and the pressure drop for the tested discs, while regression curves fitted to experimental data for each disc revealed a slightly quadratic behaviour. The analytical model successfully predicted a region containing experimental data. The information obtained may allow the development of improved disc filter designs.