Process pipeline hydraulic calculation to pump dairy products with a centrifugal pump

The purpose of the study is to develop a method for calculating a hydraulic system for pumping dairy products with a centrifugal pump, taking into account the variable value of the level difference. A system with specified parameters of a technological pipeline used for pumping dairy products was considered under conditions of the absence of cavitation in a turbulent mode of fluid movement using a centrifugal pump (CP) with an open impeller (EC). A feature of the system under consideration is the time-variable value of the level difference H(t), due to which the flow in the pipeline will be unsteady. Experimental calculations determined the operating characteristics of the ONTs 10/10 pump for water and dairy cream (fat content 18 %, density ρ = 1011 kg/m3, kinematic viscosity coefficient ν = 8.22 10-6 m2/s) at a temperature t = 20 °C. The value of the shear rate for the liquid under consideration at the pipe wall was more than 2000 s-1. When performing calculations, it is assumed that milk cream is a Newtonian liquid, since their fat content is less than 20 %, and the shear rate is more than 500 s-1. As a result of the hydraulic calculation of the technological pipeline with different diameters, it was found that: 1) with an increase in the length of the pipeline L, its hydraulic resistance increases, the liquid flow rate Q drops noticeably, while the indicator of energy costs E for pumping cream monotonously increases; 2) with an increase in the diameter of the pipeline d, its hydraulic resistance decreases, the liquid flow rate Q increases noticeably, while the indicator of energy costs E for pumping cream decreases. In both cases, the coefficient of performance (COP), in contrast to the indicator of specific energy consumption E, changes non-monotonically, but only slightly. The selection of pumping equipment by efficiency is impractical.