Energy efficiency indicators of a rotary pump when feeding semi-finished fish minced products

An assessment of the energy efficiency of a rotifer pump when pumping a highly viscous food medium has been performed. The dependences of the pump supply and spent power on the rotor rotation frequency, pressure drop and viscosity of the pumped liquid are analyzed. It has been established that the effective dynamic viscosity of minced fish significantly exceeds 10 Pa•s already at atmospheric pressure. This means that when pumping such media, the rotifer pump operates with a high load. In addition, it was shown that with increasing rotor speed and a dimensionless pressure drop, the expended pump power increases. For example, if the rotor speed is increased from 60 to 300 rpm, the power consumption will increase 4.7 times with a dimensionless pressure drop of p = 1 and 6.3 times with p = 10. The hydraulic efficiency and the indicator of specific energy costs are investigated. It was found that as the rotor speed increases, the hydraulic efficiency decreases, and the specific energy consumption increases. At the same time, an increase in the dimensionless pressure drop leads to an increase in both indicators. The results obtained allow us to conclude that to assess the energy efficiency of a pumping unit when pumping highly viscous media, an indicator of specific energy costs should be used, rather than hydraulic efficiency. This is because hydraulic efficiency is calculated based on the total pressure drop, which includes both static pressure drop and hydraulic pressure losses. Thus, an increase in the latter leads to an increase in hydraulic efficiency, which does not always reflect the actual efficiency of the pump. The obtained analytical expressions of the working characteristics of the rotifer pump can be further used to find the optimal diameter of the process pipeline for the interoperable transportation of semi-finished products from minced fish with various additives according to the criterion of the minimum present value of the equipment.