Influence of Polymer Solution on Pump Performances

Abstract

In professional warewashing machines, as for example the model of Electrolux Rack Type, the working conditions of the pump are affected by the operating fluid properties, which are different from those of pure water. In fact, the actual trend in this kind of professional appliances is to reduce both energy consumption and time needed for cleaning process: this involves short washing cycles conducted at low temperatures with a solution of water and highly concentrated chemistry. Detergents contain different components and additives, as polymers and surfactants, which can affect the performance of the pump, including cavitation inception conditions. Cavitation leads to flow instabilities, affecting pump performances and inducing an increment in the level of vibrations and noise. While cavitation phenomena in Newtonian fluids is well known, particularly as far as pure water is concerned, in literature there are also various studies on cavitating flows in presence of diluted solutions of polymers additives in water, but only few studies are available regarding the effect of detergent components on pumps cavitation and, in general, on pumps performances. The wide range of variables affecting the phenomenon has led to the development of a laboratory rig for testing centrifugal pumps with aqueous solutions representative of those used in the warewashing sector [1]. This paper presents the results of tests performed with various solutions of a polymer (Polyox WSR301) in water. A rheometric analysis has been previously performed on samples of some of the tested solutions, for characterizing their behavior in terms of both viscosity in laminar conditions and their classification as “diluted” or “concentrated”. For each solution, the resulting performance curves of the pump are then compared with those obtained with pure water

Experimental analysis of the influence of polymer solutions on performances and cavitation of small size pumps for professional appliances

“…Efficiency improvements between 6% and 9% are presented in Burlon et al. 13 In AbuYousef et al. 3 a study with a 20 ppm solution reports 12% increase of the maximum efficiency even though the head coefficient remains approximately equal compared to pure water.…”

“…Up to 1250 ppm, they behave as Newtonian fluids while at higher concentrations as shear thinning ones. 13 In presence of strength, a coil stretch transition happens in extensional flows when a critical value is exceeded. 5 In shear flows of dilute solutions, chain stretching is combined with rotation, coil interactions are negligible and viscosity increases proportionally to the polymer concentration.…”

“…The test rig, shown in Figure 2 is fully described in Burlon et al. 13 It has been realized according to ISO 9906:2012 14 and literature suggestions. 15 Pumps whose dimensions are compatible with the DN 65 pipes diameter can be tested.…”

“…The Polyox WSR 301 has been chosen as representative component of detergents, according to the analysis carried out in Burlon et al. 13 The vibration signals acquired on the pump scroll at various operating conditions are carefully analyzed, in order to correlate their energy content to both the concentration of the solutions and the working points of the pump.…”