## 4 Pump Performance  
The theoretical performance of the pump design was shown in the previous section. The pump performance obtained from the CFD simulations is presented here. The head coefficient and efficiency curves were compared with the theoretical calculation for the initial validation of the CFD results. Figure 6 shows the pump characteristic curve comparison for the analytical and CFD studies. The efficiency curve was in good agreement with the analytical estimation. The higher efficiency obtained by the CFD simulations was due to the unaccounted losses in the simulations, such as the hydraulic and mechanical losses and the losses within the input and output sections of the pipe. The head obtained from the CFD results was within the range between the maximum and minimum head, as calculated theoretically for all flow rates. Thus, the efficiency and head curves obtained from the CFD simulations had an error percentage of less than 8%. Since this is a preliminary design feasibility study before manufacturing the pump for experimental analysis, the obtained CFD results are acceptable for further analysis. The pump feasibility was tested for its operability with different chemicals used in chemical processing industries. Since normal water was used in the initial study, the pump was tested for water at a high temperature (116 \({}^{\circ}\)C) and pressure (1.73 bar). The viscosity of the water was reduced to 0.25 cP to imitate the conditions of a high-pressure boiler water pump. The centrifugal pump was also tested for hydrocarbons such as diesel (C\({}_{10}\)H\({}_{22}\)I) and debutanized diesel (C\({}_{8}\)H\({}_{18}\)I), which are common fluids pumped in petrochemical refineries. The material properties of the fluids were extracted at the fluid temperature obtained from the real site data where the pump would be installed. The dynamic viscosity, density and other fluid properties at the aforementioned particular temperature were applied to the CFD model. The simulations were carried out at an isothermal temperature and, hence, the conservation of energy equation was not solved [28; 29]. The most relevant fluid properties are given in Table 2.  
Figure 6: Performance comparison for theoretical and computational fluid dynamics (CFD) calculations. The pump operating conditions were kept similar to the previous study for comparability. The head coefficient curves and efficiency curves for the different fluids are plotted in Figure 7. The flow coefficient was normalized by the design point of the reference fluid (water) such that \(\varphi/\varphi\)d = 1 indicated the BEP of water. The efficiency curves of the low-viscous fluids had the same trend as that of the reference fluid. This means that the chemical pump could be operated in the same operating range with different fluids. However, the BEP of the low-viscous fluids shifted away from the BEP of water. The BEPs of the high-temperature water, diesel and C\({}_{8}\)H\({}_{18}\) were shifted by +1%, -3.2% and +3.43%, respectively, compared with their water equivalent. The change in the BEP was associated with the change in density and viscosity of the fluid. It should be noted that the efficiency change for the different fluids was less than 1% at the BEPs of different fluids. Therefore, the pump performance did not degrade with the fluid change, but the operating point was shifted marginally. In other words, the system must be operated at lower flow rates in case of low-viscous fluids, in comparison with water, to ensure optimum performance. The head curve also exhibited a similar trend for the fluids and fell within the theoretical head range. Compared to the reference fluid, the maximum deviation in the head curve was 2.7%, 0.45% and 5.4% for the high-temperature water, diesel and C\({}_{8}\)H\({}_{18}\), respectively, at the low flow rate, which was an acceptable consequence. At the BEP, the head decreased by 17 m, 10 m and 38 m compared with the head at the BEP of water.