Efficiency pumping liquids

It cannot efficiently pump liquids with a kinematic viscosity greater thanlOO centistokes. 

Power for pumping liquids HP = (gpm)(psi difference)/(1714) (fractional efficiency). 

Another efficiency which is important for positive displacement pumps is the volumetric efficiency. This is the delivered capacity per cycle as a percentage of the true displacement per cycle. If no slip occurs, the volumetric efficiency of the pump is 100 per cent. For zero pressure difference across the pump, there is no slip and the delivered capacity is the true displacement. The volumetric efficiency of a pump is reduced by the presence of entrained air or gas in the pumped liquid. It is important to know the volumetric efficiency of a positive displacement pump when it is to be used for metering. 

Figure 7.15. Effects of viscosity on performance of centrifugal pumps (a) Hydraulic Institute correction chart for pumping liquids, (b) Typical performances of pumps when handling viscous liquids. The dashed lines on the chart on the left refer to a water pump that has a peak efficiency at 750 gpm and 100 ft head on a liquid with viscosity 1000 SSU (220 CS) the factors relative to water are efficiency 64%, capacity 95% and head 89% that of water at 120% normal capacity (1.2QH).

On the other hand, with an efficient pumping system spectra of gaseous compounds can be observed, if the technique of differential pumping is employed. Gas spectra 29) normally show excellent resolution and no charging effects. Only water solutions as liquid beams 30) still cause severe instrumental problems and wait for a suitable solution. 

A modern high efficiency gas-liquid STR commonly consists of a radial gas dispersing impeller in combination with one or more axial down-pumping impellers, as seen in Fig. 2. The type and number of open impellers used in the tank depend on the gassed liquid height and the media viscosity (see Table 4). Recommended axial impellers are 45° four-bladed pitch blade turbines... 

All heat requirements for the process are provided in the form of open steam at 400 psia. Some is used at the bottom of S-1 to strip HjS and the rest is fed to the twelfth plate in HT-1 to control the temperature of the hot towers and to compensate for heat losses and heat exchanger inefficiencies. Steam consumption is 1778/0.28 = 6400 mol/mol of DjO produced. This is much less than the 200,000 mol/mol DjO needed in water distillation. Additional energy in the amount of 680 kWh/kg D2O is used to circulate gas and pump liquid. This, however, is much less than is used in electrolysis or hydrogen distillation (Table 13.7). The low energy consumption of the GS process is due in large measure to the efficient heat recovery obtainable in the flow sheet Fig. 13.30, which follows Spevack s patent [S7]. 

This example shows that pumping liquid can increase their temperature. In this case, the pump was only 10% efficient and it caused 18°C in the temperature of the water. The less efficient a pump is, the greater the increase in the temperatme of the fluid being pumped. This arises because in a low efficient pump, more energy is needed to pump the liquid to get the same outlet pressure of a more efficient pump. So the extra energy gets transferred to the fluid. 

In the first part of this chapter, we started with a problem to find the pump outlet temperature when given the pump efficiency. Pump basically used to move liquids. In this chapter the user operated a pump operation in HYSYS to model the pumping process. The user also been trained on how to connect streams to unit operations such as pump. 

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