Pumps/pumping total friction loss

Total friction loss for discharge side pump due to friction ... 

Determining the total friction loss, however, is not as simple. Friction loss is caused by a number of factors and all depend on the flow velocity generated by the pump. The major sources of friction loss include friction between the pumped liquid and the sidewalls of the pipe valves, elbows, and other mechanical flow restrictions or other flow restrictions, such as back-pressure created by the weight of liquid in the delivery storage tank or resistance within the system component that uses the pumped liquid. 

Pumping Head—The energy required to raise water to the distribution elevation and overcome friction losses through pipe, valves, fittings and nozzles. It is expressed in feet of liquid the pump must move and is equal to the total friction loss, static head and pressure drop through the distribution system. 

The total static head, as computed above, refers to the head on the pump without liquid flow. To determine the total head on the pump, the friction losses in the piping system during liquid flow must also be determined. 

Friction loss, J/kg or ft-lby/lb hj-, friction loss in conduit between stations a and total friction loss in pump... 

The TiTfactor for sharp entrance in 0.5. Loss during suction is 0.5 x 0.587 = 0.293 ft. On the discharge of the pump the K factor is determined as in the SI unit solution. Total friction losses are ... 

Example 13-1. Friction Loss in an Oil Line. One thousand six hundred gallons per hour of a 15 API (s — 0.966) fuel oil at a temperature of 200°F is to be pumped through a distance of 1,700 ft in a 3-in. (Schedule 40) well-insulated pipeline. Two open gate valves and six elbows are in the line, and the oil enters a tank through a sharp-edge entry flush with the side of the tank. The Saybolt viscosity of the oil is 300 at 210°F. What is the total friction loss in the line Assume no change in temperature. 

A friction loss of 37.125 m In a total length of 1000 m is quite high and will require a larger motor. Therefore, a 150 mm main pipeline will offer a better and more economical design compared to a 125 mm pipeline such as the reduced cost of the prime mover and lower power consumption during the life of pumping system, in addition to a longer life span of a 150 mm pipe compared to a 125 mm pipe. 

This total pressure loss is not necessarily required in determining the frictional losses in the system. It is necessary when establishing gravity flow or the pumping head requirements for a complete system. 

It is important to recognize that a cenlrijugal pump will operate only along its performance curve [10, II]. External conditions will adjust themselves, or must be adjusted in order to obtain stable operation. Each pump operates within a system, and the conditions can be anticipated if each component part is properly examined. The system consists of the friction losses of the suction and the discharge piping plus the total static head from suction to final discharge point. Figure 3-51 represents a typical system head curve superimposed on the characteristic curve for a 10 by 8-inch pump with a 12-inch diameter impeller. 

In some cases, friction losses are difficult to quantify. If the pumped liquid is delivered to an intermediate storage tank, the configuration of the tank s inlet determines if it adds to the system pressure. If the inlet is on or near the top, the tank will add no back pressure. However, if the inlet is below the normal liquid level, the total height of liquid above the inlet must be added to the total system head. 

In applications where the liquid is used directly by one or more system components, the contribution of these components to the total system head may be difficult to calculate. In some cases, the vendor s manual or the original design documentation will provide this information. If these data are not available, then the friction losses and back pressure need to be measured or an over-capacity pump selected for service based on a conservative estimate. 

Although not widely used for gears, oil-mist lubrication is nevertheless worth mentioning here. It is a total loss technique in which the oil is supplied in the form of fine droplets carried by compressed air. Two virtues are that the lubricant can be carried long distances through pipes without severe frictional losses, and that no oil pumps are needed since the motive power is provided by factory compressed-air lines. However, unless such systems are totally enclosed, the exhaust can create a build-up of oil-mist in the atmosphere. In order to maintain good standards of industrial hygiene, it is recommended that... 

The selection of the pump cannot be separated from the design of the complete piping system. The total head required will be the sum of the dynamic head due to friction losses in the piping, fittings, valves and process equipment, and any static head due to differences in elevation. 

Piping systems often involve interconnected segments in various combinations of series and/or parallel arrangements. The principles required to analyze such systems are the same as those have used for other systems, e.g., the conservation of mass (continuity) and energy (Bernoulli) equations. For each pipe junction or node in the network, continuity tells us that the sum of all the flow rates into the node must equal the sum of all the flow rates out of the node. Also, the total driving force (pressure drop plus gravity head loss, plus pump head) between any two nodes is related to the flow rate and friction loss by the Bernoulli equation applied between the two nodes. 

Net positive suction head available (NPSH) is the difference between the total absolute suction pressure at the pump suction nozzle when the pump is running and the vapor pressure at the flowing liquid temperature. All pumps require the system to provide adequate (NPSH). In a positive-displacement pump the (NPSH)a should be large enough to open the suction valve, to overcome the friction losses within the pump hquid end, and to overcome the liquid acceleration head. 

For 20-year-old pipe using the same formula, except with C = 90, hj = 0.0451 ft of water per foot of pipe. For 2500 ft of pipe, the total friction-head loss = 2500(0.0451) = 112.9 ft (34.4 m) of water. Thus the friction-head loss nearly doubles (from 65.9 to 112.9 ft) in 20 years. This shows that it is wise to design for future friction losses otherwise, pumping equipment may become overloaded. 

For purposes of example, assume a flow of 8.71 mVmin (2300 gal/min) through the tower The maximum head available to the recovery turbine was calculated to be 604 m (1982 ft) this value will be slightly in error when part of the flow is bypassed since frictional losses into and out of the recovery unit will change. First, assume the lean pump to be at 3.03 mVmin (800 gahmin) running at 3900 r/min with the semilean pump at 5.68 mVmin (1500 gal/min) to get the total flow of 8.71 mVmin (2300 gal/min). At 3.03 mVmin (800 gal/min) and 3900 r/min the available head of the lean pump is read from the curve. This must be greater than the required head, and the excess is plotted as in Fig. 29-60. The brake horsepower of the lean pump is also read. 

Example 4.1 It is desired to pump a wastewater to an elevation of 30 m above a sump. Friction losses and velocity at the discharge side of the pump system are estimated to be 20 m and 1.30 m/s, respectively. The operating drive is to be 1200 rpm. Suction friction loss is 1.03 m the diameter of the suction and discharge lines are 250 and 225 mm, respectively. The vertical distance from the sump pool level to the pump centerline is 2 m. (a) If the temperature is 20°C, has cavitation occurred (b) What are the inlet and outlet manometric heads (c) What are the inlet and outlet total dynamic heads From the values of the idh and odh, calculate TDH. 

The total power requirements for pumping are calculated by adding the hydraulic and the viscous power requirements. The former can be estimated from the MEB equation written for the work input, — W. We note that p — p2 and that Ef includes not only the friction losses on the discharge section but also the inlet section. The former was, as stated earlier, estimated to be 329.0 J kg , while the latter was estimated to be... 

Note that the above power values are for power dissipated by the jet or propeller and do not include motor efficiency and bearing losses for the agitator, or pump efficiency and external pipe friction losses for the jet. The head loss by the recirculating fluid in a jet mixer can be significant proportion of the total fluid head required for mixing. 

Which of the two rivers should serve as the source for the fountain To avoid the use of pumps, the Prince s architect, Le Notre, built a reservoir upstream at an elevation sufficient to project the water and to compensate for the pressure loss due to friction. If the friction loss equals 50% of the total head required, at what elevation should the reservoir be built ... 

For a forced vortex, the angular speed is constant and the liquid revolves as a solid body. Disregarding friction losses, Stepanoff (1993) claims that no power would be needed to maintain the vortex. The pressure distribution of this ideal solid body rotation is a parabolic function of the radius. When the forced vortex is superimposed on a radial outflow, the motion takes the form of a spiral. This is the type of flow encountered in a centrifugal pump. Particles at the periphery are said to carry the total amount of energy applied to the liquid. 

The impeller blades are usually mounted at a height between 0.25 and 0.5 of the height of the liquid layer. The diameter of the impeller conunonly varies between 0.2 and 0.5 of the tank diameter a diameter ratio of 1/3 is often preferred. The tanks are usually equipped with baffles (most often four), flat plates of a width of about 0.1 of the tank diameter, mounted vertically along the walls. These baffles serve to reduce liquid circulation around the axis and so to avoid the formation of a vortex in the middle they also promote vertical circulation. Propellers are usually made so that they pump downwards, as a result of which there is a liquid flow going up near the wall. Turbine impellers pump radially, so that in the lower half of the tank the liquid circulates downwards near the wall and upwards in the middle, and in the upper half the other way around. In some respects there is no important difference between these two types of impellers. Both create an effective circulation, and in both cases most of the supplied mechanical energy is eventually dissipated in small eddies. The friction losses at the wall and at the impeller blades are a relatively small fraction of the total energy dissipation. 

Because of the large flow velocities which are required (10-100 m/s) hydraulic friction losses as well as losses due to internal leakage through the rotor clearances are high. The total efficiency of centrifugal pumps depends on the specific speed rtq (Figure 9.8) [11, 12]. 

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