Pumps/pumping friction factor

If the friction factor

[Pg.370]

Water is pumped at 1.4 m3/s from a tank at a treatment plant to a tank at a local works through two parallel pipes, 0.3 m and 0.6 m diameter respectively. What is the velocity in each pipe and, if a single pipe is used, what diameter will be needed if this flow of water is to be transported, the pressure drop being the same Assume turbulent flow, with the friction factor inversely proportional to the one quarter power of the Reynolds number. 

Fanning friction factor, [—] acceleration due to gravity, [L/t2] energy dissipated per unit mass of fluid, [FL/M = L2/t2] force component in the x direction, [F = ML/t2] enthalpy per unit mass, [FL/M = L2/t2] friction loss head, [L] pressure head, [L] work (pump) head, [L] velocity head, [L] static head, [L]... 

Suppose you want to design a hydrocarbon piping system in a plant between two points with no change in elevation and want to select the optimum pipe diameter that minimizes the combination of pipe capital costs and pump operating costs. Prepare a model that can be used to carry out the optimization. Identify the independent and dependent variables that affect the optimum operating conditions. Assume the fluid properties (/i, p) are known and constant, and the value of the pipe length (L) and mass flowrate (m) are specified. In your analysis use the following process variables pipe diameter (D), fluid velocity (v), pressure drop (A/ ), friction factor (/). 

Cichelli and Brinn (1956) showed that the annual pumping loss terms in Equation (a) could be related to ht and h0 by using friction factor and y-factor relationships for tube flow and shell flow ... 

Hydrogen is to be pumped from one vessel through a pipe of length 400 m to a second vessel, which is at a pressure of 20 bar absolute. The required flow rate is 0.2 kg/s and the allowable pressure at the pipe inlet is 25 bar. The flow conditions are isothermal and the gas temperature is 25°C. If the friction factor may be assumed to have a value of 0.005, what diameter of pipe is required ... 

A useful discussion of incompressible fluid flow in pipes and the influence of surface roughness and friction factors on pumping is found in Perry s Chemical Engineer s Handbook (49). 

Since plate-and-frame exchangers are made by comparatively few concerns, most process design information about them is proprietary but may be made available to serious enquirers. Friction factors and heat transfer coefficients vary with the plate spacing and the kinds of corrugations a few data are cited in HEDH (1983, 3.7.4-3.7.5). Pumping costs per unit of heat transfer are said to be lower than for shell-and-tube equipment. In stainless steel... 

Conclusions on pipe-fitting equations. Each of the ft values given in Table 6.1 is the experimental friction factor for that pipe size. This friction factor ft is not to be mistaken for the friction factor for straight pipe f. They are different discrete values to be applied per Eq. (6.11). Ku K2, K3, and KA each represent a different pipe valve or fitting. One could also be a control valve, item 10 in the pipe fitting list. The objective here is to add up all of the fittings expressed as K values and execute Eq. (6.11) to solve the pipe run pressure drop. In summary, this tells how much head hL the pump must put out in order to do the job. 

In Eq. (65) the friction factor was introduced as an empirical factor of proportionality in the calculation of the friction loss head. If Eq. (63) is applied to a length of straight horizontal pipe with no pumps, one finds that... 

A generalized equation, describing the system curve of a process is P = H + Ff(Qx), where P is the required to pump discharge pressure, H is the static or elevation head, Ff is the friction factor, Q is the flow rate, and x is an exponent that varies between 1.7 and 2.0 usually, 2.0 is used. 

E = efficiency of motor and pump expressed as a fraction f = Fanning friction factor, dimensionless, or function for dynamic programming in Eq. (91) indicating optimum return depends on that input... 

Pmnps wear and the curve will change with time. In addition, friction factors will generally increase with time because of corrosion and deposits. For these reasons, puirqrs are usually oversized and thus will initially deliver larger flow rates than required. A control valve installed on the discharge side of the pump will bring the pump to the desired operating point on the curve. 

Tubes with rough surfaces have much higher heat transfer coefficients than tubes with smooth surfaces. Therefore, tube surfaces are often intentionally roughened, corrugated, or filmed in order to enhance the convection heat iraiisier coefficient and thus the convection heat transfer rate (Fig. 8-28). Heat transfer in turbulent flow in a lube has been increased by as much as 400 percent by roughening the surface. Roughening the surface, of course, also increases the friction factor and thus the power requirement for the pump or the fan. 

C How is lire friction factor for flow in a lube related to the pres.sure drop How is the pressure drop related to the pumping power requirement for a given mass flow rate ... 

Figure 3-4 illustrates the distribution of fluid energy with work done by the pump and heat added to the system. Table 3-6 gives friction factors for clean commercial steel pipes with flow in zones of complete turbulence. 

Although the solution of this example is long, it involves no trial and error and no complicated ideas. The procedure is problem statementfluid properties—> Reynolds number- friction factor—> —> dW f dm- pump powerpump AP. The pump power computed here is the amount of mechanical power delivered to the fluid. For a 100 percent efficient pump, this would also be the power input to the pump. Real pumps are never 100 percent efficient their actual behavior is discussed in Chap. 9,... 

This equation shows that the economic pipe diameter is independent of how long the pipe is. This should be no surprise Both the pumping and capital costs are proportional to the pipe length. The equation also shows that the economic diameter is proportional to the friction factor to the one-sixth power hence, we can use a rough estimate of the friction factor and make very little error. 

We are offered some pipes made of a new kind of plastic. To test their roughness, we pumped water through a 3-in schedule 40 pipe made of this material at an average velocity of 40 ft/s. The observed friction factor was 0.0070. Estimate the absolute roughness of this plastic. 

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