Estimation of pressure drop

Equation 4 Estimation of pressure drop, Ap (10 bar), with linear velocity (flow/cross section), u (cm/s) column length, L (cm) viscosity, rj (cP) characteristic constant (600 for spherical particle), kp, and particle size, dp (cm). 

The cyclone pressure drop can be rewritten as a function of inlet velocity head. The model used for the prediction of pressure drop depends on the cyclone operating condition. Both Shepherd and Lapple, and Dirgo models show a good prediction on cyclone pressure drop under different operational inlet velocity. However, Dirgo s model is unable to predict accurately the pressure drop under different operating temperature. For the various temperature conditions, Shepherd and Lapple s pressure drop model prediction is the best. We therefore, conclude that the Shepherd and Lapple model should be used for estimation of pressure drop in cyclone design. 

Example 6 Estimation of pressure drop in packed tower. A column 2 ft in... 

As a rough estimate of pressure drop for the gas flow through the packing, it is about 0.15 to 0.4 in of water per foot of packing. 

All of the commercial simulators include models for heaters, coolers, heat exchangers, fired heaters, and air coolers. The models are easy to configure, and the only inputs that are usually required on the process side are the estimated pressure drop and either the outlet temperature or the duty. A good initial estimate of pressure drop is 0.3 to 0.7 bar (5 to lOpsi). 

The manufacturer provides scale-up rules and correlations. These include the estimation of pressure drop and the number of elements required for a desired process result. These are reliable and may be used with confidence. 

When the porous medium is contained in a cylindrical bed, the multidimensional effect is given by equation 127. When the pressure drop is needed, there is no need to solve the governing equation numerically. Equations 106 and 128 can be used for the estimation of pressure drop as well as scaling-up of a packed bed. 

A method of interpolation for the two-phase friction factor was developed by Martinelli and Nelson [ ]. No considerable improvement over this technique has heretofore been developed and there is a need for better estimates of pressure drop for two-phase systems at pressures above 1 atm. This paper presents a solution to the problem for para-hydrogen for flow with both phases turbulent, based upon the pressure drop for liquid as the single phase. 

The final design of a heat exchanger includes pressure-drop calculations on each side. For process design when using a simulation program, preliminary conservative estimates of pressure drops due to friction are as follows as suggested in Heuristic 31 of Chapter 5. An... 

Estimates of pressure drops can be made using the traditional theory and correlations. However, accurate prediction of pressure drops in microchannels for nonslip flows is not possible [1]. Eor better prediction many models have been proposed [2]. Shockwave phenomena in microchannels have been investigated analytically and numerically, and experimental work is under way. 

Example 5,6—Estimation of Pressure Drop Through a Reservoir. A polymer flood is being designed that uses 1,000 ppm xan-than biopolymer. The polymer solution will be injected into a sandstone reservoir at a rate of 10 B/D-ft. The permeability of the reservoir is 200 md, porosity is 0.19, and thickness is 50 ft. Initial oil saturation is 0.70, and ROS is 0.30. A five-spot pattern is planned on 10-acre spacing. Radius of the injection well is 3.25 in., and there is no wellbore damage. At the beginning of the polymer flood, the reservoir is at interstitial water saturation and contains a crude oil with a viscosity of 1.0 cp at reservoir temperature and pressure. For this example, the displacement process is considered piston-like so that a sharp displacement front will form between the displaced oil and the injected polymer solution. Polymer retention and inaccessible PV are ne ected. Determine the bottomhole pressure (BHP) in the injection well when 1,000 bbl of polymer solution have been injected. The average reservoir pressure at the effective radius of the five-spot pattern is 400 psi. 

Example 5,11—Estimation of Pressure Drop During a Continuous Polymer Flood in a Linear Reservoir. Determine the pressure drop for the polymer flood in Example 5.7 when the waterflood front, xpf, is located at a distance of 0.75 from the entrance of the system. Base permeability, the permeability to oil at interstitial water saturation, is 250 md. The ipjection rate is constant at 200 B/D. Recall that the linear segment of the reservoir being simulated is 500 ft wide and 20 ft thick. Injection and production wells are 1,000 ft apart. 

A correct value of friction factor is required for the estimation of pressure drop. The value of the friction factor depends upon the flow characteristics. For laminar flow less than 2100), the friction factor varies inversely with the Re5molds number, whereas for turbulent flow, the friction factor has a complex relationship with the pipe diameter, roughness of the pipe, and the Reynolds number. 

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