Horizontal pipe pressure drop

The equations in the section Piping Pressure Drop are, of course, intended for use with full pipes. Reference 12 provides a rapid way to estimate whether a horizontal pipe carrying liquid is full. The criteria are... 

The Froude number wiU be evaluated to determine the suitability of horizontal flow. The pressure drop will then be calculated for both the gas phase and liquid phase flowing separately in the empty pipe. The pressure drop for the combined flow streams will then be determined using the method of Lockhart and Martinelli. Finally, the mixer pressure drop will be determined using the multiplier of the empty pipe pressure drop reported for the SMV mixer specified. 

In this case there is good agreement between the values calculated for total pressure drop. Since gas flow is predominant, the total empty pipe pressure drop calculated from the gas-only pressure drop using eq. (7-41b) should be used. It should be noted that this Lockhart-Martinelli correlation is considered to be conservative when used in vertical downward flow. The original work was all in horizontal flow. 

Liquids and Gases For cocurreut flow of liquids and gases in vertical (upflow), horizontal, and inclined pipes, a veiy large literature of experimental and theoretical work has been published, with less work on countercurrent and cocurreut vertical downflow. Much of the effort has been devoted to predicting flow patterns, pressure drop, and volume fractious of the phases, with emphasis on hilly developed flow. In practice, many two-phase flows in process plants are not fully developed. 

FIG. 6-26 Parameters for pressure drop in liqiiid/gas flow through horizontal pipes. (Based on Lockhatt and Maitinelli, Chem. Engr. Prog., 45, 39 [1.94.9],)... 

For pressure drop and holdup in inclined pipe with upward or downward flow, see Beggs and Brill ]. Pet. Technol, 25, 607-617 [1973]) the mechanistic model methods referenced above may also be apphed to inchned pipes. Up to 10° from horizontal, upward pipe inclination has httle effecl on holdup (Gregory, Can. J. Chem. Eng., 53, 384-388 [1975]). 

Total pressure drop for horizontal gas/solid flow includes acceleration effects at the entrance to the pipe and fric tional effects beyond the entrance region. A great number of correlations for pressure gradient are available, none of which is applicable to all flow regimes. Govier and Aziz review many of these and provide recommendations on when to use them. 

Cascade coolers are a series of standard pipes, usually manifolded in parallel, and connected in series by vertically or horizontally oriented U-bends. Process fluid flows inside the pipe entering at the bottom and water trickles from the top downward over the external pipe surface. The water is collected from a trough under the pipe sections, cooled, and recirculated over the pipe sections. The pipe material can be any of the metallic and also glass, impeiMous graphite, and ceramics. The tubeside coefficient and pressure drop is as in any circular duct. The water coefficient (with Re number less than 2100) is calculated from the following equation by W.H. McAdams, TB. Drew, and G.S. Bays Jr., from the ASME trans. 62, 627-631 (1940). 

Horizontal natl. circ. Ease of maintenance Lower skirt height than vertical Less pressure drop than vertical Longer tubes possible Less cost than kettle No theoretical tray Extra space and piping as compared to vertical Fouls easier as compared to vertical Accumulation of higher boiling point components in feed line, i.e., temperature may be slightly higher than tower bottom... 

The Lapple charts for compressible fluid flow are a good example for this operation. Assumptions of the gas obeying the ideal gas law, a horizontal pipe, and constant friction factor over the pipe length were used. Compressible flow analysis is normally used where pressure drop produces a change in density of more than 10%. 

Piping to Burners - First and second stage piping and headers, as well as the burner lines themselves, are sized to minimize pressure drop and velocity effects. Thus, maldistribution of flow to the burners will be minimized. The burner lines are fabricated from standard 1(X) mm pipe, and are arranged in a split grid layout with distribution headers and split feed lines on opposite sides, for both first and second stage burners. First and second stage headers must be sloped so that any condensate will drain back to the seal drums. However, the burner lines must be accurately installed in a horizontal plane. 

The pressure drop for a system of horizontal and vertical (or inclined) pipe is the sum of the horizontal pressure drop plus the additional drop attributed to each vertical rise, regardless of initial and final elevations of the line [33],... 

PTPh = Total two-phase pressure drop for system involving horizontal and vertical pipe, psi per foot of length... 

Sand of particle size 1.25 mm and density 2600 kg/m3 is to be transported in air at the rate of I kg/s through it horizontal pipe 200 m long. Estimate the pipe diameter, the pressure drop in the pipeline and the air flow required. 

Chenoweth, J. M. and Martin, M. W. Trans. Am. Soc. Mech. Eng., Paper 55 PET-9 (1955). A pressure drop correlation for turbulent two-phase flow of gas-liquid mixtures in horizontal pipes. 

Farooqi, S. 1. and Richardson, J. F. Trans. Inst. Chem. Eng. 60 (1982) 323. Horizontal flow of air and liquid (Newtonian and non-Newtonian) in a smooth pipe Part II Average pressure drop. 

Friedel L (1979) Improved friction pressure drop correlations for horizontal and vertical two-phase pipe flow. In 3rd International European Two-Phase Group Meeting, Ispra, Italy, 1979, vol 18, issue 7... 

Zhao TS, Bi QC (2001b) Pressure drop characteristics of gas-liquid two-phase flow in vertical miniature triangular channels. Int J Heat Mass Transfer 44 2523-2534 Zimmerman R, Gurevich M, Mosyak A, Rozenblit R, Hetsroni G (2006) Heat transfer to air-water annular flow in a horizontal pipe. Int J Multiphase Flow 32 1-19... 

The drag-reducing properties of a polyacrylamide type were tested in two-phase air/water flow, using a horizontal pipe of 31-nun diameter [1545]. The properties of the polymer were tested in single-phase water flow, and the results were found to comply with the reduction in pressure drop found by other workers. Positive effects in two-phase flow were found to depend on the Reynolds... 

It is probably beneficial to a passive system to lay a network of perforated drainage pipes in the gravel bed beneath the slab prior to the pour. The use of horizontal pipe runs and elbows in a passive system may greatly lessen the effectiveness the system and should be a voided. Some builders use a 6-in. PVC pipe in a passive system to help lessen the pressure drop. 

The maximum distance the styrene must travel horizontally is around 300 ft. The total distance traveled inside pipes is 390 ft. If a pressure drop of 2 psi per 100 ft is assumed, the pressure drop due to friction will be about 8 psi (20.5 ft of styrene) and that due to elevation is 90 ft. The total pressure drop is 110.5 ft. Usually for normal flow rates the pressure drop due to the change of velocity is ignored. 

A vacuum system like that shown in Figure 4-3 will be used,36 since delivery to a single receiver is desired. For this system there will be 100 ft of horizontal pipe and 35 ft of vertical pipe. The pressure drop across the air filter at the air inlet should be about 0.5 in. H20 and that across the receiver should be negligible. The pressure drop across the fabric filter is 4.0 in.H20 and across the receiver is 3 in H20. 

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