Friction, head loss

Friction head loss Friction match Friction materials... 

There are also many empirical formulas used for calculatiag the friction head loss in piping systems. These must be used carefuUy because many are based on the properties of specific fluids and are not appHcable over a broad range of fluids, temperatures, and pressures. For example, the Ha2en and Wdhams formula widely used for water flow ... 

Friction Head Loss (Resistance) in Pipe, Fittings, and Connections... 

Friction head loss develops as fluids flow through the various pipes, elbows, tees, vessel connections, valves, etc. These losses are expressed as loss of fluid static head in feet of fluid flowing. 

Alternate Calculation Basis for Piping System Friction Head Loss Liquids... 

The head losses calculated using K coefficients by these figures can be added directly to the total friction head loss for the straight pipe portions of a system. When equivalent lengths are determined, they must be added to the straight pipe before determining the total head loss, as shown in the example calculations for a water system. 

The total suction lift is defined as above except the level of the liquid is below the centerline of the pump or the head is below atmospheric pressure. Its sign is negative. Total Suction Lift (TSL) = static lift plus friction head losses. 

Relative roughness, pipe, 132 Friction losses, 181 also see Chapter 2 Friction, head loss, 68 Compressible fluids, 101 Factor, 68 Vacuum lines, 131 Gas constants, R, 378 Gravity settlers, 228 Head, 180-200 Calculations, 183, 184, 185 Discharge, 180, 187 Friction, 183 Liquid, 183... 

Let ccij and unit length of size j pipe in branch i. Then the actual hydraulic head at any node k must not be less than a specified minimum head h(k), that is... 

The suction head hs decreases and the discharge head hd increases with increasing liquid flow rate because of the increasing value of the friction head loss terms hfs and hfd. Thus the total head Ah which the pump is required to impart to the flowing liquid increases with the liquid pumping rate. 

It is clear from equation 4.2 that the suction head hs can fall to a very low value, for example when the suction frictional head loss is high and the static head zs is low. If the absolute pressure in the liquid at the suction flange falls to, or below, the absolute vapour pressure Pv of the liquid, bubbles of vapour will be formed at the pump inlet. Worse still, even if the pressure at the suction flange is slightly higher than the vapour pressure, cavitation—the formation and subsequent collapse of vapour bubbles— will occur within the body of the pump because the pressure in the pump falls further as the liquid is accelerated. 

Combining equation 4.5 with equations 4.6 and 4.7, which give the frictional head losses hfs and hfd respectively, allows the total head to be written as... 

Equation 4.15 shows that the available NPSH in a system decreases as the liquid throughput increases because of the greater frictional head losses. 

But under steady state conditions, since the material balance at the membrane must be satisfied, the term in the second brackets is zero. Thus, there is no observable frictional head loss and... 

Specified discharge pressure shall be at the purchaser discharge connection. Hydraulic performance shall be corrected for column static and friction head losses. Bowl or pump casing performance curves shall be furnished with the correction indicated. 

Lack of available NPSH may also be caused by high frictional loss in the suction piping. If this is the case, a small reduction in flow will not noticeably increase the pressure at the suction of the pump. A properly designed suction line to a centrifugal pump should have a frictional head loss of only a few feet of liquid. However, having a large-diameter suction line, and a relatively small draw-off nozzle, usually will lead to excessive loss of available NPSH. 

Hydraulic grade line Graphic representation of the mechanical energy equation as hydraulic or pressure head against length slope is frictional head loss per unit length. 

By using Equation (32), total frictional head loss ... 

FRICTION-HEAD LOSS IN WATER PIPING OF VARIOUS MATERIALS 6.10... 

The equivalent length is found by summing the friction-head loss for 1000 gal/min flow for each length of the four pipes—16, 12, 8, and 4 in—and dividing this by the friction-head loss for 1000 gal/min flowing through an 8-in pipe. Be careful to observe the units in which the friction-head loss is stated, because errors are easy to make if the units are ignored. 

Determine the friction-head loss in 2500 ft of clean 10-in new tar-dipped cast-iron pipe when 2000 gal/min (0.126 m3/s) of cold water is flowing. What is the friction-head loss 20 years later Use the Flazen-Williams and Manning formulas and compare the results. 

Compute the friction-head loss using the Hazen-WiUiams formula. The Hazen-Williams formula is hf = (u/1.318C/ ° 63) 85, where h j = friction-head loss per foot of pipe, in feet of water v = water velocity, in ft/s C = a constant depending on the condition and kind of pipe and Rh = hydraulic radius of pipe, in ft. 

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