Pressure drop specific

The measurement of a crude oil s viscosity at different temperatures is particularly important for the calculation of pressure drop in pipelines and refinery piping systems, as well as for the specification of pumps and exchangers. 

The constant given the value 5 in equation 1 depends on particle size, shape, and porosity it can be assumed to be 5 for low porosities. Although equation 1 has been found to work reasonably well for incompressible cakes over narrow porosity ranges, its importance is limited in cake filtration because it cannot be used for most practical, compressible cakes. It can, however, be used to demonstrate the high sensitivity of the pressure drop to the cake porosity and to the specific surface of the soHds. 

The specific cake resistance is the most troublesome parameter ideally constant, its value is needed to calculate the resistance to flow when the amount of cake deposited on the filter is known. In practice, it depends on the approach velocity of the suspension, the degree of flow consoHdation that the cake undergoes with time, the feed soHds concentration, and, most importantly, the appHed pressure drop Ap. This changes due to the compressibiHty of most cakes in practice. often decreases with the velocity and the feed concentration. It may sometimes go through a maximum when it is plotted against soHds concentration. The strongest effect on is due to pressure, conventionally expressed as ... 

Although it has been common practice to specify the pressure loss in ordinary valves in terms of either equivalent length of straight pipe of the same size or velocity head loss, it is becoming more common to specify flow rate and pressure drop characteristics in the same terms as has been the practice for valves designed specifically for control service, namely, in terms of the valve coefficient, C. The flow coefficient of a valve is defined as the volume of Hquid at a specified density that flows through the fully opened valve with a unit pressure drop, eg, = 1 when 3.79 L/min (1 gal /min) pass through the valve... 

The best approach is to have a computer program check a series of pressure drops and see how energy requirements decrease as surface increases. If this Option is not available, the following simple method can be used to obtain specification sheet values. Start with a pressure drop of 6.9 kPa (1 psi), and anolv three correction factors, F and F, as follows. 

Packed vs Plate Columns. Relative to plate towers, packed towers are more useful for multipurpose distillations, usually in small (under 0.5 m) towers or for the following specific appHcations severe corrosion environment where some corrosion-resistant materials, such as plastics, ceramics, and certain metaUics, can easily be fabricated into packing but may be difficult to fabricate into plates vacuum operation where a low pressure drop per theoretical plate is a critical requirement high (eg, above 49,000 kg/(hm ) (- 10, 000 lb/(hft )) Hquid rates foaming systems or debottlenecking plate towers having plate spacings that are relatively close, under 0.3 m. 

The design chosen in step 5 is evaluated, or rated, as to its ability to meet the process specifications with respect to both heat transfer and pressure drop. 

There is not a specific flood curve a pressure drop of 1.50 in HgO/ft is considered to represent an incipient flooding condition, although... 

FIG. 14-114 Collection efficiency of Karbate bne separator, based on particles with a specific gravity of 1.0 suspended in atmospberic air with a pressure drop of 2.5 cm water gauge. (Union Caihide Corporation Cat. Sec. S-6.900, 1960.)... 

Material balances, often an energy balance, and occasionally a momentum balance are needed to describe an adsorption process. These are written in various forms depending on the specific application and desire for simplicity or rigor. Reasonably general material balances for various processes are given below. An energy balance is developed for a fixea bed for gas-phase application and simphfied for liquid-phase application. Momentum balances for pressure drop in packed beds are given in Sec. 6. 

It is both convenient and reasonable in continuous filtration, except for precoat filters, to assume that the resistance of the filter cloth plus filtrate drainage is neghgible compared to the resistance of the filter cake and to assume that both pressure drop and specific cake resistance remain constant throughout the filter cycle. Equation (18-51), integrated under these conditions, may then be manipulated to give the following relationships ... 

AP = Line pressure drop, psi P], P2 = Upstream and downstream pressures in psi ABS S = Specific gravity of vapor relative to water = 0.00150 MP,/T d = Pipe diameter in inches Ui = Upstream velocity, ft/sec f = Friction factor (assume. 005 for approximate work)... 

G = Gas specific gravity = mol. wt./29 Pi = Valve inlet pressure, psia AP = Pressure drop across valve, psi Q = Gas flow rate, SCFH Qs = Steam or vapor flow rate, Ib/hr T = Absolute temperature of gas at inlet, °R T5I1 = Degrees of superheat, °F... 

P = Pressure drop in inches of water SG = Specific gravity of the liquid on the tray at the appropriate temperature T = Number of trays T, = Tray spacing, in. 

API mandates that the pressure drop across a clean filter element be no more than 15% of the allowable pressure drop when dirty. An upper limit of 5 psi drop is set for clean filters. This is a reasonable criterion. If a little arithmetic is performed, the head rise for a centrifugal pump may be calculated. The specifications on both of these items must be coordinated and made compatible. 

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