Frictional losses overcoming

The potential energy for a conservative system (system without frictional loss) is the negative integral of a displacement times the force overcome. In this case, the potential energy for a displacement a away from Xe, is... 

The theory of pressure losses can be established by developing Bernoulli s theorem for the case of a pipe in which the work done in overcoming frictional losses is derived from the pressure available. For a fluid flowing in a pipe, the pressure loss will depend on various parameters. If... 

The pressure required to overcome the frictional losses in the delivery pipe. 

In a synthetic ammonia plant the hydrogen is fed through a 50 mm steel pipe to the converters. The pressure drop over the 30 m length of pipe is 500 kN/m2, the pressure at the downstream end being 7.5 MN/m2. What power is required in order to overcome friction losses in the pipe Assume isothermal expansion of the gas at 298 K. What error is introduced by assuming the gas to be an incompressible fluid of density equal to that at the mean pressure in the pipe /r — 0.02 mN s/m2. 

Part of this voltage difference is required to overcome the cell resistance and is equal to the IR product. The corresponding electric energy I2 R is dissipated as heat. This is similar to the frictional losses that occur in mechanical processes that are irreversible. 

Two major effects contribute to the pressure drop in horizontal flow acceleration and friction loss. Initially the inertia of the particles must be overcome as they are accelerated up to speed, and then the friction loss in the mixture must be overcome. If Vs is the solid particle velocity and ms = ps I7s( l — ) is the solids mass flow rate, the acceleration component of the pressure drop is... 

Equation 1.16 shows that, in general, the upstream pressure Pi must be greater than the downstream pressure P2 in order to raise the fluid, to increase its velocity and to overcome frictional losses. 

For a given F, the height of hquid in the tank at steadystate would also be some constant h. The value of k would be that height that provides enough liy drau-lic pressure head at the inlet of the pipe to overcome the frictional losses of liquid flowing down the pipe. The higher the flow rate F, the higher h will be. 

Net positive suction head available (NPSH) is the difference between the total absolute suction pressure at the pump suction nozzle when the pump is running and the vapor pressure at the flowing liquid temperature. All pumps require the system to provide adequate (NPSH). In a positive-displacement pump the (NPSH)a should be large enough to open the suction valve, to overcome the friction losses within the pump hquid end, and to overcome the liquid acceleration head. 

What happens to this differential pressure of 4.7 psig It is consumed in overcoming the frictional losses, due to the flow in the... 

The liquid head driving force of 16 ft, or 4 psi, shown in Fig. 10.4, is actually not all available to overcome the higher stripper pressure. The frictional loss of the piping used to feed the stripper should be subtracted from the liquid head driving force. In the jet fuel example presented above, this frictional loss was neglected. 

Pumping Head—The energy required to raise water to the distribution elevation and overcome friction losses through pipe, valves, fittings and nozzles. It is expressed in feet of liquid the pump must move and is equal to the total friction loss, static head and pressure drop through the distribution system. 

The pumping power for a water-based versus helium-based loop was calculated at the full power condition. The fluid properties in the respective loops were used to calculate the friction loss power per unit megawatt of thermal power transported for the water-based loop as a fraction of the same in the helium-based loop. The result derived in Vilim (2009) shows that the power in the water loop is insignificant to the power in the helium loop. In the helium loop the circulating power needed is about 7 MWe or 14 MWt out of a reactor thermal capacity of 600 MWt. Thus an advantage of a water-based loop is that the pumping power to overcome frictional losses is significantly less and results in an efficiency increase. 

The dependence Ne =/ (Fr) describes bow wave development and bow wave resistance in ships. Of course, it it not existing in submarines. At moderate speeds and large ratios of boat length to boat width it is practically negligible. Only the friction loss of the ship s hull has to be overcome. Under these frame conditions (Re and Fr irrelevant),... 

Material is transferred from one process operation to another by conpres-sion, pmnping or conveying depending on whether a gas, liquid or a sohd is transferred. This operation also requires energy to overcome frictional losses. 

Biology has the power to sustain, to draw out, its environmental conditions (Lovelock, 1979, 1988), and indeed to remake them in an improbable path. Swiss travelers do not descend peaks by jumping over the cliffs. Instead they use cable cars, and as they descend they help others to ascend only a small input of energy is needed to overcome frictional losses. Indeed, consider a... 

The head loss /i(, represents the additional height that the fluid needs to be raised by a pump in order to overcome the frictional losses in the pipe. The head loss is caused by viscosity, and it is directly related to the wall shear stress. Equation 8—45 is valid for both laminar and turbulent flows in both circular and noncircular tubes, but Eq. 8-46 is valid only for fully developed laminar flow in circular pipes. 

Therefore, mechanical power input in the amount of 0.31 W is need to overcome the frictional losses in the flow due to viscosity. 

This is a perpetual motion machine of the first kind and violates the first law of thermodynamics. The transfers of energy that occur in this machine will never be able to overcome the frictional losses that are inevitable. The machine will run down. Even if it were possible to make it completely loss-less, it would never be able to produce more energy than was put into it and so at best it would be a curiosity and not a useful or practical machine. Alas even the case of 100% efficiency is impossible. 

The stack must provide enough draft to hold the firebox at a slight negative pressure and to overcome frictional losses through the convection section and stack. First, calculate the draft caused by the firebox itself. Determine whether the limiting factor is pressure drop across the burners or maintenance of negative pressure throughout the firebox. 

Liquid Flow Measurement. The requirement of accurate liquid flow measurement can also elevate process equipment (see Figure 7-8). If liquid is near the boiling point, a static head is required in the front of the control valve to overcome pipe friction losses and avoid flashing in the line. Minimum equipment elevation, orifice range and minimum line size can be used if the orifice is as close to the equipment as possible and the piping has only one elbow up to the control valve. 

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