Conversion of pressure

By measuring the kinetic effects of the fluid in motion, since at a given pressure drop, low-density steam will move at a much greater velocity than will high-density condensate, and the conversion of pressure energy into kinetic energy can be used to position a valve. 

This meter may thus be considered as an orifice meter with a variable aperture, and the formulae already derived are therefore applicable with only minor changes. Both in the orifice-type meter and in the rotameter the pressure drop arises from the conversion of pressure energy to kinetic energy and from frictional losses which are accounted for in the coefficient of discharge. The pressure difference over the float —AP. is given by ... 

Obviously the NPSH must be positive, or the liquid would be vaporized and the pump would be filled with gas. Since a pump is designed to transport liquids, if this happened it would just spin in its housing and no transfer would be accomplished. There is an increase in velocity as the liquid enters most pumps. This conversion of pressure energy to kinetic energy may reduce the pressure enough to cause fluids that have a positive NPSH to vaporize. Therefore, each pump has some minimum NPSH below which it will not operate properly. For most pumps an NPSH of 14 ft (4.2 m) of fluid is adequate. Some positive displacement pumps can operate at an NPSH of 6 ft (2 m). Use equation 5 to calculate the NPSH for each pump to be specified. 

The orifice coefficient K takes into account both frictional pressure losses, and conversion of pressure to velocity. The frictional losses represent an irreversible process. The conversion of pressure to velocity represent a reversible process. 

They lack sufficient available NPSH to satisfy the conversion of pressure to velocity, in the eye of the impeller (running NPSH). 

The third calculation is the conversion of pressure units from pounds per square inch read from a guage (psig) to pounds per square inch absolute (psia). Strictly speaking, the value of barometric pressure in psi read from a barometer at the time the pressure gauge was calibrated should be added to psig to get psia. At sea level, a value of 14.7 psi is usually sufficiently accurate. 

The loss of pressure through constrictions (where in addition to the loss of energy due to friction, there is conversion of pressure energy into kinetic energy) provides a method of measuring flow rate. Special devices have been used to measure flow. These include venturi meter, orifice plate, and nozzle meter. The pressure loss through the device may be measured by... 

Polymer films and shells are widely applicable in separating baffles of sealing devices. Pol3miers are also preferable as materials for membranes and flexible baffles separating unlike or differently loaded media intended for the conversion of pressure into motion or vice versa. The membranes should meet the requirements of high deformability, chemical resistance and perfect sealing properties. 

Venturi effect = suction created by conversion of pressure energy to kinetic (velocity) energy. 

Conversion of Pressure Measurements in Freeze Drying. In the experimental... 

The unit of pressure used in the preceding paragraph is that of the International System of Units (SI), the newton per square metre, now known as the pascal. Pa. Conversion of pressures expressed in one unit to values expressed in another unit is frequently required, and the following conversion factors will be found useful ... 

Jet pumps are devices for the transfer, compression or mixing of gases, vapours, liquids or solids, in which a gaseous or Uquid medium acts as the motive force. They operate by the conversion of pressure energy into velocity by means of suitable nozzles. They are pumps without moving parts (Figure 4.1). 

The conversion of pressure to velocity is a rather common, everyday phenomenon. Remember Hurricane Opal, which struck the Florida Panhandle in October 1995 It had peak winds of 145 miles per hour. The pressure in the eye of the hurricane was reported at 27 inches Hg. A portion of the kinetic energy of the wind in a hurricane is derived from the barometric pressure of the atmosphere. The lift that helps an airplane fly is also a result of the conversion of barometric pressure to velocity. Because of the shape of the wing, the air passes across the top of the wing at a higher speed than it... 

Nozzle exit loss Conversion of pressure into velocity. 

Pressure distribution. The pressure drop of the liquid stream through a well-designed gas separator can be approximated by assuming an efficiency of conversion of pressure to velocity in the rotation system of 90% and a recovery efficiency of 80%. Frictional drop in the vortex will be about three times that which would be predicted if the absolute velocity of the vortex near the wall were in axial flow. The Ap across the HRE-2 separator is five inlet-velocity heads or 5 psi. 

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