Orifice plate defined

When a gas flows through an orifice plate it takes a pressure drop causing the gas to expand and reduce the density. To correct for the density change the equations are multiplied by a gas expansion factor (Yj). The gas expansion factor is based on laboratory tests and is defined as follows ... 

Instruments which measure the rate of flow (velocity) of liquids and gases are called flowmeters they may be broadly defined as being mechanical or electronic in operation. Examples of mechanical flowmeters are orifice plate and float meters (Fig. 5.8), venturi meters, and pitot tube meters, all of which depend on a constriction being introduced into the flow stream in order to produce a difference in pressure across the constriction. The rate of flow can then be obtained from the difference in pressure. 

The fibre reinforcement architecture (position and alignment) of apultmded part is defined by a guiding system that consists of contact points (ceramic guidance eyes ) and orifice plates that are usually made of polished or chromed steel or high-quality polyethylene in order not to damage the fibre reinforcement. 

The reactor used for the sonochemical work was a conventional ultrasonic bath that many readers will recognise as a piece of equipment for cleaning components. The hydrodynamic cavitation reactor was a vessel with an orifice plate in the main feed line to generate cavitation. While fully acceptable yields of 97-99% were achieved with the sonochemical reactor (and also, except for the case of peanut oil feedstock, with the hydrodynanuc cavitation reactor), the most interesting data related to the energy used. These are compared in Table 8.4. The energy efficiency is defined as the yield in kg of product per kJ of energy used in the reactor. 

The setup consists of a 0.0254 m ID and 1.52 m long glass pipe, which bears a canvas filter at its upper end, and which is sealed by an orifice plate at the bottom. This latter plate contains a single 0.4 mm ID orifice in its center. The apparatus is operated in such a way that the jet gas velocity approaches the speed of sound in the orifice. The filter keeps all material inside the system. To assess the degradation extent, one should screen the material by wet sieving through —325 mesh (44 pm). The attrition rate is defined as the ratio of the... 

Thus, in an isothermal system, the mass flow rate depends on the difference in pressures of the gas across the orifice and does not depend upon the thickness of the plate. One may define an area-normalized resistance, R, for mass transfer through the orifice using a generalization of Ohm s law, i.e., Resistance = force/ flux. For Knudsen flow, the force is the pressure difference (analogous to voltage difference in Ohm s law) and the flux is the mass flow per unit area of the hole (analogous to the electrical current density in Ohm s law). Thus, we have... 

The simplest and most common device for measuring flow rate in a pipe is the orifice meter, illustrated in Fig. 10-7. This is an obstruction meter that consists of a plate with a hole in it that is inserted into the pipe, and the pressure drop across the plate is measured. The major difference between this device and the venturi and nozzle meters is the fact that the fluid stream leaving the orifice hole contracts to an area considerably smaller than that of the orifice hole itself. This is called the vena contracta, and it occurs because the fluid has considerable inward radial momentum as it converges into the orifice hole, which causes it to continue to flow inward for a distance downstream of the orifice before it starts to expand to fill the pipe. If the pipe diameter is D, the orifice diameter is d, and the diameter of the vena contracta is d2, the contraction ratio for the vena contracta is defined as Cc = A2/A0 = (d2/d)2. For highly turbulent flow, Cc 0.6. 

In extrusion, material flow through the openings of a die is very complex and related not only to the physical characteristics of the particulate mass but also to the die plate or screen configuration. As an example, Fig. 8.33 shows how the extrusion rate varies in relation to the dimension of the orifices (defined by the die thicknesses and hole diameters) as well as the percentage of free area (defined as the sum of all hole cross... 

Perforated plates are defined by a critical flow rate above which the orifice operation is asynchronous and the liquid flow in the sparger region is relatively unstable. As the hole spacing decreases, the critical flow rate decreases as well. At the same time, perforated plates require a minimum pressure drop in order to achieve uniform orifice activity. In other words, a critical flow rate is also created at the lower end such that a lower flow rate would lead to instability as well (Kang et al., 1999 Ruzicka et al., 2003 Su and Heindel, 2005a). This effect would produce additional complications in making comparative analysis between research works using different open area ratio adjustment methods. 

For a thin plate or sharp-edged orifice, the vena contracta is assumed to he one half of an orifice diameter downstream from the orifice, hut in reality the distance may he from 30% to 80% of di-For flow of water at a high Reynolds number through a small orifice diameter, Lindeburg (1998) reported that the contracted area is approximately 61% to 63%. The coefficient of contraction is defined as... 

Mass transfer during drop formation [7] whether the drops are formed at nozzles or orifices in plates or at the ends of jets and the presence or absence of interfacial turbulence or surfactants. Although fairly elaborate expressions have been devised to describe some of the data [62, 63], the great divergence of the data at present does not seem to warrant anything more than a simple estimate. The mass-transfer coefficient Kujj can be defined by [76]... 

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