Buoyancy meter

Fig. 6.35. Buoyancy meter with totally immersed float and LVDT sensing-element...

Variable-Area Flow Meters. In variable-head flow meters, the pressure differential varies with flow rate across a constant restriction. In variable-area meters, the differential is maintained constant and the restriction area allowed to change in proportion to the flow rate. A variable-area meter is thus essentially a form of variable orifice. In its most common form, a variable-area meter consists of a tapered tube mounted vertically and containing a float that is free to move in the tube. When flow is introduced into the small diameter bottom end, the float rises to a point of dynamic equiHbrium at which the pressure differential across the float balances the weight of the float less its buoyancy. The shape and weight of the float, the relative diameters of tube and float, and the variation of the tube diameter with elevation all determine the performance characteristics of the meter for a specific set of fluid conditions. A ball float in a conical constant-taper glass tube is the most common design it is widely used in the measurement of low flow rates at essentially constant viscosity. The flow rate is normally deterrnined visually by float position relative to an etched scale on the side of the tube. Such a meter is simple and inexpensive but, with care in manufacture and caHbration, can provide rea dings accurate to within several percent of full-scale flow for either Hquid or gas. 

Rotameter A rotameter consists of a vertical tube with a tapered bore in which a float changes position with the flow rate through the tube. For a given flow rate the float remains stationary since the vertical forces of differential pressure, gravity, viscosity, and buoyancy are balanced. The float position is the output of the meter and can be made essentially linear with flow rate by makiug the tube areavaiy hn-early with the vertical distance. 

With this relationship for all samples was calculated from ninh This M is used for evaluating the reaction data. The ultracen rifuge (u.c measurements were carried out in a Spinco model E analytical ultracentrifuge, with 0.4% solutions in 90% formic acid containing 2.3 M KCl. By means of the sedimenta- ion diffusion equilibrium method of Scholte (13) we determine M, M and M. The buoyancy factor (1- vd = -0.086) necessary for tSe calculation of these molecular weights from ultracentrifugation data was measured by means of a PEER DMA/50 digital density meter. 

As the density of the liquid increases the float also rises and lifts the chain. The float continues to ascend until the additional weight of the chain raised equals the additional buoyancy due to the increased density. The reverse occurs when the density of the liquid is reduced. The position of the float is detected by a linear variable differential transformer (LVTD) in which the movement of the ferromagnetic core of the displacer changes the inductance between the primary and secondary windings of a differential transformer (see also Fig. 6.13). Such meters... 

There are several instruments which employ highly sensitive weighing techniques. One particular meter is based upon the measurement of the upthrust on a float(45). Any displacement of the float due to a change in the gas density (and consequently buoyancy) is counterbalanced by a magnetic field produced by an electromagnet. The float is thus maintained in the null position by the force generated by the flow of a direct current in the coil of the electromagnet. This current is directly proportional to the density of the gas. A temperature correction is applied to the readout and densities up to 500 kg/m3 at pressures up to 17 MN/m2 can be measured. 

A solar pond is a natural or site-built pond, usually ond to five meters in depth, which has been altered to retard the loss of absorbed solar energy. The absorbed solar energy in a pond is usually lost because buoyancy of the warmed water causes it to rise to the surface and lose its heat to the atmosphere. The chief solar pond technology - the salt-gradient, or... 

The buoyancy componet made of carbon fiber shows many advantages and is suitable for development oil and gas in the depth between 1500 m and 3000 m. For example, the buoyancy upgrading component which was made of carbon fiber by the America Composite Technology Corporation is able to provide the 8.6 tons buoyancy, and the anchor can be lifted from the depth of 390 meters underwater. 

For a standard of flow rate metering, traceability is the top priority the measurement uncertainty should he sufficiently small, and a system that features single operation, low measurement uncertainty, and high repeatability is desirable. Therefore, approaches based on weighing are, above all others, favorable candidates for such a purpose. As shown in Fig. 6, a gravimetric primary metering standard has been set up to achieve these requirements [9]. Liquid water is driven by a pneumatic pressure control mechanism to obtain flow rates down to less than a microliter per minute. The measurement capabUity depends on the weighing of the collection beaker, the stability of the pressure difference, the time interval, and the variation of the ambient temperature. Buoyancy variation and liquid evaporation are critical concerns for measurements associated with such a small quantity of liquid. 

A stand-alone static method is the popular Wilhelmy plate method (Figure 1.18). In this method, a completely wetted platinum plate is brought into contact with a liquid surface, and a pull force is applied to the plate. Equilibrium is achieved when that force, corrected by the buoyancy force acting on the immersed part of the plate, is balanced by the surface tension, that is, F + dbHpg = 2(d + b)a. The force F is measured with a sensitive dynamometer, which typically forms the core of modem surface tension meters. 

Polyurethane foam is commonly used to fill the void inside a hollow part for strength or insulation. The foam density is typically in the range of 2-4 Ibs/ft. (0.03-0.06 g/cm ) and is often used to provide buoyancy in flotation devices or insulation for storage vessels. The urethane foam is created using a two-component liquid system that is metered into the part using a special mixing head and as the components react it rises to fill the void inside. 

Density and specific volume of mesophases are measured under atmospheric pressure with pycnometers [17-22], dilatometers [16, 23-25] (e.g., differential scanning dilatometers, DSD [26-31]), with a buoyancy method [32], and with a vibrating device, known as a digital precision density meter system, or densitometer (Anton Paar K.G.) [33-38], Devices for high-pressure measurements of specific volumes have been described by Kuss [39,40] and Ddrrer et al. [41], but were also mentioned earlier [42], More recently, a device for simultaneous... 

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