TAP measurements

Pitot Tubes The combination of pitot tubes in conjunction with sidewall static taps measures local or point velocities by measuring the difference between the total pressure and the static pressure. The pitot tube shown in Fig. 10-5 consists of an impact tube whose opening faces directly into the stream to measure impact pressure, plus one... 

The EPA Method 2 probe uses a standard S-type Pitot tube to determine the velocity pressure by measuring gas flow as a unidirectional vector. This method is typically 10-20% higher than the calculated flue gas rate from the FCC heat balance. The newly develop EPA Method 2F probe is a five-holed prism tip with a thermocouple. A centrally located tap measures the stagnation pressure, while two lateral taps measure the static pressure. The yaw angle is determined by rotating the probe until the difference between the two lateral holes is zero. This method closely matches the... 

One important and as yet not fully understood feature of CO2 foam concerns delineation of the length of the foam bank. Multiple pressure tap measurements indicated that the largest pressure drop occurred within 3 to 6 inches around the bulk CO2 phase front. These and additional studies suggest that the foam bank can be relatively short compared to the length of the core. The pressure drop decreased to very low values as brine approaches its irreducible saturation. This is reasonable, since aqueous surfactant lamella cannot form or propagate when there is no mobile brine present. 

Figure 6. NO conversion (left) and N2 selectivity (right) for both model gas (MG) and TAP measurements as function of the temperature. Two different temperature scales are used to show correlation.

Figure 6 shows the NOx conversions and N2 selectivities for both model gas and TAP experiments with the stoichiometric and lean mixture as function of the temperature. The TAP measurements were carried out by simultaneously pulsing both valves. No NO2 formation was observed in TAP experiments in contrast with model gas experiments, therefore conversion and selectivity were calculated for the reaction of NOx (NOx = NO + NO2) to N2 and N2O. The equilibrium of NO and NO2 in O2 is given by ... 

This equilibrium will shift to the left side at increasing temperature and decreasing pressure. This could explain the absence of NO2 in the TAP measurements. 

When the temperature scale for the TAP measurements is adjusted to higher temperatures by approximately 100 K, a quite good correlation between the model gas and the TAP experiments is found for both the NOx conversion and the N2 selectivity and for both the stoichiometric and the lean gas mixture. The NOx conversion increases for the stoichiometric mixture with increasing temperature. The NOx conversion for the lean mixture shows a maximum in conversion at approximately 575 K (model gas temperature). The selectivity towards N2 shows for both gas mixtures a minimum around 575 K. This is of course equivalent to a maximum in N2O selectivity. In contrast to the conversion of NOx, the selectivity towards N2 is not strongly depending on the composition. From these figures it appears that the higher O2 concentration in the lean gas mixture compared to the... 

Since the flow in a vertical pipe is pseudohomogeneous, a simple instrument to measure flow rate of slurry is the inverted U column, which consists of 4 elbows and 2 vertical pipe spools (Figure 4-17). The first vertical branch must be sufficiently high to eliminate entrance effects (previously discussed in Chapter 2). Toward the top of the pipe, a pressure tap measures the static pressure. Pressure loss occurs through the two elbows. Another pressure tap is added on the downward section of the pipe. The inverted U column is calibrated on water and the pressure loss is a function of the flow rate as well as the density of the slurry ... 

The water quality (air content) and the water flow influenced the measurements using one channel. Therefore the four channel system was first tested in the laboratory with a stationary tube. The best results were obtained using tap water and a well controlled flow in a water-filled chamber. A great difference in the concentration of air in the different grades of water was obvious, and the tap water was superior to soft water during these measurements. 

The air may be collected directly into a Hempel gas-burette (Fig. 76) and there measured. This burette consists of a glass tube H calibrated in ml. from the tap E downwards, and connected by a piece of rubber tubing to the reservoir R, the height of which can be adjusted. The tap E is a 3-way tap. by which the tube H can be connected directly through to the capillary tube above, or either tube can be connected through the left- hand end of the tap to the atmosphere. 

Digestion. 20-25 mg. of the substance whose nitrogen content is to be estimated are weighed out in a stoppered weighing-tube and then transferred to the flask L that has been previously dried in an oven at izo C. With care, the substance may be transferred directly into the bulb of the flask without any adhering to the sides. If any material sticks on the way down, the flask should be tapped gently to cause the substance to fall to the bottom. 2 G. of the catalyst mixture (32 g. of potassium sulphate, 5 g. of mercury sulphate and ig. of selenium powder, well mixed) are added and 3 ml. of A.R. cone, sulphuric acid are measured out carefully and poured into the digestion... 

The following data were collected for the analysis of fluoride in tap water and in toothpaste, (a) For the analysis of tap water, three 25.0-mL samples were each mixed with 25.0 mL of TISAB, and the potential was measured with an F ISE relative to a saturated calomel electrode. Five 1.00-mL additions of a standard solution of 100.0-ppm F were added to each, measuring the potential following each addition. 

A fundamental requirement in powder processing is characterization of the as-received powders (10—12). Many powder suppHers provide information on tap and pour densities, particle size distributions, specific surface areas, and chemical analyses. Characterization data provided by suppHers should be checked and further augmented where possible with in-house characterization. Uniaxial characterization compaction behavior, in particular, is easily measured and provides data on the nature of the agglomerates in a powder (13,14). 

When determining bulk density, a distinction should be made between loose bulk density and tap density, eg, ASTM B527-81. The latter is a measure of the influence of settling on filler volume at constant mass. 

There are five locations ia use for the taps used to couple the differential to the measurement device. These locations are depicted ia Figure 7. 

The fifth type of tap is unique in that the downstream tap location varies depending of the orifice P ratio. This tap is located at the vena contracta the location where the stream issuing from the orifice attains its minimum cross section. The location of this tap is defined from the upstream face of the orifice as is the D/2 tap. The downstream tap for corner, flange, and pipe taps is measured from the downstream face of the orifice. Vena contracta taps maximize the measured differential pressure. For modem transmitters this is not an important consideration and this type of tap is no longer widely used. 

Flow Nozzles. A flow nozzle is a constriction having an eUiptical or nearly eUiptical inlet section that blends into a cylindrical throat section as shown in Figure 8. Nozzle pressure differential is normally measured between taps located 1 pipe diameter upstream and 0.5 pipe diameters downstream of the nozzle inlet face. A nozzle has the approximate discharge coefficient of an equivalent venturi and the pressure drop of an equivalent orifice plate although venturi nozzles, which add a diffuser cone to proprietary nozzle shapes, are available to provide better pressure recovery. 

Pitot Tubes. The fundamental design of a pitot tube is shown in Eigure 9a. The opening into the flow stream measures the total or stagnation pressure of the stream whereas a wall tap senses static pressure. The velocity at the tip opening, lA can be obtained by the Bernoulli equation ... 

Advantages of the pitot method of measurement are low pressure loss and easy installation. In some cases, installations in existing lines are made without process shutdown by hot tapping the line (7). 

Standard Test Methodfor Laboratory Measurement of Impact Sound Transmission Through Thor—Ceiling Assemblies Using the Tapping Machine, ASTM E492-90, ASTM, Philadelphia, Pa., 1990. 

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