Isokinetic sample probe

Schraub, F. A., 1968, Isokinetic Sampling Probe Technique Applied to Two-Phase Flow, ASME 67-WA/FE-28, Annual Meeting, ASME, New York. (3)... 

FIGURE 2.7 Bohnet velocity-sensing isokinetic sampling probe (Bohnet, 1978). 

Ito, K., Kobayashi, S., and Tokuda, M., "Mixing Characteristics of a Submerged Jet Measured Using an Isokinetic Sampling Probe", Metallurgical Transactions B (Precess Metallurgy), 22, 439 (1991). 

Zhang, G. J., and Ishii, M., "Isokinetic Sampling Probe and Image Processing System for Droplet Size Measurement in Two-phase Flow", Int. J. of Heat and Mass Transfer, 38, 2019 (1995). 

Isokinetic sample probe. (From U.S. EPA, 40 CFR 60 Standards of Performance for New Stationary Sources, Washington, DC U.S. Environmental... 

Nozzle for isokinetic sampling probe (not to scale). (From Baukal, C. E., Industrial Combustion Pollution and Control, Marcel Dekker, New York, 2004.)... 

Nguyen T, Nguyen A, Nieh S. An improved isokinetic sampling probe for measuring local gas velocity and particle mass flux of gas-solid suspension flows. Powder Technol 59 183-189, 1989. 

The gas and liquid velocities at key points are measured by hot film anemometers. The locations of the hot film probes are rotated in several similar experiments to get fiill information on velocity distributions. The amount of entrained droplet flow and droplet sizes are measured by several isokinetic sampling probes. The Thermal-hydraulic and Reactor Safe Laboratory has recently developed the isokinetic sampling probe to measure the droplet entraimnent rate and droplet size distribution. For droplet size distribution, the droplets are collected into a oil bath and the CDC pictures of the suspensions are obtained. Using digital image processing system... 

A new fleld sampling tool for pressurized gas streams, the Laser Isokinetic Sampling Probe (LISP ) was developed, custom-designed, and built to speciflcations. It collects... 

For sampling particulate matter, one is dealing with pollutants that have very different inertial and other characteristics from the carrying gas stream. It becomes important, therefore, to sample so that the same velocity is maintained in the probe tip as exists in the adjacent gas stream. Such sampling is called isokinetic. Isokinetic sampling, as well as anisokinetic sampling, is illustrated in Fig. 13-3. 

Isokinetic A process in which the velocity at the entrance to the sample probe in a gas stream is the same as the velocity at a given point in the duct or stack at a given time. 

All samples should be collected using isokinetic sampling when determining mass emissions. This means the gas sample should be pulled through the sample probe at the same velocity as the velocity of the process gas. If not, the total particulate catch will not be representative of the gas stream. 

Figure 2. Diagram of a typical sharp-edged probe for isokinetic sampling of aerosol particles from an aircraft. The probe is sized to provide 500 L/m at a sampling velocity of 50 mis. The 7° expansion of the probe behind the probe tip is to slow the air velocity. The interior of the probe is polished to a mirror...

Thin L-shaped probes are commonly used to measure solids concentration profile in slurry pipelines (28-33), However, serious sampling errors arise as a result of particle inertia. To illustrate the effect of particle inertia on the performance of L-shaped probes, consider the fiuid streamlines ahead (upstream) of a sampling probe located at the center of a pipe, as shown in Figure 2. The probe has zero thickness, and its axis coincides with that of the pipe. The fluid ahead of the sampler contains particles of different sizes and densities. Figure 2A shows the fluid streamlines for sampling with a velocity equal to the upstream local velocity (isokinetic sampling). Of course, the probe does not disturb the flow field ahead of the sampler, and consequently, sample solids concentration and composition equal those upstream of the probe. 

The next step was to test the probe performance in the pipeline in comparison with accepted methods for measuring solids concentrations isokinetic sampling and y-ray absorption methods. 

Figure 31 shows the resistivity measured by the conductivity probe and the local concentration measured by the isokinetic sampling method. Measurements were made for slurries of polystyrene particles of 1.4-mm mean diameter at the pipe center and at radial positions of R = 0.8. Good agreement with calibration results is seen in these tests. Because the particles used in these experiments were large, no samples could be withdrawn from the center of the pipe at concentrations higher than 35%. Also, no voltage measurements could be taken closer to the pipe wall because particles tended to be trapped between the probe and the wall. 

Probe issues Isokinetic/non-isokinetic sampling, sampling temperature, material. 

Isokinetic sampling with realistic probe dimensions requires, even at ambient pressures, high gas velocities up to 20 m/s with corresponding gas flow rates between... 

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