Steady flow tests

Curing Study. Although the data on the mechanical properties of the uncured inks provide information that is useful in fabricating the inks, no explanation for the poor performance of BK-62 was found. As a result, experiments aimed at examining the cure behavior of the inks were conducted. Samples of the inks were cured on a heated 2 roller apparatus, and, after various curing times, small portions of ink were removed and characterized for oscillatory and short term steady flow viscosity. In view of the complexity of the oscillatory behavior, most of the emphasis is on the steady flow tests however, it is useful to examine the general trends exhibited in the oscillatory data. 

Steady flow tests were obtained by progressively increasing the shear stress applied to the sample at 135 °C [American Society for Testing and Materials (ASTM) D4402-87]. 

Many experimenters have adopted the practice of feeding a preformed mixture of steam and water to their test sections, either out of interest in this type of system or else to avoid the power demanded by long channels. The CISE Laboratories in Italy have produced a considerable amount of data of this kind (S4), and a typical example of their results is shown in Fig. 13. The curves have a characteristic swan-neck shape similar to the Russian data for unstable flow conditions shown in Fig. 9, and the burn-out flux values are generally below those for normal steady-flow conditions. 

Flow Tests. Results of the flow tests are shown in Figures 3 through 6. Figure 3 shows the results of a typical run with a brine saturated sand pack wherein a 300 ppm polymer solution in 1 wt% NaCl was injected at a pH of 8.26. Before this, steady state conditions were established in the core by injecting 1 wt% NaCl. The pH values were stabilized at 8.0 and viscosity at around 1.1 cp. The pressure drop across the core stayed constant up to about 8 PV of polymer injection, the pH stayed in the acidic range, and effluent viscosity was consistently lower than the influent value. At about 8 PV the pressure drop started to build and within 2 PV, increased up to about 100 psi essentially plugging the core. No polymer was eluted until the end of the run. 

Because oxygen is used up in the ageing process it is important that an air flow is maintained and the test pieces are exposed to air on all sides. With either type of oven, there must be a steady flow of air through the oven. IEC 60216 [2] specifies between 5 and 20 complete changes per hour which means that some general purpose laboratory ovens would not be suitable. The air velocity will also affect the rate of ageing but this is said to be under consideration in IEC 60216-4 [7]. 

Koido, Furusawa, and Moriyama [206] used a technique based on the steady-state test method for reservoir rock, sandstone, and other porous media. In this method, a DL is sandwiched between similar DLs on the inlet and outlet sides. The material on the inlet is used to guarantee homogeneous distribution of liquid water in the planar direction, while the material at the outlet minimizes the flow in the outlet. Liquid water is introduced first and then a constant flow rate of air is injected. Once it is at steady state, the pressure difference between the inlet and outlet is measured. The sample is then weighed and the permeability is calculated in a way similar to that of Nguyen and colleagues [205]. 

A Commercial Popcorn Popping Popcorn Popper. We are constructing a 1-liter popcorn popper to be operated in steady flow. First tests in this unit show that 1 liter/min of raw corn feed stream produces 28 liter/min of mixed exit stream. Independent tests show that when raw corn pops its volume goes from 1 to 31. With this information determine what fraction of raw corn is popped in the unit. 

An important requirement of kinetic studies for automotive aftertreatment devices is the capability of performing dynamic reactive experiments. Steady-state tests provide useful information for identification of reaction pathway and stoichiometry, but cannot capture the real operating behavior of catalytic converters for vehicles, which is transient in nature. Indeed, this is so not only because of the continuously changing conditions (temperature, composition, flow rate) of the engine exhausts as extensively addressed in the following sections, the principles of NSRC and SCR applications largely rely on the storage/reaction/release dynamics of NOx and of NH3, respectively. 

Basic Protocol 2 is for time-dependent non-Newtonian fluids. This type of test is typically only compatible with rheometers that have steady-state conditions built into the control software. This test is known as an equilibrium flow test and may be performed as a function of shear rate or shear stress. If controlled shear stress is used, the zero-shear viscosity may be seen as a clear plateau in the data. If controlled shear rate is used, this zone may not be clearly delineated. Logarithmic plots of viscosity versus shear rate are typically presented, and the Cross or Carreau-Yasuda models are used to fit the data. If a partial flow curve is generated, then subset models such as the Williamson, Sisko, or Power Law models are used (unithi.i). 

For most samples, a step maximum time of 5 to 25 min should be set, so as to interrupt the step if steady state is unlikely to be achieved. All of the acceptance parameters can. be considered as a sliding scale. A fast equilibrium flow test can be not much better than, a continuous ramp. If the sample is time dependent with slow rebuild kinetics, then the times should be pushed to their longest limits. Sample stability is an issue, so if the sample is likely to dry or gel at the temperature of interest, the analysis should be carried out quickly (i.e., with shorter step maximum times). 

A good diagnostic for creep and stress relaxation tests is to plot them on the same scales as a function of either compliance (J) or modulus (G), respectively. If the curves superimpose, then all the data collected is in the linear region. As the sample is overtaxed, the curves will no longer superimpose and some flow is said to have occurred. These data can still be useful as a part of equilibrium flow. The viscosity data from the steady-state part of the response are calculated and used to build the complete flow curve (see equilibrium flow test in unit hi.2). 

The inks were examined by using transient, steady flow, and oscillatory tests performed at room temperature, 22 0.5 C. 

When the Ink Is allowed to rest In the Instrument for 15 minutes or more and then steady shear Is Initiated, there Is a significant stress overshoot (Figure 1). Subsequently, the stress level shows a significant time dependence for a period of time that depends on the experimental conditions but Is generally less than 10 seconds. After this Initial period the stress appears to level-off at what will be termed the short term steady flow value. If the steady shear Is maintained for long periods of time, however. It Is found that the stress Is not constant but shows a small and very slow decrease. For the range of conditions tested here, the stress, and therefore the viscosity, drops by about 15% In one hour (Figure 2). The decrease Is approximately linear In a log (n) vs log (time) plot. 

ASTM C 522 covers the measurement of airflow resistance and the related measurements of specific airflow resistance and airflow resistivity of porous materials that can be used for the absorption and attenuation of sound. The method describes how to measure a steady flow of air through a test specimen, how to measure the air-pressure difference across the specimen, and how to measure the volume velocity of airflow through the specimen. The airflow resistance, R, the specific airflow resistance, r, and the airflow resistivity, rQ, may be calculated from the measurements. The apparatus includes a suction generator or positive air supply arranged to draw or force air at a uniform rate through the specimen. A flowmeter is used to measure the volume velocity of airflow through the specimen, and a differential-pressure-measuring device measures the static-pressure difference between the two faces of the specimen with respect to atmosphere. 

No simplification can be used for the problem of the backward facing penetrable step but the full Navier—Stokes equations. Therefore, no solution is available to validate the numerical algorithm. To be aware of it, the numerical algorithm shortly described in the previous section was tested over the whole range of the above-mentioned problems. In this case, the outlet boundary condition (3 = which is associated with the steady flow in an infinite duct, was used. The results of two numerical performances for the flow regime Re = 100 and EPR dimensions h = 0.3 and L x = 1, are shown in Fig. 3.16 the halves of flows in each case are symmetric. Let us analyze them. 

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