Flow ratio

Fig. 7. Design chart for estimation of average-flow ratio ia absorption (4). i 2 outlet at gas inlet ...

Molecular Weight Distribution. In industry, the MWD of PE resins is often represented by the value of the melt flow ratio (MER) as defined in Table 2. The MER value of PE is primarilly a function of catalyst type. Phillips catalysts produce PE resins with a broad MWD and their MER usually exceeds 100 Ziegler catalysts provide resins with a MWD of a medium width (MFR = 25-50) and metallocene catalysts produce PE resins with a narrow MWD (MFR = 15-25). IfPE resins with especially broad molecular weight distributions are needed, they can be produced either by using special mixed catalysts or in a series of coimected polymerization reactors operating under different reaction conditions. 

The width of molecular weight distribution (MWD) is usually represented by the ratio of the weight—average and the number—average molecular weights, MJM. In iadustry, MWD is often represented by the value of the melt flow ratio (MER), which is calculated as a ratio of two melt indexes measured at two melt pressures that differ by a factor of 10. Most commodity-grade LLDPE resias have a narrow MWD, with the MJM ratios of 2.5—4.5 and MER values in the 20—35 range. However, LLDPE resias produced with chromium oxide-based catalysts have a broad MWD, with M.Jof 10—35 and MER of 80-200. 

The molecular weight distribution of LLDPE resins is usually characterized in industry by the ratios of melt indexes measured in the same apparatus using different loads (2.16, 10.16, and 21.6 kg). The commonly used ratios are melt flow ratio, MFR) and I q/I2. Both of these ratios... 

J.m/h. Because the diamond growth takes place under atmospheric conditions, expensive vacuum chambers and associated equipment are not needed. The flame provides its own environment for diamond growth and the quaUty of the film is dependent on such process variables as the gas flow rates, gas flow ratios, substrate temperature and its distribution, purity of the gases, distance from the flame to the substrate, etc. 

In addition, sidestream flow rates are replaced with sidestream flow ratios by... 

Direction of extraction, whether from dispersed to continuous, organic hquid to water, or the reverse Dispersed-phase holdup Flow rates and flow ratio of the liquids... 

For the dispersed phase firm relationships have not been established, but at high rotor speeds, Eq may be 1 to 3 times Ec- In any event, axial mixing for the hquid flowing at the lower rate becomes very severe for extreme flow ratios (>10). 

Melt Flow Ratio 230°C/2.16kg Tensile Yield g/lOmin ISOI133 30 48 48... 

Recommended nominal steam rates at 60 m/s exit velocity for a typical flare tip are shown in Figure 2. At lower velocities, higher steam ratios are required. Typical steam control consists of a flow ratio controller with adjustable ratio set point, related to flare gas flow. The ratio adjustment, located in the control house, provides for the higher steam ratios necessary at low flaring rates. 

Dali Flow Tube - The advantage is this type of flowmeter is that it has a permanent head loss of only 5 % of the measured pressure differential. This is the lowest pressure drop of all orifice meter designs. Flow ratios as high as 1 10 (e.g., 1.0 to 10 kg/s) can be measured within + 2% of actual flow. Dali flow mbes are available in different materials and diameters up to 1500 mm. 

In practice the clamping pressure will also depend on the geometry of the cavity. In particular the flow ratio (flow length/channel lateral dimension) is important. Fig. 4.42 illustrates typical variations in the Mean Effective Pressure in the cavity for different thicknesses and flow ratios. The data used here is typical for easy flow materials such as polyethylene, polypropylene and polystyrene. To calculate the clamp force, simply multiply the appropriate Mean Effective Pressure by the projected area of the moulding. In practice it is... 

The thickness of the moulding is 1 mm, hence the flow ratio = 150/1 = 150. From Fig. 4.42 at this thickness and flow ratio, the mean effective pressure is 75 MN/m. ... 

This is also the flow ratio, so from Fig. 4.42 the mean effective pressure is 50 MN/m. Applying the viscosity factor, etc as above, then... 

The container shown at the top of p. 341 is injection moulded using a gate at point A. If the injection pressure at the nozzle is 140 MN/m and the pressure loss coefficient, m, is 0.5, estimate (i) the flow ratio and (ii) the clamping force needed. 

Fig. 5.27 shows the variation of MEP with flow ratio (R/H) for spreading flow in discs of different depths. The material is polypropylene and the constant injection rate is 3.4 x 10 m /s. This is a high injection rate but has been chosen because the clamp forces predicted by this diagram are representative of those occurring in real moulding situations (even though it is based... 

Fig. 5.27 Variation of Cavity Pressure with Flow Ratio...

Materials - LDPE, polypropylene, polystyrene, PVC, POM, acrylic, polycarbonate, nylon 66 and ABS. Note that the answers will give an indication of the flow ratios for these materials. The flow should be assumed to be non-isothermal. 

Using the data given, the flow ratios will be... 

An established design method for this type of system is not available. The practical design of the low-momentum supply with exterior hood system described in the previous part of this section used the flow ratio method. How-evec, the actual exhaust flow rate was adjusted visually to the appropriate value in order to exhaust only the contaminants transported by the supply airflow. 

The flow ratio method was first suggested for use in designing receptor hoods and then it was suggested for design of push-pull systems. The concept of the method is described as follows. 

The limit value of the flow ratio, K , is expressed as the following experimental equation for two-dimensional push-pull flows ... 

Applying the flow ratio method to the low-momentum supply system, the required exhaust flow rate is often in excess of practical values. This is because the value of is given as the value at which all the supplied airflow should be exhausted by the exterior hood. In the low-momentum supply system, contaminant sources should usually be between the supply inlet and the exterior hood. The supply airflow is contaminated at the position of the sources and it flows to the exterior hood. Therefore, all of the airflow is not always contaminated. Unfortunately, a design method considering such cases (the diffusion of contaminants within the airflow) has not been established yet, and the appropriate exhaust flow rate has to be adjusted after the system is installed. 

Conveying systems normally use air as the transport medium to convey granular, crushed, or pulverized materials. Modelling the flow of pneumatic conveying and calculating its pressure loss is a problematic task. The greatest problem arises from the fact that different mass flow ratios, solid flow rate divided by the gas flow rate, imply different flow types in pneumatic conveying. Each of these flow types, which can be classified in many different ways, requires its own specific model in order to provide a concrete calculation method. 

The mass flow ratio p, sometimes also called mixture ratio, is defined as... 

Obviously, the closer the particles are to each other, the more likely it is that they will stick together and form larger clumps, which usually means that the flow is not uniform. This view combined with Eq. (14.18) is a greatly simplified explanation of why the mass flow ratio q, for dry wood chips can rise to five or even higher and still the flow of the mixture of air and large chip particles can be handled as a uniform suspension, a uniform dilute-phase flow, although it is not actually dilute. The mass flow ratio for fine coal powder, however, has to be much less than five in order for the flow to be handled as a uniform dilute flow. 

Equation (14.91) contains only the mass flow ratio /u as a characteristic number of the mechanics of similitude of the mixture. All the other irnpor rant factors, such as particle size, solid density, etc., are contained in the additional pressure-loss coefficient of the solid particles, A, which is determined separately for each material. 

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