Isothermal injection

Figure 5. Alditol acetates as resolved on the trlfluoro-propylnethyl silicone DB-210. Split Injection, Isothermal at 220°C 30 m x 0.25 nm column coated with a bonded 0.25 pm film. Components 1, rhamnltol 2, fucltol 3, rlbl-tol 4, arablnltol 5, mannitol 6, galacltol 7, glucl-tol 8, Inositol.

A solution of a known alkali or acid (e. g. 10 g/1 NaOH) may be injected isothermally into the circulating liquor of the dyeing machine at 25 °C to eliminate any possible effects of temperature change on the measnred values. Readings by the pH meter and the controller are obtained just before the start of the next injection. Injections of known amounts of the reference solution (e.g. 10 ml) may be carried out at 5-min intervals. The valnes read by the system and pH meter should show a satisfactory agreement to ensnre a high level of consistency and accuracy, such as that depicted in Fig. 7.20. 

Solution of the model equations shows that, for a linear isothermal system and a pulse injection, the height equivalent to a theoretical plate (HETP) is given by... 

The simplest mode of IGC is the infinite dilution mode , effected when the adsorbing species is present at very low concentration in a non-adsorbing carrier gas. Under such conditions, the adsorption may be assumed to be sub-monolayer, and if one assumes in addition that the surface is energetically homogeneous with respect to the adsorption (often an acceptable assumption for dispersion-force-only adsorbates), the isotherm will be linear (Henry s Law), i.e. the amount adsorbed will be linearly dependent on the partial saturation of the gas. The proportionality factor is the adsorption equilibrium constant, which is the ratio of the volume of gas adsorbed per unit area of solid to its relative saturation in the carrier. The quantity measured experimentally is the relative retention volume, Vn, for a gas sample injected into the column. It is the volume of carrier gas required to completely elute the sample, relative to the amount required to elute a non-adsorbing probe, i.e. 

Example 5.4 Eight polypropylene mouldings, each weighing 10 g are to be moulded using the runner layout shown in Fig. 5.19. If the injection time is 2 seconds and the melt temperature is 210°C, calculate the pressure at each cavity if the injection pressure at the sprue is 80 MN/m. The density of the pwlypropylene is 909 kg/m3 and the volume of the sprue is 5000 mm. Assume that the flow is isothermal and ignore the pressure losses at comers. 

Example 5.14 A power law fluid with constants i]q= 1.2 x lO Ns/m and n = 0.35 is injected through a centre gate into a disc cavity which has a depth of 2 mm and a diameter of 200 mm. If the injection rate is constant at 6 X 10 m /s, estimate the time taken to fill the cavity and the minimum injecdon pressure necessary at the gate for (a) Isothermal and (b) Non-isothermal conditions. 

Solution (a) Isothermal Situation. If the volume flow rate is Q, then for any increment of time, dt, the volume of material injected into the cavity will be given by Qdt). During this time period the melt front will have moved from a radius, r, to a radius (r -I- dr). Therefore a volume balance gives the relation... 

Fig. 5.28 shows a comparison of the isothermal and non-isothermal situations for polypropylene. When pressure is plotted as a function of injection rate, it... 

However, in the non-isothermal case the pressure is also high at low injection rates. This is because slow injection gives time for significant solidification of the melt and this leads to high pressures. It is clear therefore that in the non-isothermal case there is an optimum injection rate to give minimum pressure. In Fig. 5.28 this is seen to be about 3.0 x 10 m /s for the situation considered here. This will of course change with melt temperature and mould temperature since these affect the freeze-off time, //, in the above equations. 

Polyethylene is injected into a mould at a temperature of 170°C and a pressure of 100 MN/m. If the mould cavity has the form of a long channel with a rectangular cross-section 6 mm X 1 mm deep, estimate the length of the flow path after 1 second. The flow may be assumed to be isothermal and over the range of shear rates experienced (10 -10 s ) the material may be considered to be a power law fluid. 

A polymer melt is injected into a circular section channel under constant pressure. What is the ratio of the maximum non-isothermal flow length to the isothermal flow length in the same time for (a) a Newtonian melt and (b) a power law melt with index, n = 0.3. 

The discussion of the last section is then useful in considering the evaporative cycles. We shall see that the effect of water injection downstream of the compressor (and possibly in the cold side of the heat exchanger) may lead towards the [CBTJiXr type of plant, with increased cold side effective specific heat and hence increased heat exchanger effectiveness. Water injection in the compressor may lead to a plant with isothermal compression. 

Heart-cutting, with trapping and re-injection, using isothermal dual capillary column chromatography for separation of the UV photolysis products of methyl... 

Note that the initial slope of the adsorption isotherm can be easily obtained from the knowledge of the retention time associated to a small injection performed on a column, as this retention time is given by t = t icj where... 

Programmed Temperature Injectors The programmed temperature injector is held near the boiling point of the solvent after injection of the sample, it is temperature programmed rapidly until it reaches the desired maximum temperature, which is normally higher than that of an isothermal (constant temperature) injector. As the sample components vaporize, they are transferred onto the head of the GC column. This technique is a varia-... 

Injection (GC) 258 interface (LC/GC) 801 Retention index system (GC) 176 choice of standards 181 isothermal 176... 

FIGURE 20.9 Freundlich isotherm for phenol adsorbed on Frio Core. (From U.S. EPA, Assessing the Geochemical Fate of Deep-Well-Injected Hazardous Waste A Reference Guide, EPA/625/6-89/025a, U.S. EPA, Cincinnati, OH, June 1990.)... 

Boundary-layer separation and Reynolds flux. Kutateladze and Leont ev (1964, 1966) suggested that the flow boiling crisis can be analyzed using the concept of boundary-layer separation (blowoff) from a permeable flat plate with gas injection (without condensation), as shown in Figure 5.14. Kutateladze and Leont ev (1966) also give the critical condition of boundary layer separation from a flat plate with isothermal injection of the same fluid as... 

Experiment C is designed to yield information on the amount of the surfactant that is actually adsorbed on the rock. This experiment measures the variation of surfactant concentration at the outlet of the core, after injection of a "slug of surfactant. The surfactant concentration in the brine depends on the position along the core and on time. The experiment is dynamic because the changing, but near equilibrium level of the adsorbed surfactant at any point along the rock sample is a function of the concentration in the solution at that point. This is described by the adsorption isotherm from a plot of M, the mass of surfactant adsorbed per gram of rock vs. Concentration. 

A PFR has been designed in which steam is injected into the whey as it enters the reactor. After it passes through the PFR, the temperature is dropped rapidly to 10 °C, where the rate of degradation is negligible. A holding time of 7 sec is needed to obtain 99.99% spore kill at a temperature of 127 CC. For the whey to meet health and flavor tests, a maximum of 10% degradation of protein is to be allowed. As a first approximation in your analysis, the reaction is to be treated as isothermal at 127 °C. 

The spray paint can was inverted and a small amount of product was dispensed into a 20 mL glass headspace vial. The vial was immediately sealed and was incubated at 80°C for approximately 30 min. After this isothermal hold, a 0.5-mL portion of the headspace was injected into the GC/MS system. The GC-MS total ion chromatogram of the paint solvent mixture headspace is shown in Figure 15. Numerous solvent peaks were detected and identified via mass spectral library searching. The retention times, approximate percentages, and tentative identifications are shown in Table 8 for the solvent peaks. These peak identifications are considered tentative, as they are based solely on the library search. The mass spectral library search is often unable to differentiate with a high degree of confidence between positional isomers of branched aliphatic hydrocarbons or cycloaliphatic hydrocarbons. Therefore, the peak identifications in Table 8 may not be correct in all cases as to the exact isomer present (e.g., 1,2,3-cyclohexane versus 1,2,4-cyclohexane). However, the class of compound (cyclic versus branched versus linear aliphatic) and the total number of carbon atoms in the molecule should be correct for the majority of peaks. 

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