Accelerated-flow apparatus

Further uncertainty arises from the environmental exposure. For accelerated tests, repeatability can be estimated from exposure of replicate test pieces and minimised by control of the exposure conditions. Particular points to consider are spatial variation in temperature as well as mean temperature and air flow in ovens. In accelerated weathering apparatus, spatial variation and variation with time of light sources can be very significant. 

B. Chance, The accelerated flow method for rapid reactions. Part II. Design, construction, and tests. I. Apparatus construction, J. Franklin Inst. 229 (1940) 737. 

According to Legros (1986), the behavior of cut lamina tobacco in a larger mobilizer is similar to that observed in the smaller one. However, the accelerating flow has a noticeably smaller effect upon the mobilizing flow rate necessary to initiate mobilization. In general, the operation remains stable on the larger-scale apparatus. 

Erosion corrosion occurs in an environment where there is flow of the corrosive medium over the apparatus surface. This type of corrosion is greatly accelerated when the flowing medium contains solid particles. The corrosion rate increases with velocity. Erosion corrosion generally manifests as a localized problem due to maldistributions of flow in the apparatus. Corroded regions are often clean, due to the abrasive action of moving particulates, and occur in patterns or waves in the direction of flow. 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

Accelerated Tests. Weather resistance in an accelerated test is defined as the resistance of plastics towards changes caused by simulated open-air weathering (simulation of global radiation by means of filtered xenon arc radiation and periodic rain). After the weathering (measured by the product of intensity and duration), defined properties of the test sample are compared with those of an identical unweathered sample. Properties should be considered which are of practical importance, such as color or surface properties. For standards, see Table 1 ( Weathering in apparatus ). Apparatus test chamber, rain and air humidification equipment, air flow equipment, radiation measuring equipment. 

A modification of the conventional flowing afterglow apparatus, in which a drift section is incorporated, is shown schematically in Fig. 6.46i-141 In the so-called flow-drift apparatus reactant ions are produced in the upstream section just as in the conventional afterglow system, but the downstream section, where reactions with neutrals occur, is a drift tube, in which a uniform electric drift field is applied. In the latter section ions can be accelerated from thermal kinetic energies to several electron volts. The two sections of the apparatus are separated by an electronic ion shutter, which makes it possible to admit narrow pulses of ions into the drift region at specified times. This permits measurements of ion-drift velocity and, in... 

During evaporation from moist soil, there is no distillation in this sense. Evaporation of both water and pesticide occurs purely by diffusion. The mechanism in a laboratory apparatus by which water accelerates diffusion into a bulk flow distillation is not operative here. 

The desired reaction will often be just maintained without the application of additional heat at the flow rates and for the tube sizes quoted. The side reaction is more exothermic than the one desired, and it may cause an accelerating temperature rise. If this is observed, the supply of reagents should be shut off and nitrogen passed through the apparatus to reduce the temperature. If the temperature should drop, as occurs when the reaction is carried out on a smaller scale, heat must be supplied to make up for the loss. 

Ito, Y. Cross-axis synchronous flow-through coil planet centrifuge free of rotary seals for preparative counter-current chromatography. Part I Apparatus and analysis of acceleration. Sep. Sci. Technol. 1987, 22, 1971. 

Ito, Y. Oka, H. Slemp, J.L. Improved cross-axis synchronous flow-through coil planet centrifuge for performing countercurrent chromatography. I. Design of the apparatus and analysis of acceleration. J. Chromatogr. 1989, 463, 305-316. 

Should this profile be distorted it may indicate that there is a problem with the smooth and rapid flow of the reagents, possibly syringes sticking or the viscosity of the solutions not permitting the solutions to accelerate fully to the desired velocity. Alternatively the pressure is low. Check the pneumatic pressure, clean the system as recommended. Possibly the apparatus needs to be adjusted to deliver more of each solution by moving the. stopping block. 

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