Chamber dynamic flow through

The cone calorimeter,71 which is a dynamic flow-through fire test, can also be used to assess smoke obscuration. The rankings tend to be quite different from those found with the static smoke chamber and are much more realistic. Several empirical parameters have been proposed to make this compensation for incomplete sample consumption, including one called the smoke factor (SmkFct), determined in small-scale RHR calorimeters.188 It combines the two aspects mentioned earlier the light obscuration (as the total smoke released) and the peak RHR. 

Abstract Adsorption and desorption of indoor air pollutants to and from indoor surfaces are important phenomena. Often called sink effects, these processes can have a major impact on the concentration of pollutants in indoor environments and on the exposure of human occupants to indoor air pollutants, Basic theories are used to describe the processes using fundamental equations. These equations lead to models describing sink effects in indoor environments. Experimental studies have been performed to determine the important parameters of the sink models. Studies conducted in dynamic, flow-through environmental test chambers have quantified adsorption and desorption rates for many combinations of indoor air pollutants and interior surfaces. Sink effects have been incorporated into indoor air quality (lAQ) models to predict how adsorption and desorption processes affect... 

A number of test methods have been used to determine sink model parameters. The most common test protocol uses a dynamic, flow-through chamber and involves challenging a test sink material with a test gas [20, 31, 35, 36]. Details on this technique are presented later. Other methods include static tests and microbalance measurements. Borrazzo et al. [37 ] took a fundamental physical chemistry approach and used static equilibrium tests to determine partition coefficients for trichloroethylene and ethanol vapors and several types... 

The use of dynamic, flow-through test chambers is common in the study of emissions from sources of indoor air pollution [39]. They are also widely used in the study of indoor sinks. Some of the earlier work on sinks examined the surfaces of the test chambers themselves and showed that chamber sink effects can be important [21]. Researchers routinely evaluate test chamber systems for sink effects [34,40]. A recent paper on the measurement of SVOC emissions showed how the chamber sink effect can be exploited [41]. In this study, SVOCs adsorbed on chamber walls were removed by heating, flushed out, and quantified to give SVOC emission rates. 

Studies conducted in dynamic, flow-through environmental test chambers have quantified adsorption and desorption rates for only a small number of the available combinations of indoor air pollutants and interior surfaces. 

Dynamic Flow-Through Chamber for Emissions at the Air-Water/Soil Interface... 

Over the years constmction of the dynamic chamber has been modified. For studies conducted recently, the chamber is generally constmcted as follows. The dynamic flow-through chamber system is cylindrical in nature and built from Plexiglas material. Chamber dimensions may vary but are generally about 23 cm inner diameter (i.d.) and 46 cm. in height. The entire closed system is lined on the inside with 2 mil fluorinated ethylene propylene (FEP) Teflon and stainless steel fittings in order to minimize chemical reactions with sample flow. 

Figure 1. Schematic of dynamic flow-through chamber system configured to measure emissions from a swine waste treatment lagoon.

The following mass balance equation may be used for the dynamic flow-through chamber system and applied to any target gaseous substance of known concentration ... 

Dynamic Flow-Through Chamber for Measuring Trace Gas Uptake by Plants... 

As with any type of experimental procedure, it is desirable to compare data acquired in field studies with controlled laboratory studies and/or related models. Various comparisons with models, as well as other measurement techniques, have been made with data collected via the dynamic flow-through chamber system. Some results are presented in the following discussion. 

For model comparisons with the dynamic flow-through chamber system, Aneja et al., (200Id) developed a mass transport model based on the quiescent thin film concept (Danckwerts,... 

The dynamic flow-through chamber system has been successfully developed in response to a need to measure emissions of nitrogen, sulphur, and carbon compounds for a variety of field applications. Moreover, similar chamber systems have also been deployed to measure uptake of nitrogen, sulphur, ozone, and hydrogen peroxide gases by crops and vegetation to examine... 

The flow analyzer involves simple apparatus such as samplers, liquid drivers (peristaltic pumps, piston pumps, solenoid pumps), injection devices (rotary valves, injector-commutators), reactors and flow lines (usually narrow bore tubing), mixing chambers, and flow-through detectors. As a rule, these devices are readily available in most laboratories devoted to chemical analysis. Regarding detection, almost all analytical techniques have been used in flow analysis a small flow cell volume and a short response time that is compatible with system dynamics are important detector parameters. 

In another version of a dynamic experiment proposed first by Gibilaro et al. [21] an impulse of the tracer is introduced into the carrier gas flowing through the first chamber, and the response CA(L,t) in the second chamber is recorded. A suitable analysis is based on the normalized first moment of the response curve, which is defmed as... 

Carrier gas techniques are commonly referred to as dynamic because gas is permitted to flow across each side of the test specimen, at equal pressure. The gas transmission cell is similar to those of the previous methods, in that the test piece forms a barrier between two chambers. In the most basic of carrier gas methods the test gas flows at a constant rate through one chamber and a second gas, the carrier, flows through the other chamber at a constant rate. Test gas permeates through the sample and is swept away to a detector by the carrier gas. The detector may be of the absorptiometric [33] or of the thermal conductivity type [34,35], although other detectors have also been used. 

The oscillatory phenomena can be visualized as follows on the basis of experimental observation under a variety of conditions. When current flows through dilute solution in compartment 11 to compartment I containing concentrated solution, electro-osmotic flow occurs in the same direction. Consequently, dilute solution flows in the same direction so that electro-osmotic pressure increases in chamber I. Both membrane resistance R and potential difference A(J) increase in this process. This flow is resisted by hydro-dynamic flow due to pressure difference AP in the reverse direction. When this happens, concentrated solution enters from compartment n, thereby decreasing the membrane resistance. Normally, when concentration difference is zero, a steady state is attained, but due to finite AC, instability is caused and under appropriate conditions rhythmic changes in AP and A(J) are observed. However, when the concentration difference is of lower magnitude, either damped oscillation or no oscillation is observed. 

The most common method employed for particle electrophoresis is the use of closed, free-fluid electrophoresis chambers (5). In this method, particles suspended in a fluid medium are electrophoresed in an enclosed electrode chamber. Particle mobility is determined optically through the chamber wall. However, if the chamber surface is charged, electroosmosis is induced at the chamber walls due to the applied electric field. A hydrodynamic circulatory flow in the chamber thus results. This hydro-dynamic flow complicates mobility determination since the flow will impose upon the particle s mobility. This hydrodynamic flow must be taken into account. Particle mobility must either be measured in regions of the cell where there is no significant fluid flow, or the fluid velocity must be measured and subtracted from the observed particle velocity. 

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