Conventional airflow

If well designed and properly used, LVHV applications have the primary advantage of effective dust control. LVHV systems also require much less replacement airflow than conventional ventilation systems. This can result in significant savings in operating costs to condition the replacement air. These savings can help to offset the typically high installation costs for LVHV systems,... 

The use of tracers for airflow measurement in ventilation ducts is not very common. There are several reasons for this. Compared to other flow measurement methods, tracers require more complicated equipment, skilled personnel, and are more expensive. There are, however, situations when conventional measurement methods are not applicable. For instance, if the space available is small, and hence the flow meter cannot be installed, or if no space is free to carry out traversing measurements, the use of a tracer might be an alternative. 

Comparing these airflow intervals with those permeable zones induced by conventional hydraulic fracturing indicated that explosive fracturing created additional communication paths to wells 2 and 5 at the 73-ft level. However, the injection capacity of well 3 was reduced 64%. This may have resulted from too wide a dispersion of the liquid explosive, so that the shot was not strong enough to lift and fracture the overburden rock permanently, or the fractures may have been plugged by fine oil-shale particles or mud. 

The temperature in the regenerator is conventionally controlled by the flowrate of air from the blower. However, many catalytic cracking units run at maximum airflow as limited by the air blower. In this situation catalyst cooling rates in the regenerator can be used to hold regenerator temperature. However, if air is at a maximum constraint, the amount of coke that can be burned is limited. Therefore, feed flowrate may have to be reduced or feed composition altered (feed more light gasoil and less heavy material). 

Many operations within the laboratory start with weighing. It is difficult to undertake precise weighing in conventional laboratory fume hoods, as the airflow and vibration inside an operating fume hood often disturb the balance. In order to accommodate the need for an engineered control at this scale of operation, dust control systems have evolved known as ventilated weighing safety enclosures or powder weighing hoods. Key characteristics of a ventilated weighing safety enclosure include ... 

On a broader scale, pharmaceutical manufacturers were beginning to utilize absolute filtration as a primary engineering control in the maintenance of large, carefully controlled clean spaces in the batch production of quality-controlled parenteral products. In this application, LAF was supplied directly to production lines and extended critical worksurfaces within defined, non-turbulent entrance and exit planes as parallel or columnated airflow (misnamed laminar flow ). This highly controlled laminar airstream was supplied to the critical worksurface, in addition to conventionally supplied turbulent airflow to the general space, provided through terminal diffusers for filtration of the balance of room air. In this manner, the stepped control of all critical, as well as support areas was achieved. 

Conventional airflow (also known as turbulent, or non-unidirectional airflow) incorporates HEPA filters, located in-duct, or as room terminal filtration modules (TPMs Fig. 5). Often confused with LAP, conventional airflow does not meet that definition because it allows multiple-pass circulating characteristics or a non-parallel airflow direction, or both. This type of airflow is incapable of producing first air, and is normally used as secondary or buffer filtration in treating a processing or compounding space that contains laminar airflow devices (LAFDs) to maintain primary critical work surface conditions, or in treating other... 

The terminal HEPA filtration module (TFM) is a self-contained HEPA filter and plenum unit (Fig. 11), which may be used to provide laminar or conventional airflow to a clean space, or may be dedicated as a LAF workstation.f The TFM is available with a 10 in. (optional 12 inch) collar for connection by a circular supply duct to a central air handling system (Fig. 5A) or as a free-standing, fully powered unit containing a motor and blower. It is normally installed in a... 

The conventional top spray method shown in Figure 2 has been used for layering and coaling for decades. It evolved from the fluidized bed dryers commercialized more than 40 years ago. The substrate is placed in the product container, which is typically an unbaffled. inverted, truncated cone with a fine retention screen and an air or gas distribution plate at its base. Perforated plates such as a Conidur or Gill plate may also achieve air distribution and product retention. These types of plates may have directed holes for guiding the airflow horizontally in the product container (for side discharge as an example). Process air is drawn through the distribution plate and into the product. 

In the limit V 0 at a single fixed point x, Eqs. (3) and (4) reduce to conventional Eulerian differential conservation equations. Anticipating application in vegetation canopies, we consider that some of the region V contains plant leaves and stems. Provided that the canopy is sufficiently finely textured to be regarded as a porous continuum from the standpoint of the airflow, a scalar source density in Eq. (3) can be defined by... 

Basic Environmental Standards Aseptic Areas For aseptic processing, rooms with conventional filtered airflows and with contained work stations in the form of filtered air hoods or laminar air flow protection at working points are usually more appropriate than laminar air flow rooms. 

Forces on the powder are balanced by the airflow (drag force and buoyancy) and the centrifugal force. It can uniformly fluidize much finer powders than conventional fluidized beds. 

Coke fired cupola gas is composed primarily of N2, CO2, H2O, and CO, with smaller amounts of SO2. On conventional cupolas, where the off-gas is collected above the charging door, a distinction has to be made between the condition of the flue-gases below and above the charging door, since ambient air is entrained through the open charge door. This input significantly changes the total airflow. 

As compared to a normal mixing plant (Figure 2.28), this technique does not require a separate cooler and associated equipment. The vacuiun plant therefore is a more compact size. Since the total airflow is reduced, the vacuum installation has a smaller central dust extraction filter. The size and energy consumption of the filter are 50 % of that of a conventional plant. The reduction of the airflow, results in a reduced removal of active bentonite and thus in an overall reduction of additive consumption. Due to the enclosed operation, the technique is not affected by outside climatic conditions. 

Reduction of the total airflow results in a reduced off-gas volume and amount of dust for disposal, as well as a reduced consumption of binder as compared to conventional cooling and mixing plants (although this also depends on the efficiency of the regeneration plant). Additionally, the system uses less energy. 

In chimney-type solar dryers the driving force of the airflow is the hydrostatic pressure difference caused by the decreasing density of the preheated air (chimney effect). Since no conventional energy sources are needed, chimney-type solar dryers can effectively be used as country dryers. For keeping the airflow on in the night, chimney-type dryers usually have some kind of heat storage. 

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