Hole nozzle arrays

By feed of a fluid through a nozzle array, which is a plate with many tiny holes, so-called micro-plume injection into a micro channel can be achieved [51, 147]. Typically, the micro channel s floor is perforated in a section in this way and a closed-channel fraction follows for completion of mixing. Large specific interfaces can in principle be achieved depending on the nozzle diameter. This mixing concept benefits from conceptual simplicity and fits well to existing MEMS techniques. Furthermore, it consumes less footprint area and therefore does not create much dead space, which is one of the prime requirements during pTAS developments. 

Currently the AERx system yields an emitted dose in a range of 60-75% of the dose inserted. A schematic diagram depicting the operation of AERx is shown in Fig. 10. The formulation is contained in a predosed blister with a volume of 50 pL and beside it a multilayer lid. The lid has a micromachined array of holes that are sealed from the blister. On pressurization of the blister, the seal breaks, which forces the liquid formulation through the nozzle array into the inhalation path. In order to reduce variability due to changes in ambient conditions, a temperature-controlling module is used to warm inspired air before the generation of aerosol. The authors believe that this last innovation is an impor-... 

There are basically three possible designs of nozzle arrays which differ with regard to the spent flow of the air (Fig. 1.2). In a field of individual nozzles the aft-can flow unimpeded between almost all nozzles however, in a hole channel the air can flow only between those above. In a perforated plate the air can only continue to flow laterally and then escape. Hole channels and perforated plates are easier to produce than single nozzles, as they only require holes to be perforated. However, the heat transfer is the highest for nozzle fields and the lowest for perforated plates, as will be subsequently shown. 

Fig. 1.2 Types of nozzle arrays, (a) Single-nozzle array (b) Hole channel (c) Perforated plate.

The fields of nozzles can be made from single nozzles, or hole channels, or from perforated plates with aligned or staggered arrangements, permitting a variety of geometric parameters. The heat transfer coefficient of nozzle arrays is therefore considered in more detail in the following. 

Nozzle arrays are technically easier to manufacture in the form of hole channels than in the form of individual nozzles such a hole channel is shown, in principle, in Fig. 1.2b. 

Based on comparisons with the corresponding functions for the single-nozzle array, it is evident that the heat transfer in hole channels is less, by about 35%. 

For hole channels, analogous results are valid, and a pitch of t = 6d is again recommended. A larger pitch will result in a decrease in the heat transfer, which will remain constant with lower pitches however, the number of nozzles and thus the flow rate, will be increased. The specific energy consumption and the required gas temperatures are slightly higher for hole channels than for single-nozzle arrays, because the heat transfer is somewhat lower. 

Micro-jet arrays are usually associated with lower energy consumption rates than sprays generated by the special (HAGO) nozzle for the same flow rate. The liquid was pushed through a 0.5 mm stainless steel orifice plate to form the jets. The holes in the plate were laser drilled and were arranged in a circular pattern giving a radial... 

The AERx pulmonary delivery system [40,41] can be regarded as a combination of a MDI and a nebulizer. This system forms an aerosol by extrusion of an aqueous drug-containing solution through a disposable nozzle containing an array of precisely micromachined holes. The droplets are entrained by the airflow passing over the blister. Control over the size distribution of the holes enables the formation of droplets having a narrow size distribution. 

It stands to reason that plumes are only formed under certain hydrodynamic conditions, e.g. ratios of flow rates of the liquids. Otherwise, simple bi-lamination with comparatively low specific interface may occur. In addition, a flow maldistribution within the array may occur for certain conditions, i.e. most flow passes the first row of nozzles at the expense of the residual holes. So far, there is, to the best of our knowledge, no detailed report on modeling these aspects or an experimental proof where indeed plume fluid structures are visualized only gross characterization of the mixing was given (see below). 

Pyronol is typically pressed to annular tablets of densities of 3.45 gcm These tablets are assembled in a steel tube dosed at one end by a multi-hole graphite nozzle to allow for an either linear or centrosymmetric array of liquid metal jets... 

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