Spinning-Disk Generator

PR Byron, AJ Hickey. Spinning-disk generation and drying of monodisperse solid aerosols with output concentrations sufficient for single-breath inhalation studies. J Pharm Sci 76 60-64, 1987. 

Early in 1970, Few et al. [10] radiolabelled polystyrene particles for a mucociliaiy clearance study. The radiolabelled aerosols were produced by a spinning-disk generator. The technique involves the key steps of extracting sodium pertechnetate (Na " Tc04) into chloroform as tetraphenylarsonium pertechnetate, followed by evaporation of the chloroform. A solution of polystyrene is added to the radioactive residue and dispersed Scheme 1). This technique has subsequently been adopted by... 

Albert, R.E., Petrow, H.G., Salam, A.S. Spiegelman, J.R. (1964) Fabrication of monodisperse lucite and iron oxide particles with a spinning disk generator. Health Physics, 10, 933. 

Mist The particulate form of a liquid (ie, droplets) suspended in air, often as a result of an explosion or mechanical generation of particles (eg, by a spinning disk generator or sprayer). Particle size is a primary factor in determining the airborne persistence of a mist and the level of its deposition in the respiratory tract. 

There are three types of mass transport processes within a microfluidic system convection, diffusion, and immigration. Much more common are mixtures of three types of mass transport. It is essential to design a well-controlled transport scheme for the microsystem. Convection can be generated by different forces, such as capillary effect, thermal difference, gravity, a pressurized air bladder, the centripetal forces in a spinning disk, mechanical and electroosmotic pumps, in the microsystem. The mechanical and electroosmotic pumps are often used for transport in a microfluidic system due to their convenience, and will be further discussed in section 11.5.2. The migration is a direct transport of molecules in response to an electric field. In most cases, the moving... 

In an evaluation of various techniques for droplet generation,1[88] periodic vibration of liquid jet, spinning disk and ultrasonic atomization techniques have been rated as the most appropriate methods for producing monodisperse sprays. These techniques were found to be very effective and appeared promising for refinement,... 

Some design concepts for generating uniform droplets have been proposed by Lee et al.[88] These include (a) centrifugal type chamber, (b) atomization by two opposing air-liquid jets, and (c) spinning disk coupled with an ultrasonic field. Some other conceptions include (d) rocket nozzle chamber, (e) frozen particles, (f) rotating brush, and (g) periodic vibrations using saw-tooth waves, etc. 

There are a number of techniques for generating aerosols, and these are discussed in detail in the LBL report (1979) and in volumes edited by Willeke (1980) and Liu et al. (1984). We briefly review here the major methods currently in use these include atomizers and nebulizers, vibrating orifices, spinning disks, the electrical mobility analyzer discussed earlier, dry powder dispersion, tube furnaces, and condensation of vapors from the gas phase. 

Experimental methods presented in the literature may prove of value in combustion studies of both solid and liquid suspensions. Such suspensions include the common liquid spray. Uniform droplets can be produced by aerosol generators, spinning disks, vibrating capillary tubes, and other techniques. Mechanical, physicochemical, optical, and electrical means are available for determination of droplet size and distribution. The size distribution, aggregation, and electrical properties of suspended particles are discussed as well as their flow and metering characteristics. The study of continuous fuel sprays includes both analytical and experimental procedures. Rayleigh s work on liquid jet breakup is reviewed and its subsequent verification and limitations are shown. 

Generation of radiolabeled Teflon particles by spinning-disk... 

The spinning-disk method of droplet generation is based on the breakup of ligaments of liquid created at the periphery of a rapidly rotating disk when liquid is fed slowly to the center and top of the disk. Under appropriate conditions of stable liquid feed and rotation, the ligament thrown out by the rotating disk breaks up into a primary (large) and a satellite (small) droplet. This is illustrated in Fig. 7. The satellite droplet is deflected away by an airflow and is usually rejected. 

Figure 7 Illustration of a spinning-disk aerosol generator.

Owing to the nature of thin films generated by both spinning disks and spinning cones, transport by diffusion can become a significant method of transport of both heat and mass within the film. In the case of heat transfer this is especially true and will be the dominant mode of transport within the film. The equations for transport by diffusion have been studied and solved for many simple systems. One of the most comprehensive studies of this process was given by Crank in which the equations for diffusion are examined for several generalized systems. In the solution of the diffusion equation one parameter is of paramount importance that is, the Fourier number, Fo. This can be expressed as... 

Figure 11 Magnified diagrams of monodisperse aerosol-generating devices. (A) Spinning-disk aerosol generator. (B) Vibrating orifice aerosol generator.

The droplet size delivered from a spinning-disk monodisperse aerosol generator can be derived from the following expression ... 

Y. Senuma. Generation of monodispersed polymer microspheres by spinning disk atomization. PhD thesis, EPFL, Lausanne, 1999. 

The DFT consists of a horizontal spinning disk fitted with three spring-loaded rubber sliders that contact the surface. A water supply unit delivers water to the surface being tested. The torque generated by the slider forces measured during the spin down is used to calculate... 

When dealing with foam generation techniques, it is important to break the foam efficiently after the separation has been effected. Several foam breaking techniques exist. These are fairly descriptive and include thermal, sonic, chemical, liquid spray, orifice, whirling paddle, and high-speed spinning disks. The last technique is very effective at relatively low energy demands. ... 

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