NPD-010 – Nano-Particle Diluter™

The first diluter designed specifically for use with ultrafine aerosols (dp<300nm) to limit particle loss within the diluter and provide accurate measurements of high concentration aerosols. With minimal particle loss for diameters less than 100nm, this system is able to provide these measurements without modification to the size distribution; providing true peak diameter and total number count for downstream electrical mobility sizers or tradtional counters. Pairing the diluter with industry standard fast mobility analyzers allows for per channel concentrations to exceed 1×10⁸ #/cm³ and reduces the need for complex secondary or tertiary dilution systems.
With simple use in a laboratory setting as a key design principle, Nebulae Scientific LLC engineers set out to provide a fast and efficient method to change the dilution ratio. Changing the dilution ratio is as simple as removing the diluter body using the quick change fittings, opening the latch to remove the orifice plate and replacing it with a new one featuring a larger or smaller orifice to increase or decrease the dilution ratio. All orifices are also laser marked to enable quick identification of size and robust enough to stand up to tough solvent based cleaners or ultrasonic baths.
Additionally, the integrated high resolution flow meter provides 0.0001 LPM resolution and enables the Nano-Particle Diluter™ to provide real-time dilution ratio monitoring up to 100:1 dilution. This coupled with the quick change orifice design also enables users to fine tune the desired dilution ratio using the flow meter provided dilution ratio as a feedback control.

The Nano-Particle Diluter™ uses a simple bifurcated diluter design in which a majority of the flow passes through a ULPA capsule filter, removing greater than 99.999% of the particles present, provides the bulk flow for dilution. A small portion of incoming aerosol flow bypasses this filter, typically referred to as the bypass flow, which re-combines with the particle-free dilution flow to reduce the total aerosol concentration. This ratio of bypass flow to dilution flow dictates the dilution ratio, which is controlled by using an orifice in the bypass branch to restrict flow and drive a majority of the flow through the filter.

In a laminar flow system, such as in the bypass flow, particle loss is simply proportional to flow channel length and flow rate. The shortest possible flow channel, while still providing the necessary flow restriction, is that of an orifice with its near zero length. This design solution minimizes particle loss in the bypass flow and enables the ultra-low particle loss feature of this diluter when used with ultrafine aerosols. Typical loss is less than 10% for particle sizes greater than 10nm.

Figure 1-2
Typical Particle Loss in the Nano-Particle Diluter™