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Flatter velocity profiles and more uniform thermal environments are extremely desirous factors for improved performance in flow reactors and heat exchangers. One means of achieving this in laminar flow systems is to use mixers and flow inverters. These improve performance but at higher initial and operating costs. This paper introduces a new and more effective device for flow inversion which is achieved by changing the direction of centrifugal force in helically-coiled tubes. Transient response experiments carried out under the conditions of both negligible and significant molecular diffusion reveal drastic narrowing of the residence time distribution (RTD). The effectiveness of the present device can be assessed by the fact that even at a Dean number of 3 the value of dispersion number as low as 0.0013 is obtained under the condition of significant diffusion, and in the case of negligible diffusion the value of dimensionless time at which the first element of tracer appears at the outlet is as high as 0.85.

The potential industrial applications of curved tubes for single- and two-phase flow are reviewed within the context of physics of flow, trends in the development of technology, and its laboratory to industrial-scale commercialization. Comparison of the performance of curved tube configurations demonstrates its edge over the conventional motionless mixers, heat exchangers, and reactors. Alongside, their respective advantages and limitations are also highlighted. Further, a compendium of the available correlations for single- and two-phase friction factor and heat- and mass-transfer coefficient in curved tubes has also been presented. Key issues regarding the design parameters governing the performance of the curved tubes for mixing and heat- and mass-transfer that impact the research, development, and scale-up or scale-down of such devices are also analyzed. Emerging trends for the development of a new class of curved tubes, namely, inverters and serpentine and chaotic devices are also presented.

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Significant efforts have been made to fabricate drug-loaded nanoparticles for drug delivery. Nanoprecipitation is a simple and versatile method for making various types of polymer nanoparticles with well-controlled particle size, size distribution, and surface properties. This review presents a critical overview of three different widely used nanoprecipitation techniques, namely, traditional nanoprecipitation in bulk solutions, flash nanoprecipitation, and microfluidic-based nanoprecipitation. The review starts with the comparison of these three different nanoprecipitation methods summarizing their key characteristics, advantages, and disadvantages. Then, different types of nanoparticles synthesized using nanoprecipitation are presented including di-block copolymer nanoparticles and natural polymer nanoparticles. A special focus is placed on comparing different drug-loaded polymer nanoparticles prepared using different nanoprecipitation approaches including their synthesis methods, drug loading, encapsulation efficiency, nanoparticle properties (e.g., size, PDI, etc.), and stability. Finally, the principle of forming nanoparticles with well-controlled properties is discussed to fundamentally understand the intricate interplay between mixing, supersaturation, nucleation, and particle growth, aiming to provide a general guideline for making drug-loaded nanoparticles based on nanoprecipitation.

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