Solidification characteristics in a spherical capsule integrated with pin fins and rectangular fins - a comparative study

This study aims at investigating the solidification characteristics in a spherical capsule with pin fins and rectangular fins of same length and volume immersed in a constant temperature bath (-6°C, -9°C, -12°C). The fins are made of copper and are attached to the inner surface of the spherical capsule. The fin lengths correspond to the annulus fill volume margin of 75% taken on the inside wall of the spherical container. The findings showed that the overall solidification period of the capsules with rectangular fins was reduced. Also, the subcooling phenomena is completely eliminated at bath temperature of -6°C. Results also indicated that 50% PCM mass is reduced effectively with the provision of fins. Thus, with the employment of rectangular fins better potential energy savings can be attained when operated at partial charging mode at higher bath temperature.

Effect of Fin Orientation on PCM Melting in a Spherical Enclosure for Latent Heat Storage

The present work is focused on numerical investigation of melting of Phase change material (PCM) filled in a spherical capsule integrated with a metallic fin. n-octadecane having melting temperature of 28° C is selected as PCM and aluminum is considered as fin material. The effect of fin orientation on PCM melting in a spherical enclosure is analyzed considering constrained melting conditions. The orientation angle of the fin is varied from 0–30° in both clockwise and anticlockwise directions. The computational model is considered as two dimensional axisymmetric with laminar flow condition. To ascertain the validity of our numerical methodology present computational model is validated with the test results available in the literature and are found to be in good agreement. The numerical result reveals that employing fin at the center of the capsule (θ = 0°) decreases the melting time and increases the heat transfer performance of the system.

Research of Spherical Capsule Feeding System in Hydraulic Pipelines

Feeding the material to be transported in the hydraulic pipelines to the system is a subject open to research. The shape, size and density of the material gain importance in the selection of feeding systems. Finding the pressure drops that occur in the flow of spherical ice capsules with water is the basis of the research. However, before the measurements were made, preliminary research was carried out on feeding the capsules to the system during the installation of the experimental set-up. In the experimental study with solid particles with the diameter ratios (0.8) and densities (960 kg/m3) with smaller dimensions (d=0.014m), a pipe construction was obtained in which the solid particles are easily fed into the hydraulic pipeline. Experimental study revealed that lower than predicted pressures occur at the point where solid particles are fed into the pipe. This result means a greater pressure drop than the pressure drops obtained in the venturimeter zone with the same diameter ratio. In this article includes a step-by-step method and a sample pipe geometry for studies that require a low pressure zone in hydraulic pipelines. The pipe geometry designed in this study will form a model for the supply systems in the pipelines. The low pressure region is provided with a pipe and flow arrangement without consuming energy.

Posture Dynamic Modeling and Stability Analysis of a Magnetic Driven Dual-Spin Spherical Capsule Robot

In order to realize the intervention operation in the unstructured and ample environments such as stomach and colon, a dual-spin spherical capsule robot (DSCR) driven by pure magnetic torque generated by the universal rotating magnetic field (URMF) is proposed. The coupled magnetic torque, the viscoelastic friction torque, and the gravity torque were analyzed. Furthermore, the posture dynamic model describing the electric-magnetic-mechanical-liquid coupling dynamic behavior of the DSCR in the gastrointestinal (GI) tract was established. This model is a second-order periodic variable coefficient dynamics equation, which should be regarded as an extension of the Lagrange case for the dual-spin body system under the fixed-point motion, since the external torques were applied. Based on the Floquet–Lyapunov theory, the stability domain of the DSCR for the asymptotically stable motion and periodic motion were obtained by investigating the influence of the angular velocity of the URMF, the magnetic induction intensity, and the centroid deviation. Research results show that the DSCR can realize three kinds of motion, which are asymptotically stable motion, periodic motion, and chaotic motion, according to the distribution of the system characteristic multipliers. Moreover, the posture stability of the DSCR can be improved by increasing the angular velocity of the URMF and reducing the magnetic induction intensity.

A microfluidic methodology to identify the mechanical properties of capsules: comparison with a microrheometric approach

We present a microfluidic method to measure the elastic properties of a population of microcapsules (liquid drops enclosed by a thin hyperelastic membrane). The method is based on the observation of flowing capsules in a cylindrical capillary tube and an automatic inverse analysis of the deformed profiles. The latter requires results from a full numerical model of the fluid–structure interaction accounting for nonlinear membrane elastic properties. For ease of use, we provide them under the form of databases, when the initially spherical capsule has a membrane governed by a neo-Hookean or a general Hooke's law with different surface Poisson ratios. Ultimately, the microfluidic method yields information on the type of elastic constitutive law that governs the capsule wall material together with the value of the elastic parameters. The method is applied to a population of ovalbumin microcapsules and is validated by means of independent experiments of the same capsules subjected to a different flow in a microrheological device. This is of great interest for quality control purposes, as small samples of capsule suspensions can be diverted to a measuring test section and mechanically tested with a 10 % precision using an automated process.