Design of heat exchanger for the production of synthesis silica

This study aims to analyze and develop a heat exchanger (HE) application for the manufacture of silica nanoparticles synthesis from agricultural waste. This shell and tube-type HE is designed simply, but it still refers to the existing design rules. The design of a shell and tube type HE with one pass shell and tube with turbulence flow. The specifications of the HE apparatus are 1.93 m in shell length, 0.203 m in shell diameter, 0.020 m in inner tube diameter, 0.022 m in outer tube diameter, and 0.016 m in thickness. The results showed an effectiveness value of 66.38% with an impurity factor of 0.01314. This informed that although the shell and tube-typed HE does not meet the requirements and standards for being set in industrial applications, it can be useful as a learning method regarding the design process, working mechanism, and analyzing the performance of the HE.

A hybrid computational framework for the simulation of atmospheric pressure plasma jets: The importance of the gas flow model

A hybrid computational framework, consisting of a detailed turbulence flow model, a global model, and a model for the calculation of the electron energy probability function, is developed to predict the density of plasma generated species along the axial distance of plasma jets. The framework is applied to an Ar/O2 plasma in a kINPen 09 device without a shielding gas. A reaction set of 764 reactions and 84 species is considered. The effect of different turbulence flow models, namely the detailed and high cost large eddy simulation (LES) model and the simple and low cost realizable k-ε model, on the densities of plasma generated species is investigated at different values of absorbed power. The effect is not severe on the density of the majority of the species, justified by the small differences in the inputs of the global model, i.e. the volume averaged axial velocity and density of air species (coming from the turbulence flow model). Nevertheless, the differences in the densities of O2(1Σg), O-, O2-, O(1D), O, H, H2(r), H-, N2O(v), H7O3+, H9O4+, H15O7+ and OH- are remarkably affected by the choice of the turbulence flow model and may reach an order of magnitude. The detailed LES model is a proper choice for Ar jets and this is reinforced by the comparison of the results of the framework with atomic oxygen experimental measurements along the axial distance of the jet: the use of the LES model leads to atomic oxygen density closer to the measured one compared to (the use of) the realizable k-ε model. Finally, an evaluation of the assumptions required for the use of global models in plasma jets is performed, demonstrating their validity for the case studied.

Effect of sand mining on the flow hydrodynamics around an oblong bridge pier

Extraction of sand from riverbed has catastrophic repercussions on aquatic animalia habitat, water quality, and the environment. Alongside, physical alterations in the fluvial hydraulics arising on account of sand mining are also worthy of attention. Flows passing over the pits excavated in a channel have enhanced erosive propensity, which can be a cause of concern for the downstream hydraulic structures. The complex nature of flow interacting with the bridge piers after passing over a mining pit is not fully understood. Experiments were conducted to apprehend the effects of a dredged pit on the turbulence flow-field around an oblong pier. Flow was passed in an erodible sand bed rectangular channel having an oblong pier for the first case. In the second case, a pit was dredged in the mobile bed to replicate a mined channel, and the pier was subjected to the same discharge. The streambed at the approach of the pier experiences greater mean bed shear because of dredging. The amplification of the instantaneous bed shear beneath the turbulent horseshoe vortex (THSV) zone at the pier front is almost twice due to channel dredging. The findings can be useful in understanding the streambed instabilities around bridge piers in mining-infested channels.

Numerical Investigation of Scour Beneath Pipelines Subjected to an Oscillatory Flow Condition

The present study carries out two-dimensional numerical simulations to investigate scour beneath a single pipeline and piggyback pipelines subjected to an oscillatory flow condition at a Keulegan–Carpenter (KC) number of 11 using SedFoam (an open-source, multi-dimensional Eulerian two-phase solver for sediment transport based on OpenFOAM). The turbulence flow is resolved using the two-phase modified k−ω 2006 model. The particle stresses due to the binary collisions and enduring contacts among the sediments are modeled using the rheology model of granular flow. The present numerical model is validated for the scour beneath a single pipeline, and the simulated sediment profiles are compared with published experimental data and numerical simulation results. The scour process beneath three different piggyback pipelines under the same flow condition are also considered, and the scour development and surrounding flow patterns are discussed in detail. Typical steady-streaming structures around the pipeline due to the oscillatory flow condition are captured. The scour depth during the initial development of the scour process for the piggyback pipeline with the small pipeline placed above the large one is the largest among all the investigated configurations. The phase-averaged flow fields show that the flow patterns are influenced by the additional small pipeline.

Lubrication and stability enhancement by attaching superconducting magnetic force on non-contacting mechanical seals for reusable rocket turbopump

The purpose of this paper is to investigate the lubrication performance and stability improvement of rocket turbopump mechanical seals by attaching superconducting magnetic force. A comprehensive multiphysics numerical model is presented including microscale clearance flow, magnetic field, as well as three degrees of freedom dynamic motion. The Maxwell equation and modified Reynolds equation considering mass-conserving boundary conditions and turbulence flow were solved simultaneously at each time step to obtain the transient response of sealing parameters. Results indicate that the mechanical seal attaching superconducting magnetic force could dramatically improve carrying capacity and lubrication characteristics under heavy loading conditions, and it also has an appreciable effect on dynamic stability. It is worth exploring the application of superconducting magnetic force in reusable rockets and cryogenic equipment combined with its unique advantages.

Combustion Turbulence Flow in the Advanced Vortex Combustor with Built-In Obstacles

To obtain the advanced vortex combustor (AVC) and its optimal structure parameters in light of built-in obstacles, numerical simulation was performed. This research shows that inclined struts have optimal structural parameters with inclination angle α = 30 ° and blocking ratio BR = 12 %, while guide vane and its optimal structural parameter have three layers, which are a / B = 0.1 , b / h = 0.4 , and c / L = 0.2 , respectively; blunt body has the biggest height of H 1 / B 1 = 2 / 3 . According to these statistics, the research studies how inlet factors affect turbulence flow in combustion. The research finds increases in inlet velocity and flow resistance are in positive correlation. As inlet temperature increases, the flow resistance decreases. From field synergy theory, inlet factor has different effect on the heat transfer performance.

Analysis of the Underwater Wireless Optical Communication Channel Based on a Comprehensive Multiparameter Model

A comprehensive multiparameter model is proposed for underwater wireless optical communication (UWOC) channels to integrate the effects of absorption, scattering, and dynamic turbulence. The simulation accuracy is further improved by the combined use of the subharmonic method and the strict sampling constraint method by comparing the phase structure function with the theoretical value. The average light intensity and scintillation index are analyzed using the channel parameters of absorption, scattering, turbulence, flow velocity, and transmission distance. Under weak or medium turbulence, the bit error rate (BER) performance can be effectively improved by increasing the transmitting light power. The power penalty of a 50 m UWOC channel is 5.8 dBm from pure seawater to ocean water and 1.0 dBm from weak turbulence to medium turbulence, with the BER threshold of 10−6.