Mechanical Engineering

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Shiv Nadar University

Solar colletors of Flat Plate type is a thermal transfer device that absorbs solar radiation and converts it into heat, which is mainly used to increase the water temperature, heat and dryness, dryness of crops in the region, space heating and in industries where this hot fluid is required for many chemical reactions, and for applications requiring the temperature of the fluid to be less than 100°C. As non-renewable sources of energy are becoming depleted and will soon have the power crisis. So, referring to fatigue rates, we should use our entire renewable resources so that we can control the rate of decline. The main components of the flat plate air collector are, absorbing plate, top covering plate (glass cover), insulating material and channel pipes covered with insulating material. Absorber plates are covered with a high absorbent coating. The top cover should be made of a maximum transmittance. The effectiveness of the flat plate air collector is highly affected by the losses through the top covering material and also due to the low heat transfer coefficient between the absorber plate and the air flowing through it. Most of the experiments and studies have shown that efficiency can be increased by using different types of solar collector which include double pass, a single pass with fins etc. Based on the literature survey it has been found that most of the studies on the solar collector are done to increase its thermal efficiency by enhancing the rate heat transfer between air and the absorber plate by using rough surface on the absorber plate. © Published under licence by IOP Publishing Ltd.

World University root node

(SoE) School of Engineering

Fulltext

IOP Conference Series: Materials Science and Engineering

Heat Transfer Analysis of Flat Plate Air Collector

A computational study on active and passive evacuated tube solar collector system is examined in this paper. The paper gives us an understanding of the performance of the ETC system under natural flow as well as forced circulation. Major parameters for useful solar thermal energy gain by evacuated tube solar collector are tilt angle, mass flow rate and specific heat capacity of working fluid. To make sure that the system receives maximum useful heat gain, the optimum mass flow rate has been analyzed using ANSYS Fluent CFD. Thermal efficiency of active evacuated tube solar collector at optimum mass flow rate is compared with thermal efficiency of passive evacuated tube solar collector. It is observed from the numerical modeling of the evacuated tube solar collector that passive system is more efficient than active system. © Springer Nature Singapore Pte Ltd. 2019.

Lecture Notes in Mechanical Engineering

Computational analysis of active and passive evacuated tube solar collector

Surface phenomenon such as cavitation erosion-corrosion limits the working life and durability of the fluid machines through significantly altering the efficiency. Surface modification is an apparent and economical route for improving the sustainability of these components. Recently developed complex concentrated alloys (CCAs) or high entropy alloys (HEAs) possess exceptional properties owing to high configurational entropy. We developed CCA coatings on the stainless steel using a facial and effective microwave processing technique. The effect of Al molar fraction in AlxCoCrFeNi (x = 0.1–3) CCAs on ultrasonic cavitation erosion-corrosion was investigated in 3.5\% NaCl solution. For comparison, cavitation erosion and electrochemical corrosion behavior of the pre- and post-tested samples was also performed. Detailed microstructure and mechanical characterization of the developed coatings were also preformed using different analytical techniques. The equimolar CCA coating showed apical degradation resistance under both pure erosion and erosion-corrosion conditions. The observed behavior is attributed to high strain hardening, optimal hardness, fracture toughness, and utmost stability of the passive layer. The phenomenal conjugation of these properties was associated with highest configurational entropy for equimolar composition resulting in sluggish diffusion, and severe lattice straining. Compared to pits, striations and cracks characterizing the morphology of the degraded stainless steel, the equimolar and Al0.1CoCrFeNi CCAs showed TTS (tearing topograph surface) as the dominant failure mode characterized by presence of microplastic deformation. The degradation of the Al3CoCrFeNi CCA occurred mainly through brittle failure mode. The difference in failure mechanism is related to the mechanical properties and underlying microstructure. © 2018 Elsevier B.V.

Ultrasonics Sonochemistry

Microwave synthesized complex concentrated alloy coatings: Plausible solution to cavitation induced erosion-corrosion

Tailored multifunctional capabilities, demanded in domains ranging from aerospace to biomedical fields, are achieved through judicious combinations of structural/nonstructural fibers, matrices, and coatings. Multifunctional composite structures are thus designed to perform a variety of secondary functions (sensing, actuation, energy storage/harvesting, etc.) apart from their primary structural functions (strengthening, stiffening, and stabilizing). In realizing such multifunctional capabilities, complex stress-prone assemblies of low-length-scale components/coatings of materials with distinct properties are essential. Fortunately, additive manufacturing has demonstrated the potential to efficiently and effectively enable such robust assemblages. Apart from such three-dimensional (3D)-printed spatial nonuniformity, four-dimensional (4D) printing renders time-dependent properties to be triggered by various stimuli; 3D/4D printing of multifunctional composites possesses advantages over conventional manufacturing (where even feasible!) in term of time, mass, volume, overall cost, and efficiency. This chapter reviews various printing methods, candidate materials, and characterization of multifunctional printed components. The emphasis is on structural members integrated with electronic components, photovoltaic solar cells, piezoelectric materials, and battery fiber composites. A short review of 4D structures due to various stimuli is also carried out. Such 3D/4D printed flexible/wearable electronics, smart devices, and adaptive structures could find applications all the way from household appliances to satellites. © 2020 Elsevier Inc. All rights reserved.

3D and 4D Printing of Polymer Nanocomposite Materials: Processes, Applications, and Challenges

Multifunctional polymer composites for 3D and 4D printing

In this work, a new methodology is developed for constructing the stiffened panel structure. Here we introduce the constraint method to integrate the stiffener and plate. The geometric nonlinear analysis is performed to analyze the stiffened panel behavior in terms of load-deformation response curve. Variational Asymptotic Method (VAM) is applied to analyze composite flat stiffened panels. The VAM development begins with the 3-D nonlinear strain energy functional which splits into a 1-D through-the-thickness analysis and a 2-D plate analysis. The 2-D constitutive law that is an output of 1-D analysis is used as an input to perform the 2-D nonlinear plate analysis. The integration of skin and the stiffener technique is implemented by introducing a constraint matrix. At the skin and stiffener interface, the developed constraint matrix is used in realization of 3-D displacements of stiffener and skin are same. The proposed approach is simple and reliable to address the complexity in analyzing stiffened structures. This methodology is developed using a computational symbolic tool Mathematica and the implemented computer program named as NASSVAM (Nonlinear Analysis of Stiffened Structures using Variational Asymptotic Method). The obtained results from NASSVAM are compared and showed good agreement with the 3-D FEA results. © 2019

Thin-Walled Structures

Constraint method for laminated composite flat stiffened panel analysis using variational asymptotic method (VAM)

<p>Biofilm related bacterial infection is one of the primary causes of implant failure. Limiting bacterial adhesion and colonization of pathogenic bacteria is a challenging task in health care. Here, a highly simplistic processing technique for imparting antibacterial properties on a biomedical grade stainless steel is demonstrated. Low-temperature high strain-rate deformation achieved using submerged friction stir processing resulted in a nearly single phase ultra-fine grain structure. The processed stainless steel demonstrated improved antibacterial properties for both Gram-positive and Gram-negative bacteria, significantly impeding biofilm formation during the in vitro study. Also, the processed stainless steel showed better compatibility with human fibroblasts manifested through apparent cell spreading and proliferation. The substantial antibacterial properties of the processed steel are explained in terms of the favorable electronic characteristics of the metal-oxide and by using classical Derjaguin–Landau–Verwey–Overbeek (DLVO) and the extended DLVO (XDLVO) approach at the cell–substrate interface. © 2019, © 2019 Informa UK Limited, trading as Taylor &amp; Francis Group.</p>

Life Sciences

(SoNS) School of Natural Sciences

Biofouling

Enhanced antibacterial properties and the cellular response of stainless steel through friction stir processing

The interaction of an elastic structure such as an airfoil and fluid flow can give rise to nonlinear phenomenon such as limit cycle oscillations, period doubling or chaos. These phenomena are indicated by a change in the stability behaviour of the dynamical known as bifurcations. Presence of viscous effects in the fluid flow can give rise to flow separation which causes a stability change in the system that is identified to happen via a Hopf bifurcation. In such cases, the airfoil exhibits limit cycle oscillations which are torsionally dominant, known as stall flutter. Despite identifying the route to stall flutter under uniform flow conditions, investigating a stall problem under stochastic wind has received minimal attention. The ability of fluctuating flows to change the stability boundaries and disrupt the route to flutter, compels the need to carry out a stochastic analysis of stalling airfoils. Study of stall flutter in such systems under the influence of a time varying sinusoidal gust is undertaken and the route to flutter is identified by carrying out a stochastic bifurcation analysis. © The Authors, published by EDP Sciences, 2018.

MATEC Web of Conferences

Identifying route to stall flutter through stochastic bifurcation analysis

Wind tunnel experiments carried out on a pitch-plunge aeroelastic system in the presence of fluctuating flows reveal that flutter instability is presaged by a regime of intermittency. It is observed that as the flow speed gradually increases towards the flutter speed, there appears intermittent bursts of periodic oscillations which become more frequent as the wind speed increases and eventually the dynamics transition into fully developed limit cycle oscillations, marking the onset of flutter. The signature from these intermittent oscillations are exploited to develop measures that forewarn a transition to flutter and can serve as precursors. This study investigates a suite of measures that are obtained directly from the time history of measurements and are hence model independent. The dependence of these precursors on the size of the measured data set and the time required for their computation is investigated. These measures can be useful in structural health monitoring of aeroelastic structures. © 2018 Elsevier Ltd

Journal of Sound and Vibration

Investigations on precursor measures for aeroelastic flutter

Aeroelastic systems with freeplay nonlinearity can exhibit a wide variety of qualitatively different dynamical responses such as limit cycle oscillations and chaos in the pre-flutter regimes. Consequently, the bifurcation scenario in an aeroelastic system with freeplay nonlinearity under uniform flows have received considerable attention in the literature. However, in reality flows are far from deterministic and often possess a small temporal random fluctuations about a mean value. Input flow fluctuations have the potential to alter the stability and give rise to atypical routes to flutter. Indeed, recent studies have shown that under flow fluctuations the aeroelastic systems loses its stability via a regime of oscillations called intermittency. Further, it is observed that the presence of cubic hardening nonlinearity and input flow fluctuations with predominantly long time scales can give rise to "on-off" type intermittency. This dynamical behaviour is attributed to type of nonlinearity and relatively short time scale for the system to stay and exhibit distinct dynamics. Extending the mechanism of intermittency route to flutter in aeroelastic systems with other prominent types of nonlinearities, such as, freeplay have however, received minimal attention in the literature. The present study devotes itself to investigate the response dynamics of an airfoil with freeplay nonlinearity subjected to long time scale input flow fluctuations. © The Authors, published by EDP Sciences, 2018.

Investigating the route to flutter in a pitch-plunge airfoil with freeplay nonlinearity subjected to input flow fluctuations

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al0.1CoCrFeNi HEA in two different media: distilled water with and without 3.5 wt\% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al0.1CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA. © 2017 Elsevier B.V.