Analysis of Heat Transfer in Channel Flow Subject to Sine-Bump Heating

AbstractConvection in a channel subject to a distributed sinusoidal bump like heating applied at the lower wall has been studied. It is found that small wave number heating provides large plumes whereas large wave number heating provides a uniform temperature distribution at the upper part of the channel. Heat transfer is more efficient at low Reynolds number with small wave number heating

Desalination Performance of Nano porous Mos2_2 Membrane on Different Salts of Saline Water: A Molecular Dynamics Study

The freshwater crisis is a growing concern and a pressing problem for the world because of the increasing population, civilization, and rapid industrial growth. The water treatment facilities are able to supply less than 1% of the total water demand. Water desalination can be a potential solution to deal with this alarming issue. Researchers have been exploring for quite some time to find novel nano-enhanced membranes and manufacturing techniques to increase the efficiency of the desalination process. Graphene and graphene modified membranes showed huge potential as desalination membranes for comparatively easier synthesis process and higher ion rejection rate than conventional filter materials. Currently, single-layer Mos$_2$ has been discovered to have the same potential of water permeability and ion rejection rate as graphene membrane in a more energy-efficient way. For almost analogous nano porous structure of the graphene membrane, almost 70% of the higher water flux is obtained from the Mos$_2$ membrane. In this work, it has been shown that nano porous Mos$_2$ membranes provide a promising result for desalinating other salts of seawater alongside NaCl. We have also observed the effect of variations in ions, pore size, and pressure on water permeation and ion rejection rates in the water desalination process. In this study, water permeation increased significantly by increasing the pore area from 20{\AA} to 80{\AA}. The rate of water filtration increases in proportion to both applied pressure and pore size, sacrificing the ion rejection rate for the type of ions studied. A combination of salt ions in the saline water for desalination has also been studied, where the rejection rates for the different ions are separately represented for various applied pressures. For seawater, the Mos$_2$ membrane has showed quite promising performance in the study of ion variation

EFFECT OF SCOURING AND BLEACHING TREATMENT ON KNITTED COTTON FABRICS FOR ECONOMIC STUDY

Cotton is the leading fibre in Textile Industry. Cotton is still the "King" of fibers because most of the world's apparel is made of Cotton. Apart from its fairly good strength, it is considered to provide comfort due to good moisture absorption and wicking properties. It is estimated that approx. 20 million tons of Cotton is processed worldwide yearly. Unlike man made cellulosic fibers such as Rayon and Lyocell, Cotton must be properly prepared for Dyeing, printing and finishing. To prepare the cotton fabric ready for Dyeing, printing and finishing scouring & bleaching is the fundamental step. Scouring of cotton textiles is an essential treatment in textile wet processing in order to obtain a sufficiently hydrophilic fabric. During scouring, waxes and other hydrophobic materials are removed from the cotton fibers. cotton fibres are off-white in color due to having colour bodies with it and the process of destruction these colour bodies from fibres is known as bleaching. The problems involved in normal scouring & bleaching using H2O2 is requirement of higher amount of alkali that will result higher cost in Effluent Treatment Plant to remove the alkalinity, use of wetting agent, sequestering agent, detergent & stabilizer and also require acetic acid to neutral the fabric. The aim of our work is to reduce the amount of alkali that is used in scouring , no use of acetic acid after scouring for neutralization and use of single chemical in place of that is cost effective. To fulfill our aim we use Imerol Blue Liquid in place of wetting agent, sequestering agent, detergent & stabilizer that is supplied by Clairiant and compare the Imerol Blue process with classical scouring & bleaching process using stabilizer

EFFECT OF SCOURING AND BLEACHING TREATMENT ON KNITTED COTTON FABRICS FOR ECONOMIC STUDY

Cotton is the leading fibre in Textile Industry. Cotton is still the "King" of fibers because most of the world's apparel is made of Cotton. Apart from its fairly good strength, it is considered to provide comfort due to good moisture absorption and wicking properties. It is estimated that approx. 20 million tons of Cotton is processed worldwide yearly. Unlike man made cellulosic fibers such as Rayon and Lyocell, Cotton must be properly prepared for Dyeing, printing and finishing. To prepare the cotton fabric ready for Dyeing, printing and finishing scouring & bleaching is the fundamental step. Scouring of cotton textiles is an essential treatment in textile wet processing in order to obtain a sufficiently hydrophilic fabric. During scouring, waxes and other hydrophobic materials are removed from the cotton fibers. cotton fibres are off-white in color due to having colour bodies with it and the process of destruction these colour bodies from fibres is known as bleaching. The problems involved in normal scouring & bleaching using H2O2 is requirement of higher amount of alkali that will result higher cost in Effluent Treatment Plant to remove the alkalinity, use of wetting agent, sequestering agent, detergent & stabilizer and also require acetic acid to neutral the fabric. The aim of our work is to reduce the amount of alkali that is used in scouring , no use of acetic acid after scouring for neutralization and use of single chemical in place of that is cost effective. To fulfill our aim we use Imerol Blue Liquid in place of wetting agent, sequestering agent, detergent & stabilizer that is supplied by Clairiant and compare the Imerol Blue process with classical scouring & bleaching process using stabilizer

EFFECT OF FABRIC STRUCTURE ON RIB FABRIC PROPERTIES

In this work,1×1Rib,1×1Skeleton rib, 2×2English rib, 2×2Swiss rib, 6×3Derby rib were produced with 20/2 Ne and 32/2 Ne combed ring yarn and V-bed knitting machine of 14 Gauge. In addition, Wales per 3cm, Course per 3cm, Stitch density, Stitch length, Tightness factor, GSM, Dimensional Stability of fabric were tested. According to test result, Wales per 3cm, Stitch density, Cover factor, GSM of 1×1Rib were higher than the 1×1Skeleton rib;Wales per 3cm, Course per 3cm, Stitch density, Stitch length, Cover factor, Shrinkage%, extension% of 2×2English rib were higher than the 1×1Rib; Wales per 3cm, Stitch density, GSM, Shrinkage%, extension% of 2×2Swiss rib were higher than the 1×1Rib; in 6×3Derby Rib values of the properties were higher than other structure; shrinkage and extension percentage increase with the increase of needle drop in knitting

A study on labour rights implementation in readymade garment (RMG) industry in Bangladesh: Bridging the gap between theory and practice

The Readymade Garment (RMG) industry of Bangladesh has emerged as a competent garment producer in global garment business in recent times. This industry has successfully transformed Bangladesh into an export-oriented economy. The RMG industry also became the major foreign currency-earning sector with highest rates of absorption of industrial employment. Interestingly, women comprise more than 80 percent of the total labour force and most of them could be otherwise destitute or empty handed. In a patriarchal society like Bangladesh, the RMG industry effectively challenged the traditional view of conflating domesticity with femininity by allowing women of low-income backgrounds to move from the household to the labour market. Garment trade is regarded as a leading driver of globalisation. Though garment workers gain much by working in the garment industry the informal nature of job and adverse working conditions often threaten the livelihood possibilities of workers. This study focuses on the labour rights implementation in the RMG industry in Bangladesh. It is assumed that labour rights safeguard workers from negative consequences. It is also evident that labour rights increase labour productivity. Theoretically there are opportunities to establish labour rights in the RMG industry but in practice the picture is simply unsatisfactory. The recent labour unrest in Bangladesh is the outcome of longstanding violation of labour rights in the RMG industry. Labour rights can be ensured if Bangladesh Government can formulate and implement a comprehensive and effective labour law that incorporates labour rights in the RMG industry. The existing business model favoured multinational enterprises headquartered in developed countries and largely overlooks labourers’ interests especially in developing countries. The organizations such as ILO, WTO, which are supposed to protect labourers from insecurity, vulnerability and injustice, are somehow problematic in relation to the implementation of labour rights in Least Developed countries. The RMG industry is the lifeline of Bangladesh economy and it has the potentialities to reduce poverty to a large extent by gaining increasing share in the world apparel market. Implementation of labour rights can ensure sustainable livelihood of the garment workers, which in turn enhances sustainability of the RMG industry

Thermal Transport Across Nano Engineered Solid-Liquid Interfaces

Liquid molecules located at the interfacial region behave differently than they do in the bulk. These interfacial liquid molecules play a very crucial role in heat transfer from solid to liquid, especially when the system dimension shrinks to the nanoscale range. Behavior of these interfacial liquid molecules depends on the characteristics of the interface. All the interfaces have different characteristics that can be tailored precisely with the aid of advanced manufacturing technology. Study of thermal transport across different solid-liquid interfaces is important to understand different natural systems and to manipulate thermal transport in different engineering systems, e.g. thermal management of micro/nano electronics, energy conversion devices, micro/nano fluidics devices, energy storage system, drug delivery, and to understand different biological systems. The present work focuses on the fundamental understanding of thermal transport across solid-liquid interfaces having different characteristics and exploration of techniques to manipulate these interfaces for different thermal devices. The study starts by modeling thermal transport across the nanoscale interfaces. As continuum approximation is not applicable for the nanoscale phenomena, molecular dynamics (MD) simulation is used to explore the mechanism of thermal transport at the nanometer scale interfaces. With the aid of MD simulation, several interfacial geometric parameters are investigated. It was found that solid-liquid interaction strength plays a dominating role in interfacial heat transfer; additionally the role of interfacial nanostructure\u27s length was also found to be significant. Distribution, shape and density of the nanostructures also influence the energy transfer but the effect is of less extent. One useful application of the nanoscale interface engineering is in thermal management of microelectronics. The insight obtained from the MD simulations in this study is extended into experimental diagnostics of convective heat transfer performance of microchannel with integration of nano- engineered interfaces. Interface characteristics of the microchannel are modified with three different types of nanostructures: CuNWs, Cu-Al2O3 nanocomposite and Al2O3 nanoparticles. Experimental results reveal that interfacial nanostructures positively affect Critical Heat Flux (CHF) irrespective of the type of nanostructures. Whereas Heat Transfer Coefficient (HTC) may increase or decrease depending on the type of nanostructures. In the last part of this study, a low cost simulation approach is outlined to evaluate system level application of a conceptual thermal system considering micro/nano engineered interfaces

A Comparative Study of Thermal Aging Effect on the Properties of Silicone-Based and Silicone-Free Thermal Gap Filler Materials

Thermal conductive gap filler materials are used as thermal interface materials (TIMs) in electronic devices due their numerous advantages, such as higher thermal conductivity, ease of use, and conformity. Silicone is a class of synthetic materials based on a polymeric siloxane backbone which is widely used in thermal gap filler materials. In electronic packages, silicone-based thermal gap filler materials are widely used in industries, whereas silicone-free thermal gap filler materials are emerging as new alternatives for numerous electronics applications. Certainly, characterization of these TIMs is of immense importance since it plays a critical role in heat dissipation and long-term reliability of the electronic packages. Insubstantial studies on the effects of various chemical compounds on the properties of silicone-based and silicone-free TIMs has led to this study, which focuses on the effect of thermal aging on the mechanical, thermal, and dielectric properties of silicone-based and silicone-free TIMs and the chemical compounds that cause the changes in properties of these materials. Characterization techniques such as dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and broadband dielectric spectroscopy (BbDS) are used to study the mechanical, thermal, and dielectric characteristics of these TIMs, which will guide towards a better understanding of the applicability and reliability of these TIMs. The experiments demonstrate that upon thermal aging at 125 °C, the silicone-free TIM becomes hard, while silicone-based TIM remains viscoelastic, which indicates its wide applicability to higher temperature applications for a long time. Though silicone-based TIM displays better mechanical and thermal properties at elevated temperatures, dielectric properties indicate low conductivity for silicone-free TIM, which makes it a better candidate for silicone-sensitive applications where higher electric insulation is desired