Phase change materials (PCMs) have been envisioned for thermal energy storage (TES) and thermal management applications (TMAs), such as supplemental cooling for air-cooled condensers in power plants (to obviate water usage), electronics cooling (to reduce the environmental footprint of data centers), and buildings. In recent reports, machine learning (ML) techniques have been deployed to improve the sustainability, performance, resilience, robustness, and reliability of TES platforms that use PCMs by leveraging the Cold Finger Technique (CFT) to avoid supercooling (since supercooling can degrade the effectiveness and reliability of TES). Recent studies have shown that reliability of PCMs can be enhanced using additives, such as nucleators and gelling agents, including for organic (paraffin wax) and inorganic (e.g., salt hydrates and eutectics) PCMs. Additionally, material compatibility studies for PCMs with different metals and alloys have also garnered significant attention. Long-term studies for demonstrating the material stability and reliability of candidate PCMs will be summarized in this review book chapter.

This paper presents an analysis of viscous fluids and a Rivlin–Ericksen (R‐E) viscoelastic fluid interface under the influence of heat and mass transfer, while both fluids are exposed to an axial electric field. The fluids are restricted within an annular region that is enclosed by two rigid cylinders. The outer section of the annular region holds the R‐E viscoelastic fluid, while the inner section is filled with the viscous fluid. To ascertain the correlation between perturbation growth and wavenumber, the theory of potential flow on viscoelastic–viscous fluids is applied, and the result is represented as a second‐order polynomial. This correlation is numerically solved using the Newton–Raphson method. Variables of viscous flow, such as electric field strength, heat transfer coefficient, viscoelasticity, viscosity, and so forth, are numerically studied. With an increase in electric field strength, the perturbation growth decays and expands for the particular combinations of permittivity and conductivity ratio, showing the dual effect of the axial electric field.

Energy demand has grown rapidly with increase of global population. Surge in energy consumption is mainly driven by both economic and technological advancement. The conventional fossil fuels sources (coal, oil, and natural gas) and nuclear energy are depleting in nature known as non-renewables. Burning of fossil fuels contribute significant amount of greenhouse gases emissions, which negatively impact the global ecosystem. Access to energy is essential for modern civilization, yet we must seek alternative energy sources to protect our planet by controlling the emissions. Capturing harmful Green House Gases (GHG) with the help of advanced technologies helps reduce the risk to some extent. However, alternative energy sources must be renewable and sustainable. Renewable energy resources vary by geographical location and include solar, wind, hydro, and bioenergy, among others. The most appealing primary benefits of renewable energy include its low environmental impact, consistent availability even in challenging weather conditions, and its effectiveness in reducing pollution. Additionally, renewable energy contributes to economic growth, fosters job creation, and enhances energy security. However, there are challenges associated with renewable energy storage, which scientists are actively working to address. In addition, public opposition for the installation of renewable energy infrastructure also create difficulties. Increasing public education and awareness regarding the advantages of renewable energy can assist increasing the acceptability, which can further help policymakers in making well-informed decisions. This paper provides a comprehensive overview of diverse renewable energy sources and their current advancements in development. This review further finds that effective government policies aimed at reducing carbon emissions, coupled with improved technology and storage solutions, the adoption of renewable energy will expand significantly in the coming years.

Energy is the core of human civilization's development and progress. Global population increase and fast industrialization have led to the imbalanced exploitation of fossil fuels without taking into account their environmental effects. The continuous combustion of fossil fuels, deforestation, and industrial processes has resulted in deterioration of climate. Harmful Greenhouse Gases (GHG) traps the heat leading to an overall rise of earth’s temperature, change in precipitation, and weather events. Climate change poses risk to economies, human societies, and the natural environment. A well-defined urgent measure including the policy changes are needed to be adopted to mitigate its effects. To address this issue, 196 countries agreed to sign the Paris Agreement in 2015, which aims to limit the global reduction in GHG emissions to limit the warming to 1.5 °C above pre-industrial levels. However unique challenges posed by COVID-19 pandemic and slow action of countries is hindering the goals to allow maximum temperature to rise of 1.5 °C by this century (i.e., year 2100). The threat of climate change is real and there is growing recognition among international communities. However, the level of commitment varies across nations and is influenced by a number of variables, including domestic conditions, economic priorities, and political will. Providing accessible and clean energy is a challenge for governments which can be addressed by prioritizing renewable energy investments. Affordable clean energy is crucial for upholding fundamental human rights such as a healthy environment, suitable housing, and access to information. The paper discusses the challenges posed by climate change, role of renewable energy and technological advancements, and necessary actions that are necessary to accomplish the objectives of NZE for our future generations.

Spreading patterns of the coronavirus disease (COVID-19) showed that infected and asymptotic carriers both played critical role in escalating transmission of virus leading to global pandemic. Indoor environments of restaurants, classrooms, hospitals, offices, large assemblies, and industrial installations are susceptible to virus outbreak. Industrial facilities such as fabrication rooms of meat processing plants, which are laden with moisture and fat in indoor air are the most sensitive spaces. Fabrication room workers standing next to each other are exposed to the risk of long-range viral droplets transmission within the facility. An asymptomatic carrier may transmit the virus unintentionally to fellow workers through sporadic sneezing leading to community spread. A novel Computational Fluid Dynamics (CFD) model of a fabrication room with typical interior (stationary objects) was prepared and investigated. Study was conducted to identify indoor airflow patterns, droplets spreading patterns, leading droplets removal mechanism, locations causing maximum spread of droplets, and infection index for workers along with stationary objects in reference to seven sneeze locations covering the entire room. The role of condensers, exhaust fans and leakage of indoor air through large and small openings to other rooms was investigated. This comprehensive study presents flow scenarios in the facility and helps identify locations that are potentially at lower or higher risk for exposure to COVID-19. The results presented in this study are suitable for future engineering analyses aimed at redesigning public spaces and common areas to minimize the spread of aerosols and droplets that may contain pathogens.

The largest consumer segment of fresh water resources in the US are cooling towers that are deployed typically for cooling steam (from turbine exhaust) in condensers in thermal power plants. With growth in population and human economic activity (e.g., cooling of data centers) the fresh water resources are being stressed to capacity. Alternate technologies need to be developed to reduce consumption of fresh water in the process industries (including power plants). Dry cooling is an attractive option for obviating wet cooling (i.e., for obviating usage of cooling towers). Dry cooling platforms suffer from reduced operational efficiency, higher costs (both for capital costs and operating costs), weak resiliency and compromised reliability. Particularly, in arid climates, air cooled heat exchangers are inoperable during peak summer days when the ambient air temperature exceeds critical limits (e.g., when the ambient air temperature exceeds the temperature of the steam at the turbine exhaust). This may lead to abrupt power plant shutdown, which in-turn, is a recipe for disaster due to instability induced in the electric supply grid infrastructure due to abrupt shutdown of a power plant with significant power generation capacity (thus compromising reliability). Supplemental cooling can be used for improving the resiliency and reliability of these dry cooling platforms. Thermal Energy Storage (TES) platforms are an attractive option for supplemental cooling. Phase Change Materials (PCM) are often used for TES. Latent Heat Thermal Energy Storage Systems (LHTESS) are attractive for their small footprint accruing from the high latent heat values of PCM. The objective of this study is to design, develop and test the performance of a candidates LHTESS platform. The scope of this study was limited to a Chevron Plate Heat Exchanger (CPHX). The thermal performance characteristics (e.g., power rating and heat-exchanger effectiveness) was determined experimentally for ascertaining the efficacy of the LHTESS during both melting and solidification of the PCM for different flow rates and inlet temperature values of the working fluid. In this study, organic PCM (PureTemp29) was incorporated into a Chevron Plate Heat Exchanger (CPHX) to serve as a LHTESS platform. The PCM was commercially procured from Pure Temp Inc., Minneapolis, MN. The thermal-hydraulic performance of this LHTESS platform was explored in this study. The flow of hot Heat Transfer Fluid (HTF) through the CPHX leads to melting while flow of cold HTF leads to solidification of the PCM. Experiments were performed using hot and cold HTF (for operating temperatures ranging from 34°C–24°C) at different flow rates of the HTF (5, 8 and 10 GPH). The array of thermocouples were strategically mounted at different locations within the LHTESS containing the PCM. The transient temperature profiles recorded by the sensor array enabled the estimation of the fluctuations of the power ratings and energy-storage capacity ratings for the LHTESS. The bulk temperature of the HTF flowing between inlet and outlet ports of the LHTESS was correlated with the transient temperature profiles along with the location.

More than 320 million people worldwide were affected by SARS-CoV-2 or COVID-19, which already caused more than 5.5 million deaths. COVID-19 spreads through air when an infected person breathes, coughs, or sneezes out droplets containing virus. Emerging variants like Omicron with positivity rate of 16 (highest among others) present a greater risk of virus spread, so all types of indoor environments become critically important. Strategically adopted Heating Ventilation and Air Conditioning (HVAC) approach can significantly reduce the virus spread by early removal of contaminated aerosolized droplets. We modeled different HVAC configurations to characterize the diffusion of contaminated droplets cloud through Computational Fluid Dynamics (CFD) simulations of sneeze in standard hospital room as indoor scenario. Injection of saliva droplets with characteristics of exhaled air from lungs was applied to mimic real sneeze. CFD simulations have been performed for three HVAC configurations at two Air Change per Hour (ACH) rates; 6 and 15 ACH. For the first time, use of air curtain at low flow rate has been examined. Simulations provide high fidelity spatial and temporal droplets cloud diffusion under different HVAC configurations, showing spread in room indoor environment up to 360 s. Over 92% of ejected sneeze mass is removed from room air within seconds while the remaining 8% or less becomes airborne with droplets (<50 mu m size) and tends to spread uniformly with regular HVAC configuration. Low-speed air curtain accelerates decontamination by efficiently removing aerosolized 1-50 mu m size droplets. Study investigates role of droplets removal mechanisms such as escape, evaporation, and deposition on surfaces. Interestingly, results show presence of contaminated droplets even after 5 min of sneeze, which can be effectively removed using low-speed air curtain. Study finds that high ventilation rate requirements can be optimized to modify earlier and new hospital designs to reduce the spread of airborne disease.

Advanced nuclear reactors use large pool of water inventory with an immersed heat exchanger to remove decay heat especially in the case of Station Black Out (SBO). The isolation condenser (IC) immersed in Gravity Driven Water Pool (GDWP) of Advanced Heavy Water Reactor (AHWR) is an example of such systems. Heat rejected by the IC is absorbed in the pool. As a result, water density decreases and moves towards the free surface of pool causing layers of hot water piling up over colder one giving rise to stratified water inventory. consequently, the pool at the free surface starts boiling before the grace period (7 days). In the present paper, thermal stratification has been modeled in a power to volume scaled experimental setup. The study is focused on investigating the effect of heater orientation on suppression of thermal stratification in the pool for both the cases of with and without shrouds around heat exchanger.

This paper deals with experimental and numerical investigation on thermal stratification phenomenon conducted in a scaled transparent pool using Particle Image Velocimetry (PIV) technique and Computational Fluid Dynamics (CFD) simulations respectively. Experiments were designed to simulate thermal stratification in a pool with an immersed heat exchanger. In general, pools with an immersed heat exchanger tend to get thermally stratified; preventing mixing and participation of the whole pool during the heat removal process. The study presented in the paper, focuses on quantification of thermal stratification in the pool without shrouds and examines the effect of shrouds on suppression of thermal stratification. The installation of three shrouds divides the pool in four compartments and ensures participation of the whole pool inventory in the heat removal process. In all the four compartments, pool water circulation was observed since the beginning of the heat transfer from the heater. In a three-shroud configuration, because of mixing, rate of rise of temperature of water near the top decreases.

This paper deals with experimental and numerical investigations on thermal stratification phenomenon conducted in Integral Test Loop (ITL) scaled test facility for Advanced Heavy Water Reactor (AHWR). Experiments at decay power level were designed to simulate thermal hydraulic performance of Isolation Condenser (IC) system of AHWR at prototypical pressure (70 bar) and temperature (285 degrees C). The experiments were simulated using the Best Estimate (BE) thermal hydraulic system code RELAP5. Two different pool side nodalizations were tried for simulation of IC-pool. Nodalization, where the IC-pool was simulated with one lumped volume did not simulate the observed thermal stratification behavior appropriately. However, it simulated the Main Heat Transport System (MHTS) behavior well. To simulate pool side stratification a three volume pool nodalization was adopted, which simulated the observed thermal stratification behavior in the pool well apart from simulating MHTS system behavior. Study shows a characteristic thermal stratification behavior in pool, which prevails for the initial few hours of IC functioning. The characteristic curve showing various stages of observed pool thermal stratification development and decay during experiment has been presented in the paper. An interrelation between pressure and water level into the pool has been observed in studies. (C) 2016 Elsevier Ltd. All rights reserved.

This paper deals with the numerical investigation on thermal stratification phenomena in the Gravity Driven Water Pool (GDWP) of the Advanced Heavy Water Reactor (AHWR). Study has been performed at decay power level to simulate thermal stratification in GDWP for Station Black-Out (SBO) conditions. Thermal stratification in GDWP has been simulated using a three-volume pool nodalization approach. The study points to characteristic nature of progress of thermal stratification in the GDWP. Full potential of the pool water can be realised only if the entire inventory of water rises to saturation temperature. This can be achieved only by mixing of water. Thermal stratification prevents realisation of the full heat removal potential of the pool water volume particularly below the Isolation Condenser (IC). The single vertical shroud deployed in the pool is the simplest passive internal, which ensures participation of whole pool inventory. A parametric study on single and three-shroud configurations has been performed by varying shroud location or spacing and shroud height. The study indicates limited suppression of thermal stratification by single-shroud configuration compared to three-shroud configuration. The performance of both single and three-shroud configurations was found to be similar for the first three days. However, during a prolonged SBO, the three-shroud configuration was found to be superior due to enhanced mixing. Parametric study was conducted to arrive at an optimum spacing and shroud height for three-shroud configuration. Studies were also conducted to understand the influence of conductivity of shroud material and leakage through shroud on its performance. (C) 2017 Elsevier Ltd. All rights reserved.

This paper deals with a 3‐leg VSC (Voltage Source Converter) with a zigzag transformer as a DSTATCOM (Distribution Static Compensator) for load compensation in 3‐phase 4‐ wire distribution system using ISCT (Instantaneous Symmetrical Component Theory) based control algorithm which is modified for the voltage regulation and used with indirect current control technique. The DSTATCOM is controlled to compensate the reactive power, harmonics currents, the neutral current and balance the unbalanced loads in the distribution system. Simulations are performed for the various load conditions such as a reactive linear load, an unbalanced load and a non‐linear load in PFC (Power Factor Correction) as well as in ZVR (Zero Voltage Regulation) modes in MATLAB environment using SIMULINK and SimPowerSystem toolbox. Extensive tests have been performed on a developed prototype of DSTATCOM to validate the control algorithm.

............................................................................................iii TABLE OF CONTENTS...............................................................................v LIST OF ACRONYMS...............................................................................viii LIST OF FIGURES......................................................................................x LIST OF TABLES......................................................................................xi CHAPTER 1 : INTRODUCTION 1.1 Background.................................................................................................................1 1.2 Problems in wireless communication..........................................................................2 1.3 Motivation...................................................................................................................2 1.4 Technological review...........................................................................3 1.5 Problem formulation...........................................................................5 1.6 Organisation of thesis..........................................................................5 CHAPTER 2 : LITERATURE SURVEY.........................................................7 CHAPTER 3 : INTRODUCTION TO OFDM WIRELESS COMMUNICATION SYSTEMS 3.1 Basics.........................................................................................................................15 3.2 Block diagram............................................................................................................16 3.3 Problems with OFDM system...................................................................................18 3.4 Symbol synchronization.......................................................................19 3.5 Carrier synchronization.........................................................................22 3.6 Sampling-frequency synchronization.......................................................23