Emmanuel C. Nsofor

Measurements of the gas-particle convective heat transfer coefficient in a packed bed for high-temperature energy storage

Experimental measurements of the forced convection gas-particle heat transfer coefficient in a packed bed, high-temperature, thermal energy storage system were performed using a custom-made experimental facility. Special attention was paid to the application of uncertainty analysis (a very important concept in experimentation). General and detailed uncertainty analyses were carried out, which identified the choices that were made in the experimental planning and procedure to ensure reliable final results. The experimental data reduction program used the governing equations and the results of the uncertainty analysis while making allowance for media property variations with temperature. Results were correlated in terms of Nusselt number, Prandtl number and Reynolds number and comparisons were made with existing correlations developed with similar storage media. The maximum temperature for the bed was about 1000°C (1830°F) with flue gas as the operating fluid in the storage mode and atmospheric air in the recovery mode. Because most related previous studies were not necessarily focused on high-temperature applications, the published gas-particle heat transfer correlations were obtained at relatively low temperature ranges, generally at room temperature or at temperatures slightly above room temperature. Moreover, only a few of the previously reported correlations associated the results with the corresponding uncertainty margins. The results from this study give a convective gas-particle heat transfer correlation for high-temperature thermal energy storage applications. Also, due to substantial uncertainties normally associated with the measurements of this heat transfer coefficient, it is significant to note that no firm conclusions can be reached on the validity or non-validity of previously reported related correlations for which the uncertainty margins were not reported.

Computer Simulation of a High-Temperature Thermal Energy Storage System Employing Multiple Families of Phase-Change Storage Materials

Previous work by one of the authors entailed modeling of a packed bed thermal energy storage system utilizing phase-change materials (PCM). A principal conclusion reached is that the use of a single family of phase-change storage material may not in fact produce a thermodynamically superior system relative to one utilizing sensible heat storage material. This paper describes the model constructed for the high-temperature thermal energy storage system utilizing multiple families of phase-change materials and presents results obtained in the exercise of the model. Other factors investigated include the effect on system performance due to the thermal mass of the containment vessel wall and variable temperature of the flue gas entering the packed bed during the storage process. The results obtained indicate efficiencies for the system utilizing the five PCM families exceeding those for the single PCM family by as much as 13 to 26 percent. It was also found that the heat transfer to the containment vessel wall could have a significant detrimental effect on system performance.

Recent Patents on Nanofluids (Nanoparticles in Liquids) Heat Transfer

Advances in high power technology are demanding size reduction of thermal systems resulting in constrained spaces for increased heat transfer. This has led to thermal management problems in emerging systems which have defied solution by conventional cooling methods. Due to recent developments in nanotechnology, a new class of heat transfer fluids called nanofluids was discovered. A nanofluid is a solid-liquid mixture produced by dispersing metallic nanoparticles in a liquid to enhance the heat transfer performance. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. This application of nanometer-sized particles in liquids holds huge prospects for confronting cooling problems in thermal systems. This paper summarizes the explanations that have been presented for the enhanced thermal conductivity of nanofluids, the methods of preparation as well as recent and important patents on nanofluids heat transfer. It also identifies areas for further research. This review indicates that exploitation of nanofluids could lead to development of coolants that can be applied in thermal systems leading to remarkable impact in many sectors especially energy and transportation. Also, the principles of nanoparticles in biofluids can be applied to drug delivery in body tissues thus providing new medical treatment methods.

Investigations on the Packed Bed for High-Temperature Thermal Energy Storage

Modeling and experimental studies were performed on a packed bed for high-temperature energy storage using Zirconium oxide pellets as the storage material. This is an advanced ceramic material that can withstand corrosion and high temperatures. Model predictions compare favorably with experimental results. Zirconium oxide demonstrated great potential as thermal energy storage material. More energy was recovered from the bed in the opposite direction than in the direction used during storage. The gas inlet temperature to the bed showed dominant influence on the uncertainty in the model predictions, implying that special attention should be paid to the measurement of this temperature.

Forced-convection gas-to-wall heat transfer in a packed bed for high-temperature energy storage

Measurements of the gas-to-wall forced-convection heat transfer coefficient in a packed-bed, high-temperature, thermal energy storage system were carried out. The maximum temperature attained was 1,000°C. Effects of media property variations with temperature were incorporated along with detailed uncertainty analysis. Results were correlated in terms of Nusselt number, Prandtl number, and Reynolds number. The operating fluid during energy storage was flue gas and air during recovery, making this more applicable to industrial waste recovery and similar systems. Similar studies used air for both storage and recovery and developed correlations from experiments at either room temperature or slightly above. Few associated results with corresponding uncertainty margins. Due to substantial uncertainties associated with the measurements of this heat transfer coefficient, it is significant to note that no firm conclusions can be reached on the validity or otherwise of existing similar correlations for which the uncertainty margins were not reported.

A symmetric angle-ply composite flywheel study for high-speed energy storage

T conservation of mass of incompressible flows poses a major difficulty in their numerical solutions. That difficulty arises from the lack of pressure term in the conservation of mass equation. Several methods have been developed to introduce the pressure into the continuity equation directly or indirectly such as the Artificial Compressibility method and the Pressure Poisson equation method respectively. Unlike compressible flows, the incompressible flow dependent variables are the velocity and the pressure derivatives. Therefore, deriving a pressure equation, for incompressible flows, imposes additional constrains such as compatibility condition and Neumann boundary conditions for the pressure. In this study, we modified the continuity equation to calculate the pressure derivatives leading to Dirichlet boundary conditions which enhances the convergence of the numerical solution. The pressure is then calculated to within an arbitrary constant from the computed pressure derivatives. The present method is consistent with physics of incompressible flows, accurate, robust and efficient. Numerical solutions are obtained for the driven cavity problem for validation.C manufacturing demands engineering design and production planning to be fully integrated. This study proposes a generic feature association method and a detailed framework for the implementation of an advanced Enterprise Resource Planning (ERP) system that can unify product and process models in order to fulfill customer orders with small batch and high variation production nature. A conceptual solution is introduced for the information integration between design configuration features and manufacturing process features. To achieve this, three feature classes, customer feature, capacity feature and welding feature are suggested. Specific effort has been spent to model welding features which are currently not well studied. With the associative integration between product design and process feature domains, a preliminary order acceptance and scheduling prototype system has been implemented within an ERP order management system and its semantic model is demonstrated within a unified and multi-facet feature framework.T interaction between a solid surface of an air vehicle and surrounding air is knows as the main phenomenon affecting the aerodynamics. The surface roughness has a great effect on the aerodynamic performance by reducing the drag and delaying the separation at high Reynolds numbers which results in increasing the lift coefficient. The effects of different types of paint with different types of finish on the aerodynamics of commercial aircrafts have been investigated in this research. It was shown that reducing the surface roughness leads to drag reduction and lift improvements. However, the surface roughness non-uniformity can result in early separation. The paint quality was found to be very critical in protecting the composite body of the aircraft against excess loads and UV radiation as well as maintaining the integrity of the fuselage and wing.

A Study on Materials for Improved Energy Conservation in Buildings

ABSTRACTResearch on reducing energy demand by buildings frequently focuses on developing new building materials or formulating alternative heating and cooling schemes aimed at reducing the energy demand. This study focuses on using existing materials more efficiently. It involves the simulation of energy requirements of a model family home using a wide range of building construction materials. The EnergyPlus program was used for the study. Materials used for floor covering, floor insulation, door wrap, door core, window gas, external wall siding, external wall insulation, internal wall paneling, ceiling panels, ceiling insulation, roofing, and roofing insulation were investigated. Energy demand by the building for each material studied was measured relative to other materials used for the same purpose—to investigate and identify the one that saved the most energy. The study found that phenolic foam was the best material for insulating roofing, ceiling, and outdoor exposed walls. Fiber cement was found to ...

Flywheel Energy Recovery and Storage System from Aircraft Brakes

This study is on harvesting of energy from aircraft brakes leading to results for the development of advanced flywheel (made of composite materials) for high-speed energy storage. The flywheel is aimed at converting the high landing kinetic energy (KE) of aircrafts to useful electrical energy. Energy recovered from the brakes was established by determining the KE of the landing aircraft after the action of other decelerating mechanisms of the aircraft. This is the energy usually dissipated at the wheel brakes as heat. With the aid of the modified Breguet range equation and other useful parameters, the energy of the flywheel was determined leading to the amount of electrical energy that can be stored in batteries. Results show that more than half of the dissipated energy at the wheel brakes can be harvested and converted to electricity. Consequent additional weight to the aircraft due to this system was found to be much less than 0.01% of the aircraft’s maximum takeoff weight. This can be offset by slightly reducing the design pay load to ensure that structural efficiency of the aircraft is maintained. It was also found that applying this system with a conservative estimate of 5 landings per day to the Boeing 777 aircraft family in active service today, results in total energy savings comparable to electricity generation from a 4.6 MW coal-fired power plant. A sample composite material with mechanical properties suitable for high-speed flywheel energy storage was developed in this study. The material outperformed existing flywheel composite materials such as Boron/Epoxy and Graphite/Epoxy in terms of energy storage density, high rotational speed and maximum stress. Finite element analysis was used to determine the maximum allowable stress to ensure safety operation of the flywheel.

Pipe Insulation Model for Energy Conservation in Buildings

Piping insulation as an energy conservation measure was studied for a commercial facility. A model with a flowchart for steam piping insulation was developed. By applying a simplified method and energy data for the facility, the methodology calculates the current energy consumption and future operating costs, savings, and simple payback for an upgrade of the piping system with recommended fiberglass insulation. It was determined that using the strategy would result in significant energy savings, with an appreciable payback for the investments made. The approach developed here can serve as a relatively less expensive framework for evaluating and improving energy conservation in old and new building systems.

Boiler Energy Conservation Performance Studies in a Commercial Facility: Setting the Stage for Cogeneration and Distributed Generation

ABSTRACT Growing attention is now being paid to energy conservation that was once considered insignificant for energy resource development. An energy efficiency study on the heating system for a commercial facility was performed using the BIN method that can be adopted by energy management practitioners. Such data-based method calculates the load and energy savings for the recommended boiler replacement. Energy consumption data, measurements and flowcharts developed were used to study the operating costs and energy savings for the facility. The study shows that the method can be used to decide if a boiler or heater replacement is worthwhile. Moreover, this study sets the stage for further energy management and reliability investment in the form of cogeneration of heat and power (CHP) or distributed generation (DG). It was determined in this study that using the prescribed strategy will result in significant energy savings for the investments made. Finally, basic data needed for cogeneration analysis resul...