Modeling the mechanical behavior of sodium borohydride (NaBH 4 ) powder Yakir Nagar a , Alex Schechter b , Boaz Ben-Moshe c , Nir Shvalb d, ⁎ a Department of Electrical Engineering, Ariel University, Israel b Department of Chemical Sciences, Ariel University, Israel c Department of Computer Science, Ariel University, Israel d Department of Industrial Engineering, Ariel University, Israel abstract article info Article history: Received 2 January 2016 Received in revised form 19 June 2016 Accepted 20 June 2016 Available online 27 June 2016 This paper addresses the numeric optimization for NaBH 4 powder flow which is commonly used for hydro- gen gas production. During the motion process of the powder, a high number of collisions occur between particles constituting the powder. This paper focuses on modeling and finding the parameters that govern these collisions. We use a discrete element method to model the powder and assume that the powder is composed of tiny spheres interacting according to a specific spring damping model. In a series of appropri- ate physical wedge penetration experiments, force-displacement graphs were measured. In addition, a set of shear tests were conducted from which normal-shear force graphs were extracted. Analytical estimations were formulated for each of the experiments. These graphs were then compared with graphs generated by corresponding simulation tests. Using Genetic Algorithm optimization we obtained a set of governing pa- rameters that best fits the powder behavior. In order to refine our results we have used our analytical for- mulations to manually search the parameter space for a better fit. Lastly, an angle of repose test validated our model. © 2016 Elsevier Ltd. All rights reserved. Keywords: Powder simulated behavior Discrete element simulation NaBH 4 mechanical parameters Genetic algorithm as a search method 1. Introduction Sodium borohydride, NaBH 4 , is an air stable salt considered as a promising hydrogen storage material for energy conversion in fuel cells. Hydrogen can be generated from NaBH 4 by heating-pressure cy- cles or via hydrolysis reaction with water over a catalytic surface. These methods require the transport of the solid salt into the reaction zone. Yet the flow of the powder is a non-trivial task due to forces and interactions between the particle grains: 1.1. Motivation and related works Fuel cells are electrochemical devices which convert chemical ener- gy directly to usable electrical energy in a most efficient and highly clean manner. When operated with hydrogen fuel and oxygen from air, a fuel cell produces clean water and some heat in addition to electrical power. In recent years the development of polymer electrolyte fuel cells (PEMFC) for low temperature all-electrical vehicles has made impres- sive progress towards commercialization with respect to cost, durability and power density (size). However, hydrogen generation remains a critical barrier for large-scale commercialization of the PEMFC technology, especially for portable applications. The need to store hydrogen safely and ef- ficiently has provided a vast domain for considerable research [1]. In general, hydrogen can be stored using several methods by vary- ing their volumetric and gravimetric hydrogen densities. These methods include high pressure gas cylinders, liquid hydrogen in cryogenic tanks [2], adsorbed hydrogen on materials with a large specific surface area (e.g., intermetallic compounds) [3], metal hy- drides [4,5], carbon nanotubes [6,7], metal-organic framework [8], reforming of hydrocarbons, hydrolysis of reactive metals (e.g., Al , Li , Na) and metal hydrides (e.g., LiH , MgH 2 , LiAlH 4 ) with water [9]. The last method has the potential to provide the highest gravimetric hydrogen storage density. Metal hydride reacting with protons from the water molecules releases highly pure hydrogen gas. For example, MgH 2 , NaAlH 4 , LiBH 4 and NaBH 4 have a hydrogen gravimetric density of 7.6% , 7.4% , 18.4% and 10.8% respectively [10]. Among these materials, sodium borohydride, NaBH 4 , is an air stable, commercially available salt, considered as a promising hydrogen storage material for energy conversion in fuel cells. Review papers have been dedicated to various aspects of hydrogen production from NaBH 4 [11,12,13,14] describing the properties, challenges and current development status of this tech- nology. In general, hydrogen can be generated from NaBH 4 by heating- Materials and Design 108 (2016) 240–249 ⁎ Corresponding author. E-mail address: [email protected] (N. Shvalb). http://dx.doi.org/10.1016/j.matdes.2016.06.077 0264-1275/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes
Modeling the mechanical behavior of sodium borohydride (NaBH4) powder
Jun 15, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
