Research Projects

Rationale The growing environmental concern has hydrogen Fuel Cell Vehicles (FCVs) seem to be promising considering their zero carbon emissions at the point of use, longest driving range, and shortest filling time. Being the lightest element known, storage of hydrogen is a challenge and has been studied extensively to evolve different storage methods. For hydrogen storage to be economically viable the density (and hence the operating pressure) of the stored hydrogen should be sufficiently high. At 800 bar pressure, hydrogen can attain density of 36 kg/m3 that can be further increased up to 70 kg/m3 at 2000 bar operating pressure. Thus, economic and safe storage and quick refueling are key bottlenecks of the hydrogen value chain, specifically for automotive applications. However, there is serious concern with rise in temperature during rapid filling due to steep gradients in pressure and velocity inside the cylinder leading to failure of the tank liner as well as the winding filament. Some standards such as ISO TS 15869, and the American Society of Automotive Engineering Standard SAE J2601 have specified maximum allowable temperature of 85C inside a cylinder. These standards specify the allowable temperature, however, do not throw any light on mass flow rate or filling protocol. The standards suggest installing controls to ensure maximum temperature in the cylinder within the safety limits and to stop filling as soon as temperature reaches 85C. However, the temperature inside the cylinder is not uniform due to turbulent nature of filling as well as uneven heat flux at different surfaces. The situation is even tough for the tropical climate of India with drastic variation in temperature across geographical locations. Thus, there is a strong need to understand the underlying physics and the behavior of temperature rise in response to different filling protocols to establish safe and efficient filling strategy. Model: Proposed work aims to simulate hydrogen refuelling process at hydrogen dispensing station as per actual field conditions. The output of the work includes transport based model that can be operated for different geometries to estimate velocity, temperature, and pressure distribution inside the cylinder. The momentum and energy transport phenomena along with the real gas behaviour accompanied by the thermodynamic process of throttling at the nozzle end will be modelled using COMSOL multi-physics. Turbulent fluid flow behaviour will be modelled using , turbulence k- model. This will be solved simultaneously along with the energy transport equations including the Joule Thomson heating, conducting heat transfer through the cylinder wall, and convective heat transfer from the cylinder surface wall. Standard type IV cylinder with polymer liner and surrounding composite winding will be considered of varying capacities. The model-based predictions will be validated using experimental data from real life filling of Hydrogen dispensing station proposed at Visakhapatnam. Significance: Proposed work is crucial for optimizing safety, efficiency, and performance of hydrogen refuelling process at dispensing stations. The expertise in this field is still in proliferation stage and requires thorough understanding. This will be the first of its kind in India where hydrogen filling process will be simulated based on actual field conditions and validated using real-life vehicular applications.