Experimental Investigation Of Energy And Mass Transfer Characterization Of Electrolyser

Hydrogen,the clean energy carrier with the highest specific energy density,is considered as the best alternative to fossil fuel in order to ensure sustainability of energy.Water electrolysis is one of the most promising methods for large-scale hydrogen production and is also the most important step to towards a sustainable ?hydrogen economy ? society.Thus,it is necessary to deeply carry out the research on water electrolysis systems for hydrogen production.This work is the intersection of engineering thermophysics and electrochemistry.It is devoted to the study of hydrodynamics behavior and mass transfer performance in water electrolysis processes,two configurations of containers and electrodes are studied in laboratory experiments under different current densities in an acidic environment(CH3COOH solution).The system is studied using particle image velocimetry(PIV),microscope enhanced visualization.Particle image velocimetry(PIV)is a measurement technique used to obtain the instantaneous velocity filed in a cross section of a flow.In the PIV system the property actually measured is the distance that the particles make in the flow known as ?seeding‘.Fine and non-agglomerated particles are required for PIV measurements under the condition of electrolysis water.Ti O2 particles with nominal diameter of 200 nm are chosen as the tracers in the present flow measurement.After many experiments,a seeding method is developed to disperse the suspension of tracer particles in the electrolyte,Titanium dioxide powder is blended with 36% CH3 COOH aqueous solution in deionized water as a tracer solution,then the tracer solution is sprinkled in the experiment fluid.The electrolytic will attach to the surface of the particles and reduce the surface energy,the agglomeration of tracer particles is mitigated.The experimental results show that the velocity distribution in most regions of electrolyser is dominated by two asymmetry bubble buoyancy induced flow patterns.The bigger clockwise rotate flow is generated by hydrogen bubble(cathode,left)driven flow,the smaller counter clockwise rotate flow is generated by oxygen bubble(anode,right)driven flow.Bubble driven convection has a pronounced impact on the convective transport of electrochemically active species.The greater reaction rates of water electrolysis arises in the smaller space of electrodes,at the same time,it shows the better mass transfer.Joule heat generation in the process of water electrolysis is observed,there is not noticeable natural convection induced by the Joule heat,this can be explained that the bubble-driven convection is more predominated.By comparing hydrodynamic behavior in the two containers with different current densities,the results state that gas evolution increases at higher current densities,?nucleate-boiling-like? phenomenon is observed,at the same time,bubble-driven convection and convective mass transfer increases,however,large number of gas bubbles can adversely hinder the contact between the electrodes and the electrolyte,the inactive fraction of the electrode surface may be affected by adhering bubbles and partial passivation of electrochemical reaction,so this increase is not linear.