Effect Of Supergravity On The Motion State Of Hydrogen Bubbles Generated By Water Electrolysis

Since the beginning of the new century,with the increasingly serious crisis of fossil energy and the aggravation of environmental pollution,it has gradually become a hot topic to search for green,clean and sustainable alternative energy in the energy field.As a pollution-free alternative energy,hydrogen energy has received more and more attention,and how to efficiently produce hydrogen energy has become the key point of research.At present,hydrogen energy is mainly prepared by fossil energy,and a large amount of CO₂ will be produced in the production process.Hydrogen production by electrolysis of water is a new method for hydrogen production,which has been studied extensively by scholars at home and abroad.In the process of producing hydrogen by electrolysis of water,hydrogen and oxygen are generated at the cathode and anode of the electrolytic cell,respectively,and will gather near the electrode plate.When these bubbles adhere to the surface of the electrode plate,the impedance on the electrode plate will increase,leading to a higher overpotential,and at the same time,the effective contact area of the electrode plate will be reduced.When the bubbles are concentrated in the electrolyte,the gas volume fraction in the electrolyte also affects the conductivity of the solution.These problems will cause power consumption increase of electrolytic process.In order to reduce the energy consumption of electrolytic water and improve the energy use efficiency,in this paper,a process intensification technique is introduced to study the movement of hydrogen bubbles in the supergravity field,including the separation from the electrode plate and the movement of hydrogen bubbles in the electrolyte.The research has attained some results,and the content is summarized as follows.First,through the construction of water electrolysis hydrogen production model with centrifugal rotation device,the hydrogen bubble from the electrode plate model,and hydrogen bubble movement model in the electrolyte are respectively established by using COMSOL Multiphysics software,which both are in supergravity field.And reliability of the models is verified by theoretical analysis.Secondly,through the simulation of the process of hydrogen bubbles escaping from the electrode plate,it can be found that in this process,the bubbles escape from the plate in a circular arc trajectory after sliding,and the larger the supergravity coefficient,the shorter the time of escaping,and the faster the movement speed after escaping from the plate.At the same time,the larger bubbles also take less time to escape the electrode plate.When the hydrogen bubbles are under normal gravity,they are affected by the adhesion and buoyancy forces of the electrode plate,and the bubbles can only slide along the electrode plate until they break off at the top of the electrode plate.Compared with the hydrogen bubbles in the supergravity field,the sliding speed on the electrode plate is very slow under the normal gravity.Thirdly,by simulating the movement of hydrogen bubbles in electrolyte,the average velocity of the bubbles increases with the augment of the high gravity coefficient when the hydrogen bubbles of the same size move in different gravitational fields.When the supergravity coefficient is the same,the larger the size of the bubble is,the greater the buoyancy force the bubble receives and the faster the velocity is.As the supergravity coefficient becomes larger and larger and the normal gravity in the vertical direction remains unchanged,then the inclusion Angle between the bubble displacement path and the horizontal direction becomes smaller and smaller.That is,the direction of the resultant force on the bubble is increasingly offset towards the center of rotation.At the same time,it is found that the change of the shape of the hydrogen bubble and the disturbance to the surrounding flow field will also affect the bubble’s motion state.It is noted,the method used for the numerical simulation of the H₂ bubble’s behaviors in electrolyte can be adopted to that of O₂ bubbles,due to the method’s generality.In conclusion,the addition of the supergravity field can not only improve the velocity of hydrogen bubbles escaping from the electrode plate,but also effectively increase the actual contact area between the electrode plate surface and the electrolyte,increase the conductive area and improve the activation level of the electrode.It can also increase the movement rate of bubbles in the electrolyte,so that the bubbles leave the electrolyte more quickly after leaving the electrode plate,so as to reduce the gas volume fraction in the electrolyte,improve the conductivity of the electrolyte,and improve the working efficiency of the electrolytic hydrogen production device.