Search results for "current"
showing 10 items of 2224 documents
Monitoring of Rouging and De-Rouging of Stainless Steel for Chemical Reactors by Photoelectrochemical and Impedance Measurements
2016
The food and fine-chemical industry has for a long time been troubled by red brown to dark violet deposits in distillation columns, storage vessels and distribution systems for purified water and clean steam. Owing to the visual appearance of those deposits, the phenomena was referred as rouge. Although formation of rouge, i.e. rouging, is a commonly known phenomenon in stainless steel systems, the basic mechanism is still not fully understood. The phenomenon causes precipitation of iron as fine red-brown ferric oxide or hydroxide particles. Moreover adherent discoloration of the stainless steel surface is often observed in conjunction with the loosely adhered rouge particles. The affected …
Experiments and modelling for determining the Limiting Current Density in Electrodialysis units
2018
In the present work, in order to explore such issues on the LCD identification, we performed in-situ measurements with ED units, assessing the influence of operating conditions and validating a purposely implemented process simulator, which was then used for further investigation
Effect of membrane profiles on the limiting current density in electrodialysis
2019
In the present work, we experimenrtally investigated the effect of different membrane profiles on the LCD, testing also different operating conditions.
Ionic shortcut currents via manifolds in reverse electrodialysis stacks
2020
Abstract Reverse electrodialysis (RED) is a blue energy technology for clean and sustainable electricity harvesting from the mixing entropy of salinity gradients. Recently, many efforts have been devoted to improving the performance of RED units by developing new ion-exchange membranes and by reducing the detrimental phenomena affecting the process. Among these sources of “irreversibility”, the shortcut currents (or parasitic currents) flowing through alternative pathways may affect the process efficiency. Although such phenomena occur in several electrochemical processes (e.g. fuel cells, bipolar plate cells and vanadium redox flow batteries), they have received a poor attention in RED uni…
Current distribution along electrodialysis stacks and its influence on the current-voltage curve: behaviour from near-zero current to limiting plateau
2023
The current maldistribution along the flow path of electrodialysis (ED) units is a well-known phenomenon. However, it has been poorly quantified via experimental tests so far. This work aimed at measuring the current distribution in an ED stack with 40 cm path length, provided with four-segment electrodes. The current-voltage curve (CVC) of each segment was recorded under several operating conditions of inlet concentrations and feed velocity. In the CVC of the first segment, the current increased approaching a saturation, while in that of the remaining segments it passed through a maximum and then settled at near-zero values when high voltage values were applied. The current fraction on the…
Limiting current phenomena in electro-membrane processes: local occurrence or stack-dependent one?
2021
Background Electro-membrane processes are gaining great interest in the field of desalination and brine valorisation. However, limiting current phenomena can be a bottleneck for their techno-economic performances. In the present work, the in-out distribution of current density is measured to elucidate the achievement of limiting conditions in real stacks. Materials and Methods A 10-cell pairs Electrodialysis stack (10×40 cm2 active area), equipped with four-segmented electrodes, was tested. NaCl solutions at an inlet concentration ranging from 0.5 to 60 g/l were fed at velocities of either 2 or 4 cm/s in parallel flow. Current density-voltage curves were built by applying equal increasing s…
ELECTRICAL ENERGY STORAGE DEVICES BASED ON pH AND SALINITY GRADIENTS: MODELLING, EXPERIMENTS AND PILOTING
2021
Safety Concerns on Ground Fault Application Transfer Phenomenon in HV Installations
2007
When a fault to ground occurs in HV/MV substations supplied by a combined overhead-cable line, most of the fault current can be transferred and injected into the soil several kilometers far away from the fault location. This phenomenon is called "fault application transfer" and mostly concerns transition stations, where cables are connected to the overhead line. If the transition station is a dead-end steel pole structure, usually accessible to the general public, the local ground electrode could be inadequate to maintain ground potential rise within safety limits. Hence, dangerous touch and step voltages may appear at exposed locations. In the paper results of various computer simulations …
Ground Fault Current Distribution in Substations Supplied by Nonuniform Multi-Section Lines
2007
he paper presents a general method for computing the distribution of substation ground fault current. The feeding line can be entirely homogeneous along its whole length or consisting of two or more different sections, i.e. part overhead and part underground cable. Based on the two-port theory, the proposed method allows to take into account all the relevant conductively and inductively coupled parameters which take part to the distribution of the fault current and can be easily implemented in a computer program. Numerical examples demonstrate the high efficiency of the proposed method.
A Model Modulated Predictive Current Control Algorithm for the Synchronous Reluctance Motor
2022
This paper proposes a Model Modulated Predictive Control (M2PC) specifically developed for Synchronous Reluctance Motors (SynRM) drives and based on a purposely developed magnetic model taking into account both self- and cross-saturation. The proposed M2PC exploits the discrete-time version of the dynamic model to compute the current prediction and the resulting predicted current error. The built-in PWM modulator chooses the optimal pair of voltage space-vector to be applied by the inverter to minimize the current error. The magnetic model permits obtaining good dynamic performance in every working condition.