This paper presents a superparamagnetic nanofluid (SMP-NF) and three of its applications. The SPM-NF particles were suspended in oleic acid as surfactant, and then dispersed in UTR 40 transformer oil (TO). The average particle size obtained from X-ray diffraction is 14 nm, and from scanning electron microscopy is between 10 and 30 nm. The magnetic measurements for the oleic-oil transformer acid-magnetite nanoparticles of 27 nm diameter in size and 9.78×10²⁵ nanoparticles/m³ particle density system provide for specific saturation magnetization, Ms. The volume fraction is 1.1% and the magnetization is 62 Gs. The SPM-NF may be designed to be used either as coolant or as magnetic medium in three electrotechnic devices: a power electric transformer TMOf 2-36 kV-40 kVA, at 50 Hz, a microactuator that implements the pulse width modulation (PWM) principle, and in miniature planar spiral transformers, for galvanic separation or step-up/step-down conversion. The paper presents experimental and numerical simulation results that confirm that the SPM-NF usage open new venues in optimizing conventional electrotechnic constructions or to design novel devices.

This paper presents the work conducted on prototyping a step-up/step-down, single-phased, low-power, and medium-voltage electrical transformer cooled by a fluid with colloidal magnetic nanoparticles. The magnetic and fluid dynamic properties and the heat capacities of the ferrofluid (magnetic nanofluid) and that of the regular coolant (UTR-40 transformer oil) were experimentally determined and comparatively evaluated. Mathematical models for the electromagnetic field and the heat transfer were defined and numerically solved to assess the capacity of the transformer to sustain the working conditions. The simulation results were utilized to improve the design of a prototype, where the UTR-40 regular coolant is replaced by ferrofluid. The numerical simulation results and the experiments evidence the superior performance of the prototype.

The use of hydrogen as fuel presents many safety challenges due to its flammability and explosive nature, combined with its lack of color, taste, and odor. The purpose of this paper is to present an electrochemical sensor that can achieve rapid and accurate detection of hydrogen leakage. This paper presents both the component elements of the sensor, like sensing material, sensing element, and signal conditioning, as well as the electronic protection and signaling module of the critical concentrations of H₂. The sensing material consists of a catalyst type Vulcan XC72 40% Pt, from FuelCellStore, (Bryan, TX, USA). The sensing element is based on a membrane electrode assembly (MEA) system that includes a cathode electrode, an ion-conducting membrane type Nafion 117, from FuelCellStore, (Bryan, TX, USA). and an anode electrode mounted in a coin cell type CR2016, from Xiamen Tob New Energy Technology Co., Ltd, (Xiamen City, Fujian Province, China). The electronic block for electrical signal conditioning, which is delivered by the sensing element, uses an INA111, from Burr-Brown by Texas Instruments Corporation, (Dallas, TX, USA). instrumentation operational amplifier. The main characteristics of the electrochemical sensor for hydrogen leakage detection are operation at room temperature so it does not require a heater, maximum amperometric response time of 1 s, fast recovery time of maximum 1 s, and extended range of hydrogen concentrations detection in a range of up to 20%.

Nanofluid with Colloidal Magnetic Fe3O4 Nanoparticles and Its Applications in Electrical Engineering | InTechOpen, Published on: 2017-03-15. Authors: Lucian Pîslaru-Dănescu, Gabriela Telipan, Floriana D. Stoian, et

A ferrofluid-cooled low power, single-phased electric transformer was designed and prototyped with the aim of investigating the performance that such an apparatus may exhibit. The nanometric, colloidal, super-paramagnetic fluid used as coolant has specific electric, magnetic, and thermal properties, and presents an overall better stability and capacity to withstanding electromagnetic and thermal stress. This paper addresses also the electromagnetic and heat transfer processes that occur. First, the physical, mathematical, and numerical models are introduced. Numerical simulation results suggest that the magnetization body forces may add to the thermal, buoyancy body forces in providing for better heat transfer. To outline this, several numerical models that may conveniently be treated numerically within the current hardware and software limits, while still providing for satisfactory accuracy were developed. The results may be utilized also in the design phase of the transformer.

Three types of dry polarizable electric bioimpedance sensor for skin bioimpedance monitoring without skin preparation have been developed. The sensitive materials as a component of these sensors are the conductive polypyrrole and hybrid nanocomposite polypyrrole-Ag, with 10% and 20% Ag incorporated in the polypyrrole matrix. The hybrid nanocomposites Ag nanoparticles (NPs)/polypyrrole were obtained by introducing the colloid solution of Ag NPs in pyrrole solution, followed by polymerisation, and calculated for 10% and 20% of monomer’s mass. The structural characterisation and morphological analysis of these sensitive materials were carried-out by Raman spectrometry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. In making the electrodes, the technique of pressing powders of polypyrrole and hybrid composites Ag NPs/polypyrrole in a hydraulic press was used in the form of a disk. The electric bioimpedance performance of sensors was investigated using a two-point method in the frequency range of 1–300 kHz, at a voltage of 2 V_peak-peak, on six human subjects, three men and three women. For these three bioimpedance sensors, it was found that the electric bioimpedance of the skin decreases across the frequency range and shows good linearity of the impedance-frequency curve on the range frequency of interest in bioimpedance measurements.