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[en] The first part of the present work is an experimental investigation of the influence of an imposed magnetic field on the local flow pattern in (a) a mercury-nitrogen pool experiment and (b) in a vertical mercury-nitrogen pipe flow. The emphasis was put on demonstrating the feasibility of using the hot-film technique for simultaneous measurements, in a liquid metal-gas mixture, of both the liquid phase and gas phase parameters. The two-phase pool facility was used for investigating the effect of the injection of gas bubbles on the turbulent intensity in the pool. Preliminary measurements in water-nitrogen have shown the turbulent intensity to increase as a function of the square-root of the local void fraction. In the measurements with mercury-nitrogen, the turbulent intensity was found to be about twice higher than in water at the same void fraction, and to increase with the void fraction at a lesser rate than the 1/2 power. The spectral distribution of the turbulent fluctuations exhibited, in two-phase flow, a region with a negative slope of about (-2.5) as opposed to the (-5/3) slope known from the single-phase turbulence spectra. The magnetic field was found to be less effective than in single-phase flow in suppression the turbulent fluctuations; this effect is believed to be due to the buoyant energy supplied continuously to the flow by the gas bubbles. In the mercury-nitrogen pipe flow, the magnetic field was found to cause dramatic changes in the void distribution of a bubbly flow in which asymmetric conditions existed at the inlet (mixing) section. This effect was attributed to the suppression of the bubble dispersion across the test section. In the second part of the work, a mathematical model of a MHD generator channel was used to study the reduction of end effects by changing the geometry of the channel, the magnetic field distribution or by inserting electrically insulating vanes in the magnetic end regions. (author)
[en] Highlights: • Flexible thermoelectric generators are screen printed with low cost metallic inks. • Thermoelectric generators are integrated into radial pipe insulation. • 15 cm section of pipe insulation is used to power a wireless sensing circuit. • Electrical configuration of thermoelectric device is optimized for a D.C. to D.C. converter. - Abstract: The Internet of Things (IoT), coupled with advanced analytics, is poised to revolutionize manufacturing maintenance and efficiency. However, a practical route to powering these many IoT devices remains unclear. In this work, flexible thermoelectric generators (TEGs) are fabricated from low cost, screen printed silver and nickel inks before being integrated into a novel form factor device based on commercial steam pipe insulation. Through optimization of internal resistances and total device design, this 420-junction TEG device produces 308 µW of power at a temperature difference of 127 K. This is sufficient to power a temperature sensing circuit with wireless communication capabilities. In this report we demonstrate that, after an initial 4 h of charging, this TEG can power a standard RFduino microcontroller for 10 min while sending temperature readings every 30 s via Bluetooth Low Energy (BLE) to a cell phone. Additional optimization and scaling could further increase system efficiency and provide a viable route to powering an industrial wireless sensing network (WSN).
[en] Highlights: • Construction & operation of bufferless & membraneless MFC under recirculation flow mode. • Novel attempt to insert honey comb flow straightener into MFC flow chamber. • High power density & low charge transfer resistance at 40 ml/min flow rate. • Recirculation flow stabilized the pH under bufferless conditions. • This study proved that bufferless, membraneless MFCs will be a practical possibility. - Abstract: Biocathode microbial fuel cells are cost-effective and environmentally sustainable bio-electrochemical devices. However, the usage of buffer solution will significantly reduce the feasibility of the MFCs (Microbial Fuel Cells) for practical applications in the future. Therefore, in this study the function of PBS (Phosphate Buffer Solution) was substituted by application of recirculation flow mode to enhance the proton transfer. An innovative and novel endeavor of inserting a honey comb structure into an MFC for uniform influent flow was also performed. pH and power performance were investigated in aerobic biocathode MFCs at recirculation flow rates of 0 ml/min, 4 ml/min, 40 ml/min, and 240 ml/min. The results showed that higher recirculation flow rates maintained a steady pH after 1 h of MFC operation and efficiently reduced the time to achieve the favorable pH environment (7.0–7.55) for the growth of electrochemically active bacteria (EAB). Furthermore, the highest power density of 5.71 mW/m2 and lowest charge transfer resistance of 267.7 Ω were obtained at the flow rate of 40 ml/min. But, extremely high flow rate of 240 ml/min was found to be detrimental to the biocathode MFC and reduced the power density and charge transfer resistance. Therefore, these findings would provide useful and progressive insights for pilot and industrial scale studies with bufferless biocathode MFCs in the future.
[en] Highlights: • Microbial anodes formed twice as fast at 40 °C as at 25 °C. • Bioanodes formed at 40 and 25 °C developed different electron transfer systems. • Bioanodes formed at 40 and 25 °C produced similar current densities when used at 25 °C. • Bioanodes formed at 40 and 25 °C showed similar redox systems when used at 25 °C. • Temperature impacted the biofilm structure. - Abstract: Reducing the time required for the formation of microbial anodes from environmental inocula is a great challenge. The possibility of reaching this objective by increasing the temperature during the bioanode preparation was investigated here. Microbial anodes were formed at 25 °C and 40 °C under controlled potential with successive acetate additions. At 25 °C, around 40 days were required to perform three acetate batches, which led to current density of 9.4 ± 2 A.m−2, while at 40 °C, 20 days were sufficient to complete three similar batches, leading to 22.9 ± 4.2 A.m−2. The bioanodes formed at 40 °C revealed three redox systems and those formed at 25 °C only one. The temperature also impacted the biofilm structure, which was less compact at 40 °C. When the bioanodes formed at 40 °C were switched to 25 °C, they produced current densities similar to those of bioanodes formed at 25 °C; they recovered the single redox system that was developed by the bioanodes formed at 25 °C and the difference in biofilm structures was mitigated. It is consequently fully appropriate to accelerate the formation of microbial anodes by increasing the temperatures to 40 °C even if they are finally intended to operate at room temperature.
[en] This report presents the development a TEG-powered WSN prototype that could be used in nuclear applications. Different design considerations that are important in assembling different components of a WSN were carefully taken into consideration. In designed WSN is compatible to operate with low-power generating TEG and high-power generating TEG based on application requirements. Also, to maintain appropriate power level across different sensor node components, direct current-to-direct current converter with maximum peak power tracking algorithm is implemented. Storage device with real-time clock is embedded to enable local data storage and real-time time stamping. The wireless communication module selected and implemented is Zig Bee protocol. To accommodate different operating conditions and any loss of power from TEG due to unforeseen reasons, backup battery system is also implemented. Entire assembly is performed on a 2-layer printed circuit board and tested for operation. The outcome was successful and it also provided data to validate the mathematical model developed to estimate average power consumption of a WSN under different operating conditions.
[en] The discharge of untreated soak liquor from tannery industry causes severe environmental pollution. This study is characterizing the soak liquor as a substrate in the microbial fuel cell (MFC) for remediation along with electricity generation. The dual chamber MFC was constructed and operated. Potassium permanganate was used as cathode solution and carbon felt electrode as anodic and cathodic material, respectively. The soak liquor was characterized by electrochemical studies viz., cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and polarization studies, respectively. The removal percentage of protein, lipid, and chemical oxygen demand (COD) were measured before and after treatment with MFC. The results of MFC showed a highest current density of 300 mA/cm2 and a power density of 92 mW/m2. The removal of COD, protein, and lipid were noted as 96, 81, and 97% respectively during MFC process. This MFC can be used in tannery industries for treating soak liquor and simultaneous electricity generation.
[en] In this paper, we review the fuel cell innovative technologies announced at Fuel Cell Seminar & Energy Exposition 2017, where the whole process of hydrogen energy is discussed. Reviewing area is listed as follows: fuel pre-treatment, material processing, component production/connection, system design, and operation control. The main contents of reviewed innovative technologies are as follows. 1) Passive sorbent systems provide a simple solution for desulfurization. 2) High velocity forming through adiabatic softening cuts manufacturing cost of metal bipolar plates. 3) Coating using functional materials solves the durability issue of metals bipolar plates. 4) Using low sealing stress compression gasket enhances compatibility with high-temperature fuel cells. 5) Regenerative fuel cell system simplifies the configuration of fuel cell and electrolysis systems. 6) Periodic current interruption enables the sustainable operation of direct hydrocarbon-fueled low-temperature fuel cells.
[en] Highlights: • Conventional equivalent circuits have been derived from electrical terminal quantities. • Anodic electron flow and electric charge storage were not well modeled electrically. • Novel equivalent-circuit-based model and straightforward test methods are developed. - Abstract: To describe the anodic electron flow and electric charge storage behavior of an MFC system from an electrical perspective, a dynamic model based on a novel electrical equivalent circuit is developed. Conventional equivalent circuits typically have series impedances to model the system from the standpoint of terminal quantities: output voltage and current. However, the conventional approaches do not properly explain internal anodic electron flow and double-layer charge storage characteristics of MFCs. The proposed model uses an equivalent capacitance in parallel and series resistances to accurately model and characterize the anodic electron flow, electrical charge storage, and the dynamic characteristics of both output voltage and current. Two straightforward test methods are proposed to determine the equivalent circuit parameters. Experimental results showed the validity of proposed MFC model.