Application of Flexible Micro Temperature Sensor in Oxidative Steam Reforming by a Methanol Micro Reformer

Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM), with the relevant parameters optimized as well

Fabrication of a Flexible Micro Temperature Sensor for Micro Reformer Applications

Micro reformers still face obstacles in minimizing their size, decreasing the concentration of CO, conversion efficiency and the feasibility of integrated fabrication with fuel cells. By using a micro temperature sensor fabricated on a stainless steel-based micro reformer, this work attempts to measure the inner temperature and increase the conversion efficiency. Micro temperature sensors on a stainless steel substrate are fabricated using micro-electro-mechanical systems (MEMS) and then placed separately inside the micro reformer. Micro temperature sensors are characterized by their higher accuracy and sensitivity than those of a conventional thermocouple. To the best of our knowledge, micro temperature sensors have not been embedded before in micro reformers and commercial products, therefore, this work presents a novel approach to integrating micro temperature sensors in a stainless steel-based micro reformer in order to evaluate inner local temperature distributions and enhance reformer performance

Use of Multi-Functional Flexible Micro-Sensors for in situ Measurement of Temperature, Voltage and Fuel Flow in a Proton Exchange Membrane Fuel Cell

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased

An air-breathing, portable thermoelectric power generator based on a microfabricated silicon combustor

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections."February 2011." Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 224-237).The global consumer demand for portable electronic devices is increasing. The emphasis on reducing size and weight has put increased pressure on the power density of available power storage and generation options, which have been dominated by batteries. The energy densities of many hydrocarbon fuels exceed those of conventional batteries by several orders of magnitude, and this gap motivates research efforts into alternative portable power generation devices based on hydrocarbon fuels. Combustion-based power generation strategies have the potential to achieve significant advances in the energy density of a generator, and thermoelectric power generation is particularly attractive due to the moderate temperatures which are required. In this work, a portable-scale thermoelectric power generator was designed, fabricated, and tested. The basis of the system was a mesoscale silicon reactor for the combustion of butane over an alumina-supported platinum catalyst. The system was integrated with commercial bismuth telluride thermoelectric modules to produce 5.8 W of electrical power with a chemical-to-electrical conversion efficiency of 2.5% (based on lower heating value). The energy and power densities of the demonstrated system were 321 Wh/kg and 17 W/kg, respectively. The pressure drop through the system was 258 Pa for a flow of 15 liters per minute of air, and so the parasitic power requirement for air-pressurization was very low. The demonstration represents an order-of-magnitude improvement in portable-scale electrical power from thermoelectrics and hydrocarbon fuels, and a notable increase in the conversion efficiency compared with other published works. The system was also integrated with thermoelectric-mimicking heat sinks, which imitated the performance of high-heat-flux modules. The combustor provided a heat source of 206 to 362 W to the heat sinks at conditions suitable for a portable, air-breathing TE power generator. The combustor efficiency when integrated with the heat sinks was as high as 76%. Assuming a TE power conversion efficiency of 5%, the design point operation would result in thermoelectric power generation of 14 W, with an overall chemical-to-electrical conversion efficiency of 3.8%.by Christopher Henry Marton.Ph.D

Experimental Investigation on the Characteristics of the Annular Type Composite Wick Heat Pipe

An experimental investigation was conducted on the hydraulic characteristics of annular type wick structures for heat pipes. An experimental facility that can measure porosity, permeability and effective pore radius of the wick structures in a vacuum condition is established. Nine different multi-layered (6 layers in total) composite screen meshes are characterized. Based on the measurement results, a wick structure composed of one layer of 100×100 mesh, three layers of 400×400 mesh, and two layers of 60×60 mesh is determined to have the highest permeability to effective pore radius ratio and was selected as a targeted sample. The wick-to-wall gap effect on the hydraulic characteristics of annular type wick structure is also investigated by measuring the permeability and effective pore radius of the sample wick structure with varying gap widths. The result shows that the permeability increases as the gap increases from 0 mm to 1.2 mm. After a peak at 1.2 mm, the permeability decreases as the gap increases and converges to the value of the case measured without a wall structure. The effective pore radius becomes smaller as the gap increases, making a peak at a gap size of 1.2 mm. This result implies that there is an optimal point in gap size which is determined to be 1.2 mm for the selected composite mesh structure. To describe and model the advantage of this gap, the rising of a wetting liquid in the gap between a vertical solid plate and a mesh (with a small angle between them) was experimentally measured and analyzed. An additional experiment was performed to investigate the effect of curvature on the capillary rise using tubes and meshes of varying radii. Resultantly, we confirmed that the linear combination of the contact angles of the solid plate and mesh could be applied to calculate the rising height from the Laplace–Young equation. Furthermore, the effect of curvature on the rising height of the liquid was negligible. We observed that a gap distance of 1.27 mm provided the largest permeability over the effective pore radius value for a heat pipe with ethanol, which in turn resulted in the highest capillary limitation. Finally, an annular wick-type heat pipe is constructed and tested. The capillary limitation of the heat pipe showed good agreement with the suggested correlation. Additional research on measuring temperature distribution and visualizing the inside of the heat pipe is performed to understand the heat pipe behavior. A fiber optic sensor was used to measure the temperature distribution of the heat pipe during the transient and steady-state. Compared to the previously used sensors, thermocouples, for example, the fiber optic sensor provides more precise and detailed temperature data. A complete clear glass tube heat pipe was constructed using a transparent glass heater, allowing a fully visualized heat pipe experiment to observe the phenomena inside the heat pipe

Solid State Energy Conversion Alliance Delphi Solid Oxide Fuel Cell

The objective of this project is to develop a 5 kW Solid Oxide Fuel Cell power system for a range of fuels and applications. During Phase I, the following will be accomplished: Develop and demonstrate technology transfer efforts on a 5 kW stationary distributed power generation system that incorporates steam reforming of natural gas with the option of piped-in water (Demonstration System A). Initiate development of a 5 kW system for later mass-market automotive auxiliary power unit application, which will incorporate Catalytic Partial Oxidation (CPO) reforming of gasoline, with anode exhaust gas injected into an ultra-lean burn internal combustion engine. This technical progress report covers work performed by Delphi from July 1, 2003 to December 31, 2003, under Department of Energy Cooperative Agreement DE-FC-02NT41246. This report highlights technical results of the work performed under the following tasks: Task 1 System Design and Integration; Task 2 Solid Oxide Fuel Cell Stack Developments; Task 3 Reformer Developments; Task 4 Development of Balance of Plant (BOP) Components; Task 5 Manufacturing Development (Privately Funded); Task 6 System Fabrication; Task 7 System Testing; Task 8 Program Management; Task 9 Stack Testing with Coal-Based Reformate; and Task 10 Technology Transfer from SECA CORE Technology Program. In this reporting period, unless otherwise noted Task 6--System Fabrication and Task 7--System Testing will be reported within Task 1 System Design and Integration. Task 8--Program Management, Task 9--Stack Testing with Coal Based Reformate, and Task 10--Technology Transfer from SECA CORE Technology Program will be reported on in the Executive Summary section of this report

Catalytic combustion of methanol on structured catalysts for direct methanol fuel cell

Thesis (Master)--Izmir Institute of Technology, Energy Engineering, Izmir, 2011Includes bibliographical references (leaves: 46-50)Text in English; Abstract: Turkish and Englishx, 59 leavesThe major goal of this study is to investigate the effect of metal loading, space velocity and the outside temperature on both the steady state temperature of the alumina supported platinum catalysts and on time to reach at the temperature of 60 oC of a typical direct methanol fuel cell operating temperature in methanol combustion reaction. Alumina supported platinum catalysts were synthesized by using impregnation method and sol-gel made alumina. The methanol combustion reaction was performed in a tubular reactor.The characterization of the catalysts was performed by XRD and BET techniques. Particle size of Pt and surface area of the catalysts were compared before and after the reaction. In this study, it was found that the pure alumina was not active in methanol combustion whereas Pt/Al2O3 catalysts with varying loadings were active starting at room temperature. 2, 3 and 5% Pt loading catalysts showed the similar activity so it is possible that the average crystallite size and the crystallite size distribution of Pt on these catalysts would be similar. The space velocity tests indicated that low space velocity is required to quickly reach at 60 oC and also to achieve the highest steady state temperature for fresh catalyst whereas high space velocity is required to quickly reach at 60 oC and to achieve the highest steady state temperature for reused catalyst. The activity of the catalyst was also tested at sub-room temperatures. It was observed that the steady state temperature of the catalyst decreased and the time to reach at 60 oC increased when the outside temperature was below the room temperature. In addition to the tubular reactor, plate reactor was prepared for the methanol combustion. For this purpose, varying concentration alumina sols were coated on the stainless steel plates. However, optimum coating thickness could not be obtained because of the crack formation and peeling offs; thus, further detailed studies are necessary for obtaining stable coating suitable for the catalytic combustion

Micromachined nanocrystalline graphite membranes for gas separation

Carbon nanoporous membranes show promising performance for the passive separation and sieving of different gases, for example for helium and hydrogen separation. In this paper, nanocrystalline graphite (or nanographite) has been evaluated as a membrane material for molecular sieving of helium and hydrogen from larger gas constituents. Nanographite of 350 nm thickness was prepared using plasma-enhanced chemical vapour deposition onto fused silica substrates, from which membranes were microfabricated using deep wet etching. Permeability of hydrogen and helium were 1.79 ×10-16 and 1.40×10-16 mol·m·m-2·s-1·Pa-1 at 150 °C respectively, and measured separation was 48 for He/Ne, >135 for H2/CO2 and >1000 for H2/O2. The gas separation properties of the nanographite membranes were tested in the temperature range of 25 to 150 °C, and the permeation measurements show nanographite to be highly selective of helium and hydrogen over all larger gas molecules, including neon

An investigation of the feasibility of a process-intensified differential temperature water-gas shift reactor with integrated Pt/Al2O3 catalyst

There has been serious interest in hydrogen as a source of energy in the United States due to its capability of delivering a sustainable, carbon-free energy future. Currently, most hydrogen in the United States is produced via the steam methane reforming of natural gas, which converts methane to hydrogen through a series of energy-intensive and carbon-producing reactions, one being the water-gas shift (WGS) reaction. Previous research suggests that the implementation of a differential temperature WGS reactor operating under optimal temperature conditions reduces the required reactor volume to achieve a specific CO conversion level and the hydrogen production cost associated with the overall steam reforming process. This thesis investigates the feasibility of utilizing a plate architecture WGS microreactor with integrated platinum-ceria catalyst to intensify the WGS reaction with the goal of increasing overall hydrogen yield of the steam-methane reforming process and bridging the gap towards a sustainable hydrogen future. First, modeling from previous research was used to inform the design and manufacture of a sub-scale WGS microreactor prototype. Next, a catalyst recipe for a platinum catalyst with ceria precursor supported on washcoated alumina was developed and coated onto the walls of the reaction channels in the prototype. Finally, an experimental test set-up with a reacting gas loop and integrated cooling loop was designed, constructed, and configured to enable chemical testing of the WGS reactor prototype. The WGS reactor prototype with integrated catalyst was assembled and integrated onto the test loop. The thermal behavior of the prototype was validated using inert gases, but sealing challenges arose due to the high number of mechanically sealed surfaces. The results of catalyst adhesion characterization studies suggest that enhancing the surface roughness of the substrate's surface greatly improves the adhesion of the platinum catalyst. The results of the test loop experiments suggest that difficulties in sealing plate architecture-style reactors make this type of design mechanically feasible but impractical for realizing the potential of the intensified water-gas shift reaction