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Global warming, climate change, and ever-increasing energy demand are among the pressing challenges currently facing humanity. Particularly, indoor air conditioning, a major source of energy consumption, requires immediate improvement to prevent energy crises. In this study, various airfoil profiles were applied to create a window-type convection device that entrains air to improve convection between indoor and outdoor airflows and adjust the indoor temperature. How the geometric structure of the convection device affects its air entrainment performance was investigated on the basis of various airfoil profiles and outlet slit sizes of the airflow multiplier. The airfoil profiles were designed according to the 4-digit series developed by the National Advisory Committee for Aeronautics. The results revealed that airfoil thickness, airfoil camber, and air outlet slit size affected the mass flow rate of the convection device. Overall, the mass flow rate at the outlet of the convection device was more than 10 times greater than at the inlet, demonstrating the potential of the device to improve air convection. To validate these simulated results, the wind-deflector plate was processed using the NACA4424 airfoil with a 1.2 mm slit, and various operating voltages were applied to the convection device to measure the resulting wind speeds and calculate the corresponding mass flow rates. The experimental and simulated results were similar, with a mean error of <7%, indicating that the airfoil-shaped wind-deflector plate substantially improved air entrainment of the convection device to the goal of reduced energy consumption and carbon emissions.
Han-Tang Lin; Yunn-Horng Guu; Wei-Hsuan Hsu. Design and Fabrication of a Novel Window-Type Convection Device. Applied Sciences 2020, 11, 267 .
AMA StyleHan-Tang Lin, Yunn-Horng Guu, Wei-Hsuan Hsu. Design and Fabrication of a Novel Window-Type Convection Device. Applied Sciences. 2020; 11 (1):267.
Chicago/Turabian StyleHan-Tang Lin; Yunn-Horng Guu; Wei-Hsuan Hsu. 2020. "Design and Fabrication of a Novel Window-Type Convection Device." Applied Sciences 11, no. 1: 267.
With technological advancement, energy consumption and lack of energy supply are inevitable. Approximately 20% of total energy consumption is used for artificial light in standard office buildings. To reduce energy consumption for illumination purposes, a sunlight guiding panel was used to increase the amount of sunlight available indoors. However, in most designs of a sunlight guiding panel, the panel has to be placed on the outdoor surface of a window glass. This type of design is inconvenient for assembling and cleaning. To enhance the practicality of a sunlight guiding panel, we attempted to place the sunlight guiding panel on the indoor surface of a window glass. The simulation results revealed that when the sunlight guiding panel was placed on the indoor surface of a window glass, the aspect ratio of the light-guiding structure of the sunlight guiding panel had to be increased for guiding the sunlight from outdoors so as to increase the amount of sunlight indoors. To fabricate the proposed sunlight guiding panel, UV nanoimprint lithography was applied to pattern the light-guiding structure of the sunlight guiding panel. Moreover, a mold with a high-precision light-guiding structure was used in UV nanoimprint lithography. The mold was fabricated using ultraprecision machining technology. Both analytical and experimental investigations were conducted to confirm the proposed design. The average light-guiding efficiency was 89.9% with a solar elevation angle range of 35° to 65°, and the experimental results agreed well with the simulation results. This study elucidates light-guiding efficiency when the sunlight guiding panel is placed on the indoor surface of a window glass, which can increase the usage convenience and application potential of sunlight guiding panels.
Wei-Hsuan Hsu; Yi-Zhang Xie. Design and Manufacture of a Novel Sunlight Guiding Panel. Coatings 2019, 9, 562 .
AMA StyleWei-Hsuan Hsu, Yi-Zhang Xie. Design and Manufacture of a Novel Sunlight Guiding Panel. Coatings. 2019; 9 (9):562.
Chicago/Turabian StyleWei-Hsuan Hsu; Yi-Zhang Xie. 2019. "Design and Manufacture of a Novel Sunlight Guiding Panel." Coatings 9, no. 9: 562.
Microbial fuel cells (MFCs), which can generate low-pollution power through microbial decomposition, are a potentially vital technology with applications in environmental protection and energy recovery. The electrode materials used in MFCs are crucial determinants of their capacity to generate electricity. In this study, we proposed an electrode surface modification method to enhance the bacterial adhesion and increase the power generation in MFCs. Graphene suspension (GS) is selected as modifying reagent, and thin films of graphene are fabricated on an electrode substrate by spin-coating. Application of this method makes it easy to control the thickness of graphene film. Moreover, the method has the advantage of low cost and large-area fabrication. To understand the practicality of the method, the effects of the number of coating layers and drying temperature of the graphene films on the MFCs’ performance levels are investigated. The results indicate that when the baking temperature is increased from 150 to 325 °C, MFC power generation can increase approximately 4.5 times. Besides, the maximum power density of MFCs equipped with a four-layer graphene anode is approximately four times that of MFCs equipped with a two-layer graphene anode. An increase in baking temperature or number of coating layers of graphene films enhances the performance of MFC power generation. The reason can be attributed to the graphene purity and amount of graphene adhering to the surface of electrode.
Hung-Yin Tsai; Wei-Hsuan Hsu; Yi-Jhu Liao. Effect of Electrode Coating with Graphene Suspension on Power Generation of Microbial Fuel Cells. Coatings 2018, 8, 243 .
AMA StyleHung-Yin Tsai, Wei-Hsuan Hsu, Yi-Jhu Liao. Effect of Electrode Coating with Graphene Suspension on Power Generation of Microbial Fuel Cells. Coatings. 2018; 8 (7):243.
Chicago/Turabian StyleHung-Yin Tsai; Wei-Hsuan Hsu; Yi-Jhu Liao. 2018. "Effect of Electrode Coating with Graphene Suspension on Power Generation of Microbial Fuel Cells." Coatings 8, no. 7: 243.
Microbial fuel cells (MFCs) generate low-pollution power by feeding organic matter to bacteria; MFC applications have become crucial for energy recovery and environmental protection. The electrode materials of any MFC affect its power generation capacity. In this research, nine single-chamber MFCs with various electrode configurations were investigated and compared with each other. A fabrication process for carbon-based electrode coatings was proposed, and Escherichia coli HB101 was used in the studied MFC system. The results show that applying a coat of either graphene or carbon nanotubes (CNTs) to a stainless steel mesh electrode can improve the power density and reduce the internal resistance of an MFC system. Using the proposed surface modification method, CNTs and graphene used for anodic and cathodic modification can increase power generation by approximately 3–7 and 1.5–4.5 times, respectively. Remarkably, compared to a standard MFC with an untreated anode, the internal resistances of MFCs with CNTs- and graphene-modified anodes were reduced to 18 and 30% of standard internal resistance. Measurements of the nine systems we studied clearly presented the performance levels of CNTs and graphene applied as surface modification of stainless steel mesh electrodes.1. IntroductionAs technology advances, energy consumption and shortfalls of energy supply are inevitable. Moreover, the rise of environmental awareness has motivated the development of minimally polluting renewable energy sources, such as microbial fuel cells (MFCs). Thus, MFCs have been extensively studied in the last decade. MFCs utilize microorganisms as catalysts to decompose organic or inorganic matter and harvest electrical energy [1].The major obstacles towards commercialization of MFC are its high cost of fabrication and low power output. The cost of MFC mainly depends on the design of reactors, membrane separator, and electrode catalysts [2–4]. A typical MFC system comprises two chambers (i.e., an anode and a cathode) separated by a proton exchange membrane (PEM). Chemical energy can be converted to electric energy through anodic oxidation and cathodic reduction. Microorganisms oxidize the organic compound and produce electrons and protons in the anode chamber. Electrons are transported to the cathode by an external circuit, whereas the protons are transferred internally to the cathode chamber through the PEM. Subsequently, the electrons and protons react with oxygen to form water. According to the energy conversion process, the electric current can be generated continuously between the anode and cathode [5–7]. To allow the easy construction, a single-chamber MFC system was proposed [8], in which the cathodic and anodic electrodes were placed in a reaction chamber and a proton exchange membrane (PEM) was fused to the cathodic surface. Later, the performance of air-cathode single-chamber MFCs was further investigated to reduce the cost of MFC, and the feasibility of MFC systems without PEM materials was demonstrated [9]. Because oxygen can pass through the cathode directly in air-cathode MFC designs, these designs reduce the cost of equipment required to regulate air exposure. Thus, a single-chamber MFC has some advantages over a traditional double-chamber MFC and has potential for development.The power output of an MFC is affected by several factors, including the microbial inoculation, electrode materials, ionic concentration, catalyst, internal resistance, and electrode spacing [10–13]. The electrode materials play a critical role in electricity generation. An electrode with high electrical conductivity can effectively collect electrons and reduce ohmic loss. Therefore, metal electrodes are crucial for MFC systems. Conventionally, designers choose stainless steel and titanium for electrodes in MFC systems [14]. Stainless steel has the advantages of low cost and anticorrosive properties, and it has become one of the major research materials for electrodes in MFCs. However, in MFC systems, electrons are generated by metabolically and electrochemically active microorganisms at the interfaces between anodic surfaces and microbes [15, 16], and the generated electrons transfer to anode surfaces through direct contact, microbial pili, or soluble mediators [17, 18]. Thus, an electrode with a large surface area and high specific surface area can demonstrate high microbe attachment and low internal resistance [19]. To improve the attachment of bacteria on the anode, an electrode with a high specific surface area is necessary. For this purpose, numerous studies have utilized three-dimensional structures of stainless steel, such as stainless steel mesh (SSM) [20–25], stainless steel foam [26], stainless steel felt [27], and stainless steel fiber felt [28–31]. But the surface areas of this type of electrode are limited when compared with those of nanomaterial-based electrodes. Nanomaterials offer exceptionally large surface-area-to-volume ratios as well as unique electrochemical properties such as strong charge interactions with organic matter [32]. Therefore, most of the aforementioned studies have used nanomaterials for electrode modification treatment.In recently years, carbon nanotubes (CNTs) and graphene have been intensively studied and explored in various applications for advanced technologies due to their fascinating properties, such as high electrical conductivity, surface area, and stability [33, 34]. Moreover, CNTs [21, 23, 32, 35–37] and graphene [20, 30, 37] have been used as an electrode modified material in MFC systems. Research has confirmed that SSM electrodes modified with CNTs or graphene can improve the characteristics of MFCs. For anode modification, graphene can improve electrode surface area, adhesion of bacteria, and efficiency of electron transfer [20]. Some MFCs with CNTs-SSM cathodes have achieved levels of maximum power density and Coulombic efficiency higher than those of MFCs with bare SSM cathodes [21, 23]. However, the aforementioned studies have studied diverse modification processes and coating materials with different properties. To accelerate the development of MFCs, the performance effects of SSM electrodes coated with CNTs or graphene must be comprehensively compared using the same modification process and coating materials. Thus, in this study, a set of mediatorless single-chamber MFCs was designed to examine the performance effects of different SSM electrodes coated with CNTs or graphene. The power density and internal resistance values of the MFCs with CNT- or graphene-coated electrodes were evaluated as the performance indices.2. Materials and Methods2.1. Electrode ModificationThe process of electrode modification was described as follows. For anodic modification, carbon ink was prepared by dispersing 20 mg of multiwall CNTs (MW-CNTs; average diameter larger than 50 nm, length between 10 and 20 μm, and specific surface area approximately 60 m2/g) or multilayer graphene sheets (MG; specific surface area approximately 20 m2/g, average sheet thickness smaller than 50 nm, and lateral size approximately 20 μm) in 95% ethanol (10 mL). Ethanol with MW-CNTs or MG was ultrasonicated to obtain a homogeneous solution. A piece of SSM (average hole diameter 40 μm, thickness 100 μm, and diameter 50 μm) was then dipped into the carbon ink for 1 hour, removed, and finally baked at 150°C for 1 hour to obtain an SSM anode coated with MW-CNTs or MG.For cathodic modification, polytetrafluoroethylene (PTFE) solution, with or without carbon-based materials, was used for waterproofing. The treated PTFE solution was prepared by dispersing 20 mg of MW-CNTs or MG in 19.98 g of PTFE solution (preparation 60 wt% dispersion in H2O). The dispersion was performed using ultrasonic vibration to obtain a homogeneous solution. A piece of SSM was soaked in the pure or treated PTFE solution for 1 hour, removed, and then baked at 235°C for 1 hour. The soaking-baking process was repeated four times to obtain a cathode with excellent waterproofing. In some study cases, platinum (0.5 mg/cm−2, 20 wt% Pt/C) was used to catalyze the oxygen reaction. For those case studies, the inner side of the cathode, which served as the contact surface with the reaction environment, was covered with a Pt catalyst after waterproofing and baked for 30 minutes at 350°C.2.2. Microorganism CultureA single bacterium, Escherichia coli HB101, was used to convert energy; this reduced the experimental variability and facilitated precise estimation of the effects of electrode modifications on MFC performance levels. The culture process resembled the methods of a previous study [37] and is briefly described as follows: E. coli HB101 was grown anaerobically in an atmosphere of N2 gas for 40 hours until it reached its stationary phase in lysogeny broth medium at 37°C. After culturing, the microbe was obtained by 5000 rpm centrifugation and then dissolved in M9 medium.2.3. MFC StructureThe structure of the air-cathode MFC used in this study, which resembles previously reported MFCs [37], is shown in Figure 1. In this air-cathode MFC, the material of the cylindrical chamber was polymethylmethacrylate (PMMA) and its diameter, length, wall thickness, and reactor volume were approximately 50 mm, 60 mm, 5 mm, and 75 mL, respectively. Anodic and cathodic electrodes were placed at the ends of the cylindrical chamber; the cathodic electrode was on the side with air, and the anodic electrode was on the opposite side. The surface areas of the cathode and anode were approximately 1257 mm2. Additionally, copper wires and resistors were used to connect the circuit.Figure 1: Schematic of the air-cathode MFC used in this study. Different types of SSMs can be used as electrodes and connected to external resistance loads with copper wires.2.4. Experimental Planning and MeasurementNine types of single-chamber MFCs were constructed, as shown in Figure 2, to compare the effects of electrodes coated wi
Wei-Hsuan Hsu; Hung-Yin Tsai; Ying-Chen Huang. Characteristics of Carbon Nanotubes/Graphene Coatings on Stainless Steel Meshes Used as Electrodes for Air-Cathode Microbial Fuel Cells. Journal of Nanomaterials 2017, 2017, 1 -9.
AMA StyleWei-Hsuan Hsu, Hung-Yin Tsai, Ying-Chen Huang. Characteristics of Carbon Nanotubes/Graphene Coatings on Stainless Steel Meshes Used as Electrodes for Air-Cathode Microbial Fuel Cells. Journal of Nanomaterials. 2017; 2017 ():1-9.
Chicago/Turabian StyleWei-Hsuan Hsu; Hung-Yin Tsai; Ying-Chen Huang. 2017. "Characteristics of Carbon Nanotubes/Graphene Coatings on Stainless Steel Meshes Used as Electrodes for Air-Cathode Microbial Fuel Cells." Journal of Nanomaterials 2017, no. : 1-9.
Titanium alloys have several advantages, such as a high strength-to-weight ratio. However, the machinability of titanium alloys is not as good as its mechanical properties. Many machining processes have been used to fabricate titanium alloys. Among these machining processes, electrical discharge machining (EDM) has the advantage of processing efficiency. EDM is based on thermoelectric energy between a workpiece and an electrode. A pulse discharge occurs in a small gap between the workpiece and electrode. Then, the material from the workpiece is removed through melting and vaporization. However, defects such as cracks and notches are often detected at the boundary of holes fabricated using EDM and the irregular profile of EDM holes reduces product quality. In this study, an innovative method was proposed to estimate the effect of EDM parameters on the surface quality of the holes. The method combining the finite element method and image processing can rapidly evaluate the stress concentration factor of a workpiece. The stress concentration factor was assumed as an index of EDM process performance for estimating the surface quality of EDM holes. In EDM manufacturing processes, Ti-6Al-4V was used as an experimental material and, as process parameters, pulse current and pulse on-time were taken into account. The results showed that finite element simulations can effectively analyze stress concentration in EDM holes. Using high energy during EDM leads to poor hole quality, and the stress concentration factor of a workpiece is correlated to hole quality. The maximum stress concentration factor for an EDM hole was more than four times that for the same diameter of the undamaged hole.
Wei-Hsuan Hsu; Wan-Ting Chien. Effect of Electrical Discharge Machining on Stress Concentration in Titanium Alloy Holes. Materials 2016, 9, 957 .
AMA StyleWei-Hsuan Hsu, Wan-Ting Chien. Effect of Electrical Discharge Machining on Stress Concentration in Titanium Alloy Holes. Materials. 2016; 9 (12):957.
Chicago/Turabian StyleWei-Hsuan Hsu; Wan-Ting Chien. 2016. "Effect of Electrical Discharge Machining on Stress Concentration in Titanium Alloy Holes." Materials 9, no. 12: 957.