Power generation characteristics of a sandwich‐type self‐heating thermoelectric generator with spatially varying embedded heat source

Power generation characteristics of a sandwich‐type thermoelectric generator in which the heat source is embedded into thermoelectric elements are investigated. Our previous work on a similar concept only considered a uniform heat source distribution inside thermoelectric elements. In this work, the effect of the spatial distribution of a heat source is examined. In particular, the effect of the concentration of heat source near the one end, that is, the hot end, is intensively studied as a potential means of improving the efficiency of the device. Although the effects of heat source concentration in impractical cases without heat transfer limitations on the cold side remain ambiguous, it become clear that heat source concentration indeed has positive effects in more realistic cases with finite heat transfer coefficients imposed on the cold side. Because of the relatively low efficiency of typical thermoelectric generation, a significant amount of heat must be dissipated from the cold end of the thermoelectric element. Greater heat source concentration near the hot end leads to more effective utilization of available heat source, reduces the amount of heat rejected at the cold end, and lowers the hot end temperature of the thermoelectric element. Overall, it is suggested that heat source concentration can be used as a method to achieve more efficient operation and better structural integrity of the system. Copyright © 2015 John Wiley & Sons, Ltd.     

Designing for an imagined user: Provision for thermal comfort in energy-efficient extra-care housing

Regarded as one solution to the problem of how to enable older people to retain their independence, extra-care housing, where each resident has their own self-contained dwelling and access to communal facilities and to care, has received extensive funding in recent years. Implicit in the concept of specialist housing is the notion of ‘special’ occupants, imagined older people. Adopting a socio-technical approach, this paper considers how ideas about ageing inform those aspects of extra-care-housing-design that relate to thermal comfort. The paper draws on semi-structured interviews with 13 people involved in the design, development and management of UK-based extra-care housing. Participants characterised imagined occupants as vulnerable to cold, at risk from fuel poverty and liable to be burned by hot surfaces or fall from high windows. These user representations were reportedly inscribed into the design of extra-care housing schemes through the inclusion of building features such as communal heating, under-floor heating, restricted window opening and heated corridors. The utilisation of stereotypical user representations of older people raises questions, given that older people's thermal comfort needs can be highly diverse. The paper explores the implications for energy demand.     

火箭发动机试验台快速高效高可靠试验技术

随着卫星系统组网及发射任务的增加,某运载火箭上面级发动机需求量猛增,试验系统和试验流程已经无法满足形势任务的需求。通过技术改造和流程优化,采用了一系列多余物控制、试验流程监控及可靠性提升等技术,实现了某试验台试验的快速、高效、高可靠,大大提高了试验效率。     

Dielectric response and energy storage efficiency of low content TiO2-polymer matrix nanocomposites

TiO₂/epoxy nanocomposites were prepared at different filler concentrations varying from 3 to 12 phr (parts per hundred resin per weight). The dispersion of TiO₂ was examined by Scanning Electron Microscopy and proved to be adequate. Differential Scanning Calorimetry was implemented to determine the glass to rubber transition temperature of the polymer matrix. The dielectric analysis was performed via Broadband Dielectric Spectroscopy in a wide frequency and temperature range. Five different mechanisms were observed in the spectra of the examined composites which are identified, in terms of increasing temperature at constant frequency, as γ, β, Intermediate Dipolar Effect (IDE), α and Interfacial Polarization (IP) relaxation modes. The activation energies of all relaxation modes were calculated. Finally, the dielectric response of the TiO₂ nanocomposites compared to that of the TiO₂ microcomposites reveals that the former exhibit significantly higher energy storage efficiency even at lower TiO₂ concentration than the corresponding of the microcomposites.     

Exploring the relationship between the physical properties of activated carbon catalysts and their efficiency in catalyzing hydrogen iodide decomposition to produce hydrogen

Using simple and efficient methods to synthesize biological activated carbon catalysts (ACCs) with the decomposition of hydrogen iodide (HI) in the sulfur-iodine cycle as a typical reaction is urgently needed for the commercialization of hydrogen energy production and development. In this study, a series of ACCs with different specific surface areas (SSAs) and pore structures are prepared by comparing and controlling the changes in carbonization and activation methods of activated carbon (AC) preparation process. Hierarchical porous AC with larger SSA has higher HI decomposition efficiency. The representative samples H240H1h and H240C4h are hierarchical porous ACCs with 48.96% and 46.88% micropores, respectively, and have the highest catalytic activity in the entire series. The nitrogen adsorption and desorption curve is combined with pore size distribution data and analyzed using the capillary aggregation (Kelvin) and monolayer adsorption (Langmuir) theories. And ACC pore grading coefficient—which can improve data visualization—is introduced.     

Collection efficiency of liquid‐based samplers for fungi in indoor air

This study assessed the collection efficiency (CE) of two popularly used sampling devices (BioSampler and Coriolis sampler) for fungal aerosols. Phosphate‐buffered saline (PBS) supplemented with or without surfactant (Tween‐20, Tween‐80, or Triton X‐100) and antifoam agent was prepared and used as collection liquids. The agar impactor (BioStage) was simultaneously operated with liquid‐based samplers to collect fungi from seven sites located at a university building, public library, and animal farming. Fungal concentrations determined by liquid samplers were divided by those by BioStage, and the ratio values represented CE. Results indicate that the CE of BioSampler was superior to that of Coriolis (P = 0.0001) and the PBS containing surfactant collected fungi better than that without surfactant (P < 0.0001), whereas antifoam agent showed no influence (P = 0.8). Moreover, fungal concentrations determined by BioSampler with surfactant‐added PBS were statistically indifferent from those by BioStage (P > 0.05) with a Spearman correlation coefficient of 0.81‐0.83 (P < 0.01). In addition to sampler and collection liquid, sampling location was also identified as a significant CE factor (P = 0.006), implying potential influences by fungal genera in the studied fields. Overall, BioSampler with surfactant‐supplemented PBS (eg, Triton X‐100) is recommended considering the great CE and compatibility with a variety of analytical assays.     

Additively manufactured respirators: quantifying particle transmission and identifying system-level challenges for improving filtration efficiency

The COVID-19 pandemic has disrupted the supply chain for personal protective equipment (PPE) for medical professionals, including N95-type respiratory protective masks. To address this shortage, many have looked to the agility and accessibility of additive manufacturing (AM) systems to provide a democratized, decentralized solution to producing respirators with equivalent protection for last-resort measures. However, there are concerns about the viability and safety in deploying this localized download, print, and wear strategy due to a lack of commensurate quality assurance processes. Many open-source respirator designs for AM indicate that they do not provide N95-equivalent protection (filtering 95% of SARS-CoV-2 particles) because they have either not passed aerosol generation tests or not been tested. Few studies have quantified particle transmission through respirator designs outside of the filter medium. This is concerning because several polymer-based AM processes produce porous parts, and inherent process variation between printers and materials also threaten the integrity of tolerances and seals within the printed respirator assembly. No study has isolated these failure mechanisms specifically for respirators. The goal of this paper is to measure particle transmission through printed respirators of different designs, materials, and AM processes. The authors compare the performance of printed respirators to N95 respirators and cloth masks. Respirators in this study printed using desktop- and industrial-scale fused filament fabrication processes and industrial-scale powder bed fusion processes were not sufficiently reliable for widespread distribution and local production of N95-type respiratory protection. Even while assuming a perfect seal between the respirator and the user’s face, although a few respirators provided >90% efficiency at the 100−300 nm particle range, almost all printed respirators provided <60% filtration efficiency. Post-processing procedures including cleaning, sealing surfaces, and reinforcing the filter cap seal generally improved performance, but the printed respirators showed similar performance to various cloth masks. The authors further explore the process-driven aspects leading to low filtration efficiency. Although the design/printer/material combination dictates the AM respirator performance, the identified failure modes originate from system-level constraints and are therefore generalizable across multiple AM processes. Quantifying the limitations of AM in producing N95-type respiratory protective masks advances understanding of AM systems toward the development of better part and machine designs to meet the needs of reliable, functional, end-use parts.     

A generalized method for the inherent energy performance modeling of machine tools

Machine tools (MTs), as the key equipment of manufacturing systems, have enormous quantities and consume a great amount of energy. However, the diversity of both machines and their energy consumption properties make it difficult to transfer the energy-saving knowledge and services among different MT. To facilitate the initialization configuration of energy-saving services, the inherent energy performance (IEP) is investigated to describe the differences in energy consumption among MTs, and a generalized method for modeling the IEP of MT and its electrical subsystems is proposed. Three key enablers, including generalized experimental design rules, automatic coding, and data processing algorithms, are presented and integrated into a supporting system to reduce the modeling efforts and knowledge requirements. Case studies of an offline manufacturing scenario and an Internet of Things (IoT)-enabled manufacturing scenario were carried out to verify the effectiveness and convenience of the proposed method. The results show that the proposed method can provide essential modeling support for large-scale energy-saving service configurations and energy-efficient MT development.     

Optimized techniques for driving and control of the switched reluctance motor to improve efficiency

This work presents modeling, driving and classical speed control techniques for the switched reluctance motor. The aim is to improve the computational model, the control response and the machine efficiency. A parametric regression model was used to find the inductance profile of the switched reluctance motor and from the new inductance profile model. The drive and control techniques are shown: (i) with speed control acting on the excitation voltage and fixed switching angles, (ii) with speed control acting on the switching angles and fixed excitation voltage and (iii) with speed control acting on the excitation voltage, in this case, with dynamic switching angles and controller parameters. The inductance profile is represented by expression and inserted into the machine computer model, allowing greater precision and low computational cost. The speed control acting on the excitation voltage with dynamic controller parameters and dynamic switching angles allowed: (i) shorter response time for a wide range of control, (ii) higher efficiency, (iii) low computational cost and (iv) simplified implementation and maintenance. The techniques proposed in this work obtained precision of the computational model with respect to the system (in workbench) and optimized parameters in a wide range of the speed control, allowing an improvement of switched reluctance motor efficiency.