Browsing by Subject "214 Mechanical engineering"

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  • Yang, Huan; Ding, Dian; Skyttä, Aurora; Cai, Runlong; Kulmala, Markku; Kangasluoma, Juha (2022)
    Condensation and evaporation of vapor species on nanopartide surfaces drive the aerosol evolution in various industrial/atmospheric systems, but probing these transient processes is challenging due to related time and length scales. Herein, we present a novel methodology for deducing nanoparticle evaporation kinetics using electrical mobility as a natural size indicator. Monodispersed nanopartides are fed to a differential mobility analyzer which serves simultaneously as an evaporation flowtube and an instrument for measuring the electrical mobility, realizing measurements of evaporation processes with time scales comparable to the instrument response time. A theoretical framework is derived for deducing the evaporation kinetics from instrument responses through analyzing the nanopartide trajectory and size-mobility relationship, which considers the coupled mass and heat transfer effect and is applicable to the whole Knudsen number range. The methodology is demonstrated against evaporation but can potentially be extended to condensation and other industrial/atmospheric processes involving rapid size change of nanoparticles.
  • Jääskeläinen, Jaakko J.; Höysniemi, Sakari Hannu; Syri, Sanna; Tynkkynen, Veli-Pekka (2018)
    Studies on energy security in the context of relations between European Union (EU) and Russia tend to focus on cases, with an open conflict related to supply, such as “hard” energy weapons, or on only one fuel, often natural gas. However, there is a need to understand the long-term impacts that energy relations have politically, economically and physically, and their linkages between resilience, sustainability and security. We analyse the Finnish-Russian energy relations as a case study, as they are characterised by a non-conflictual relationship. To assess this complex relationship, we apply the interdependence framework to analyse both the energy systems and energy strategies of Finland and Russia, and the energy security issues related to the notable import dependence on one supplier. Moreover, we analyse the plausible development of the energy trade between the countries in three different energy policy scenarios until 2040. The findings of the article shed light on how the trends in energy markets, climate change mitigation and broader societal and political trends could influence Russia’s energy trade relations with countries, such as Finland. Our analysis shows that Finland’s dependence on primary energy imports does not pose an acute energy security threat in terms of sheer supply, and the dependence is unlikely to worsen in the future. However, due to the difficulty in anticipating societal, political, and economic trends, there are possible developments that could affect Finland.
  • Voss, Antti; Seppänen, Aku; Siltanen, S.; Salokangas, Lauri; Baroudi, Djebar (TU Verlag, Wien, 2016)
    The current study investigates whether an electrical imaging modality, electrical capacitance tomography (ECT), could provide information on the moisture content in wood. In ECT, a set of electrodes are placed around the surface of the object, and based on electrical capacitance measurements from the surface, the spatial distribution of the electrical permittivity inside the object is reconstructed. In this experimental study, water is infiltrated in a wood sample for 7 days, and ECT measurements are sequentially collected during the absorption of water. The reconstructed ECT images show a constant increase of electrical permittivity in the location of water absorption. The results support the feasibility of ECT for imaging the water content in wood.
  • Lajunen, Antti; Kivekas, Klaus; Vepsalainen, Jari; Tammi, Kari (2020)
    Different estimations have been presented for the amount of electric vehicles in the future. These estimations rarely take into account any realistic dynamics of the vehicle fleet. The objective of this paper is to analyze recently presented future scenarios about the passenger vehicle fleet estimations and create a foundation for the development of a fleet estimation model for passenger cars dedicated to the Finnish vehicle market conditions. The specific conditions of the Finnish light-duty vehicle fleet are taken into account as boundary conditions for the model development. The fleet model can be used for the estimation of emissions-optimal future vehicle fleets and the evaluation of the carbon dioxide emissions of transportation. The emission analysis was done for four different scenarios of the passenger vehicle fleet development in Finland. The results show that the high average age of the fleet and high number of older gasoline vehicles will slow down the reduction of carbon dioxide emissions during the next five to ten years even with a high adoption rate of electric vehicles. It can be concluded that lowering the average age, increasing biofuel mixing ratios, and increasing the amount of rechargeable electric vehicles are the most effective measures to reduce carbon dioxide emissions of the Finnish passenger vehicle fleet in the future.
  • Moula, Munjur E; Nyári, Judit; Bartel, Angela (2017)
    The Finnish transportation sector is the second biggest greenhouse gas emitting sector in Finland. Despite large-scale investment and government commitments to promote biofuels for transport sectors in Finland, little is known about the public acceptance of this alternative transport fuels. Public’s opinion, awareness and knowledge can contribute to social acceptance of new renewable energy and to the overall improvement of consumers' energy behaviour. This study examines public acceptance in terms of public’s opinion and knowledge about biofuels and their consumer patterns of transportation fuels by designing a multiple-choice questionnaire with four groups of questions: background information, community perspective, social perspective, and market perspective. The analysis of 90 respondents’ survey shows that 50% of the respondents think that there is a direct effect of biofuel production on food prices and would not buy biofuels derived from food crops. Only 60% of them are willing to switch towards purchasing biofuels; however, the lack of information about biofuels prevents them to use biofuels for their transports. Finally, 63 respondents of the car owners, their ideal fuel would be hydrogen (20%), electricity (60%), and other (20%), which meant hybrid. Study findings have important policy implications related to the public acceptance of biofuels in the transport sector.