Heat transfer in horizontal tubes at supercritical pressures for organic Rankine Cycle applications

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Today process industry has to deal with a lot of waste heat. Very often this waste heat is dumped to the environment, while it could be efficiently used. Low grade heat is also available in solar thermal systems, geothermal systems, biomass combustion and etc. This heat can be converted into electricity using an organic Rankine cycle (ORC). This thermodynamic cycle is similar to the well-known Rankine steam cycle, but it works with an organic working fluid instead of water/steam. As a consequence, the temperature of the heat source at the evaporator is typically lower compared to the steam cycles. To increase the cycle efficiency, supercritical cycles seem very promising. The advantage of supercritical ORCs is a better thermal match between the heat source and the working fluid temperature profiles in the supercritical heat exchanger. Consequently, the overall system efficiency improves. In the current literature, research work on heat transfer mechanisms under supercritical conditions in ORC is very limited. Therefore, it is an essence to study and investigate the relatively unknown heat transfer phenomena at supercritical working conditions for organic fluids in the temperature and pressure ranges relevant for ORCs. Heat exchanger design and heat transfer coefficients are factors that have great influence on the heat transfer and the overall cycle efficiency. Furthermore, special attention must be drawn to the choice of appropriate working fluid, which is a factor of great importance because the organic fluid properties also affect the overall efficiency of the cycle. In this paper, relevant researches are reviewed regarding Supercritical Organic Rankine Cycle applications, selection of working fluids and description of newly designed test facility is presented.dc201

Highly Stable and Reactive Platinum Single Atoms on Oxygen Plasma-Functionalized CeO₂ Surfaces: Nanostructuring and Peroxo Effects

Atomically dispersed precious metals on oxide supports have recently become increasingly interesting catalytic materials. Nonetheless, their non-trivial preparation and limited thermal and environmental stability constitutes an issue for their potential applications. Here we demonstrate that an oxygen plasma pre-treatment of the ceria (CeO2 ) surface serves to anchor Pt single atoms, making them active and resistant towards sintering in the CO oxidation reaction. Through a combination of experimental results obtained on well-defined CeO2 films and theory, we show that the O2 plasma causes surface nanostructuring and the formation of surface peroxo (O22-) species, favoring the uniform and dense distribution of isolated strongly bonded Pt2+ atoms. The promotional effect of the plasma treatment was further demonstrated on the powder Pt/CeO2 catalysts. We believe that plasma functionalization can be applied to other metal/oxide systems to achieve tunable and stable catalysts with a high density of active sites

Highly Stable and Reactive Platinum Single Atoms on Oxygen Plasma-Functionalized CeO₂ Surfaces: Nanostructuring and Peroxo Effects

Atomically dispersed precious metals on oxide supports have recently become increasingly interesting catalytic materials. Nonetheless, their non-trivial preparation and limited thermal and environmental stability constitutes an issue for their potential applications. Here we demonstrate that an oxygen plasma pre-treatment of the ceria (CeO2 ) surface serves to anchor Pt single atoms, making them active and resistant towards sintering in the CO oxidation reaction. Through a combination of experimental results obtained on well-defined CeO2 films and theory, we show that the O2 plasma causes surface nanostructuring and the formation of surface peroxo (O22-) species, favoring the uniform and dense distribution of isolated strongly bonded Pt2+ atoms. The promotional effect of the plasma treatment was further demonstrated on the powder Pt/CeO2 catalysts. We believe that plasma functionalization can be applied to other metal/oxide systems to achieve tunable and stable catalysts with a high density of active sites

Describing dialogue between persons with profound intellectual and multiple disabilities and direct support staff using the scale for dialogical meaning making

Background The dialogical approach of meaning making forms a rich and renewing theoretical perspective to study communication between presymbolic communicators and their interaction partners. The aim of this study is to investigate whether an observation scale based on the dialogical theory, the Scale for Dialogical Meaning Making (S-DMM), has potential to describe these communicative interactions. Methods Eighteen videotaped observations of persons with profound intellectual and multiple disabilities and their support staff were coded using the S-DMM and a consensus-rating procedure. Results Sufficient inter-rater agreement and an acceptable range in scores confirm the usefulness of the S-DMM. Strong sub-scale intercorrelations were identified. The quantitative scores and the qualitative arguments supporting the ratings, demonstrate how the S-DMM aids to significantly describe staff-client dialogue. Conclusions Using the S-DMM to describe dialogue with persons with profound intellectual and multiple disabilities appears to be promising. The value of the S-DMM and its consensus-rating procedure are reflected upon and discussed with regard to implications for research and practice