Phase Change Material Systems for High Temperature Heat Storage

Efficient, cost effective, and stable high-temperature heat storage material systems are important in applications such as high-temperature industrial processes (metal processing, cement and glass manufacturing, etc.), or electricity storage using advanced adiabatic compressed air energy storage. Incorporating phase change media into heat storage systems provides an advantage of storing and releasing heat at nearly constant temperature, allowing steady and optimized operation of the downstream processes. The choice of, and compatibility of materials and encapsulation for the phase change section is crucial, as these must guarantee good and stable performance and long lifetime at low cost. Detailed knowledge of the material properties and stability, and the coupled heat transfer, phase change, and fluid flow are required to allow for performance and lifetime predictions. We present coupled experimental-numerical techniques allowing prediction of the long-term performance of a phase change material-based high-temperature heat storage system. The experimental investigations focus on determination of material properties (melting temperature, heat of fusion, etc.) and phase change material and encapsulation interaction (stability, interface reactions, etc.). The computational investigations focus on an understanding of the multi-mode heat transfer, fluid flow, and phase change processes in order to design the material system for enhanced performance. The importance of both the experimental and numerical approaches is highlighted and we give an example of how both approaches can be complementarily used for the investigation of long-term performance

Atmospheric organic vapors in two European pine forests measured by a Vocus PTR-TOF : insights into monoterpene and sesquiterpene oxidation processes

Atmospheric organic vapors play essential roles in the formation of secondary organic aerosol. Source identification of these vapors is thus fundamental to understanding their emission sources and chemical evolution in the atmosphere and their further impact on air quality and climate change. In this study, a Vocus proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF) was deployed in two forested environments, the Landes forest in southern France and the boreal forest in southern Finland, to measure atmospheric organic vapors, including both volatile organic compounds (VOCs) and their oxidation products. For the first time, we performed binned positive matrix factorization (binPMF) analysis on the complex mass spectra acquired with the Vocus PTR-TOF and identified various emission sources as well as oxidation processes in the atmosphere. Based on separate analysis of low- and high-mass ranges, 15 PMF factors in the Landes forest and nine PMF factors in the Finnish boreal forest were resolved, showing a high similarity between the two sites. Particularly, terpenes and various terpene reaction products were separated into individual PMF factors with varying oxidation degrees, such as lightly oxidized compounds from both monoterpene and sesquiterpene oxidation, monoterpene-derived organic nitrates, and monoterpene more oxidized compounds. Factors representing monoterpenes dominated the biogenic VOCs in both forests, with lower contributions from the isoprene factors and sesquiterpene factors. Factors of the lightly oxidized products, more oxidized products, and organic nitrates of monoterpenes/sesquiterpenes accounted for 8 %-12% of the measured gas-phase organic vapors in the two forests. Based on the interpretation of the results relating to oxidation processes, further insights were gained regarding monoterpene and sesquiterpene reactions. For example, a strong relative humidity (RH) dependence was found for the behavior of sesquiterpene lightly oxidized compounds. High concentrations of these compounds only occur at high RH; yet similar behavior was not observed for monoterpene oxidation products.Peer reviewe

Collision Dynamics and Solvation of Water Molecules in a Liquid Methanol Film

Environmental molecular beam experiments are used to examine water interactions with liquid methanol films at temperatures from 170 K to 190 K. We find that water molecules with 0.32 eV incident kinetic energy are efficiently trapped by the liquid methanol. The scattering process is characterized by an efficient loss of energy to surface modes with a minor component of the incident beam that is inelastically scattered. Thermal desorption of water molecules has a well characterized Arrhenius form with an activation energy of 0.47{\pm}0.11 eV and pre-exponential factor of 4.6 {\times} 10^(15{\pm}3) s^(-1). We also observe a temperature dependent incorporation of incident water into the methanol layer. The implication for fundamental studies and environmental applications is that even an alcohol as simple as methanol can exhibit complex and temperature dependent surfactant behavior.Comment: 8 pages, 5 figure

Rethinking the law and politics of democratic police accountability

This paper evaluates the work and impact of a number of Police and Crime Commissioners (PCCs) in England and Wales and attempts to refocus public discourse and scrutiny on their Police and Crime Plans as a key prism through which their performance should be measured. Drawing upon the literature published by various PCCs, the Stevens Commission, the Home Affairs Committee and numerous academics, the paper will argue that a major reform of democratic police accountability in England and Wales is needed. Due to the often voluminous and piecemeal nature of the documents published on the PCCs’ websites, the textual analysis is limited to the Police and Crime Plans for Greater Manchester, the West Midlands and the London Metropolitan are

From silence to primary definer: The rise of the Intelligence lobby in the public sphere

Until the end of the Cold War the UK intelligence services were not officially acknowledged, and their personnel were banned from entering the public sphere. From 1989 the UK government began to put the intelligence services on a legal footing and to release the identity of the heads of the intelligence agencies. Since then, public engagement by the intelligence agencies has gathered pace. What this article hypothesises is that there is now, in the UK, an effective intelligence lobby of former insiders who engage in the public sphere – using on the record briefings – to counter criticism of the intelligence community and to promote a narrative and vision of what UK intelligence should do, how it is supported and how oversight is conducted. Content analysis and framing models of non-broadcast coverage of intelligence debates, focusing on the 36 months after the Snowden revelations, confirm an active and rolling lobby of current and former intelligence officials. The paper concludes that the extent of the lobby’s interventions in the public sphere is a matter for debate and possible concern

Reconciling care and justice in contesting social harm through performance and arts practice with looked after children and care leavers

The proportion of young people taken into the care of the state has increased recently and there is evidence that this social group suffer negative long-term outcomes that might be conceptualised by the emergent criminological category of ‘social harm’. This discussion is then related to debates on social work which have juxtaposed an ethics of care and justice. This paper reports findings from an innovative arts-based intervention with Looked After Children and Young People and concludes that holding these competing value sets in creative tension is central to the success of the programme in helping young people to cope with and contest social harm.DANCOP. The Mighty Creatives