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The many advantages of slug flow pneumatic conveying are outweighed by the lack of understanding of the flow mechanisms. For horizontal slug flow, the unique feature is the stationary layer of material found between the travelling slugs, which was recently shown to be characterised by two constants. This paper looks to utilise the vast data available in the literature, which is representative of the entire mode of flow, and relates the stationary layer and slug velocity to predict the two constants from only these inputs. It was found that, even for the vast range of materials and systems considered, slug flow encompasses a narrow bound of the two constants. Furthermore, an empirical approach that was developed to relate the layer fraction and particle velocity was found to provide good agreement to measurements and may be of use in other investigations that require an additional equation for modelling.

Abstract Thermal energy storage with phase change materials (PCM) provides high storage capacities in small temperature intervals. For the design of storage systems, the enthalpy curve of the used PCM has to be known with high precision. The T-History method has evolved to a widely used method for the measurement of the enthalpy as a function of temperature of PCM because of its simplicity and the advantage to be able to investigate larger sample volumes than typically used for differential scanning calorimeters. In order to ensure isothermal specimen during the measurement a thermal insulation is often mounted around the sample holder, but this insulation material is not considered in the evaluation model. In this work a new evaluation model for insulated T-History setups is developed by an analytical heat balance. This model is validated by numerical simulations of insulated T-History measurements and experimentally. By the use of the new model for the evaluation of the enthalpy a significant increase of accuracy can be achieved.

Abstractπ‐Conjugated polyelectrolytes (CPEs) have been studied as interlayers on top of a separate hole transport layer (HTL) to improve the wetting, interfacial defect passivation, and crystal growth of perovskites. However, very few CPE‐based HTLs have been reported without rational molecular design as ideal HTLs for perovskite solar cells (PeSCs). In this study, the authors synthesize a triphenylamine‐based anionic CPE (TPAFS‐TMA) as an HTL for p‐i‐n‐type PeSCs. TPAFS‐TMA has appropriate frontier molecular orbital (FMO) levels similar to those of the commonly used poly(bis(4‐phenyl)‐2,4,6‐trimethylphenylamine) (PTAA) HTL. The ionic and semiconducting TPAFS‐TMA shows high compatibility, high transmittance, appropriate FMO energy levels for hole extraction and electron blocking, as well as defect passivating properties, which are confirmed using various optical and electrical analyses. Thus, the PeSC with the TPAFS‐TMA HTL exhibits the best power conversion efficiency (PCE) of 20.86%, which is better than that of the PTAA‐based device (PCE of 19.97%). In addition, it exhibits negligible device‐to‐device variations in its photovoltaic performance, contrary to the device with PTAA. Finally, a large‐area PeSC (1 cm2) and mini‐module (3 cm2), showing PCEs of 19.46% and 18.41%, respectively, are successfully fabricated. The newly synthesized TPAFS‐TMA may suggest its great potential as an HTL for large‐area PeSCs.

This paper presents an experimental study of indoor thermal environment near a full-scale glass facade with different types of shading devices under varying climatic conditions in winter. Interior glazing and shading temperature, operative temperature and radiant temperature asymmetry were measured for facade sections with roller shades and venetian blinds at different positions. Interior glass surface temperatures can be high during sunny days with low outdoor temperature. Shading systems significantly improved operative temperature and radiant temperature asymmetry during cold sunny days, depending on their properties and tilt angle. During cloudy days the impact was smaller, however the shading layers could still decrease the amount of heat loss through the facade. A transient building thermal model, which also calculates indoor environmental indices under the presence of solar radiation, was developed and compared with the experimental measurements. Part II of this paper uses this validated model with a transient, two-node thermal comfort model (including transmitted solar radiation) for assessment of indoor environmental conditions with different building envelope and shading properties, facade location and orientation.

Sustainability has emerged, arguably, as the premiere mission of contemporary architecture. Green assessment tools abound, consultancy services flourish, buildings are marketed on the basis of sustainability performance, and government, media, and corporations seem preoccupied with assessing the quality of the built environment through a green lens. Yet for all the effort, and indeed for all the progress made, fundamental issues resistant to the structural change that is essential for genuine sustainability remain. This paper reviews the state of play of sustainability across the urban landscape. It considers the road travelled so far, and points out some of the major challenges that lie ahead.

Power system reactive power planning has long been an important issue for the power industry. The widely used VAr compensation device is a SVC with its controller. The problem of planning falls into determination of optimal locations and settings of SVC devices in the power system to be compensated. We propose a new approach of reactive planning using SVCs and nonlinear SVC controllers. This approach considers not only system buses but also the transmission lines to achieve more comprehensive compensation and better system performance especially in view of voltage stability enhancement and control.

Abstract Background Parabolic Trough Solar Collector (PTSC) is one of the most popular and an effective device that converts solar radiation into a heat or useful energy. However, it suffers from high temperature gradient and low thermal efficiency. The solution for this problem is to use new advanced coolants (hybrid nanofluids) in order to enhance PTSC's thermal efficiency. Methods A numerical analysis on the thermo-hydraulic performance of a PTSC receiver's tube equipped with conical turbulators is presented. The Navier-Stokes equations are solved using Finite Volume Method (FVM) coupled with Monte Carlo Ray Tracing (MCRT) method. The flow and thermal characteristics as well as entropy generation of the PTSC's receiver tube are investigated for three hybrid nanofluids (Ag-SWCNT, Ag-MWCNT, and Ag-MgO) having a mixing ratio of (50:50) dispersed in Syltherm oil 800, Reynolds number (5000 to 100,000) and fluid inlet temperatures (400 to 650 K). Significant findings The conical turbulators effectively augmented the thermal performance by 233.4% utilising Ag-SWCNT/Syltherm oil instead of pure Syltherm oil. The performance evaluation criterion is found to be in the range of 0.9–1.82. The thermal and exergetic efficiencies increased by 11.5% and 18.2%, respectively. The maximum decrement in the entropy generation rate and entropy generation ratio are 42.7% and 33.7%.

Abstract Residues from the liquefaction of Black Thunder subbituminous and Illinois No. 6 bituminous coals in an autoclave and a bench unit were examined petrographically. Optical microscopy proved valuable for ranking the samples on the basis of overall coal conversion and presence of vitroplast, granular residue and inertinite. It was observed that in the autoclave that runs on Black Thunder coal, K 2 CO 3 was a superior water gas shift reaction catalyst to NaAlO 2 , or a combination of CS 2 and Fe or Mo catalysts. The amount of vitroplast showing vacuoles and cenospheric morphology in the residues was inversely related to the CO conversion, indicating that the mechanism of vitroplast dissolution is linked to the availability of active CO intermediates (e.g. formate ion, HCOO − ). A CO-steam mixture was more effective than syngas or pure H 2 and N 2 in increasing Black Thunder coal conversion, and resulted in greater morphological changes to the coal particles. In contrast, for Illinois No. 6 coal pure H 2 had a greater effect on coal solubilization and overall conversion than pure CO at the same temperature; this was attributed to the absence of carboxylates to react with the formate ions. Higher mesophase and coke contents were detected in some bench unit runs on Black Thunder coal that were operated in counterflow mode. Higher severity, poorer mixing, longer residence time and a reduction in pressure by almost 3.5 MPa are believed to be responsible for the retrogressive reactions forming mesospheres in these cases.

The author comments on the paper by J. Ma et al. (see ibid., vol.17, p.881-5, 2002), pointing out the practical aspects to be considered for actual conditions in the field.