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This paper examines a Distributed Propulsion (DP) concept and involves CFD verification, optimisation and evaluation. The first part of the study validates the employed simulation methods using experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the Folding Conformal High Lift Propeller (HLP) project, for isolated and installed cases under various conditions. Additionally, validation for rotor-rotor interactions was also conducted using the GARTEUR Action Group 26 measurements. The second part of the paper examines installed propeller configurations to identify performance differences based on their position relative to a lifting wing. The results indicate that distributed propellers with small radii interfere more with the wing, than tip-mounted, large propellers. Additionally, propeller and wing performance vary with respect to the propeller installation location. The propeller in tractor configuration showed higher efficiency than the over-the-wing (OTW) configuration by about 7%. However, results from this work showed a 2% improvement in the propeller efficiency when the OTW configuration had a pylon installed. This study also found that optimising the propeller from a tractor to OTW configuration, significantly improved the wing performance. At take-off and landing, the Lift-to-Drag (L/D) ratio of the OTW configuration almost quadrupled, and the overall propulsive efficiency increased by about 5%. The simulations showed that the OTW configuration with different numbers of propellers, outperformed the tractor configurations with the same number of propellers. Furthermore, up to 26% improvement in lift and overall propulsive efficiency was found by introducing the DP system in the OTW configuration. [ABSTRACT FROM AUTHOR]

Abstract This paper concerns the effects of MgO particle size and density on microstructure development of MgO based composite phase change materials (CPCMs) made of a eutectic carbonate salt of NaLiCO 3 (phase change material, PCM), MgO (ceramic skeleton material, CSM) and graphite flakes (thermal conductivity enhancement material, TCEM). Such composite has a melting point around 500 °C and offers a great potential for medium and high temperature thermal energy storage applications including peak shaving of power grids, effective use of curtailed wind energy and solar thermal power generation. Two CPCMs, a light MgO based CPCM and a heavy MgO based CPCM were prepared and investigated. Scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) was used to measure salt distribution and redistribution within the composite structure during melting-solidification thermal cycles. The results showed that smaller MgO particles yielded smaller internal pores and more rigid/compact composites, leading to better encapsulation of PCM and structural stability through thermal cycles. Concerning the effect of MgO density, the higher surface energy of light MgO induced better particle rearrangement, coarsening and composite densification compared to heavy MgO. These phenomena translated into excellent rigidity, strength and PCM encapsulation. The observation results also showed that the increasing size-similarity between MgO, PCM and graphite leaded to better distribution of components before and after sintering. Upon heating 5 µm sized MgO composites, strong capillary action due to narrow pores, surface energy and MgO distribution, caused excellent PCM migration and graphite distribution. The opposite was observed in large MgO-size composites, which developed large internal voids after initial sintering. [ABSTRACT FROM AUTHOR]

Abstract Cold energy storage has attracted considerable attention due to the increasing cooling demand, which provides an isothermal environment for users. Salt-water solutions are suggested as phase change materials (PCMs) for sub-zero applications because they have favourable thermoproperties. Binary salt based PCMs have been widely studied. However, choices are limited for PCMs with the phase change temperature between -15 and -30 °C for cold chains. In this paper, three ternary salt-water solutions (NaCl-NaNO 3 -H 2 O, NaCl-Na 2 SO 4 -H 2 O and NaCl-KCl-H 2 O) are formulated, characterised and compared, where NaCl solution is selected as the base material. The experimental results show that ternary salt-water solutions have lower phase change temperatures than the NaCl solution. NaCl-Na 2 SO 4 solution has the highest phase change temperature of -21 °C, while NaCl-NaNO 3 solution has the lowest value around -27 °C. The fusion heat of the ternary salt-water solutions depends on the components and salt ratio. NaCl-KCl solution has the highest fusion heat among NaCl solution and ternary PCMs, while NaCl-NaNO 3 solution shows the lowest fusion heat. NaCl-Na 2 SO 4 solution does not have a significant difference with NaCl solution due to the limited solubility. Finally, a new approach is proposed for formulating a set of ternary salt based PCMs, which helps to bridge the gap in this temperature range for cold chain applications. [ABSTRACT FROM AUTHOR]

Chloride molten salts are promising candidates for high temperature thermal storage applications, owing to their energy storage density and thermal stability. Nevertheless, the main disadvantage of them is their corrosive behaviour with metal containers, which narrows down the range of applications. Encapsulation is considered a favourable method to prevent the corrosion. In this work, composite thermal storage materials consist of a phase change material (PCM) and a encapsulation material are studied, where the PCM is a mixture of sodium and potassium eutectic salts and the encapsulation material is diatomite. The composite materials which consist of PCMs & encapsulation materials are fabricated using a micro encapsulation method which is a combination of mixing and sintering. After applying the aforementioned method, it is observed that the PCMs are distributed homogeneously in the composite materials. With the help of XRD, it is found that the compounds stay unchanged after the encapsulation process, which indicates that the materials are compatible to each other. In this study, the composite material containing 70 wt% PCM exhibits the most favourable thermal energy storage properties, stability and capsule integrity as it is shown that the latent heat of the aforementioned composite material is observed 179.3 J/g and no significant decline or salt leakage is found after hundreds of heating-cooling cycles. [ABSTRACT FROM AUTHOR]

This work is concerned about form-stable phase change materials (FPCM) for thermal energy storage consisting of Erythritol as the phase change material (PCM) and Vermiculite as a supporting material (SM). The materials were fabricated using a method derived from the pharmaceutical and ceramics industry, involving milling, mixing/granulation, shaping, drying and sintering. It is found that the PCM can distribute evenly in SM and composites present an excellent chemical compatibility. The materials containing 70% PCM give an optimal formulation in terms of energy density, extent of PCM leakage during sintering and thermophysical properties. FT-IR analyses suggested an excellent chemical compatibility between vermiculite and the Vermiculite. Scanning electron microscope (SEM) analyses demonstrated an even distribution of the PCM within the diatomite structure. Differential scanning calorimetry (DSC) measurements showed that melting temperature of the material was approximately 118.6 °C with a latent heat of 216.7kJ/kg, and the effective thermal storage density was 605.56 kJ/kg (0~200 °C). The latent heat of the aforementioned composite material decreased only 3.41% and no significant decline was observed after 300 times of heating-cooling cycles. [ABSTRACT FROM AUTHOR]

We performed Molecular Dynamics (MD) simulations to study the mechanism of the specific heat enhancement in nitrate salt based nanofluids. 26.6% enhancement of specific heat capacity was observed by introducing nanoparticles into the salt system. Our simulations showed that the nanoparticles caused a layering effect in the adjacent region of the liquid molten salt. Hence we attribute the enhancement in the specific heat capacity of molten salts with the addition of nanoparticles to a previously undiscovered structural arrangement of salt atoms around the nanoparticles. [ABSTRACT FROM AUTHOR]

A fatty acid based phase change dispersion (PCD) for efficient high voltage electrical devices cooling has been developed and investigated in this paper. Experiments were firstly conducted to characterise the PCD thermophysical properties and to measure the bulk fluid and inner wall temperature of PCD flowing in a circular pipe by a self-designed rig. A 3D modelling based on the Euler-Euler model and homogenous single-phase model were then performed and validated through experiments, and further employed to evaluate the effects of particle size, concentration and operating conditions on flow characteristics, pressure drop, heat transfer and energy transport performance of the PCD. The results showed that both the particle size and concentration presented significant influences on heat transfer between the two phases, and average friction factor as well as heat transfer coefficient of the PCD. A higher averaged Nusselt number and a larger pressure drop were observed when the PCM particle diameter decreased to 7 μm. For the investigated conditions in this work, an optimal set of cooling performance for the developed fatty acid PCD was proposed and a PCM particle size of 7 μm under a flow velocity of 4 m/s and a concentration of 35% was recommended for industrial cooling applications. • Dielectric phase change dispersion designed for HVDC converter cooling developed. • 3D modelling based on Euler-Euler and homogenous models performed and compared. • Improved pressure drop and heat transfer correlations of PCD proposed. • The importance of averaging wall temperature along perimeter addressed. • Optimal PCD cooling condition based on overall performance evaluation given. [ABSTRACT FROM AUTHOR]

In cold climates, heating the cabin of an electric vehicle (EV) consumes a large portion of battery stored energy. The use of battery as an energy source for heating significantly reduces driving range and battery life. Thermal energy storage (TES) provides a potential solution to the problem. Such a technology is also known as thermal batteries or heat batteries, which can store heat at a high energy density. Thermal energy storage is generally much cheaper with a longer cycle life than electrochemical batteries. Therefore, using thermal batteries with high energy storage density to provide heat for EVs in cold environments can reduce vehicle costs, increase driving range, and prolong battery life. This is especially so for large EVs with a high heat demand such as electric buses. This article examines the influence of temperature on EVs and heat demands of different EVs in low temperature environments. The heat storage concepts, devices and systems proposed and developed for EVs are then reviewed, and potential TES materials for different types of TES devices are discussed. Different TES technologies for EVs are compared and analysed. Finally, the advantages and disadvantages and applicable scenarios of different thermal batteries are discussed, and research gaps are identified for further research and development. • Different TES technologies for EVs are reviewed, compared and analysed. • Potential TES materials for different TES devices are reviewed and screened. • High-temperature metal phase change TES device has the highest energy density. • Thermal insulation is a limiting factor of high-temperature TES devices for EVs. • The application of thermal energy storage in electric buses has great potential. [ABSTRACT FROM AUTHOR]

• Properties of a phase change dispersion are experimentally determined • Phase change material in the dispersion was two fatty acid esters • Supercooling was reduced by 10 K using nucleating agents • Apparent specific heat of 8.5 kJ kg−1 K−1 over the temperature range 47.5–50.0 °C. Phase change dispersions have recently gained interest in isothermal cooling applications. So far, almost all of the investigated phase change dispersions consist of paraffins as the phase change materials. This paper presents a phase change dispersion with two fatty-acid esters as the phase change material, Crodatherm-53/Crodatherm-47 (50:50). The dispersion has a melting temperature of 50 °C and is foreseen in high-voltage direct current component cooling. The phase change dispersion was stabilised with emulsifiers to prevent phase separation and nucleation agents were added to supress supercooling. From thermal history calculations, the supercooling of the dispersion was reduced by 10 K with the addition of the nucleation agent. A monomodal particle size distribution was achieved. The viscosity of the dispersion at 20 wt.% and shear rate of 100 1s−1 was found to be 4.9 mPa۰s at 25 °C, and 2.0 mPa۰s at 60 °C.The viscosity at different temperatures, mass fractions and shear rates was also assessed. From DSC analysis, an apparent specific heat capacity of 8.5 kJ kg−1 K−1 was measured for the phase change dispersion. This value is double the apparent specific heat capacity of water within the desired melting range (47.5–50.0 °C). Thermal conductivity measurements showed in the emulsion form, at 25 °C the phase change dispersion had a thermal conductivity of 0.529 W m−1 K−1 and in suspension form at 60 °C was 0.561 W m−1 K−1. Both thermal conductivity values were lower than water at each temperature. [ABSTRACT FROM AUTHOR]

• Compatibility of Solar Salt and four metal alloys for CSP plants is studied. • A static corrosion test at 500 °C and in air is performed. • The descaled and gravimetrical corrosion rate methods are compared and analysed. • An economical study assessing cost, mechanical properties and corrosion rate is done. • 304H and 316L have the best cost-corrosion rate-mechanical properties performance. One of the main limitations concerning the implementation of heat transfer fluids in Concentrated Solar Power (CSP) plants, are their compatibility with the construction material. Hence, the study of this interaction over cycles is crucial for a proper material selection and life span forecast. In this work, the chemical compatibility of four commonly used metals in CSP plants; low carbon steel-A1045, stainless steel-304H and 316L, and nickel alloy-Inconel 600, with one of the most promising HTFs, Solar Salt, was evaluated. Two different methodologies (gravimetrical and descaled method) were compared and used to characterise the corrosion behaviour depending on the metal coupons analysed, concluding that the best method for most of the metals is the descaled one. The corrosion oxides were also characterized using a combination of different techniques: SEM, EDX, and XRD. Inconel 600 showed the best corrosion resistance among the metals evaluated. However, a further brief economical study concludes that a compromise between the overall metal loss cost per year and the price of the construction material over the lifetime of the plant must be found. The two stainless steels (304H and 316L) were identified as the best performing according to metal loss vs. material price and mechanical properties vs. corrosion rate. [ABSTRACT FROM AUTHOR]

Highlights • New selection methodology for molten salt based nanofluids for CSP systems. • Nanoparticles in molten salt nitrates can increase energy density but also viscosity. • Specific heat capacity enhancement and viscosity increment is base fluid dependent. • Conflictive effects understanding assesses the suitable nanoparticle concentration. • Selection parameter shows if energy density enhancement overcomes pumping power. Abstract A high-performance heat transfer fluid (HTF) plays a crucial role in the overall performance and efficiency of concentrating solar power (CSP) systems for utilizing solar energy. Molten salt-based nanofluids, which may offer a promising solution to help reduce the size and cost of CSP systems, have attracted increasing attention. However, there is still no comprehensive assessment strategy that considers the conflictive effects of adding nanoparticles in HTFs, such as the compromise between energy storage capacity increase and pumping cost increase. In this work, a methodology for nanofluids screening and selection is proposed and a novel parameter (R) is determined to assess the conflictive effect. The parameter (R) considers the ratio between the relative pumping power and the relative energy stored of the nanofluid compared to its base fluid. Three promising eutectics nitrate based nanofluids (NaNO 3 –KNO 3 , LiNO 3 –NaNO 3 –KNO 3 , LiNO 3 –NaNO 3 –KNO 3 –Ca(NO 3) 2) doped with 0.5 wt.% and 1 wt.% silica nanoparticles were selected and evaluated by the proposed methodology. As a result, adding nanoparticles into binary salts always present a negative effect (R = 1.03–1.22) when considering the ratio between the relative pumping cost and the relative energy stored. For ternary salt, adding 1 wt.% silica nanoparticles would be more preferable with a decrease of the parameter (R = 0.89–0.97, R < 1). In terms of quaternary, adding nanoparticles into quaternary does not change the parameter significantly (R = 0.96–1.04). [ABSTRACT FROM AUTHOR]

Recently, corrosion of nanoparticles molten salt-based nanofluids studies have emerged as Concentrating Solar Power plants provide a low carbon alternative to produce electricity. Enhancing the heat capacity and thermal conductivity of molten salts by using inorganic nanoparticles has been targeted as a strategy to decrease the overall investment cost of CSP systems. However, there is scarce and insufficient information about their effect on the corrosion behaviour of nanofluids, whether the nanoparticle content increases it or have no significant effect. The scatter data found show no clear agreement and the measurements are done under different conditions (temperature, time, impurities, nanoparticle's chemical nature and concentration, metal and alloy composition, testing method). In this context, the authors evaluated the effect of SiO 2 nanoparticles concentration in an industrial-grade Solar Salt in contact with four different alloys; AISI 1045, 304H, 316L and Inconel 600 by isothermal tests, 500 °C up to 2160 h. The effect of nanoparticles, 0.5% and 1% wt., was evaluated in comparison with Solar Salt industrial grade. The corrosion rate of the samples decreased in the following order AISI 1045 > 304H > 316L > Inconel 600 and nanoparticles increased in general and to a different extent the corrosion rate of the alloys. The one that experiences the highest nanoparticle effect is stainless steel 304H, followed by AISI 1045 and Inconel. For 316L, no significant differences can be seen. The applicability assessment carried out has shown that molten salt nitrate-based nanofluids can be used with Inconel 600, 304H and 316L in long-term service high-temperature applications such as CSP. • SiO 2 nanoparticles affect the corrosion behaviour of molten salt nitrates. • Nanoparticles increase the corrosion rate of the studied alloys. • The increase of nanoparticles from 0.5 to 1 % wt. does not affect significantly corrosion. • 304H, 316L and Inconel 600 can be used for long-term service with 1 % wt. SiO 2 Solar Salt. [ABSTRACT FROM AUTHOR]

This work explores the use of sodium sulfate and diatomite to formulate composite materials for high temperature thermal energy storage applications. Sodium sulfate in the composite functions as a phase change material (PCM) and diatomite as a structural skeleton for shape stabilization. It is found that sodium sulfate and diatomite have an excellent chemical compatibility with the PCM melting temperature at around 880 °C. It is shown that the composite containing 45% diatomite gives an optimal formulation in terms of energy density, salt leakage and mechanical strength. The results also suggest that the composite with the optimal formulation has an application window of 890–980 °C. Failures occur to the composite materials at temperatures above 1000 °C. [ABSTRACT FROM AUTHOR]

• A 35kWh battery pack with a novel hybrid thermal management system is prototyped. • Phase change material is innovatively integrated with cooling plate. • The battery thermal management at the battery pack level and module level is studied. • Both cooling and thermal insulation performances are investigated. • Desirable control strategies are obtained for battery pack under 0.5C to 1.5C discharge rates. Controlling the temperature of a battery pack within an optimal range and ensuring uniform temperature distribution are the key to improving battery life. With the elevating energy density of batteries, more efficient and energy-saving thermal management system is urgently required for improving electric vehicle (EV) performance in terms of safety and long-term durability. In this work, a novel hybrid thermal management system towards a high-voltage battery pack for EVs is developed. Both passive and active components are integrated into the cooling plate to provide a synergistic function. A 35kWh battery pack incorporated with electrical, mechanical and thermal management components was designed, manufactured and integrated. As the core hardware, a pack-level cooling plate set was innovatively designed by integrating with phase change material (PCM). The results show that the combined passive and active cooling strategy ensured a desirable working temperature below 40˚C and a uniform heat distribution across the entire pack at discharging rates ranging from 0.5C to 1.5C under customized control strategies. Moreover, the cycling performance of air cooling and hybrid cooling, as well as the thermal insulation performance at both battery module level and pack level are compared, demonstrating the superior thermal management capability of the hybrid solution. [ABSTRACT FROM AUTHOR]