•Paraffin/metal foam composite PCMs were prepared with vacuum assistance.•The impregnation ratios showed impregnation with vacuum assistance was effective.•The thermal conductivities of the composite ...PCMs were significantly enhanced.•Porous metal foam induced slight shift of the phase change temperatures of PCMs.
The utilization of paraffin in the latent thermal energy storage (LTES) system for solar energy storage is hampered by its low thermal conductivity. Paraffin/nickel foam and paraffin/copper foam composite phase change materials (PCMs) were prepared using a vacuum impregnation method in the present study. The impregnation ratios which reflect the actual mass fraction of pure paraffin impregnated were studied comparatively for the impregnations with and without vacuum assistance. The surface porosity was obtained by employing the image processing approach. The thermal conductivities of the composite PCMs were measured by the transient plane heat source technique (TPS) as well as the steady state method, and the thermal behaviors were analyzed with a differential scanning calorimeter (DSC). It is found that the surface porosity obtained from image analysis was in the range of 90–94%, whereas the bulk porosity predicted by the mass fraction was about 97%. Compared with pure paraffin, the thermal conductivities of the composite PCMs were drastically enhanced, e.g., the thermal conductivity of the paraffin/nickel foam composite was nearly three times larger than that of pure paraffin. The presence of porous metal foam made the phase change temperatures shift slightly, e.g., the deviations of the peak melting temperatures of the paraffin/nickel foam composite and paraffin/copper foam composite with the pore size of 25PPI from those of pure paraffin were 0.55°C and 0.40°C, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study presents indoor and field validation results for two versions of the “DUSST” optical soiling sensor, intended to be a low-cost and low-maintenance device for measuring photovoltaic soiling ...losses. Indoor testing covers irradiance calibration and temperature dependencies, which are necessary to achieve high accuracy, low uncertainty field measurements. Field testing includes an array of different environments including Saudi Arabia, California, Utah, and Colorado. DUSST versions include a configuration with a 530-nm light emitting diode (LED) (discussed in previous work) and a unit with seven white LEDs and a polycarbonate collimating optic. The new design increases light intensity fivefold and demonstrates a single linear calibration coefficient is effective to measure soiling losses as high as 75%. Field data from Utah and California demonstrate that daily soiling loss measurements and soiling rate calculations closely match both reference cell and full-size module measurements of soiling losses and soiling rates. Corrective methods employed on the Utah DUSST sensor suggest that it is possible to achieve measurement errors as low as ±0.1% at two standard deviations. Field data from both Colorado and Saudi Arabia demonstrate that LED lens soiling can occur and that further design optimizations are needed. The lesson learned from all the field deployment locations suggests directions for future design improvements.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•A new curcumin derivative with excellent chemical, physical and optical properties was synthesized.•The obtained crystals were characterized and analyzed using NMR, FT-RAMAN, FTIR, UV–VIS, PL ...spectra and Fluorescence lifetime analysis.•The compound was screened for third order nonlinear optical studies (Z Scan) and TG/DTA thermograms.•Derived results were highly promising and the synthesized compound can be used as lead material for industrial and optoelectronic device applications.
A novel Curcumin derivative 1-(4-chlorobenzoyl)-3,5-bis((E)-3,4-dimethoxybenzylidene)piperidin-4-one (CDMBP) has been synthesized by Claisen-Schmidt condensation and Schotten-Baumann reaction methods. CDMBP single crystal was grown from acetone by slow evaporation method at ambient temperature. The crystal structure of the compound was derived by Single Crystal X-ray Diffraction studies (SCXRD). The title compound CDMBP was crystallized in a triclinic crystal system with a P ͞1 space group. NMR spectral analysis reveals the different types of carbon and proton in the molecular structure of the title compound. The modes of vibrations of different chemical groups were identified using FT-Raman and Fourier Transform Infrared spectral analysis (FTIR). Utilizing the UV–Vis spectrum, the cutoff wavelength and linear optical constants such as the band gap, extinction coefficient, and refractive index were calculated. The Photoluminescence spectrum (PL) has been studied and it shows a high-intensity peak at 504 nm and belongs to the green emission radiation region. Fluorescence profiling of the compound was done to get an outline of the emission features of the excited states with the emission decay mechanisms using Lifetime measurements. The third-order nonlinear optical property (NLO) of CDMBP was investigated in detail using a Z-scan technique with a He–Ne laser at 632.8 nm as a laser source. The nonlinear optical susceptibility (χ3), absorption coefficient (β), and refractive index (n) were calculated using transmittance data. The thermal stability of the grown crystal was investigated from the Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA).
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•GO nanosheets were fully exfoliated and decorated with CoFe2O4 nanoparticles.•Gallic acid as a green agent was used to prepare the highly stable ferrofluids.•CoFe2O4/rGO nanohybrid ...is a promising material for the coolant applications.•Enhancement in thermal conductivity with rising temperature and concentration.•The Nusselt number enhancements of 27.8 % were obtained for 0.9 wt% at Re = 1713.
The application of spinel ferrite decorated graphene hybrids in heat transfer has been limited mostly due to their poor stability in water. This study reports a straightforward strategy to synthesis a cobalt ferrite/reduced graphene oxide (CoFe2O4/rGO) nanocomposite with high water dispersibility characteristics through the treatment of synthesized hybrid material with Gallic acid (GA) as a green agent at room temperature. A π-π interaction between graphene and the aromatic ring of GA results in a suspension with high stability. The structure of the nanocomposite was investigated in detail by FTIR, XRD, TGA, VSM, Raman spectroscopy, FESEM, and TEM. Also, UV–vis spectroscopy is used to examine the stability of the stability of the CoFe2O4/rGO in the base fluid. The highly stable aqueous nanofluids were subsequently prepared from the products. Thermo-physical analyses of nanofluids revealed that the thermal conductivity ratio of ferrofluid prepared by the obtained CoFe2O4/rGO with 0.9 wt.% load of nanoparticles at 60 °C is rose to 1.46. Besides, the convective heat transfer in laminar flow regime conditions which passes a circular tube under uniform heat flux was examined. The nanofluid with the highest load of nanoparticles (0.9 wt.%) shown the maximum enhancement in Nusselt number of 27.8 % at Reynolds number of 1713.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Enzymatic treatments produced a homogeneous cellulose surface for subsequent activation.•Removal of thermally labile pectic and hemicellulosic content resulted in improved thermal stability.•The ...ultra structure of flax fibres (versus hemp) renders it more susceptible to enzymatic degradation.
Natural fibres are a potential replacement for glass fibre in composite materials. Inherent advantages such as low density, biodegradability and comparable specific mechanical properties (relative to glass fibre composites) make natural fibres an attractive option. However, limitations such as poor thermal stability, moisture absorption and poor compatibility with polymeric matrices are challenges that need to be resolved. The primary objective of this research was to study the effect of five enzymatic systems on the surface chemical, morphological and thermal properties of natural fibres. Flax and hemp fibres were treated with hemicellulases, pectinases and oxidoreductase. Surface and thermal properties were measured using X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and force tensiometry. Each treatment rendered the surface topography of both fibres free of contaminants and exposed the individual fibre bundles. Treatment with hemicellulase and pectinase improved the thermal properties for both fibres. XPS measurements confirmed reduction of the hemicellulosic content of both fibres for xylanase and pectinases (polygalacturonase and pectinmethylesterase). Removal of amorphous hemicellulosic material from the fibre surface and consequent exposure of the crystalline cellulose network resulted in a lower contact angle for all the treated samples. This work demonstrated that enzymes offer an inexpensive and environmentally attractive option to improve the surfaces of natural fibres for composite applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A state diagram is a helpful tool to visualize the stability limits of a material subjected to different conditions. The equilibrium state diagram for pure anhydrous beta lactose (Lβ) stability is ...reported in this work. For this purpose, adsorption isotherms were built at three storage temperatures (15, 25 and 35 °C) in a wide range of water activity (0.07–0.972). The powders obtained were characterized by Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and modulated differential scanning calorimetry (MDSC). The results showed high stability of Lβ at the storage temperatures, indicating an adsorption similar to the monolayer content. Conversely, the mutarotation process was triggered by the adsorption of water beyond the monolayer content. Under these conditions, the presence of alpha lactose (Lα) was observed. Furthermore, the glass transition temperature (Tg) of the Lβ was determined in the range of −15 to −1.4 °C at the storage conditions. The present work contributes to the study of the stability of Lβ to establish its technological application as a carrier agent or in the microencapsulation of active ingredients.
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•Pure beta-lactose (Lβ) stability is altered in a storage environment at aw > 0.742•SEM observed a mixture of lactose anomers (Lβ and Lα) particles at high aw.•MDSC identified the mutarotation of Lβ toward Lα.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The design and the features of the soiling optical detector DUSST are presented.•The thermal characterization of the components of the detector is performed.•A factor of 0.052 mA/°C can correct the ...effect of the LED temperature.•A validation of the performance of DUSST is made using masks and natural soiling.•DUSST can estimate the transmittance losses with high accuracy (R2 > 0.94).
Nowadays, photovoltaic (PV) technology has reached a high level of maturity in terms of module efficiency and cost competitiveness in comparison with other energy technologies. As PV has achieved high levels of deployment, the development of devices that can help to reduce PV operation and maintenance costs has become a priority. Soiling can be cause of significant losses in certain PV plants and its detection has become essential to ensure a correct mitigation. For this reason, accurate and low-cost monitoring devices are needed. While soiling stations have been traditionally employed to measure the impact of soiling, their high cost and maintenance have led to the development of innovative low-cost optical sensors, such as the device presented in this work and named “DUSST” (Detector Unit for Soiling Spectral Transmittance). The thermal characterization of DUSST’s components and the methodology used to predict soiling transmittance losses are presented in this study. The results show that the losses can be predicted with an error lower than 1.4%. The method has been verified with an experimental campaign with naturally soiled coupons exposed outdoors in Jaén, Spain.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Temperature based measurement of incident IR intensity in free convection.•Two dry and one wet surface yield agreeably (∼10 % deviation) similar results.•IR camera distinguishes thermal boundary ...layer and a hot plume.•Low response time finds real time application to areas like in building management.
The study aims to characterize external IR heating sources, operating in free convection atmosphere, qualitatively and quantitatively for various applications. It employs non-invasive IR thermography to measure steady-state irradiations from a ceramic IR heater at variable voltages (60–150 V) using the surface energy budget (SEB) method which relies on only two measured parameters (surface and ambient temperature). The free convection heat transfer from the plate is demarcated between the thermal boundary layer (TBL) and buoyant plume-dominated region by temperature histogram tool. Nearly 78 ± 5 % of the plate area is occupied by the hot plume(s) in the studied voltage range. Estimated irradiation agrees fairly well with one another (within ± 10 %). Additionally, the time response of the plate was measured to be ∼ 120 s. This fast response can be made even faster, by reducing the thermal mass, eventually leading to low-cost IR sensors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The electrochemical-thermal performance of large-format batteries are investigated.•A new pseudo-4D battery model is established to capture battery thermal behavior.•A scalable and efficient ...dew-point evaporative cooling technology is developed.•Battery thermal management with dew-point evaporative cooler is evaluated.•Battery temperature is lowered by 3.0–13.6 °C with dew-point evaporative cooling.
Thermal management is critical to safety, stability, and durability of battery energy storage systems. Existing passive and active air cooling are not competent when the cooling performance, energy efficiency and cost of the thermal management system are drawing concurrent concerns. Here we propose dew-point evaporative cooling as a novel active air-cooling approach for large battery systems. Its capability of cooling the air towards its dew-point temperature with simple working principle and great electrical efficiency offers an ideal solution. Therefore, a scalable dew-point evaporative cooling technology was developed, and a large-scale cooler was constructed which could deliver 2.9–6.7 kW cooling capacity with 8.9–28.9 coefficient of performance (COP). To demonstrate its performance for battery thermal management, we took a 20 Ah lithium iron phosphate (LFP) prismatic pouch cells for a case study whose complex dynamic electrochemical and thermal responses were investigated via lock-in thermography experiments and electrochemical-thermal modeling. The potential of dew-point evaporative cooling for battery cooling was explored via the multi-physics coupling of battery and cooler models. This study elucidates that dew-point evaporative cooling can efficiently cool a battery by 3.0–13.6 °C lower than the cases with only forced convection, and control the battery operating temperature within an ideal operating range of 20–40 °C.
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GEOZS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Thermal transient measurement (TTM) utilizes temperature-sensitive electrical parameters (TSEP) to analyze the thermal structure of power semiconductor devices. However, the measured physical ...quantities are essentially electrical parameters rather than direct temperatures. Determining whether these measurements reflect correct temperature or thermal structure of the tested device remains unclear. This limitation becomes more pronounced with emerging silicon carbide (SiC) devices. To address this issue, this paper provides a figures-of-merit (FOM) study for the TTM applied to SiC MOSFETs. The FOM comprises three static and two dynamic factors. The proposed FOM is employed to evaluate ten plausible testing circuits of a SiC MOSFET, where four of them are identified as providing reproducible thermal structures. A high-fidelity finite-volume method simulation is also used as a benchmark to validate the result. This study highlights some important facts, notably that successful TSEP calibration does not guarantee reproducible TTM, and compliance with current standards may also yield incorrect results. These insights hold significant implications for the field of SiC MOSFETs and the future development of the TTM method.
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