Search

Harvesting energy from nature, such as mechanical energy, thermal energy, and biomass energy, has become an effective way to supply power for self-driven sensing and Internet of Things (IoT) applications. Among that, solar-driven thermoelectric (STE) device takes advantage of all-solid-state energy conversion, such as no noise, easy access, and free of wear, exhibiting great potential. Here, we propose a solar-driven thermoelectric device for harvesting solar energy, based on Micro Electromechanical System (MEMS) technology. Specifically, the optimization of solar absorptances of structural layers significantly improved the photo-thermo-electric conversion performance. Furthermore, the electrical output strongly depends on temperature difference dominated by the absorptance difference. Therefore, the reported device can be free of traditional heat sink, which greatly simplifies its structure and expands the working conditions, especially in microdevices. Particularly, a continuous output voltage of 0.34 V/cm2 is achieved with concentrated solar radiation, demonstrating its potential under no heat sink conditions. Besides, a fast response (4.2 ms under 660 nm laser) is achieved benefitting from the micron-size solar absorber, showing its significance in sensing applications. Finally, the proposed STE device is utilized to harvest outdoor solar energy, displaying promising potential in solar energy harvesting devices and providing an insightful perspective for thermoelectric applications. [Display omitted] • The enhancement of absorptance difference on the STE device output is verified. • MEMS-based technology is utilized to fabricate STE device with in-situ deposited photothermal top connection. • The heat-sink-free character of the STE device are demonstrated. [ABSTRACT FROM AUTHOR]

• The coking of supercritical pressure n-decane and its effect on heat transfer are investigated. • The influence of coking on heat transfer can be divided into three regions. • The coking precursor content and running time are key factors that influence the coke characteristics. • The fluid temperature and coking precursor content are key factors that influence the heat transfer. • The value of c C 2 H 4 + c C 3 H 6 e - T r e f T f is recommended as an indicator to evaluate the impact of coking on heat transfer in the pyrolytic coking region.. Coking of endothermic hydrocarbon fuels can affect heat transfer performance and block the cooling channels, threatening the safe operation of regenerative cooling system for hypersonic aircraft. In this study, an experimental investigation of the influence of coking of supercritical-pressure n-decane on heat transfer was presented. The mechanism by which coking affects heat transfer was analyzed by scanning electron microscopy (SEM), Raman spectroscopy, and other characterization methods. The influence of coke on heat transfer can be divided into three regions. In oxidative coking region, coke is generated primarily through catalytic reactions, and coking leads to a slight heat transfer deterioration. In the lower conversion region, filamentous coke is generated, which improves porosity and surface roughness, and leads to heat transfer enhancement. In the higher conversion region, the increase of coking rate leads to an increase in the thickness of the coke and uniformity of coke distribution. The thermal resistance effect exceeds that of rough surfaces, leading to heat transfer deterioration. From the heat transfer and coke characterization results, an indicator related with temperature and coking precursor content was proposed for evaluating the impact of pyrolytic coking on heat transfer. This study can help design the regenerative cooling system more accurately. [ABSTRACT FROM AUTHOR]

Family selection is an important method in fish aquaculture because growth is the most important economic trait. Fast-and slow-growing families of tiger puffer fish (Takifugu rubripes) have been established through family selection. The development of teleost fish is primarily controlled by the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis that includes the hypothalamus-pituitary-liver. In this study, the molecular mechanisms underlying T. rubripes growth were analyzed by comparing transcriptomes from fast- and slow-growing families. The expressions of 214 lncRNAs were upregulated, and those of 226 were downregulated in the brain tissues of the fast-growing T. rubripes family compared to those of the slow-growing family. Differentially expressed lncRNAs centrally regulate mitogen-activated protein kinase (MAPK) and forkhead box O (FoxO) signaling pathways. Based on the results of lncRNA-gene network construction, we found that lncRNA3133.13, lncRNA23169.1, lncRNA23145.1, and lncRNA23141.3 regulated all four genes (igf1 , mdm2 , flt3 , and cwf19l1). In addition, lncRNA7184.10 may be a negative regulator of rasgrp2 and a positive regulator of gadd45ga , foxo3b , and dusp5. These target genes are associated with the growth and development of organisms through the PI3K/AKT and MAPK/ERK pathways. Overall, transcriptomic analyses of fast- and slow-growing families of T. rubripes provided insights into the molecular mechanisms of teleost fish growth rates. Further, these analyses provide evidence for key genes related to growth regulation and the lncRNA expression regulatory network that will provide a framework for improving puffer fish germplasm resources. [Display omitted] • Total of 7372 lncRNAs were obtained in T. rubripes families with distinct growth rates. • Enrichment analysis revealed that MAPK and FoxO signaling pathway were highlighted. • The lncRNA7184.10 may regulate the growth of T. rubripes by PI3K - AKT related-genes. • The lncRNAs may regulate the growth of T. rubripes by targeting igf1 , mdm2 and cwf19l1. [ABSTRACT FROM AUTHOR]

• Novel method to develop Nu and Sh correlations of SCP fuel considers pyrolysis reaction. • Internal heat and mass sources simplified as pseudo-wall fluxes based on DGR model. • Thermophysical property variation due to pipe wall-bulk flow ε differences considered. • Max relative deviation to Nu e less than 15% for Nu Π- ρ after considering coking empirically. The convective heat and mass transfer characteristics of the supercritical pressure (SCP) fuel in the regenerative cooling channel of hypersonic vehicles are significantly affected by pyrolysis reactions. In this study, we proposed a novel method to develop the Nusselt number (Nu) and Sherwood number (Sh) correlation of SCP fuel that considers the influence of pyrolysis reaction by simplifying internal heat and mass sources as pseudo-wall fluxes based on the differential global reaction (DGR) model of pyrolysis. The convective heat and mass transfer and pyrolysis characteristics of n-decane were investigated experimentally and numerically in a vertical downward-flow heated tube at pressures of 3-7 MPa. Theoretical analysis of the experimental conditions was conducted sequentially according to the partial differential equations (PDEs) of species continuity and energy, in which the internal source terms of heat and mass due to pyrolysis reactions were simplified and predicted using the DGR model of n-decane pyrolysis. A semi-empirical Sh correlation for predicting the radial distribution of fuel conversion was proposed associated with computational fluid dynamics (CFD) data by equivalently simplifying the internal mass source as pseudo-wall mass flux. A Nu correlation for convective heat transfer was proposed using the same methodology considering the influences of pyrolysis. The correction terms consider pyrolysis endothermicity and thermophysical property variation due to the conversion differences between the pipe wall and the bulk flow. Finally, the Nu correlation was compared to the experimental data, and the influence of heat transfer deterioration (HTD) due to pyrolysis coking was also analyzed quantitatively and empirically. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel online analysis method for pyrolysis products with significant volatility differences. • Sampling based on instant cooling–flashing to avoid gas–liquid separation. • The accuracy of measured mass fraction was highly improved, by 40–80% for C 3 –C 4. • The kinetic constants of SCP n-decane pyrolysis were determined and verified. Pyrolysis is widely applied in industrial fields including waste-to-energy conversion and hypersonic-vehicle cooling technology. Traditional offline analysis methods for fluid products based on cooling, depressurization, and separation processes often impart measurement uncertainties. Here, we propose a novel online analysis method for fluid pyrolysis products with significant volatility differences. High-frequency sampling based on instant cooling–flashing was used to avoid gas–liquid separation, where the fluid mixture is directly transported into an online-GC system as a vapor through a preheated vacuum tube. The method reliability was evaluated experimentally. Pyrolysis of supercritical-pressure n-decane (3–7 MPa) in a mini-tubular reactor was analyzed using both the proposed online method and an offline method. The gas yield measured using the offline method is significantly lower than that measured online due to the dissolution and volatilization loss of gaseous products during gas–liquid separation. The mass fraction of C 3 –C 4 products measured using the offline method was 40–80% less than the online results. The maximum deviation in the mass fraction of the main products obtained offline was reduced to 20–25% after dissolution-loss correction. The kinetic constants of n-decane pyrolysis were determined based on product-yield data, and the calculated residence time was experimentally verified using particle image statistics. The proposed model was implemented in a computational fluid dynamics model. The deviation between the predicted conversion and experimental results was below 11%, while the deviations of the predicted mass fraction of typical products was significantly higher based on the offline model than the online model. [ABSTRACT FROM AUTHOR]

• New nonintrusive, in-situ method for the visualization and measurement of MRT. • Consideration of optical distortion caused by drastic changes in the fluid properties. • Two optical arrangements were proposed and compared. • Correcting uneven radial distortion of the tracer particles for NOA. • Accurate measurement of MRT at pyrolysis reaction conditions. This paper proposed a nonintrusive, in-situ experimental method for visualizing and measuring the mean residence time (MRT) of supercritical-pressure pipe flow with/without chemical reactions based on the high-frequency sampling of laser-induced particle images. Normal and oblique optical arrangements (NOA & OOA) for the incident laser were applied to induce particle scattering in the JP-10 pipe flow, using SiO 2 microsphere as tracers. Optical distortion caused by drastic change in fluid properties was analyzed. The relative deviation of the proposed particle image statistics (PIS) method was within ±4% with NOA after considering optical distortion and uneven radial distribution of particles. Although the same level of accuracy was achieved with OOA without the need for correction, the noise in images became significant when the fuel approached pseudo-critical temperature. When there was no influence from pyrolysis, the MRT simulated using 1D subroutine agreed well with measured data. However, the relative deviation increased after pyrolysis. [ABSTRACT FROM AUTHOR]

• Effects of secondary reactions and pressure on pyrolysis of JP-10 are investigated. • The formation of gas products is suppressed by increasing the pressure. • Gas and liquid products are categorized as two and six types, respectively. • A differential global reaction (DGR) model for JP-10 predicts pyrolysis accurately. • An increase in pressure increases residence time and chemical heatsink. Regenerative cooling is widely employed for thermal protection of hypersonic vehicles. Hydrocarbon fuels undergo pyrolysis in regenerative cooling channels at supercritical pressures, which affects the performance of regenerative cooling. Pressure and secondary reactions are the key factors that influence pyrolysis. Pyrolysis experiments of JP-10 (exo-tetrahydrodicyclopentadiene) were performed in an electrically heated vertical tube in the pressure range of 3.5–7 MPa and the conversion range of 0%–45%. The formation of gas products was suppressed by increasing the pressure. The effects of pressure and secondary reactions were significant on the distribution of some of the main products, such as ethylene and 1,3-cyclopentadiene, but not for products such as propylene. A method for categorizing gas and liquid products was proposed. The gas and liquid products of JP-10 could be divided into two and six categories, respectively. Based on the differential global reaction modeling approach, a one-step reaction model for the pyrolysis of JP-10 at supercritical pressures was proposed, in which the stoichiometric coefficients were expressed as binary functions of pressure and fuel conversion to reflect the coupling effects of pressure and secondary reactions. The proposed model was implemented in one-dimensional theoretical model and a computational fluid dynamics model to predict JP-10 pyrolysis coupled with flow and heat transfer. The results demonstrated that the model accurately predicts the effects of both pressure and secondary reactions on pyrolysis. The results also showed that an increase in pressure increases the residence time at a fixed mass flow rate, which promotes fuel conversion and chemical heat sink. [ABSTRACT FROM AUTHOR]

3D printing has revolutionised the design and manufacturing of high-temperature thin/thick-film sensors (TFSs). However, existing printable high-temperature materials face cost-performance trade-offs. This study proposes a silicate and RuO 2 composite for the 3D printing of TFSs. A silicate compound (SiO 2 –Al 2 O 3 –CaO, SAC) was used as a sintering aid to reduce the sintering temperature of RuO 2 , forming a silicate glass phase that enhanced film density and substrate adhesion. The SAC also minimised RuO 2 particle volatilisation at high temperatures, thus enhancing the stability of the SAC/RuO 2 composite. The SAC/RuO 2 TFSs demonstrated exceptional performance, with a positive temperature coefficient (502 ppm/°C) from room temperature to 800 °C, high linearity, and stability (resistance drift rate of 0.1 %/h at 800 °C), extending the application temperature of RuO 2 by nearly 200 °C from the previous application temperature of 600 °C. Therefore, the SAC/RuO2 composite offers a new low-cost and high-performance solution for using 3D printing technology in harsh environmental sensors such as turbine blades. [ABSTRACT FROM AUTHOR]

• Effects of pressure on supercritical pyrolysis of n-decane are investigated. • The formation of liquid products is preferred at higher pressures. • A novel global reaction modelling approach is proposed for hydrocarbon fuels. • Stoichiometric coefficients are expressed as functions of fuel conversion and pressure. • The new model predicts pyrolysis accurately at both low and high pressures. Pressure is one of the key factors in pyrolysis of hydrocarbon fuels at supercritical pressures, which changes the relation between the product distribution and fuel conversion. However, reaction model with both high accuracy and efficiency to predict pressure effects is lacking. A comprehensive experimental investigation of pressure effects on supercritical pyrolysis of n-decane in the pressure range of 3–7 MPa and temperature range of 560–670 °C is presented. The formation of liquid products is preferred at higher pressures. Gas and liquid products of n-decane pyrolysis can be categorized into three and four types, respectively, according to the formation characteristics. Results show that pressure had more profound effects on the formation of most products without C–C double bonds or benzene rings in their molecular structures (i.e., C 3 –C 9 n-paraffins or cycloparaffins). A novel global reaction modeling approach was presented to solve the effects of both pressure and secondary reactions on pyrolysis of hydrocarbon fuels, in which the stoichiometric coefficients of each product are expressed as binary functions of fuel conversion and pressure. The proposed model was implemented in a computational fluid dynamics (CFD) simulation to predict the n-decane pyrolysis coupled with flow and heat transfer. The results show that the model predicts n-decane pyrolysis more accurately at both low and high pressures. This study can help design regenerative cooling systems with high accuracy and efficiency for engineering applications. [ABSTRACT FROM AUTHOR]