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• The v shape pressure reflects interaction relations among 3 thermodynamic mechanisms. • FFC reflect the intensity and rate of progress of flash at unique start stage. • The factors influencing flash rate and intensity are analyzed. • FFC rises with initial temperature and valve opening degree at unique start stage. • Expanders with larger outlet area or higher working temperature have larger flash intensity. Our experiments showed that a V shape pressure drop appeared at start stage of non-equilibrium flash. V shape pressure drop firstly denoted the generating of superheat degree, which should be the starting force driving the non-equilibrium flash. Then evaporated vapor made up the pressure drop. Finally, a dynamic equilibrium was reached between the flash rate and the outflow rate, and the pressure behaved decreasing gradually. However, few published references focus on this start stage of the non-equilibrium flash. In this paper, experiments of the flash were conducted to investigate the heat and mass characteristics during V shape start stage. Dimensionless flash conversion coefficient (FCC) was proposed to normalize the flash with different initial liquid mass at start stage. The effects of initial temperature and the valve opening degree on the heat and mass characteristics of flash during the V drop start stage were studied. The results showed that the pressure of the working fluid changed dramatically during the V drop start stage. The peak of instant liquid superheat was proportional to the opening degree of the valve, which controlled the outflow rate. The flash rate increased with increasing initial temperature and valve opening degree, which had an approximately linear relationship with the flash time. FCC increased with valve opening degree. It could be deduced that flash intensity or flash rate would be higher for an expander with larger outlet area or higher working temperature. [ABSTRACT FROM AUTHOR]

• Interfacial damage of two DBBT with four interfacial CZMs under various environment conditions were analyzed. • The outdoor nature experiment was conducted to verify the transient heat transfer model of the DBBT. • The damage factors of the unitized DBBT are much larger than those of the longitudinal DBBT under evaluated temperatures. • The first and second interfaces have different damage development after considering interfacial CZMs. • Thermal responses of two DBBT increase with the increase of humidity coupling with temperature. The natural environment has a great effect on the interfacial bonding performance of ballastless track in high-speed railways, and the interfacial damage analysis models of the double-block ballastless track (DBBT) on subgrade with two connections and four interface conditions are proposed in this paper. Firstly, the cohesive zone models (CZM) parameters of two interfaces of the DBBT were calculated and the thermal responses of a 1/4 scaled DBBT in an outdoor natural environment were measured. After the validation of outdoor experimental results, the transient heat transfer models of the unitized and longitudinal DBBT with four interfacial CZMs were then established to study their interfacial damage properties under three elevated temperatures, respectively. Thermal responses of the unitized and longitudinal DBBT are also compared under the coupling effect of high temperature and humidity. Results show that the temperature and longitudinal stress generally decrease from the sleeper to the supporting layer in a natural environment. The CZM has a great effect on interfacial thermal responses, and the stresses of the track slab in the longitudinal DBBT are much larger than those of the unitized DBBT under three elevated temperatures. More importantly, the damage factors of the two interfaces of the unitized DBBT are much larger than those of the longitudinal DBBT, and the interfacial damage development of the two interfaces of the unitized DBBT is different from the longitudinal DBBT. In addition, the coupling effect of a high temperature and humidity could effectively increase the thermal responses of the track slab for two DBBTs, especially for the higher humidity that exceeds RH=65 % of the unitized DBBT. [Display omitted] [ABSTRACT FROM AUTHOR]

Cell to pack design concept for energy storage in automotive applications leads to a substantially increased cell size that results in temperature gradients over the surface induced by non-uniform heat transfer linked to the cooling system design, which influences the cell performance. In this paper, temperature gradient effects on life performance of a large-format cell are experimentally investigated, using a developed device that can actively control appropriate gradients in the longitudinal direction and simultaneously measure the heat generation rate (HGR). Performances under uniform and non-uniform temperature conditions (MMM: uniform temperature, LMH: low-mean-high, HLH: high-low-high) are compared and quantified. At beginning of life (BOL), the low-temperature regions in the HLH and LMH conditions dominantly limit the cell capacity, and the HLH condition suppresses the HGR at high C-rates. During aging, the cell experiences a larger capacity fade and HGR increase under the HLH than MMM condition. The analyses of half coin cell, differential capacity (dQdV), dynamic resistance and impedance reveal that the attributing mechanisms are mainly the loss of Cathode active material, potentially the loss of lithium inventory, and the increase of impedances, indicating the electrochemically promoted side reactions and corrosions in the high-temperature regions of the HLH condition. • A calorimeter with controlled temperature gradient is developed. • Heat generation rates under temperature gradients are quantified and compared. • Cell teardown, dQdV, dynamic resistance and impedance analyses are conducted. • Temperature gradient effects on cell performance during aging are analyzed. [ABSTRACT FROM AUTHOR]

• A methodology to evaluate residuals temperature and composition effects is proven. • Internal residuals provide faster kernel growth and shorter combustion duration. • Composition of internal residuals has a positive combustion impact at high rates. • Internal residuals imply higher heat transfer, compensating combustion benefits. • Correlations for combustion timings vs. residuals characteristics are developed. Several technologies are being put in place to improve the efficiency of spark-ignition engines. Two of these technologies are variable valve actuation and exhaust gas recirculation, both of which can have an impact on combustion according to the literature. However, this impact is due to variations in both the in-cylinder temperature and composition, linked to the different characteristics of internal and external residuals, which are difficult to decouple. In this paper, a methodology aimed at improving the understanding of the temperature and composition effects on combustion parameters is developed. Internal residuals are controlled through a variable valve timing actuation, and evaluated thanks to a previously validated one-dimensional engine model, while the externally-circulated exhaust are extracted after the catalyst through a low-pressure system. Combustion is analyzed based on in-cylinder pressure acquisition and emissions measurement at the engine-out, before the aftertreatment module. Different combinations of internal and external residuals are tested with different strategies from the point of view of the spark actuation: first, a constant spark timing for each value of total residuals; then, a spark timing adapted to maintain the same temperature inside the cylinder at the combustion start, and finally an optimized calibration from the point of view of the engine efficiency. Results show a general trend to enhance combustion timings as higher share of internal residuals are introduced for the same amount of total residuals. It can be seen how this trend comes mostly from the temperature effect at low total residuals fraction, while composition effects are more significant as the amount of total residuals increase. Empirical correlations developed in the paper confirm the need to decouple internal and external residuals to have a proper estimation of the combustion timings. Despite the positive impact of internal residuals on the combustion duration, a small fuel consumption benefit is reached with cooled exhaust gas recirculation thanks to lower heat transfer losses. In terms of emissions, unburned hydrocarbon emissions tend to be reduced with increasing the share of internal residuals thanks to the higher combustion speed, while other gaseous emissions are mostly affected by the total residuals amount. Therefore, internal and external residuals could be combined to achieve the best trade-off between fuel consumption and hydrocarbon emissions. [ABSTRACT FROM AUTHOR]

Water huff-n-puff technology is an effective method of enhancing oil recovery in ultra-low permeability reservoirs. However, due to the different temperatures between injection water and the reservoir, the water huff-n-puff inevitably causes the change in reservoir temperature, further affecting oil production. Based on the modified embedded discrete fracture model method, this paper proposes a coupled solution framework of temperature field and flow field considering the complex mass transfer and heat transfer mechanism. Compared with the traditional EDFM method, this method has higher calculation accuracy and more complex coupling mechanisms. The influence degree of five thermal influence mechanisms on oil production is quantified and analyzed, including thermal viscosity reduction, thermal expansion, stress sensitivity considering thermal stress, fracture width change, and change of relative permeability curve with temperature. When the injection temperature is lower than the reservoir temperature, the three mechanisms of thermal viscosity reduction, thermal expansion, and the change of relative permeability curve with temperature have significant adverse effects on oil production. The mechanism simplification strategy of the numerical simulation of the actual model is given, which improves the simulation efficiency. The proposed simulation framework and simplification method have reasonable practicability. This work provides a valuable reference for water huff-n-puff. • An modified EDFM method is proposed considering complex thermal mechanisms. • Quantify the influence degree of different injection temperature effects. • A simplified approach to complex mechanisms to accelerate simulation. [ABSTRACT FROM AUTHOR]

• SiO 2 -PCMs has been successfully prepared and features excellent compatibility, thermal performance and anti-leakage ability. • PEG/SiO 2 shows excellent ability to adjust the pavement temperature. • The heat transfer model provide reference and theoretical support for temperature adjustment. In recent years, extreme temperatures have occurred frequently in summer, which is a challenge to asphalt pavement and its surrounding environment. Phase change materials (PCMs) have unique energy storage characteristics, which provide a new idea for alleviating the high-temperature damage of pavement and reducing the environment temperature. In this paper, the silica composite phase change materials (SiO 2 -PCMs) were prepared by the sol–gel method, and SiO 2 -PCMs with better performance was applied to the asphalt mixture. The finite element heat transfer model was established by measuring the boundary conditions, and the temperature adjustment effect was predicted and analyzed. SiO 2 -PCMs meet the mixing temperature requirements of asphalt mixtures and have excellent compatibility, thermal cycle stability and anti-leakage ability. Asphalt mixture with PEG/SiO 2 has an excellent temperature adjustment effect, and it can reduce the upper surface temperature of the asphalt mixture by about 9 °C. The high unity of theory and experiment is implemented by establishing the heat transfer model. PCMs reduce the temperature of asphalt pavement by storing and transforming energy, which provides reference and theoretical support for improving the near-surface thermal environment and prolonging the service life of asphalt pavement. [ABSTRACT FROM AUTHOR]

• A linear relationship between wall heat flux and temperature (enthalpy) in hypersonic laminar flow was found. • The heat transfer patterns were compared between isothermal wall and radiation equilibrium wall. • A new method for estimating wall heat flux was proposed, which can be applied to the uncoupled fluid-solid heat transfer simulation. The effects of wall temperature variation on heat transfer in the hypersonic laminar boundary layer are investigated using a typical blunt-headed cone under isothermal and radiation equilibrium wall boundary conditions, respectively. It is found that, under the isothermal wall boundary condition, the wall heat flux is strongly linearly related to the wall temperature for perfect gas flow, while linearly related to the wall enthalpy for chemical nonequilibrium flow. Under the radiation equilibrium wall condition, even for the same wall point with the same wall temperature, the heat flux may show significant difference from the result of the isothermal wall due to the spatial variation of wall temperature on the upstream flow filed. Consequently, using the heat flux under the isothermal condition to estimate the heat flux under the radiation equilibrium condition by linear interpolation based on the local wall temperature would introduce considerable errors. Further, the analysis of the heat transfer for the radiation equilibrium wall with different emissivity reveals that the heat flux has a strong linear relationship with the local wall temperature (for perfect gas flow) or wall enthalpy (for chemical nonequilibrium flow). Finally, a new method using the heat flux results obtained under known wall parameters to estimate the heat flux under new wall parameters based on the local wall enthalpy linear interpolation is proposed, and the numerical experiments show that the relative errors are basically below 5% for the isothermal wall and the radiation equilibrium wall cases studied in this paper. [ABSTRACT FROM AUTHOR]

• Thermally-thick particles featured with intra-particle temperature inhomogeneity. • Effect of intra-particle temperature inhomogeneity considered by corrected 0D model. • The multi-fluid model evaluated with bubbling fluidized bed experiments. • Intra-particle temperature inhomogeneity plays an important role in CFD simulation. • The computational efficiency of the corrected 0D model comparable to a 0D model. The multi-fluid model has been widely used to study heat transfer between gas and solid in bubbling fluidized beds. However, zero-dimensional (0D) model has been commonly used. The model assumes a uniform temperature distribution, which is only reasonable for thermally-thin particles (Biot number (Bi) < 1). However, one-dimensional (1D) model considering intra-particle temperature inhomogeneity inside particles is difficult to be implemented in multi-fluid model. To solve this issue, a corrected coefficient is introduced to quantitively feature the effects of intra-particle temperature inhomogeneity inside particles on external heat transfer, which forms a corrected 0D model. The corrected coefficient is correlated as a binary function of Bi and dimensionless temperature. The results of particle-scale modeling show that temperature profiles predicted by the corrected 0D model are the same as those of the 1D model for both thermally-thin and thermally-thick particles, while the 0D model overestimates heat transfer between particles and surrounding gas. The corrected 0D model is further implemented in the multi-fluid model to simulate particle cooling and heating process in bubbling fluidized beds. The results predicted by CFD simulations with both the 0D and the corrected 0D models are in good agreement with the experimental data of thermally-thin particles. For both the cooling and heating processes, a significant difference is observed for thermally-thick particles, indicating the importance of considering intra-particle temperature inhomogeneity in multi-fluid modeling. Consistent with the results of particle-scale modeling, the corrected 0D model predicts a smaller heat transfer rate between the gas and solid phases, as compared to the 0D model. Additionally, computational efficiency of the corrected 0D model is comparable to that of the 0D model. [ABSTRACT FROM AUTHOR]