Mixtures containing HFOs have emerged as promising alternatives to HFCs due to their environmentally friendly properties, and the vapor-liquid equilibrium (VLE) of HFO-containing mixtures is a critical thermodynamic property for practical engineering applications. Although the experimental VLE behaviors of HFO mixtures have been investigated, there are studies unavailable on the binary interaction parameters of HFO-containing mixtures in the literature. Therefore, in this work, the model for binary interaction parameter of van der Waals (vdW) mixing rule oriented to Peng-Robinson equation of state is developed to predict the VLE of binary mixtures. The binary interaction parameters in the vdW mixing rules are regressed using experimental VLE data for 64 sets of binary mixtures, and then, on the basis of the regressed binary interaction parameters, a general nonlinear correlation is proposed by incorporating the thermophysical properties, such as critical temperature, critical pressure and acentric factor. The proposed model is subsequently applied to predict the VLE behavior of all 66 sets of binary mixtures, including two independent test cases, and the predicted results are validated against experimental data. The results indicate that the proposed model exhibits high accuracy in predicting bubblepoint pressure, vapor phase mole fraction and relative volatility, and pressure has the average absolute relative deviation of 1.07%, while vapor-liquid mole fraction possesses the average absolute deviation of 0.0059, with the 4.63% average absolute relative deviation of relative volatility, so it is thus clear that the proposed model shows good applicability and accuracy in VLE predictions for HFO-containing mixtures.

Accurately modeling acoustic-enhanced heat and mass transfer remains difficult due to the nonlinear acoustic-fluid coupling. To address this challenge, the Lattice Boltzmann Method (LBM) is naturally advantageous for capturing the intricate interaction between acoustic and flow fields. Based on the fundamental framework of the LBM point source method (PSM), the governing equations for a point source within a background flow are derived. This derivation adopts the continuity and momentum equations, along with a small-disturbance assumption. Furthermore, the Oscillation Momentum Method (OMM) is proposed. The OMM incorporates the momentum oscillations generated by a point acoustic source into the discrete Lattice Boltzmann equations as a forcing term, effectively overcoming the limitation of the PSM that occupy fluid boundary nodes. Moreover, the reliability of the derived equations and the proposed methodology are systematically validated through several benchmark cases. Consequently, this work advances the theory and application of LBM in elucidating the mechanisms of acoustic-enhanced heat and mass transfer.

In the field of ultrasonic enhanced heat transfer, the acoustic flow effect is the most common physical effect that enhances the heat transfer rate. This paper investigated the phase change heat storage process with enhanced acoustic flow effect under low sound power. First, the simulated work revealed the impacts of different acoustic vibration surface area on the phase change heat storage process under same sound power. The results show that the decreasing area of the acoustic vibration surface can improve the melting rate, which has the optimal value of the area. The general laws of forced convection and natural convection on promoting the melting process of phase change material (PCM) were further discussed. Then, the effectiveness and economy of the enhanced effect were quantitatively analyzed. The results indicate a strong correlation between the melting time of PCM and economy of the strengthening effect. Finally, the research further indicates that the acoustic flow effect not only promotes the melting of PCM, but also leads to the reduction of total heat storage. The significance of this study lies in providing a theoretical foundation for the development of new heat storage device.

Windows, as the weak link in energy-saving of building envelopes, consume about 40% of building energy consumption, and it is crucial to improve window performance and achieve carbon neutrality goals in the building sector. Current static windows, such as Low-E glass, cannot adapt to seasonal demand, while dynamic windows like electrochromic (EC) and thermochromic (TC) windows suffer from high haze, low visible light transmittance (T-lum) and limited solar modulation capability (Delta T-sol). To address these issues, a temperaturetriggered switchable pressure-driven smart window (PD window) filled with CuSO4 solution is proposed, and PD windows employ Cu2+ ions to absorb near-infrared radiation in summer selectively and transmits full solar spectrum in winter, with low haze (<1%), high Delta T-sol (64%) and T-lum (76% in summer, 90% in winter). An outdoor chamber experiment is carried out to evaluate the PD windows' indoor daylighting environment with the effect of CuSO4 concentrations, window orientations and weather conditions, especially daylighting performance and visual comfort. Results show that PD windows improve the proportion of useful daylight illuminance (UDI100- 2000) and reduce glare risk under all tested conditions. For example, the UDI100- 2000 proportion of the 5%, 10% and 20% CuSO4 solutions reach 83%, 85% and 84%, respectively. Furthermore, the PD windows filled with 5% CuSO4 solution achieve a Color Rendering Index (CRI) of 89, with excellent color rendition.

Thermal-management systems for electric vehicles have become a key research focus for enhancing cabin thermal comfort and battery performance.This study proposes a direct-cooling system architecture to address the different temperature-response characteristics of cabins and power batteries.A dual-objective temperature-control strategy is developed based on ambient temperature,vehicle operating status,and real-time load temperature information,enabling the dynamic adjustment of thermal-control priorities between the cabin and battery to ensure optimal system performance.A thermal-management system test bench is constructed in an environmental chamber,and a simulation model of the vehicle thermal-management system is developed.Performance comparisons are conducted between the three control strategies under various driving conditions and ambient temperatures.The results demonstrate that the dual-objective strategy exhibits superior temperature-control capability and energy efficiency across different environmental conditions,along with optimal battery state-of-charge(SOC)recovery performance.Under 35℃ high-temperature conditions,the cabin and battery reach target temperatures within 51 s and 547 s,respectively.Under-7℃ low-temperature conditions,they reach preset values within 127 s and 365 s,respectively,with significantly improved SOC recovery rates.Although the dual-objective strategy slightly increases energy consumption(approximately 1.2％-3.0％ higher than the cabin-priority strategy),it substantially enhances the battery thermal-control efficiency and overall system performance,demonstrating high potential for practical applications.

Windows, as a bridge connecting the interior and exterior, are crucial for regulating indoor lighting, cooling and heating. However, most smart windows ignore the effect of solar altitude, resulting in poor light and heat management performance in practical applications. To address this issue, a solar altitude-triggered passive window (SAT window) is proposed to adjust solar radiation entering the room according to solar altitude. To investigate the indoor environment of the SAT windows, indoor and outdoor chamber experiments were carried out with the effect of solar radiation, solar altitude and hour angle. The results indicate that the indoor air temperature of SAT windows is lower than that of normal windows, with the highest indoor temperature difference of 12.4 degrees C, and the maximum temperature difference between the outer surfaces of the two windows is 22.5 degrees C. Meanwhile, the SAT windows have a more prominent energy-saving effect, especially at noon with high solar radiation. In addition, through theoretical calculations, the SAT windows can reduce cumulative annual indoor solar radiation heat gain by 1000-3000 MJ/m2.

The traditional working pairs in absorption refrigeration system are ammonia-water and aqueous lithium bromide solutions. In recent years, several new water-based and ionic liquid-based working pairs are proposed. This paper discusses the applicability, research progress and future prospects of these new types of working pairs. For water-based working pairs, the optimization methods of absorbents are as follows: 1) Adding alcohol can improve the absorption capacity and reduce the surface tension; 2) Adding lithium salts can reduce the corrosiveness of the solution and improve its thermal stability; 3) Adding other highly hygroscopic substances can improve the hygroscopicity and reduce costs; 4) Adding nanoparticles to improve the heat and mass transfer. For the ionic liquid-based working pairs, the selection and optimization methods of absorbents are predicted as follows: 1) Selecting cations and anions with appropriate alkyl chain lengths, the longer the alkyl chain, the higher the viscosity; 2) Adding salts to reduce viscosity; 3) Adding surfactants to improve absorption capacity. Meanwhile, the refrigerants with great potential are as follows: 1) RE170 exhibits excellent overall performance; 2) New hydrofluoroolefins (HFOs) have great trade-off advantage in environmentally friendly and 'drop- in' substitution; 3) R744 is environmentally friendly and highly safe. For system optimization, there are three attracting methods: 1) Developing membrane-type absorbers; 2) Using double-effect or multi-effect systems; 3) Using compression-assisted refrigeration systems. In the future, by following the optimization methods and using AI technology, which enables the absorption refrigeration system to develop in a more low-carbon way.

As an emerging active control strategy, acoustic technology has been widely applied to regulate fluid flow and heat transfer process. This study investigates the interaction mechanism between localized directional acoustic waves and natural convection in a square enclosure using the Lattice Boltzmann Method (LBM). Meanwhile, the impacts of acoustic actuation position, flow intensity, and acoustic geometric length on flow and heat transfer are systematically elucidated. The results reveal that the regulatory outcome is fundamentally governed by the actuation configuration: assisting positions intensify flow circulation and enhance heat transfer, whereas opposing positions yield converse suppressive effects. This modulation originates from the attenuation of directional waves, which induces localized acoustic streaming that initially alters local dynamics before propagating to reshape the global flow field. Furthermore, a competitive mechanism between acoustic and buoyancy forces is identified. Under the opposing configuration, sufficiently high acoustic intensity will generate vortices dominated by streaming. This competition is quantitatively evaluated using two newly proposed criteria. Moreover, the geometric length defines the acoustic streaming barrier that reconstructs flow and thermal fields. The impact of geometric length is non-monotonic on enhancement or attenuation of convection, exhibiting an optimal value that correlates with the background flow field.

Windows, as a weak link in building energy consumption, directly affect indoor thermal/lighting environment. Although the mainstream electrochromic (EC) and thermochromic (TC) smart windows can regulate solar radiation heat gain, they often suffer from high haze and low visible light transmittance during summer. Additionally, these smart windows primarily emphasize energy-saving features, with less focus on enhancing the indoor lighting environment. To address this issue, a real-time controllable pressure-driven smart window (PD window) filled with Cu2+ solutions is proposed. This window allows real-time control of solar radiation transmittance, with about 50% in summer and nearly 100% in winter, comparable to a normal window filled with air. To demonstrate the actual indoor lighting environment using PD windows, the effect of CuSO4 solution concentration, working fluid, windows orientation and outdoor weather on indoor daylighting illuminance are investigated experimentally. The results indicate that while PD windows reduce indoor illuminance relative to normal air-filled windows, the decrease remains within acceptable limits. For example, with a 20% CuSO4 solution, indoor illuminance retention reaches 77-79% of that under a normal window. This illuminance reduction is compensated by reduced solar heat gain in summer to enhances thermal comfort. Generally, the PD window achieves a balance between daylighting and thermal performance, addressing season-specific demands.

Unsaturated falling film evaporation possesses high energy efficiency due to its evaporation. Its heat transfer performance significant affect by the air parameters. The effect of air velocity has been explored, whereas the influence mechanism of air temperature and relative humidity has rarely investigated. This study aims to assess the spatial distribution and heat transfer performance of liquid film under varying air temperature and relative humidity with transient simulation model. Simulation model is validated by experimental data in liquid film distribution and heat transfer performance with a mean discrepancy of 6.7 %, 8.5 %. It is found that the effect of air temperature on the film thickness is not evident, while the film thickness becomes larger with the increase of relative humidity, leading to the thinnest point move towards to liquid column. The local heat transfer coefficient increases with the decrease of air temperature due to the enlargement of sensible heat transfer, while the variation magnitude gradually reduces from 15.6 % to 6.5 %. The small relative humidity enlarges the HTC by increasing the evaporation rate, and the heat transfer coefficient increment increases from 4.3 % to 24.3 % with the relative humidity reduce from 90 % to 10 %. Furthermore, a correlation for reflecting the matching characteristics between relative humidity and air velocity is derived. The findings provide a theoretical support for the promotion and application of unsaturated falling film evaporation technique in air conditioning system.

In this work, molecular dynamics simulations were conducted to explore the effects of surface wettability and roughness on the bubble evolution characteristics during the ultrasonic cavitation process. In the calculation, the vibrating wall models with different wettabilities and varying roughness were constructed to reveal the cavitation process of water molecules under periodic ultrasonic excitation. The simulated results indicated that the hydrophobic surface facilitates the early formation of bubbles, but the hydrophilic wall contributes to the stabilization of bubble structures and their expansion into the bulk liquid. Meanwhile, the cavitation effect can be enhanced with the increasing roughness due to the generation of geometric traps. In addition, the geometric traps can promote the generation and persistence of bubbles near the boundary. Finally, the appearance, growth, and collapse of bubbles were related to the oscillation of pressure.

To expand the application of solar chimneys in multi-storey buildings and mitigate non-uniform airflow rate distribution across storeys, a multi-storey stepped solar chimney with channel gaps increasing from bottom to top was proposed. Numerically analysis was carried out on the ventilation performance of solar chimneys in two-tofive-storey buildings. Results indicate that both top vertical outlet and top side outlet uniform gap solar chimneys exhibit non-uniform flow rate distribution across storeys. Additionally, air re-entry occurs at inlets of the third and higher storeys in top side outlet solar chimney, therefore the chimneys with top vertical outlet were advisable to adopt. The Floor Flow Rate Uniformity Index (ei) and Building Flow Rate Uniformity Index (Eb) were developed to quantitatively evaluate the airflow rate uniformity and to determines the optimal channel gap specifications for stepped solar chimneys with top vertical outlet. The optimized channel gap specifications are: 0.1 m and 0.15 m for two-storey buildings; 0.2 m,0.4 m and 0.65 m for three-storey buildings; 0.2 m,0.4 m,0.6 m and 0.8 m for four-storey buildings; and 0.2 m,0.4 m,0.5 m,0.6 m and 0.8 m for five-storey buildings. The ei values mostly range between 0.95 and 1.1, while the Eb values increase by 39.8 % (four-storey) to 55.3 % (twostorey) compared to top vertical outlet uniform gap solar chimneys. Furthermore, the optimized structure enables all storeys to meet indoor Air Changes per Hour (ACH) requirements. An achievable energy saving rate is approximately 5.8 % to 30 % compared with the conventional solar chimney. The stepped solar chimney can be applied as a unit module in various multi-storey and high-rise buildings. It is highly significant for facilitating the green and low-carbon transformation of multi-storey and high-rise buildings.

To address the limitations of traditional auto-cascade refrigeration cycles (TACR) regarding low-temperature efficiency and refrigeration temperature limits, this study proposes a two-stage dephlegmation auto-cascade refrigeration cycle (TDACR), which enhances the purity of low-boiling-point composition by utilizing multi-temperature-level cooling capacities. A thermodynamic mathematical model has been developed using R1150/R600a as the refrigerant. The impact of various operating parameters, including the composition ratio, compression ratio, and dephlegmation temperature, on the thermodynamic performance of the cycle has been analyzed using the controlled variable method. A genetic algorithm is employed for global optimization, and Pearson correlation coefficients are used to evaluate parameter interactions. The results indicate that the TDACR increases the R1150 mass fraction in the evaporator refrigerant by 33.65%. Additionally, the R1150 mass fraction in the evaporator refrigerant exhibits a strongly positive correlation with the coefficient of performance (COP) at 0.77. When the condensation temperature ranges from 30 degrees C to 40 degrees C, the refrigeration capacity of the TDACR increases by 7.37%-28.68% compared to the TACR. Furthermore, at evaporation temperatures ranging from-70 degrees C to-90 degrees C, the COP of the TDACR improves by 54.55%-258.73% relative to the TACR.

As a UNESCO World Cultural Heritage site, the Longmen Grottoes have long suffered from the erosion of cultural relics due to water leakage. The slow evaporation of liquid films formed on cave walls exacerbates the physical and chemical deterioration of the dolomitic rock surfaces. This study integrates a coupled heat-mass transfer model with numerical simulation to quantitatively assess the evaporation time of these films and identify the primary environmental drivers, such as wind speed, air moisture content, and temperature. Simulation results, validated by infrared monitoring, demonstrate a model error of less than 1%, confirming its accuracy. The findings reveal that increasing wind speed from 0.1 m/s to 3 m/s reduces evaporation time by approximately 5.5fold. Lowering the moisture content from 0.005 kg/kg to 0.003 kg/kg shortens evaporation by 1.6 times, while raising the temperature from 10 degrees C to 40 degrees C enhances the evaporation rate by more than 15-fold. These results uncover the dynamic regulatory effects of microclimatic parameters on surface film evaporation and provide a scientific foundation for optimizing ventilation strategies in cave environments. The work holds significant theoretical and practical implications for the conservation and management of dolomitic rock heritage sites.

Highly integrated electronic devices require more efficient heat dissipation solutions. It is therefore necessary to further enhance heat transfer performance in jet-impinged microchannel heat sinks. This study proposes three jet-impinged microchannel heat designs featuring symmetrical wavy paths that incorporate triangular (T-JSMC), square (S-JSMC) and circular ribs (C-JSMC), which can enhance cooling capacity and temperature uniformity. The microcapsulated phase change material slurry (MPCS), which offers high energy density as a coolant, comprises a polymethyl methacrylate shell and an n-octadecane core. The mixture model in COMSOL 6.2 was employed to simulate MPCS flow and heat transfer at a 20% volume concentration across a flow Reynolds number range of 200-1000. The results indicate that the S-JSMC enhances heat transfer performance, as the square rib effectively synergizes with the symmetrical wavy flow path. Compared with the JFMC, the S-JSMC increased the performance evaluation criterion (PEC) value by 30.7% and decreased the bottom wall temperature difference by 9.3 K. Furthermore, a Sobol sensitivity analysis was performed on the S-JSMC design parameters. Multi-objective optimization was conducted by combining a Random Forest model with the NSGA-II genetic algorithm to optimize the S-JSMC's structure, and the entropy-weighted similarity to the ideal solution (TOPSIS) method was used to identify the optimal compromise solution from the Pareto front. Compared with the initial S-JSMC design, the optimized design increases Rtby 50%, decreases Pp by 67.7%, and enhances PEC by 8.72%. This study provides a reliable reference for the multi-objective optimization of jet-impinged micro-channel heat sinks and provides an effective thermal management solution for highly integrated electronic devices.

Due to the different thermal physical properties of solids and fluids in porous media, there exists a serious local thermal nonequilibrium phenomenon in the flow and heat transfer process in porous media, especially under conditions of higher thermal conductivity ratios and heat capacity ratios. Therefore, accurately and delicately capturing the flow and temperature changes in porous media has become a hot and difficult issue. The traditional BGK model relies on a single relaxation parameter, which results in poor computational stability of the model, while the MRT model, due to the introduction of multiple relaxation factors, causes large computational workload and implementation complexity. To address the issues of accuracy, stability, and complexity in numerical simulation of flow and heat transfer processes in porous media, a TRT-LB model is innovatively developed based on the REV scale under local thermal nonequilibrium conditions. In this model, two TRT-LB equations are introduced to calculate, respectively, the temperature distribution in the fluid and solid regions. The external term and source term are introduced into the model to predict the internal heat source and convective heat transfer process in the porous media more accurately. Then, the correctness of the model is verified by deducing the macroscopic control equation from the proposed model using the Chapman-Enskog method. Subsequently, the model is verified by using three classic benchmark cases: mixed convection in a porous channel, steady-state natural convection in a porous medium containing a heat-generating solid matrix, and transient natural convection in foam metals. The results show that the TRT-LB model can accurately and stably capture the flow and heat exchange processes in porous media, more accurately display the subtle differences in temperature in porous media under local thermal nonequilibrium conditions, and significantly reduce the implementation complexity and computational cost.

Thermal management systems (TMS) serve as core technologies ensuring battery safety, cabin comfort, and reliable operation of battery electric vehicle (BEV). However, under complex dynamic operating conditions, existing static control strategies struggle to meet dynamic demands, while resolving performance conflicts among multi-thermal objectives and achieving energy-consumption co-optimization remain critical challenges. To address these issues, this study proposes a variable priority control (VPC) strategy and a multi-objective optimization method for operational parameters, balancing thermal control performance and system energy efficiency in BEV-TMS during transient operations. An experimental-simulation co-platform was established based on the proposed TMS architecture for data acquisition. Variable-condition experiments revealed coupling mechanisms between key operational parameters and system performance. The results show that mode switching significantly impacts system behavior: closing the battery circuit reduces instantaneous coefficient of performance (COP) by over 1.2 and decreases cabin temperature by 1.7 °C. Optimal control parameter combinations exist across all tested conditions. Guided by experimental findings, a dynamic decision criterion integrating battery safety, cabin comfort, state of charge (SOC), and environmental factors was formulated, forming the foundation of the VPC strategy. The non-dominated sorting genetic algorithm-II (NSGA-II) achieved multi-objective parameter optimization, enhancing thermal control efficiency by 13.2% and 14.8% in two typical modes while reducing energy consumption by 4.8% and 6.5%, respectively. Validation on a full-vehicle virtual simulation platform confirms that the proposed VPC strategy and parameter optimization method significantly improve thermal distribution capability while rationally controlling energy consumption, demonstrating substantial practical potential.

The secondary flow generated in twisted elliptical tubes enhances near-wall heat transfer but has limited influence on the core flow region, thereby restricting the overall convective heat transfer performance. To address this limitation, a novel configuration combining twisted elliptical tubes with spiral fin inserts is proposed to improve thermohydraulic performance. Experimental investigations are conducted to evaluate the heat transfer characteristics of tubes equipped with solid and hollow spiral fins. The effects of twist ratio and Reynolds number are systematically examined, and empirical correlations for the Nusselt number and flow resistance factor are developed for engineering applications. The results show that the insertion of spiral fins significantly enhances internal convective heat transfer by strengthening flow mixing and secondary flow intensity. Decreasing the twist ratio and increasing the Reynolds number both improve heat transfer performance but lead to higher flow resistance. Compared with the tube without inserts, the solid spiral fin increases the Nusselt number by up to 129.5% with a 179.6% rise in flow resistance factor, while the hollow spiral fin achieves a maximum Nusselt number increase of 251.9% accompanied by a 546.2% rise in flow resistance. Based on the comprehensive performance evaluation criterion, the optimal performance is obtained using a solid spiral fin with a pitch of 0.140 m.

Unsaturated falling film evaporation has numerous applications on sustainable energy domain due to its larger heat transfer efficiency. Falling film evaporation associated with round tube has received extensive attention. To improve the efficiency, a half-oval tube is proposed and explored. The impact of wind velocity has been studied, whereas the influence of air temperature and relative humidity is rarely assessed. In this paper, the effect of air temperature and relative humidity on the liquid film distribution and heat transfer over a half-oval tube is numerically investigated. The model reliability is validated by experimental data in film thickness and heat transfer coefficient with the mean difference of 4.5% and 5.1%. Results confirm that air temperature shows a slight influence on the liquid film distribution, while the film thickness become thinner with the decrease of relative humidity, leading to the axial thinnest point move away from liquid column. Meantime, the HTC increase with the decrease of air temperature, and the HTC increment is within 4.7% to 14.3% compared to 25 degrees C. The HTC increase with decrease of relative humidity due to the enlargement of latent heat transfer, and the variation magnitude increase from 5.1% to 25.6% with the relative humidity decrease from 90% to 10%. The finding of this study provides a promising option for enhancing the unsaturated falling film efficiency.

Fine mineral particles have low inertia and tend to follow fluid streamlines, resulting in inefficient bubble–particle collisions during flotation. In this study, a hydrodynamic whistle acoustic generator was introduced into the pipe-flow mineralization process to convert part of the fluid kinetic energy into acoustic-flow oscillations through jet-reed interaction. Unlike conventional electrically driven acoustic flotation, this passive approach generates in-situ periodic pressure and velocity fluctuations in an energy-efficient manner. The innovation lies in coupling a hydrodynamic acoustic source with fine-particle flotation and revealing how the induced unsteady fluctuations regulate turbulence micro-timescales to enhance inertial collisions. Two-way fluid–structure interaction simulations were conducted to characterize the jet–reed coupling, reed vibration, and induced oscillatory flow. At an inlet velocity of 2.5 m/s, the whistle produced 45 Hz oscillations with a reed vibration amplitude of 0.72 μm, reducing the volume-averaged Kolmogorov time scale by 49% to 83 μs and increasing the estimated Stokes number of 20 μm talc particles to 0.426. Flotation experiments confirmed the intensification effect: the recovery with the hydrodynamic whistle reached 47.36%, outperforming a nozzle-only pipe (37.33%) and an empty pipe (31.23%). This work provides a passive hydrodynamic acoustic route for fine-particle flotation intensification.