This study investigates the thermal performance of diffusion‑bonded hybrid heat exchangers through wind tunnel experiments and numerical simulations. Comparative analysis was conducted on the adaptability of heat transfer and friction factor correlations obtained by different methods for stainless steel plain fins. Results indicate that the thermal load of the heat exchanger increases with rising air‑side velocity，while the pressure loss grows more significantly. When air velocity increases from 8.1 m/s to 28.2 m/s，the thermal load increases by 2.9 times，and the pressure loss escalates by 9.82 times. Within the air‑side Reynolds number range of 2 440≤Re≤8 502，the theoretical thermal load calculated using statistically derived Colburn factor correlations deviates by 0.34%~16.55% from numerical and experimental results. Theoretical pressure loss predictions show less than 3% deviation from measured values. The study verifies the accuracy of the heat transfer/friction factor correlations and numerical models，providing practical guidance for thermal design of single‑phase diffusion‑bonded hybrid heat exchangers.

This study investigates the dehumidification and heating performance of a dual‑evaporator heat pump system for electric vehicles，which operates in two modes：Single‑evaporator mode （SEM） and dual-evaporator mode （DEM）.Experimental evaluations were conducted under varying operating conditions to compare system characteristics.Results demonstrate that at 60%~90% inlet air humidity and 4 000 r/min compressor speed，SEM achieves 26.2%~62.8% higher dehumidification rates and 25.7%~43.9% greater D_SMER than DEM. Conversely，DEM exhibits 26.6%~67.6% superior effective heating capacity and 11.2%~50.0% higher COP compared to SEM.When maintaining equivalent dehumidification performance，DEM delivers 43% higher outlet air temperature and 28% improved COP over SEM. These findings provide critical insights for expanding application scenarios of electric vehicle heat pump systems and advancing their technological development.

To address restart challenges in heavy oil‑water ring pipelines caused by water ring instability，an experimental study was conducted using a laboratory‑scale restart loop system with four conventional heavy oils. The research investigated flow pattern evolution and pressure drop characteristics during pipeline restart under constant water velocity，analyzing effects of oil holdup （H_o），oil viscosity （μ_o），shutdown duration （t_st），and water velocity （U_cl）. An exponential decay model was established to describe time‑dependent restart pressure drop. Results reveal four distinct flow pattern phases during constant‑flow restart： water shear stripping of oil layer，oil droplet/cluster migration，wall‑adherent film formation and film detachment. The pressure drop exhibits initial peak followed by decay and equilibrium stages，with model predictions showing excellent agreement （goodness‑of‑fit values approaching 1）.Within tested ranges （H_o=0.26~0.76，μ_o=1.055 3~3.02 Pa·s，t_st=0.5~1.0 h，U_cl=0.25~1.01 m/s），maximum restart pressure drop increases with H_o，μ_o，t_st，and U_cl （up to 30.38 kPa），while restart duration extends with H_o，μ_o，and t_st but shortens with U_cl （up to 3 616.78 s）.This study provides theoretical and practical guidance for optimizing pipeline restart operations.

This study investigates the feasibility of applying CO₂ systems to thermal management in temperature-controlled rail transport vehicles. A transcritical CO₂ refrigeration heat pump system for thermostatic transport vehicles was developed based on a multiphysics simulation platform，with simulation results validated through experimental testing. Further research was conducted on system discharge pressure and charge amount under varying operating conditions. Results indicate that optimal discharge pressure increases with rising ambient temperature and indoor heat exchanger inlet air temperature. A predictive correlation for optimal discharge pressure，using ambient temperature and inlet air temperature as independent variables，was established through data simulation. Both ambient and inlet air temperatures significantly influence the system's refrigerant charge amount，with an optimal charging range of 3.2~6.1 kg across all operating conditions. The well-designed transcritical CO₂ system demonstrates excellent performance over a wide temperature range，particularly achieving heating COPs above 3.2. The optimized thermal management system maintained stable temperature control with only two start-stop cycles within 300 000 seconds. These findings provide theoretical support for promoting transcritical CO₂ thermal management technology in thermostatic transport vehicles.

In order to solve the problem that the inlet flow field of a centrifugal compressor distorts under the elbow intake mode，which in turn has a significant impact on the performance of the compressor，through the self‑designed compressor test device，combined with characteristic tests and PIV flow field measurements，the correlation mechanism between the performance of the compressor and the flow field structure under the elbow intake is quantitatively revealed. The results show that，compared with the straight pipe intake，the elbow intake causes the pressure ratio and efficiency of the centrifugal compressor at the highest efficiency point to decrease by up to 2.7% and 9.8% respectively，indicating that the elbow structure significantly deteriorates the performance of the compressor. PIV testing revealed the presence of a reverse rotating twin vortex structure in the inlet section，whose strength is positively correlated with compressor flow rate and speed； Based on the analysis of the velocity uniformity index of the inlet pipe path cross-section，the interface velocity uniformity is good，and the radial velocity uniformity has a weak influence （the absolute value of γ is less than 0.2）. The asymmetry of the circumferential velocity distribution is strongly negatively correlated with the pressure ratio （γ=-0.976） and efficiency （γ=-0.923），indicating that circumferential distortion is the dominant factor in performance degradation. The research results can provide a reference for the performance improvement of centrifugal compressors.

In order to achieve stable operation of a shaftless magnetic suspension centrifugal pump，this study investigates the hydrodynamic forces acting on the suspended rotor through numerical simulations and experimental validation. The internal flow field was analyzed under varying inlet flow rates，focusing on temporal variations of radial and axial forces. Additionally，the effects of valve plate height and rotor inlet diameter on rotor forces were examined. Results demonstrate that at 7 000 r/min with flow rates below 43.3 L/min，a stable vortex core forms at the rotor center accompanied by uniform low‑pressure distribution，yielding periodic hydraulic excitation forces with amplitude stability. At 75.0 L/min，vortex breakdown induces chaotic low‑pressure fluctuations and irregular high‑amplitude force oscillations. Valve plate height negligibly affects radial forces but significantly influences axial forces，showing a 20 N reduction per 1 mm height increase at 65.0 L/min.Although rotor inlet diameter minimally impacts force characteristics，the D+1 configuration improves efficiency by 2.1% than D configuration at high flow rate of 65.0 L/min.These findings provide critical guidelines for optimizing pump geometry to minimize rotor loads and enhance hydraulic performance.

To address the issue of rising energy consumption and decreased efficiency in air source heat pumps caused by outdoor heat exchanger fouling，taking finned tube heat exchanger as the research object，this study utilized Fluent computational fluid dynamics software to investigate particulate matter deposition on a finned tube heat exchanger with six rows of tubes.SST k-ω model was adopted.The research deposition patterns of particulate matter with varying sizes on heat exchanger surfaces.At the same time，an experimental setup dedicated to ash deposition is constructed with the objective of validating numerical simulation outcomes.The CCD industrial camera is used to capture the image of the fin surface during the ash deposition process.Subsequently，the captured images and generated data underwent meticulous processing and analysis utilizing MATLAB software.Based on the conclusion drawn，the particle deposition distribution on the surface of the heat exchange tube primarily occurs within the ±75°area，constituting 94% of the total deposition.On the back of the heat exchange tube，the deposition ratio is only 2% with the ± （160~180）°area.At low wind speed，the mass of particle deposition on the heat exchanger surface decreases as wind speed increases.When the wind speed reaches 1.5 m/s，the deposition quality begins to rise.The findings reveales a distinct pattern in the ash deposition process：The mixed particles exhibit a synergistic effect on the fouling of the heat exchanger.The maximum deposition mass on the heat exchanger surface and the resulting pressure drop and fouling coefficient are higher than those of single particle size particles.The research results can provide reference for the maintenance and optimization of air source heat pump system in practical application.

To investigate the impact of the impeller design on the cavitation performance of disc pumps，a blade root arc modification method was introduced for a specific type of disc pump. The simulations employed the SST k-ε turbulence model combined with the Zwart-Gerber-Belamri cavitation model. Verification through external characteristics testing confirmed an error margin within 5%. Analysis of pressure distribution，cavitation volume，and turbulent kinetic energy within the impeller revealed that the blade root arc structure enhances both the head and efficiency of the disc pump. When the cavitation margin is 2.5 m，the head for the blade root arc model was 12.373 3 m，compared to 7.456 6 m for the original model，marking an increase of 65.94%. Under different cavitation margin （2.5，3.0，8.0，12.0 m），the average pressure of the blade root arc model is 1.23%~23.13% higher than that of the original model，The diffusion of the low pressure region is suppressed，and the pressure gradient between the pressure surface and the suction surface of the impeller is reduced，lessens the cavitation volume inside the impeller，significantly reduces turbulent kinetic energy at the impeller outlet，decreases energy dissipation，and stabilizes the flow channel. In conclusion，the blade root arc model notably suppresses cavitation in disc pumps and enhances their hydraulic performance. This study provides some reference for the performance optimization design of disc pump.

This study investigates the influence of axial deformation on the sealing performance of ultra‑high speed dry gas seals under combined mechanical and thermal loads.A 3D geometric solid domain model and fluid domain model were established，incorporating complex effects such as real gas behavior and turbulence. The axial deformation patterns of the rotating and stationary rings，as well as their impact on sealing performance，were analyzed under extreme operating conditions （rotational speed n=40 000 r/min，inlet pressure P_i=8~14 MPa，inlet temperature T_i=373.15~493.15 K）. Results show that mechanical deformation under n=40 000 r/min，P_i=11 MPa，and T_i=3373.15 K yields the maximum leakage rate （MS-DGS，4.19 g/s），while thermal deformation produces the minimum leakage （MS-DGS，1.69 g/s）. The leakage rate under heat‑flow-solid coupled deformation falls between these extremes （MS-DGS，3.66 g/s）. Compared to conventional S-DGS，the MS-DGS exhibits reduced axial deformation and a 1.94% lower leakage rate. These findings provide critical insights for optimizing ultra‑high speed dry gas seal design.

Under the promotion of the clean heating policy of "coal to electricity"，air source heat pump heating technology has developed rapidly.On the basis of introducing the research on traditional hot water and hot air source heat pump heating technology，this paper focuses on analyzing the principle，terminal development types，and structural characteristics of the new direct expansion air source heat pump heating technology，such as condensation direct heat dissipation，condensation indirect heat dissipation，and condensation heat storage heat dissipation terminal.A comprehensive evaluation of its application fields and actual operating effects is also conducted.The direct expansion air source heat pump heating with natural convection heat dissipation has no intermediate heat medium secondary heat exchange，fast heating speed，effectively improves indoor thermal comfort，and enhances energy efficiency.In addition，the future development direction of air source heat pump heating technology is discussed，which will be further improved from the aspects of end of pipe high efficiency and serialization，low global warming potential （GWP） working fluid，rational operation and regulation，multifunctional heat pump，and compatibility with residential buildings，providing reference for promoting and expanding its engineering applications.

To improve the efficiency of double‑suction centrifugal pumps，this study optimizes the impeller design for a specific water intake pump. Key parameters such as the inlet and outlet installation angles of the rear and front cover plates （β_1h，β_1s，β_2h，β_2s） and the blade wrap angle （φ） were systematically varied. Geometric reconstructions of the impeller were made within these parameter ranges to create a training dataset，and a high‑dimensional surrogate model based on response surface methodology was developed，and the reliability of the model was verified by comparing the numerical simulation results and experimental results of the optimized double suction pump head and efficiency.The results show that the optimized impeller enhanced flow distribution，reduced turbulence at the inlet，and increased outlet velocity，resulting in approximately 3% efficiency improvement，especially notable at the pressure chamber outlet. Efficiency gains of over 3% were observed at flow rates of 0.7Q_d，0.8Q_d，0.9Q_d，and Q_d，with the greatest head increase of about 0.8 m at 0.7Q_d and 0.8Q_d. This optimization extends the high‑efficiency range of the pump and provides an effective method for impeller design.

To meet the demand for fast response in the range of 5%~15% small opening by the rubber‑lined centerline‑typebutterfly valve under specific working conditions in the post‑rolling cooling system，the design principle of the conventional type was analyzed，especially in terms of structural sides，sealing modes，opening and closing strokes of the sealing pair.Based on the process requirements and the advantages and disadvantages of the conventional structure，the valve seat design was improved by leveraging the good plasticity of the rubber‑lined valve seat.The design ideas and corresponding advantages were elaborated.Finally，a simulation combined with flow test verification was conducted to compare and analyze the flow rate between the improved structure and the conventional structure.The results indicate that the Cv value of the improved structure at 5% opening is comparable to that of the conventional structure at 15% opening.The improved valve can produce flow at 5% opening，and within the range of 15% opening，the Cv value of the improved structure is 100%~250% higher than that of the conventional structure.Within the range of 20%~50% opening，the Cv values of the two structures tend to be the same，while in the range of 50%~100% opening，the Cv value of the improved structure is 10%~25% lower than that of the conventional structure.Additionally，by comparing actual flow test data with simulation results，the flow trend is consistent，particularly in the small‑opening range，confirming the credibility of the improved design.The findings of this study provide a reference for optimizing the small‑opening and flow rate performance of centerline‑type rubber‑lined butterfly valves.

This study investigates performance optimization of dual‑circulation air dehumidification system by analyzing compressor operating frequency and electronic expansion valve （EEV） opening configurations. A comprehensive thermodynamic model was developed to correlate EEV openings with critical performance indicators including refrigeration capacity，refrigerant mass flow rate，coefficient of performance （COP），and dehumidification capacity. Experimental validation confirmed the optimal compressor-EEV coordination patterns under specific operating conditions. The results demonstrate that maximum COP values occur at EEV openings of 18%，25%，and 30% corresponding to compressor frequencies of 38，42，and 45 Hz respectively，revealing a monotonically increasing relationship between optimal frequency and valve opening. System optimization achieved a COP enhancement from 0.993 to 1.817 through implementation of 42 Hz compressor operation with 25% EEV opening，representing an 83% efficiency improvement. The established control strategy provides a methodological framework for operational optimization of dual‑circulation air dehumidification system under variable load conditions.

To investigate the reliability of electric gate valves and challenges in minor fault identification，reliability enhancement testing （RET） technology was applied to simulate valve faults under non‑destructive conditions. Response data from two typical failure modes were collected and analyzed using three machine learning methods （decision tree，random forest，gradient boosting） combined with two optimization approaches （grid search，actor‑critic reinforcement learning）. Results indicate that RET effectively simulates valve sticking and jamming faults without physical damage，achieving cost‑efficient fault replication. The integration of current and vibration features significantly enhances fault recognition accuracy： normal data identification accuracy reaches 98% with random forest and gradient boosting，while fault data identification peaks at 82% using random forest and decision tree. Multi‑feature fusion improves model performance by leveraging data characteristics. Reinforcement learning boosts random forest accuracy by 21% （vibration features），15% （vibration‑current features），and 6% （current features），but degrades gradient boosting performance. Decision Tree excels in processing multi‑feature data with superior fault recognition，while random forest maintains robust performance across single and combined features. Gradient boosting exhibits instability requiring feature‑specific optimization. For industrial applications，random forest and decision tree with multi‑feature fusion are recommended to enhance classification performance. This study provides technical references for electric gate valve fault diagnosis.