To address the commercial demand for replacing copper heat transfer tubes with aluminum tubes in the air conditioning field，a high‑precision single‑tube condensation performance test bench was constructed.Using R134a refrigerant，experimental studies were conducted on the external condensation heat transfer characteristics of ⌀19.05 mm aluminum smooth tubes，aluminum three‑dimensional enhanced （3D） tubes，and copper 3D tubes under varying inlet water temperatures，saturation temperatures，and water flow rates.The condenser performance and cost were compared.The results show that the external condensation heat transfer coefficient of copper 3D tubes is 1.38 times that of aluminum 3D tubes；the external condensation heat transfer coefficient of aluminum 3D tubes is approximately 7.43 times that of aluminum smooth tubes.As the saturation temperature increases，the condensation performance of aluminum 3D tubes also improves.At the same saturation temperature，the external condensation heat transfer coefficient can be fitted as a function of heat flux.Under a heat exchange capacity of 2 227.7 kW，the cost of copper tube condensers is 3.4 times that of aluminum tube condensers.The research results can provide reference for material substitution studies in commercial air conditioning units.

To investigate the thermodynamic performance variation of a two‑stage hydraulically driven piston compressor for hydrogen refueling stations under varying suction pressures，a thermal simulation model of the two‑stage hydraulically driven piston compressor coupling the hydraulic system and gas compression system was constructed，and the model was experimentally validated.The results show that the maximum error between the simulated and experimental thermodynamic performance parameters is 2.7%，indicating good agreement.When the second‑stage discharge pressure remains unchanged and the first‑stage suction pressure decreases from 20.0 MPa to 3.0 MPa，the first‑stage pressure ratio remains essentially constant，while the second‑stage pressure ratio increases；the discharge temperature of the first‑stage cylinder remains around 120.0 ℃；the discharge temperature of the second‑stage cylinder increases from 54.1 ℃ to 224.1 ℃，the first‑stage shaft power decreases from 60.2 kW to 14.9 kW，the second‑stage shaft power increases from 12.7 kW to 35.5 kW，and the mass flow rate decreases from 55.5 kg/h to 7.1 kg/h.The two‑stage dual‑cylinder hydraulically driven unit is suitable for constant suction pressure conditions.When operating under varying suction pressure conditions，issues such as excessively high discharge temperature，unbalanced shaft power，and low motor efficiency occur.To address this problem，an operational strategy of using high speed under low‑pressure conditions and low speed under high‑pressure conditions can be adopted.The study provides a theoretical basis for the optimization of hydraulically driven piston compressor systems.

To expand the application of multistage series centrifugal extractors in corrosive working conditions，a proposal was made to use polyvinylidene fluoride （PVDF） fluoroplastic to replace conventional metal materials for manufacturing centrifugal rotors.The structural design for molding of centrifugal rotors，molding process and key parameter control，strength check，power calculation，and safety design were analyzed.The CTX350-PVDF centrifugal extractor was developed，performance tests were conducted on it，and it was successfully applied in phenol‑ammonia wastewater engineering.The results show that the performance indicators of the CTX350-PVDF centrifugal extractor meet national standard requirements，with a vibration velocity of 3.4 mm/s under load operation，bearing temperature of 38.6 ℃，and bearing temperature rise of 6.5 ℃；in the phenol‑ammonia wastewater engineering application，it operated well.Through 5‑stage extraction and 3‑stage back‑extraction processes，the extractant was regenerated and recycled，wastewater chemical oxygen demand （COD） was reduced by approximately 89%，and phenol content was reduced to 2 430 mg/L，meeting the requirements of downstream production processes.The research can provide technical support for the promotion and application of centrifugal solvent extraction technology in fields such as waste battery recycling and rare precious metal extraction.

In order to improve the sealing performance of hard‑sealed ball valve，we optimized the sealing surface according to the distribution of sealing pressure.Based on the Roth model，we calculated the leakage under uniform and U‑type sealing pressure distributions，found that there is less leakage in the uniform one.We regarded the average of sealing pressure in valid sealing zone and the proposed non‑dimensional number‑leakage index as two criteria of the sealing performance.On this basis，we separately analyzed the radius of the main sealing surface，R，and the radii of the chamfers，r₁ and r₂​.In the context of this study，optimal sealing performance is achieved when R matches the radius of the ball，resulting in improvements of 32.2% and 65.0% in the two evaluation criteria compared to a flat sealing surface.The edge effect can be mitigated by limiting r₁​ and r₂ within narrow ranges—specifically，r₁=1.2~4.0 mm，and r₂=0.5~2.0 mm.Beyond these ranges，a new edge effect emerges within the sealing area，leading to degraded performance.Considering both factors，the hard‑sealed ball valve exhibits peak sealing performance when R=72 mm，r₁=1.2 mm，and r₂=0.5 mm，with the two criteria improved by 38.5% and 66.4%，respectively.This research provides theoretical guidance for the structural design of sealing surfaces in hard‑sealed ball valves.

To investigate the influence of drainage holes on the operating characteristics of diffuser‑type self‑pumping hydrodynamic mechanical seals （DSPHMS），the finite difference method （FDM） was used to solve the steady‑state and perturbation Reynolds equations，analyzing the effects of drainage hole distribution circle radius，hole diameter，and operating parameters on steady‑state and dynamic sealing performance.The results show that increasing the drainage hole distribution circle radius shortens the effective action radius of the spiral grooves on the face fluid，leading to a decrease in opening force，but enhances the pumping effect of the spiral grooves on the inner leakage fluid，significantly reducing the leakage rate by 44.5%；there exists a threshold value for the drainage hole diameter （0.6 mm），when the hole diameter is less than 0.6 mm，the flow resistance of the drainage holes significantly weakens the face static pressure effect；small hole diameters （0.3 mm） limit sealing performance at high rotational speeds，while hole diameters larger than 0.3 mm improve sealing performance with increasing speed；although medium pressure can significantly increase the opening force，it reduces sealing stability.The research results provide theoretical guidance for the face design and stable operation of DSPHMS.

To improve the energy efficiency of screw compressors for high‑temperature heat pumps，focusing on their high temperature rise characteristics，the temperature distribution of the screw rotor was calculated using a CFD model incorporating conjugate heat transfer based on experimental data.Utilizing the obtained temperature distribution，the deformation characteristics of the rotor were analyzed using the finite element method.On this basis，the axial deformation of the screw rotor，the meshing clearance at the suction and discharge ends under thermal conditions，and the tooth tip deformation were calculated for three test conditions.Integrating the maximum deformation across the three conditions，the clearance configuration at various parts of the rotor was optimized，and the performance of the screw compressor under different conditions was evaluated with the new clearance arrangement.The results show that the circumferential temperature distribution of the rotor is highly uniform；after increasing the center distance by 0.02 mm，reducing the meshing clearance at the suction end by 0.045 mm，and decreasing the tip clearance by 0.05 mm，the mass flow rate of the screw compressor under the three conditions can be improved by 3.49% to 5.57%.This study provides a theoretical basis for clearance calculation and setting in screw compressors for high‑temperature heat pumps.

To address the problem of minor leakage and accumulation of powdered media in the labyrinth seal of the new dynamic shaft seal device for a plow blade mixer，the working principle of the seal device was analyzed.A centrifugal sealing enhancement technology and design method based on floating blocks in spiral grooves was proposed，and optimization of the number of floating blocks and material selection was studied.Through simulation analysis and experimental verification of the centrifugal sealing enhancement structure with floating blocks，the results show that as the number of floating blocks increases，the leakage of powder particles decreases significantly；when the number of floating blocks increases from 2 to 4，the leakage rate decreases the fastest；when the number of floating blocks is 12，the leakage of powder particles decreases to 75 particles，indicating that the leakage situation has been significantly improved；when the number of floating blocks is designed to be 6，the leakage of powder media in other seals such as the labyrinth seal is 1.25 g，meeting the test requirements，and the leakage is about one‑third of that of the centrifugal seal structure without floating blocks，significantly improving the sealing performance of the dynamic shaft seal device and extending the service life of the seals.Since the floating blocks are in a floating state during operation，they can automatically compensate for the increased clearance due to wear，thereby ensuring continuous sealing effect.The research has certain guiding significance for improving the dynamic shaft sealing performance of plow blade mixers and other types of powder machinery equipment.

In response to the design requirements of the nuclear island chemical and volume control system（RCV） charging pump，which no longer undertakes high‑pressure safety injection tasks and requires a steeper H-Q curve，a design method for a high‑performance centrifugal charging pump hydraulic model was proposed.Based on a single‑stage initial model pump （IMP），the impeller outlet diameter and blade outlet angle were increased，the outlet width was reduced，and the structural parameters of the diffuser were adjusted to construct two design model pumps，DMP 1^# and DMP 2^#.Meanwhile，analyses were conducted on the full flow range and cavitation flow under maximum operating conditions for all three pumps.The results show that compared to IMP，the best efficiency points of both DMP 1^# and DMP 2^# shift toward lower flow rates，and the steepness of the H-Q curves increases.At operating flow rates of 70，48，32 m³/h，the head of DMP 1^# and DMP 2^# increases by 14，22，24 m and 20，31，33 m，respectively.Based on entropy generation theory and the Omega vortex identification criterion，the internal flow field of the pumps was analyzed.Turbulent dissipation and wall effects are the main causes of flow losses，and under low flow conditions，entropy generation is primarily induced by vortex enhancement at the trailing edge of the impeller blade pressure side and flow separation caused by rotor‑stator interaction between the impeller and diffuser.Under the maximum operating condition at a flow rate of 70 m³/h，the Net Positive Suction Head required （NPSHr） of DMP 1^# and DMP 2^# is 4.3 m and 4.2 m，respectively，meeting the technical specification requirement of NPSHr<7.8 m in the nuclear power field.This study provides a theoretical basis for the design optimization and flow analysis of charging pumps.

To address the sealing failure caused by jamming of metal hard‑sealed triple‑offset butterfly valves during high‑temperature service，a combined method of finite element simulation and experimental verification was used to study the stress and strain distribution of metal hard‑sealed tripleoffset butterfly valves from room temperature to 450 °C.The results show that as the temperature increases from room temperature to 450 °C，the maximum stress of the sealing ring，stress non‑uniformity coefficient，maximum deformation，and minimum deformation increase linearly.Specifically，the maximum stress increases by 175.3%，the stress non‑uniformity coefficient increases by 174.64%，the maximum deformation increases by 131.67%，and the minimum deformation increases by 354.56%，primarily due to the linear correlation between the material properties of the butterfly valve and temperature.The minimum stress and average stress of the sealing ring non‑linearly correlate with temperature，related to the temperature characteristics of the material properties and the sealing structure of the butterfly valve itself.The temperatures at which the minimum stress of the sealing ring is lower than the required specific sealing pressure are 300 °C and 350 °C，and the temperature threshold at which the maximum deformation exceeds 1 mm is 300 °C.When the sealing ring is made of a material with a lower coefficient of thermal expansion than the valve seat and a comparable elastic modulus，the minimum stress of the sealing ring can be significantly increased and higher than the required specific sealing pressure，while the deformation of the sealing ring can be reduced by 7% to 10%，helping to improve the sealing performance of the butterfly valve above 300 °C.The research results provide a reference for the design of sealing pair structures and the improvement of sealing performance in metal hard‑sealed butterfly valves.

Aiming at addressing issues such as noise，vibration，and component wear caused by rotor system imbalance and hydraulic excitation in high‑temperature molten salt circulation main pumps，this paper analyzes the influence of fluid‑induced forces on the dynamic response of the pump rotor system.Taking a new type of cold salt pump as the research object，the unsteady flow field inside the pump is calculated using Ansys CFX software to obtain the radial forces on each stage impeller under different operating conditions.Based on the SAMCEF platform，the critical speed and mode shapes of the pump rotor are analyzed，and the transient response of the rotor system under radial forces at different flow rates is investigated，with validation through clear water experiments.The results show that the discrepancy between the performance curves of clear water and 300  °C molten salt is within 5%；under the 1.0Q condition，the radial force on the first‑stage impeller is 4 350  N，which is significantly greater than that on the other impellers；under different flow conditions ranging from 0.6Q to 1.4Q，the radial forces on the first‑stage and fifth‑stage impellers exhibit opposite variation patterns due to rotor-stator interaction；the critical speed of the rotor system is 1 894.5  r/min，indicating that resonance will not occur at the rated speed；when radial forces are not considered，the transient displacements of all impellers show regular elliptical patterns，with the fourth‑stage impeller having the largest displacement of 7.1×10⁻⁶  mm；when radial forces are considered，the radial displacements of all impellers become complex due to shaft system constraints，and the fifth‑stage impeller exhibits the largest transient displacement of 0.289 4 mm.The research findings can provide a reference for the optimal design of the cold salt pump rotor system.