Aiming at the issue of insufficient accuracy in leakage prediction for metal sealing rings，which leads to increased R&D costs，a leakage prediction method based on statistical characteristics is proposed.The surfaces of C‑shaped metal sealing rings made of two materials （GH4169 and GH738） after grinding and polishing were scanned using a laser confocal microscope to obtain their micro‑anisotropic surface morphology.Based on statistical methods，an anisotropic rough surface model was constructed.This model was combined with finite element analysis and computational fluid dynamics to predict the leakage rate of the sealing ring，and a study on the influencing factors was conducted.Experimental validation shows that the error between the numerically calculated leakage and the actual measured leakage is only about 10%.Under the same working conditions，when the sealing pressure difference is reduced from 0.6 MPa to 0.3 MPa，the leakage rate of the sealing ring decreases by 49.6%；when the root mean square roughness of the sealing ring surface is reduced from 1.2 μm to 0.9 μm，the leakage rate decreases by approximately 43%；when the surface contact stress increases from 0 MPa to 380 MPa，the leakage rate decreases by about 98.7%.These results indicate that the sealing performance of the ring can be improved by reducing the surface root mean square roughness，increasing the surface contact stress，and reducing the pressure difference between the inner and outer cavities.This study provides a theoretical basis for the subsequent development and evaluation of metal sealing rings.

To address the issue of high power loss caused by lubricating oil resistance in the counterweight of scroll compressors，an optimized model was proposed featuring dome convex surfaces and circular arc chamfers on the front and rear end faces of the counterweight，along with lubricating oil diversion from the rear end face.Based on the sliding mesh model in FLUENT software，transient simulations were conducted on the rotation process of the counterweight in the backpressure chamber under variable speed conditions.The resistance torque acting on the counterweight and the resulting windage loss were calculated，and the accuracy of the simulation results was verified.The results show that the differential pressure resistance torque generated by the front and rear end faces of the counterweight accounts for 76.9% of the total resistance torque，and its increase with rotational speed is significantly greater than that of the frictional resistance torque.After optimization，the average pressure on the rear end face of the counterweight increases with rotational speed，while the differential pressure resistance torque and total resistance are reduced by 63.3% and 58.1%，respectively.Additionally，increasing the ratio of counterweight thickness to outer diameter can reduce windage loss by up to 40.6%.This study provides a reference for the optimal design of scroll compressors.

In response to issues such as damage to bearing seats or motor bearings，as well as damage to blades and air ducts，caused by excessive vibration of exhaust fans，a vibration reduction method combining flow‑induced excitation suppression design and precision machining for centrifugal exhaust fans was proposed on the basis of traditional design and manufacturing.Using numerical simulation and experimental testing methods，the effects of airfoil‑shaped blades and circular‑section volutes on the flow state of flow‑induced excitation sources and structural strength were studied.The results show that there is no significant flow separation in the flow field near the surface of flow‑passing components.The vibration acceleration of circular section casing fans at blade frequency （483.3 Hz） is 8.3 dB lower than that of square section casing fans at blade frequency （773.3 Hz），and 9 dB lower in the overall vibration acceleration level （10~10 000 Hz）.The adoption of high‑precision manufacturing processes （such as integral milling and welding） for the impeller effectively improve the uneven distribution of its mass center.Vibration test results show that the rotational fundamental frequency vibration acceleration at the machine feet reduce by approximately 11 dB，and the high‑frequency vibration is 8.5 dB lower than that of the original design.This study demonstrates that flow‑induced excitation suppression and precision machining methods can effectively reduce the vibration of exhaust fans，providing a reference for the vibration and noise reduction design of fans.

In order to solve the problems of reduced air flow area，increased heat transfer resistance，and higher refrigerator energy consumption caused by frosting on the evaporator surface，a frosting test platform for evaporators with vertical air ducts was built，and an experimental study was conducted on the distribution characteristics of the frost layer on the evaporator surface along the air flow direction.The frost layer thickness at different times was measured in zones using a timed imaging device，and the average density and average thermal conductivity of the frost layer on the evaporator surface were calculated.The experimental results show that when the inlet coolant temperature is decreased from -15 ℃ to -20 ℃，the difference in blockage rate between Zone 4 and Zone 5 is only 8%，and a lower cold surface temperature is beneficial to the uniform distribution of the frost layer.When the relative humidity increases from 75% to 85%，the average blockage rate increases by 9.4%~55.7%.An increase in relative humidity significantly promotes the growth of the frost layer.Based on the three stages of flat‑plate frosting，the changes in thermal conductivity and frost layer density over time are divided into three stages：rapid growth period，uniform growth period，and stable period.In the late frosting period，the average density is concentrated in the range of 250~300 kg/m³，and the average thermal conductivity is in the range of 0.25~0.30 W/（m·K），with an overall trend of first increasing and then stabilizing.The research conclusions can provide theoretical support for the optimal design of heat exchangers in air‑cooled refrigerators.

To investigate flow noise characteristics of single‑stage single‑suction centrifugal pumps in closed‑loop systems，internal and external noise fields were simulated using acoustic finite element method and structural‑acoustic coupling based on unsteady flow calculations.Experiments were conducted on a closed‑loop pipeline system in a semi‑anechoic chamber.Results show that rotor‑stator interaction dominates pressure pulsation spectrum variations，with significant pulsation intensity at the impeller‑volute interface （especially the tongue region）.At design conditions，head and efficiency simulation errors are 3.07% and 2.79%，verifying model accuracy.In closed pipelines，sound wave reflection and superposition cause overall sound pressure level to first decrease then increase with flow rate：minimum 152.4 dB at design point，rising to 155.4 dB （0.65Q_d） and 159.0 dB （1.175Q_d） off‑design.Internal noise spectra are dominated by blade‑passing frequency （145.02 Hz） and harmonics，decreasing with higher frequencies.External low‑frequency noise（<1 000 Hz） is governed by impeller‑volute interactions，while high‑frequency noise （>1 000 Hz） is dominated by pipeline sources.This study provides references for pipeline optimization and vibration/noise reduction in closed systems.

To address insufficient performance and excessive energy consumption in hybrid closed‑circuit cooling towers under variable operating conditions，on the basis of the prototype mixed flow closed cooling tower，it has been improved using the improved tower as the test subject，To study the effects of variations in inlet water temperature（36.9~39.9°C），circulating water flow rate （125~170 m³/h），and fan power （10.48~16 kW） on cooling capacity and energy consumption ratio.The study revealed that increasing inlet water temperature raised the circulating water temperature drop （0.8°C per 10°C increase），while cooling efficiency and cooling capacity exhibited a non‑linear initial‑increase‑followed‑by‑decrease pattern，reaching a synergistic optimization peak at 38.2°C（107.8% cooling capacity，59.7% cooling efficiency，0.146 energy consumption ratio）.Higher circulating water flow rates reduced heat transfer efficiency（12% decrease in temperature drop）but improved cooling capacity by 34.5% （89%→119.7%），concurrently lowering the energy consumption ratio by 14.9%（0.174→0.148）.Elevating fan power enhanced heat dissipation（11.4% temperature drop increase）cooling capacity improved slightly（99.5%→102%），while the energy consumption ratio increased by 25.4%（0.126→0.158）.Through multi‑parameter analysis，the research elucidates the operational mechanisms of these variables on cooling tower performance，establishes quantitative relationships between operating parameters and energy consumption metrics，and provides quantifiable optimization strategies for industrial cooling tower regulation.

To investigate the effects of key parameters such as gas & oil piston diameter and control signal of proportional valve on the actual cycle indicated energy and stability of hydrogen compressor，a numerical model of hydraulic and booster coupled systems of a two‑stage 90 MPa hydraulic‑driven hydrogen compressor is established.The effects of key parameters such as gas & oil piston diameter and control signal of proportional valve on the actual cycle indicated energy and stability of hydrogen compressor are studied.The influence behavior of above parameters acting on the displacement，velocity，pressure and temperature inside gas cylinder，and pressure inside oil cylinder are analyzed. The reliability of the prediction method is verified by the experimental test. The results show that as the gas‑piston diameter increases，the maximum velocity gradually increases. When the gas‑piston diameter of stage 1 is 140 mm，its maximum reversing velocity is 0.199 m/s，which increases by nearly 28% compared to the velocity at 130 mm. For the process of suction and discharge of hydraulic‑driven hydrogen compressor，the changes of gas & oil piston diameter have the opposite influence for the pressure and temperature inside gas and pressure inside oil cylinder. When the gas‑piston diameter and oil‑piston diameter of stage 1 are 130 mm and 160 mm，the maximum pressure inside oil cylinder is15.23 MPa，and the maximum discharge pressure and temperature are 30.3 MPa and 390.5 K，respectively. Based on the above study，optimal matching of the gas & oil piston diameter and control signal of proportional valve are carried out，which bring about the energy conservation of 90 MPa hydraulic‑driven hydrogen compressor. The research can provide reference for the optimization design of hydrogen compressors.

To address the erosion wear issue of electric ball valves used in heavy medium suspension transportation systems of coal preparation plants，a combined approach of numerical simulation and experimental study was adopted to investigate the formation mechanism of the erosion process.The erosion rate，erosion area，and damage distribution patterns of electric ball valves under different inlet flow velocities，particle sizes，and valve openings were analyzed.The results show that compared to particle size and valve opening，the inlet flow velocity has a more significant impact on the erosion wear of electric ball valves and is the dominant factor affecting the erosion rate.When the inlet flow velocity increases from 0.8 m/s to 1.5 m/s，the maximum erosion rate increases from \mathrm{1.76}\times {\mathrm{10}}^{-\mathrm{4}} kg/（m²∙s） to \mathrm{1.958}\times {\mathrm{10}}^{-\mathrm{3}} kg/（m²∙s），while the erosion area on the sphere surface expands significantly.The formation of erosion pits mainly stems from microcrack propagation and material spallation caused by high‑speed particle impact，with large‑sized particles capable of forming erosion pits 20~50 μm in diameter.By controlling the inlet flow velocity to no more than 1.0 m/s，restricting heavy medium particle size below 45 μm，and adjusting the valve opening to the optimized range of 60%~80%，the degree of spherical erosion damage can be significantly reduced，thereby effectively extending the service life of electric ball valves.This study not only provides an optimization solution for the stable operation of heavy medium suspension transportation systems but also lays a theoretical foundation for achieving precise flow control.

To improve the energy efficiency of high‑temperature heat pump （HTHP） systems，two quasi‑three‑stage compression high‑temperature heat pump cycle systems were proposed based on the two‑stage compression system.Using R1233zd （E） as the working fluid，a thermodynamic model based on the working process of the heat pump system was established to analyze the variation law of system performance with the vapor injection pressure，and discuss the changes in the optimal system performance and exergy efficiency under variable operating conditions.The results show that adding vapor injection to the compressor in the two‑stage compression system can effectively utilize the system heat，regulate the heating capacity and energy efficiency，and improve the system performance；the vapor injection effect of the high‑temperature stage compressor is better than that of the low‑temperature stage compressor，and the advantage becomes more obvious as the condensing temperature increases.When the evaporation temperature is 50 ℃ and the condensing temperature is 130 ℃，compared with the two‑stage compression system，the coefficient of performance （COP） and exergy efficiency of the high‑pressure stage vapor injection system increase by 9.42% and 7.15% respectively，while the volumetric heating capacity （VHC） and system heating capacity of the low‑pressure stage vapor injection system increase by 4.82% and 20.08% respectively.This research can provide theoretical support for the optimal operation of high‑temperature heat pump systems.

To address the low efficiency of internal circulation anaerobic reactors in treating livestock wastewater，this study focuses on the three‑phase separator.By analyzing the relationship between its structural parameters and separation efficiency，the effects of baffle plate angle，reflection cone structure，and inlet velocity on the flow distribution inside the reactor were investigated.A combination of numerical simulation and experimental verification was used to compare separation performance under different parameter conditions.The results show that the optimal structural parameter combination for the new three‑phase separator is achieved when the baffle plate angle θ is 55° and the reflection cone adopts a diamond‑shaped structure.When the inlet velocity v is 0.16 m/s，the reactor exhibits optimal wastewater treatment performance，with solid phase separation efficiency reaching 95.75% and gas phase separation efficiency reaching 81.84%.Compared to the original structure，the separation efficiencies for both solid and gas phases in wastewater improved by over 10%.This study provides valuable insights for the design of internal circulation systems and IC reactors.