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.

To address the technical challenge of erosion damage caused by sand particles to cage throttle valve sleeves during natural gas extraction，this study investigates the erosion mechanism using YW3 hard alloy sleeves as the research object.Through laboratory erosion tests，an erosion model for YW3 hard alloy was established and validated via numerical analysis.This model was further applied to erosion simulation of throttle valves to analyze solid particle trajectories，erosion mechanisms，and predict the service life of cage throttle valve sleeves.The results show that with increasing erosion angle，the erosion rate of YW3 first increases and then decreases，reaching its maximum at 45°.Under an erosion angle of 90°，the velocity exponent n and particle size function C（dp） for YW3 are 2.41 and 3.684 4×10^-9，respectively.The main damaged area of the sleeve is at the outlet of the throttle hole.This research provides reference for material selection and life assessment of throttling components in cage throttle valves used in high‑sand‑content gas fields.

In view of the problems of high noise and poor acoustic performance in the fresh air system of air conditioners，this study takes the fresh air system of a centrifugal fan for air conditioners as the research object and conducts research and analysis on the layered structure of centrifugal fan blades.Adopting the method combining numerical simulation and orthogonal experiments，the effects of the blade height ratio of upper and lower layers，the offset angle of upper and lower blades，and the number of lower‑layer blades on the aerodynamic performance of the centrifugal fan were analyzed.The research results show that the main parameters affecting the flow rate of the fan system，in order of significance，are the blade height ratio，offset angle，and number of blades.By optimizing these impeller structural parameters，the flow field in the flow passages between blades near the rear plate and at the volute bottom can be effectively improved，thereby enhancing the aerodynamic performance.Specifically，when the blade height ratio，offset angle，and number of lower‑layer blades are adjusted to 4.5，3.5°，and 57 respectively，the air volume increases by 6% at the same rotational speed，while the total noise level remains comparable.Furthermore，the low‑frequency broadband noise （0~600 Hz） is reduced by 2.1 dB（A），and the cavity noise is significantly attenuated.The research results can provide a reference for the aerodynamic optimization and noise reduction design of similar fresh air products.

To investigate the internal flow field characteristics of a straight‑tube distributor in falling film evaporators，a three‑dimensional computational model was established based on industrial design criteria for liquid distributors.Following model validation，the influence mechanisms of geometric parameters and operational conditions on distributor performance were systematically studied.Results indicate that the internal flow field of straight‑tube liquid distributors is significantly affected by inflow position and wall structure：a distinct impingement zone forms in the bottom area due to fluid impact，resulting in notably higher flow velocities at outflow holes near the inlet compared to other regions；whereas areas farther from the inlet develop stable pre‑orifice flow regions，effectively reducing mechanical energy loss.Under constant unit orifice area conditions，appropriately increasing orifice diameter and spacing significantly enhances initial distribution mass，though optimization effects exhibit parameter threshold limitations.Concurrently，increasing tube diameter ratio and branch pipe cross‑sectional area helps reduce average outflow velocity while further improving initial distribution mass.Variable‑condition studies reveal that as inlet flow rate increases，outflow velocity shows monotonic growth，while initial distribution mass first rises to a peak before stabilizing.The optimal initial distribution quality is 0.758 6，corresponding to an optimal operational flow rate of 0.453 kg/s，with distributors of different structural parameters exhibiting specific optimal operational ranges.The research can provide reference for the optimization design of straight pipe distributors

To address the efficiency reduction caused by clearance backflow at the volute tongue of a double‑suction multi‑wing centrifugal fan，a clearance adjustment control structure unit is proposed.This unit is installed on the front and rear cover plates of the volute near the volute tongue to achieve clearance adjustment.By adding structural units of different thicknesses to adjust the clearance，numerical analysis methods are used to simulate the internal flow field of the fan under different clearances.The effectiveness of the clearance adjustment is verified through aerodynamic performance and noise tests of the fan.The results show that the clearance adjustment unit can effectively reduce backflow at the volute tongue，improve the static pressure recovery capability of the volute，and ameliorate the backflow state at the impeller front shroud.It also enhances the axial distribution uniformity of the annular flow rate at the impeller outlet，thereby increasing the impeller work efficiency.However，when the axial thickness of clearance adjustment unit is excessive，it aggravates impact at the volute tongue，leading to a noise increase of 4.8 dB.When the axial thicknesses of the two clearance adjustment units are equal to the axial distances between the impeller front and rear shrouds and the volute front and rear cover plates，respectively，the measured noise can be reduced by 0.7 dB，the maximum air volume increased by 0.8 m³/min，and the efficiency improved by nearly 2%.This study provides a theoretical basis and engineering practice reference for the aerodynamic performance optimization and low‑noise design of multi‑wing centrifugal fans.

To investigate the sealing performance of the auxiliary rubber O‑ring for the compensating ring in high‑pressure pump mechanical seals，a two‑dimensional axisymmetric nonlinear contact model was established.Based on the fluid pressure penetration method，the effects of parameters such as different medium pressures，compression ratios，and installation gaps on the stress and sealing performance of the O‑ring were analyzed.The accuracy of the computational model was verified through an O‑ring axial force measurement test apparatus.The results show that the various stresses of the O‑ring increase with rising medium pressure，with contact stress exhibiting the most significant increase；when the medium pressure is in the range of 9~15 MPa，the pressure dominates the influence on O‑ring stress；when the compression ratio is >10%，its effect on O‑ring stress becomes negligible；when the medium pressure is below 20 MPa and the installation gap is <0.2 mm，the installation of the backup ring has little effect on the stress and sealing performance of the O‑ring.The research results can provide theoretical guidance for the design of rubber O‑rings in related high‑pressure pump mechanical seals.

Aiming at the problem that traditional discrete particle swarm optimization algorithm is prone to getting stuck in local optima and unable to obtain the global optimal value in the aerodynamic optimization design process of centrifugal compressors，an improved discrete particle swarm algorithm is proposed by introducing chaos operators，redefining learning factors and inertia weights，and combining control parameter descent strategy，as well as optimizing position probability iteration formula and other methods.Based on expanding the optimization range，the algorithm effectively balanced the global search ability and the local search ability，solving the problem of getting stuck in local extremums.The algorithm was adopted to conduct optimization design research on a certain centrifugal compressor.The results show that compared with the traditional particle swarm optimization algorithm，the improved algorithm can achieve a better aerodynamic design and effectively control the flow field separation at the impeller outlet.Under the premise of little change in pressure ratio，the isentropic efficiency increased from 85.7% to 88.7%.The research results can provide reference for the aerodynamic optimization of centrifugal compressors，and can also be applied to the aerodynamic optimization design of axial compressors and radial and axial turbines.

Aiming to address the issue of uneven air supply in data center fan‑wall air supply systems，a numerical model was established using computational fluid dynamics （CFD） simulation technology.The model was validated using measured data.Based on this validated model，an optimization study on airflow distribution in the data center was conducted for the air supply system.The impacts of optimization schemes，such as optimizing the air supply angle and adding rack inlet deflectors，on indicators such as the maximum inlet temperature of IT equipment，the average inlet temperature rise of risk racks，and the return air temperature index were analyzed systematically.The results show that optimizing the air supply angle and adding rack inlet deflectors can enhance the uniformity of airflow distribution；among which，when a 100 mm-wide，30°-inclined rack inlet deflector is used，the average inlet temperature rise of risk racks is significantly reduced by 0.81 °C，and the temperature uniformity in the equipment room is optimal.In contrast，reconfiguring the positions of air supply outlets does not optimize the airflow distribution in the data center.This research can provide a reference for the design of fan‑wall air supply systems.