The uniformity of gas-liquid two-phase fluid and the flow distribution relationship in the shell side space of LNG/FLNG large-scale wound tube heat exchanger directly affect its heat transfer performance.To solve this problem,a ring tube distributor suitable for large-scale wound tube heat exchanger was proposed,and an experimental platform for studying the uniformity characteristics was designed and built to study the proportion coefficient and dispersion coefficient of flow in each channel in radial and circumferential directions under different flow conditions,and the fluid distribution under the condition without distributor was compared.The results show that the fluid distribution is more uniform with the increase of flow rate,the uniformity of gas phase distribution is better than that of liquid phase,the circumferential distribution is uniform,the radial distribution decreases from inner to outer two-phase mass flow,the flow rate of the innermost ring is about 1.2 times of that of the outer ring,the volume flow rate of the two phases increases from the inside to the outside,and the flow rate of the outermost ring is about 1.5 times of that of the inner ring.After placing the distributor,the two-phase volume flow dispersion coefficient can be reduced by 64% and the two-phase mass flow dispersion coefficient can be reduced by 57%.The research results can provide a reference for the structural design of the distributor of LNG/FNG large wound tube heat exchangers in order to further improve the uniformity effect.

For the vibration and noise generated in the cavitation induction process of hydraulic model of mixed-flow pump,the vibration and noise signals of the cavitation induction process of hydraulic model of mixed-flow pump were obtained by using physical test methods in the comprehensive performance test bench for large-size pumps through vibration tests at the inlet and outlet of hydraulic model of mixed-flow pump,between stationary and moving components,and noise tests at the locations of inlet and outlet at four times pipe diameter.The frequency spectrum analysis and characteristic comparison were carried out.The results show that the noise at the outlet of the cavitation induction process of the hydraulic model of mixed-flow pump is significantly higher than that at the inlet,the radiated noise at the inlet gradually increases at first,and then decreases after reaching the extreme value where the head decreases by about 1%.The radiated noise at the outlet increases gradually,decreases after reaching the extreme value,and then increases gradually.The vibration at the inlet is consistent with the noise change law,and the maximum value appears at the point where the cavitation allowance decreases by 20%~25%.There are some differences in change of vibration and noise at the outlet,and the cavitation allowance when the peak vibration intensity appears is smaller than that when the noise pressure level intensity peak appears.The results can provide reference for vibration and noise reduction design of mixed-flow pump,and have practical engineering application significance for real-time dynamic monitoring of cavitation state of water jet propulsion pump.

Thermal-hydraulic characteristics of microchannel heat exchanger with different fin pitches and surface wettability were investigated under high air velocity and different air inlet humidity conditions.The results show that the microchannel evaporator with hydrophilic surface treatment cannot improve the thermal performance and condensate exclusion effect under wet conditions,but will deteriorate.It has no significant effect on heat transfer colbum j factor.However,the friction factor f on the wind side increases.Under the test conditions,influence of hydrophilic surface treatment on j factor is less than 1%,while the air friction factor increases by 4%~9%.Factors of j and f are insensitive to rariations of in fin density,air humidity,and air veloctiy.Hydrophilic surface could also increase the chance of continuous water-bridge formation,which increases the risk of water carryover.Under normal working conditions,no water carry-over phenomenon was found in bare foil and hydrophilic foil.Under the given high humidity condition,no water carry-over occurred for bare fins with different fin pitches and air velocity,while slight water carry-over was observed for hydrophilic surface with fin pitch of 1.7 mm and air velocity of 4.5 m/s.

For the problem of poor performance of transcritical CO₂ refrigeration system in hot areas,three improved thermodynamic models of CO₂ refrigeration system with internal heat exchanger,parallel compression and mechanical subcooling were developed.The operation characteristics of four system configurations including the basic two-stage throttling CO₂ refrigeration system were optimized and analyzed.Based on the meteorological parameters of typical Chinese cities,the seasonal and annual performance of the system was evaluated,and the carbon emissions were also evaluated.The results show that the system with internal heat exchanger has the most significant performance improvement at the ambient temperature of 7.0~14.0 ℃.When the ambient temperature is greater than 14.0 ℃,the energy efficiency is improved more obviously when mechanical subcooling system is adopted.The annual performance factor in hot climate is low,using the improved CO₂ refrigeration system can significantly enhance the system energy efficiency in hot areas.The system performance improvement ratio is the highest by adopting mechanical subcooling system,with the largest annual performance factor improvement ratio of 18.7% and annual energy consumption reduction of 19.3%.The carbon emissions can be reduced by 19.3% using mechanical subcooling system in Xiamen.

In order to study the flow separation phenomenon of centrifugal pump under different working conditions,the low specific speed centrifugal pump was used as the research object to explore the flow structure in the pump under different working conditions based on LES numerical calculation,and verify the accuracy of numerical calculation by using the performance test on the closed test bench.It was found that the highest efficiency point of the pump is at the location of about 1.1Q_d,and under the designed flow rate,the LES calculation error is less than 1.5%.Based on the distribution characteristics of flow field structure at the outlet of the impeller,the flow separation phenomenon under different working conditions was compared and analyzed,and the changing characteristics of flow separation phenomenon at the outlet in the process of the impeller sweeping the tongue and its influence on the flow field structure in the impeller were obtained.The results show that the flow separation phenomenon appears as reflux formation of the separation bubbles on the blade surface,which makes the flow at the outlet of the impeller present uneven distribution characteristics and strengthens the jet-wake structure.Especially under the condition of low flow,flow separation provides energy for the rotation of outlet vortex,resulting in large area blockage of outlet flow passage,with the blocked area up to about 55%,inducing the hump phenomenon of small flow.

For the problems of bloated control architecture,time-consuming installation site,disorder and high cost of traditional valve electric actuator,a wireless valve electric actuator based on the industrial Internet of Things was proposed.The transmission of valve control signal was completed by designing the structure of wireless antenna lead-in device and developing the hardware and software of the control system to achieve the structural integration and remote wireless control of the valve electric actuator.It is found that under the LoRa wireless control gateway based on 470 MHz propagation frequency band and the specific test environment,the signal of the electric actuator of the wireless control valve is stable within a certain range,and the farthest test range can reach 1.2 km.The wireless control method applied to the valve flow and flow resistance test system effectively solves the problems of large actual quantities such as cable laying,cable tray erection,wiring inspection,long project cycle,high cost.At the same time,by accurately mastering the real-time operation of the valve and pipeline system,the comprehensive combination of valve flow characteristic test,valve life-cycle monitoring and the Internet of Things is realized,which provides an important basis for the application of Internet of Things technology for industrial valves.

In order to solve the wear of valve body cavity and seat of V-shaped ball valve due to single point scouring,the research design of anti-scouring V-shaped ball valve with a flow stopper seat was carried out.The anti-particle,flow direction change and vortex reduction effects of the baffle were analyzed at small openings,and the pressure withstand test of the valve body,seat seal test and vortex test at small openings were conducted.The results show that the valve body has no visible deformation and leakage,the inner leakage is 12.5 mL/min,which is less than the national standard 15 mL/min leakage,and the inlet and outlet mass flow rates are 0.32,0.24,0.19 kg/s and 0.05,0.03,0.016 kg/s at 40%,30% and 20% relative openings,respectively,and the baffle plays a role of blocking and filtering sand and other particulate matter,changing the direction of liquid flow,reducing the vortex,and reducing the wear of particulate matter on the inner cavity.The results of the study are important for the V-shaped ball valve to work at small openings,block the scouring of granular media, and improve service life.

In order to improve the aerodynamic performance of a large flow centrifugal fan,the influences of the position of the reinforcing disc and the type of the impeller on the structural strength of the impeller,fan performance and pressure fluctuation were studied by using computational fluid dynamics.The results show that compared with the prototype,when the reinforcing disc is centered,the design point efficiency of the fan is increased by 3.9%,the maximum total deformation of the impeller is reduced by 56.5%,and the pressure pulsation of the volute flow domain is reduced by 5.4%.The center installation of the reinforcing disc is beneficial to enhance the structural strength of the impeller,improve the aerodynamic performance of the fan and reduce the pressure pulsation of the volute flow domain.The use of staggered blades can reduce the pressure pulsation of the volute flow domain by more than 70%,which is conducive to the discrete noise control of the fan.However,due to the influence of turbulent kinetic energy dissipation produced by mixing of low and high energy fluid,the aerodynamic loss of the fan with staggered blades is increased,and the amplitude of pressure pulsation in the blade passage is larger.The center installation of the reinforcing disc and use of staggered blades are effective ways to improve the aerodynamic performance of high flow centrifugal fans and reduce discrete noise,but the effect of them on aerodynamic losses needs to be noted.The results of the study can provide a theoretical basis for the design of reinforcing disc for large flow fans.

In order to understand the distribution and influence of entransy dissipation in the gas cooler,CFD numerical simulation technology was used to establish the model of straight tube casing gas cooler.The heat transfer process between carbon dioxide and cooling water in the supercritical carbon dioxide gas cooler was simulated by numerical simulation method.By changing the operating pressure,temperature,mass flow for numerical simulation calculation and analyzing the entransy dissipation along the tube length,the effects of temperature,mass flow and pressure variation on entransy dissipation of the casing gas cooler were studied.The results show that the entransy dissipation increases with the increase of carbon dioxide inlet temperature,but the change of cooling water temperature has little effect on the entransy dissipation,which can be ignored.With the increase of cooling water mass flow rate,the entransy dissipation decreases,and the entransy dissipation at the inlet of carbon dioxide is the largest relative to the other locations of the casing gas cooler.Compared with the cooling water mass flow rate of 0.03 kg/s,when the cooling water mass flow rate is 0.04 kg/s,the entransy dissipation decreases by 2.6%,and when the cooling water mass flow rate is 0.05 kg/s,the entransy dissipation decreases by 3.2%.With the increase of mass flow of carbon dioxide,the entransy dissipation increases.And with the increase of pressure,the entransy dissipation decreases.The research results can provide new ideas and reference for improving the structure and heat transfer performance of carbon dioxide gas cooler.

In order to reduce the pressure drop of the hydrocyclone and achieve the goal of energy saving and emission reduction,the hydrocyclone with slit structure at the bottom of the overflow pipe is designed.The separation performance of conventional(Type Ⅰ),overflow pipe double slit(Type Ⅱ) and overflow pipe single slit(Type Ⅲ) hydrocyclones was analyzed and studied when the inlet flow gradually increased from 780 mL/s to 1 000 mL/s.The test results show that with the increase of the inlet flow rate,the influence of the slit of the conical overflow pipe on the separation efficiency of the hydrocyclone decreases gradually,and the pressure drop amplitude increases gradually.When the inlet flow rate is 980 mL/s,the separation efficiency of the two improved hydrocyclones reaches the highest value.Compared with the Type I hydrocyclone,the separation efficiency of the Type II and Type III hydrocyclones are basically unchanged,while the percentage of pressure drop reduction is up to 22.85% and 27.46%,respectively.The energy saving effect is significant.The simulation results show that the axial velocity,tangential velocity and pressure of the improved hydrocyclone have decreased.The slit of the overflow pipe has a greater impact on the axial velocity,while the axial velocity at the center has a significant reduction,and has a smaller impact on the tangential velocity.It provides a basis for further exploring the law of the internal flow field of the hydrocyclone and improving the structure of the hydrocyclone.

In order to quantify the influence of adding fins outside tube on charging / replenishing process for cold panel with phase change material(PCM) in a refrigerated truck for urban cold chain logistics,the solidification process of RT5 HC was numerically analyzed.The effects of the numbers of fins,fin shape,fin thickness and fins arrangement of adjacent tubes of tube bank in cold panel on charging time and charging efficiency were discussed.The calculation results show that,when setting up fins on the charging tube,the liquid and partially solidified PCM were divided into several small areas,in which the natural convection is strengthened,meanwhile,the phase interface was extended,resulting in the increase of heat transfer area and acceleration of energy transfer.Compared with unfinned tubes in cold panel,the finned tubes shortened the charging time and improved charging efficiency considerably,meanwhile,cold storage capacity slightly decreased.When the number of fins increases from 4 to 6 and 8,the growth rate of ε and ε_f improves.While number of fins changes from 8 to 10,and the growth rate of ε and ε_f decreases.The fins with rectangle-section,by contrast,display higher fin efficiency and the value is 3.19.Larger fins thickness causes marginal promotion for charging efficiency;and fins arrangement of adjacent tubes of tube bank in cold panel has little influence on changing process.The above conclusions provide a reference for the design of tubes in cold panel filled with PCM.

In order to study the solid-liquid two-phase flow characteristics of hydrocyclone valve in urban pipeline sewage flow,based on the N-S equation of transient incompressible flow and the renormalization group RNG k-ε Turbulence model,coupled with particle trajectory tracking model,the initial boundary particle distribution model was processed with MATLAB programming,and the influences of particle mass concentrations(5%,10%,15%) on the pressure drop at the inlet and outlet of the hydrocyclone valve,the mass flow rate at the outlet,the particle trajectory distribution in the internal flow field,the particle spatial position and the liquid velocity streamline distribution were analyzed.The results show that with the increase of particle concentration,the mass flow rate at the outlet decreases(52.2~53.2 kg/s),and the pressure drop at the inlet and outlet increases linearly.The particle concentration affects the interception characteristics of the hydrocyclone valve;When the particle mass concentration is less than 15%,the particles have a good following in the flow field of the hydrocyclone valve;Through test verification,it is found that there is a gas zone rotating around a certain center inside the hydrocyclone valve,which can act on the inside of the outlet pipe of the hydrocyclone valve and play the role of interception;The hydrocyclone valve is beneficial to the technical development of sewage pipe interception control through its unique gas zone characteristics,and has a high application value.

In view of the cooling capacity attenuation problem of traditional refrigerators due to the reduction of volumetric efficiency,two different exhaust valve plate structural models were designed for reciprocating compressors under the high speed operating frequency of 100 Hz,and the movement characteristics of different exhaust valve plates as well as the impact of exhaust valve plate on the cooling capacity and performance of the compressor were analyzed.The results show that the stiffness of the exhaust valve plate is an important factor affecting the volumetric efficiency of the compressor at high speed;The combination scheme of small stiffness exhaust valve plate with spring reed can improve the high-frequency cooling capacity and low-frequency performance of reciprocating variable frequency compressor.Taking an 11 cm³ displacement compressor as an example,the total stiffness of exhaust valve plate with spring reed is 252.4% higher than that of the initial exhaust valve plate,the volumetric efficiency of the compressor operating under 100 Hz is 3.9% higher than that under the original scheme,and the performance (COP) of the compressor operating under 33 Hz is 0.04 higher than that under the original scheme.

Aiming at the problem that it is difficult to determine the optimal parameters of modified profile,comprehensively considering the influence of top modified profile on the gas force and modified scroll wrap strength of primitive cavity,the geometric model of double circular arc plus line-shaped method was deduced;the calculation formulas of compressor gas force and the end cross-section area of the scroll wrap after the scroll wrap was modified were analyzed,and the influences law of modified profile parameters on gas force and the end cross-section area was studied.Then,taking the peak value of gas force and the end crosssection area as the optimization objectives and the modified parameters of modified scroll wrap as the design variables,the modified parameters were optimized based on multi-objective genetic optimization algorithm.When the end cross-section area of the modified scroll wrap is basically unchanged,the peak value of the radial and tangential gas force decreases by up to 22.61%.The research results can provide a theoretical basis for the analytical calculation of gas force of modified scroll wrap and the selection of optimal parameters of modified profile.

In view of the difficulty in type selection of boiling pump,the advantages and disadvantages of standard centrifugal pump with mechanical seal,wet stator motor-driven centrifugal pump and canned motor-driven centrifugal pump as boiling pump were compared,and it was recommended to prefer the centrifugal pump driven by wet stator motor or the centrifugal pump driven by canned motor.In order to solve the problem of “stuck neck” in the supply of boiling pumps,an attempt was made to use the domestic wet stator motor-driven centrifugal pump as a boiling pump.The prototype was evaluated for industrial operation in the 2-million-ton liquid-phase diesel hydrogenation unit and achieved phased success.In view of the problems of insufficient performance and excessive current in the operation assessment,the causes were analyzed and improvement was made.The improved pump was evaluated again,and the continuous and stable operation of 5 040 hours without failure can basically meet the operation needs of the device.