In order to improve the scientificity and rationality of cold chain system design, the plate heat exchanger of a branch of the nuclear power plant cold chain system of nuclear power plants is taken as the research object. Based on the basic principles of optimization design, appropriate optimization calculation algorithms are developed and plate type heat exchangers are developed. The design program of the heat exchanger forms an optimal design analysis tool. Taking a plate heat exchanger as an example, taking its mass, flow resistance on the hot side and flow resistance on the cold side as the optimization objectives, a new hybrid genetic algorithm was used to carry out a multi-objective optimization case analysis. The calculation results show that there is a competitive relationship between the mass of the plate heat exchanger of the nuclear island cold chain system of the nuclear power plant and the flow resistance on the hot and cold sides, and the optimal solution cannot be obtained at the same time. There is a correlation between the flow resistance on the cold side and the flow resistance on the hot side. If the heat exchanger mass is reduced by 6.39%, the flow resistance of the hot side and cold side will increase by 6.55% and 7.71% respectively; if the flow resistance on the hot side and cold side are reduced by 32.22% and respectively 32.01%, its mass will increase by 2.16%; on the premise of keeping the mass of the heat exchanger basically unchanged, the flow resistance on the hot side of the heat exchanger is reduced by 23.84% and at the same time the flow resistance on the cold side is reduced by 19.77%, and the flow resistance on the cold side is reduced by the largest 23.35% and at the same time reduce the flow resistance on the hot side by 12.54%. Therefore, there is a lot of room for optimization in the design of nuclear island cold chain system of nuclear power plant and there are many optimization schemes. The research results can provide reference for the subsequent optimization of nuclear power plant cold chain system design and improve the scientific and economic efficiency of system design.

Based on the one-dimensional simulation model of lubricating oil system is established and analyzed by using FLOWMASTER software, this paper proposes a new method of optimizing lubricating oil system by PID technology. Ensure that the configuration requirements and control strategies of the relevant accessories of the simulation model are satisfied with the design requirements. Firstly, by simulating lubricating oil pressure fluctuation and lubricating oil flow distribution under Open/Close Valve in different opening and closing time, the optimal opening/closing time of Open/Close Valve is determined to be 0.2 s and 0.5 s respectively. Secondly, by writing the controller script file combined with a controller to realize automatic unloading relief valve simulation, determine the relief valve pressure regulating range of 0∼0.38 MPa, For precision of constant pressure valve of oil spill, the simulation results show that the average 10 m 3 /h flow caused by pressure changes of about 0.06 MPa. Under the flow sudden change signal of about 40 m 3 /h, the maximum pressure change is less than 0.1 MPa. Through the simulation results, it is found that most of the lubrication parts in the original design have the phenomenon of flow redundancy, which causes unnecessary pump power loss. The system is optimized by PID technology. By comparing the simulation results before and after optimization, it is found that the speed of constant displacement pump could be changed in time by PID controller, and the flow redundancy could be improved significantly, so the lubricating oil system could be lower consumption and achieve the purpose of optimization.

High-resolution particle image velocimetry (PIV) was used to study the flow characteristics in the nearfield of a turbulent round water jet issuing from a circular nozzle. Mean velocity, velocity gradient, turbulence intensity, Reynolds stress and other turbulence statistics are investigated over a range of jet Reynolds number Re (based on jet exit velocity and equivalent nozzle diameter) varying from 531 to 13500. The distribution of parameters of different Reynolds numbers and different height sections was studied. The velocity measurements reveal that all exit jet profiles in the near-field closely approximate a single peak shape, and they show strict self-similarity. Compare turbulence intensity, Reynolds stress with different Reynolds number jet, the self-similarity is shown along jet path when Reynolds number is low, and the self-similarity is shown after the turbulence is fully developed when Reynolds number is high. The shapes of Reynolds stress of high Reynolds number jet change from double peak to single peak along jet path, and the shapes are always single peak at low Reynolds numbers. This critical Reynolds number is about 2000. In addition, the turbulence statistics can be used to correct the coefficients of the turbulence equation and large eddy simulation.

Single-phase natural circulation experiments were conducted to study the flow resistance and heat transfer characteristics in a 3 × 3 rod bundle channel with the ratio of rod pitch and rod outer diameter ( P / D ) 1.38. The range of inlet subcooling degree is 30∼90K and the heating power is 1∼20kW. The rods are heated with constant heat flux. According to the experimental results, the flow regime under natural circulation condition is divided and the transition Reynolds number is considered as 800. The flow transition is recognized by the slope change of friction factor curve since the flow transition in the rod bundle channel is not as obvious as that in round pipe. Simultaneously, the flow transition in the rod bundle is much earlier and the upper critical Reynolds number is much larger compared to regular channel like round pipe and rectangular channel. Two correlations for laminar and transition regime are fitted to calculate the friction factor. As for the grid spacer local resistance coefficient, there is slight change at Reynolds number 800 and similarly two correlations are fitted to calculate the local resistance coefficient. The Nusselt number tendency changes at around Reynolds number 4000 but keep unchanged at transition point, which means the flow transition has no obvious effect to the heat transfer. The heat transfer results are compared with different single-phase convective heat transfer correlations. D-B and Gnielinski correlations are not suitable for the heat transfer prediction in rod bundle channel and the relative deviation is more than 20%. Weisman, Presser and Markoczy correlations predict relatively well in high Reynolds number region, and Markoczy correlation is the best of them. In low Reynolds number region, most experimental results are larger than the correlations. D-B correlation based methods may be unsuitable for the heat transfer prediction in rod bundle channel and a new correlation needs to be proposed.

The plate-type fuel element is widely used in ship-based nuclear reactors. The typical coolant channel in such reactor is a narrow rectangular one with a relatively large aspect ratio. The thermal-hydraulic characteristics in narrow rectangular channels may be different from that in conventional pipe. It could be expected that the geometry of narrow channels has some impact on the bubble behaviors in subcooled flow boiling. In this paper, the bubble behaviors were simulated by using CFD software FLUENT in narrow rectangular channel with different widths under both stagnation conditions and flow conditions. The main concern was placed on the parameters of bubble departure time, departure diameter and departure velocity. In the model setup process, the VOF model and PISO algorithm were selected. The results were compared against the experimental data and showed the models good capability of capturing the interface between gas and liquid. Furthermore, for stagnation cases, the width of the channel played an important role for bubble departure diameter. In flow cases, the width also had a great impact on departure diameter and departure velocity as well. The departure time and departure velocity showed strong relevance with each other under different contact angle conditions.

Experiments on onset of nucleate boiling (ONB) have been performed for the natural circulation flow in a one-sided heated narrow rectangular channel. With fast camera putting into use, the visualization study was conducted to capture the location of ONB. The experiments were performed at pressure of 0.2 MPa and 0.3 MPa, with subcooling temperature ranging from 40 to 60 K, and heating flux ranging from 70 to 220 kW/m 2 . Differing from conventional channel, the superheats of wall surface in the narrow rectangular channel needed for ONB is larger, and can be predicted with Thom’s correlation in developed flow region. Moreover, the superheat needed for ONB will decrease for the existence of entrance effect. The visualization study indicated that the traditional determination of ONB will bring in more error. In this study, valuable data and image have been provided for the error analysis of ONB.

Double nodal diameter spectrum (DNDS) method which is used to analyze nodal diameter (ND) components of the vibration modes of impellers with splitters is proposed and its application in quantification of mode localization has been studied. Firstly, ND characteristics of the typical impeller with splitter blades are analyzed by mode shapes and representative subeigenvectors. Secondly, DNDS method is proposed and DNDSs of the representative modes indicate that the tuned modes of impellers with splitter blades contain two ND components. By applying the simplified engine order (EO) excitation in the form of a travelling wave, harmonic response analysis has been carried out by which double nodal diameter vibration characteristics of the structure and the effectiveness of the DNDS method are both validated. Lastly, in terms of quantifying mode localization, the definition of mode localization factor (MLF) is improved based on DNDS. The numerical example proves that the pairing process of choosing the tuned mode corresponding to the mistuned one by utilizing both DNDS and the vibration pattern of blades when calculating the improved MLF could pick out the closest tuned mode to the mistuned one, which has a more explicit physical meaning.

Rotor systems carried in transportation system or under seismic excitations are considered to have a moving base. The objective of this paper is to develop a general model for flexible rotor systems subjected to time-varying base excitations and study the direct effects of angular base motions on the dynamic behaviors of a simple rotor. The model is developed based upon finite element method and Lagrange’s equation. Two groups of Euler angles are introduced to describe the rotation of the rotor and the base, respectively. Six types of base motions are considered in the model. In the numerical simulations, three types of angular base motions (pitching, rolling and yawing) are considered and assumed to be sinusoidal varying with time. The effects of base angular amplitudes, base frequency and rotation speed on the system dynamic behaviors are discussed in detail. It is shown that pitching and yawing have a great influence on the response amplitudes and the shape of the rotor orbits. Especially, resonances occur when the base frequency meets the natural frequencies. The FFT and waterfall plots of the disk horizontal and vertical vibrations are marked with multiplications of the base frequency and sum and difference tones of the rotating frequency and the base frequency.

Machining errors have a significant effect on the gear engagement, so it is necessary to learn the mechanism of action for the reduction of vibration. The contact finite element method was utilized to study the effect of machining errors on the gear pair’s vibration. The 3D shape deviation caused by machining errors was decomposed into pitch error, profile error and helix error, the precise modeling method was first presented, on this basis the dynamic engagement process of one spur gear pairs was simulated continuously using contact finite element method as an example. The time-domain response of various dynamic parameters was obtained, and the angular velocity, dynamic meshing force and stress distribution showed significant differences between the ideal gear pairs and the gear pairs with machining errors. Then the influence mechanism of profile error, pitch error and helix error on the gear vibration was researched respectively, quantitative analysis of meshing characteristics including dynamic transmission error and angular acceleration was done using the FFT. The results show that the proposed modeling method can simulate arbitrary form of machining errors even if in small order and reflected in the contact finite element analysis. It is not only effective to investigate how the machining errors impact the meshing process, but also to study the influence mechanism of individual machining error. Furthermore, the conclusions can be used to guide the anti-vibration design and accuracy design.

Gas-structure coupling vibration is one kind of vibration caused by air pulsation. This coupling vibration causes widespread damage and deformation of three-stage cyclone separator used in Residue Fluid Catalytic Cracking (RFCC). After theoretically analyzing the mechanism of the generation of the gas-structure coupling vibration, the numerical simulation of three-dimensional swirling flow the cyclone separator was performed by using Reynolds Stress Model (RSM). The results showed the existence of processing vortex core (PVC) in the cyclone separator. The PVC phenomenon and motion of PVC were described in detail. Furthermore, the amplitude and frequency of gas fluctuation in the PVC region at different axial positions were quantitatively analyzed. The simulation results agreed with the experimental results of Laser Doppler Velocimetry (LDV). Finally, considering the characteristics of transient torsional pendulum of PVC in cyclone separator, the fluid-solid coupling dynamic characteristics of three-stage cyclone separator were analyzed by the finite element method, which provides references for the structure optimization design of new type cyclone separator.

An open natural circulation system applied to the passive containment cooling system is proposed for the large dry double-wall concrete containment after severe accidents. In order to investigate the operating behaviors of the open loop, a numerical code is developed to simulate the transient flow characteristics from the startup to the long-term operation. The results show that the open system may experience such four stages as startup process, quasi-steady single-phase flow, transition stage and quasi-steady two-phase flow. Flashing is the dominated factor in the last two flow phases. Additionally, the effects of some systematic parameters on the mass flow rate are analyzed in detail. Both increasing the condensation heat transfer coefficient and the containment temperature can enhance the flow effectively whichever stage the system operates in. But the the initial fluid temperature can only affect the duration of the single-phase flow but has little impact on the mass flow rate. Moreover, greater riser height can lead to bigger single-phase flow rate, but nearly has no influence on the long-term two-phase flow and the flashing region.

In this paper, we deal with a typical pressurizer surge line in a conventional pressurized water reactor (PWR). This study is performed to develop an understanding of thermal stratification phenomenon, which may occur in the surge line during either normal condition or transient process, in the pressurizer surge line. The pressurizer surge line model of Daya Bay nuclear power plant is used as base analysis model, in which the hot leg is taken into account. The transient temperature distribution required to assess the phenomenon along the pressurizer surge line is obtained through CFD analysis technology using ANSYS FLUENT. The temperature loads are transferred to ANSYS Mechanical for stress evaluation for the heat up transient process. Subsequently, the usage factor is calculated on the basis of ASME Section-III design curve. The possible mitigation scheme for the thermal stratification phenomenon of changing the layout angles is also simulated and analyzed in detail. The results show that the thermal stratification phenomenon will occur both in normal operating condition and in heat up transient process. The circumfluent effect makes the thermal stratification phenomenon exhibit unique profile due to the introduction of the hot leg. The continuous spray mass flow rate may influence both the temperature difference and the occurrence range for the thermal stratification phenomenon. The stress analysis incorporating both temperature load and pressure load is performed for pressurizer surge line model with hot leg for the conservative and complete heat up case.

A method of selecting master degrees of freedom (DOFs) for rotating substructure is presented in this paper to obtain reduced 3D rotor models. Fixed modes of the substructure below thrice the operating frequency are analyzed. According to each mode shape, the DOFs at where main kinetic energy locates are selected as master DOFs to decrease missing of dynamic coupling. Additional DOFs may be selected based on traditional substructure method. In the stationary reference frame, frequency-dependent gyroscopic effects can be included as damping matrices changing with spin speed. Besides, by selecting appropriate substructure, localized damping and key parts of the rotor for analysis can be kept the same as the original model. A reduced model of a high pressure rotor amply demonstrated the capability of the method in reducing the model size and increasing the computational efficiency with less than two percent error.

3D finite element modeling is a promising method, but it is not well extended to the dynamic analysis of anisotropic asymmetric rotor bearing systems. This paper is aimed at proposing a dynamic analysis method of anisotropic asymmetric rotor bearing systems based on 3D finite element method. In the proposed approach, the advantages of 3D finite element modeling are used to accurately simulate the dynamic characteristics of the asymmetric rotor. The asymmetric characteristics of the stator are considered and simplified as time-varying bearing stiffness parameters in the rotating frame. The time-varying coefficient differential equation of motion of the rotor bearing system is established in a rotating frame by taking consideration of the bearing characteristics. Floquet theory and Hill expansion method are adopted to obtain the set of equivalent linear time-invariant equations of the original time-varying coefficient differential equations. Frequency characteristics and stability of the system were obtained by solving the equivalent linear time-invariant equations. Two numerical examples are analyzed. The results of the two examples show that the proposed 3D finite element method is a good tool for dynamic analysis of anisotropic asymmetric rotor bearing systems.

On the basis of passive containment cooling system concept, the one-dimensional codes are developed for the analysis of containment thermal-hydraulic characteristics under accident conditions, which can be applied to deal with large dry concrete containment in nuclear power plant. In order to build up the hypothesis flowing path, the containment space is divided into a rising channel and downward ring during the geometric modeling process. In this paper, the physical models, the identification of solving methods and the verification of the codes are introduced. It is assumed that the control volumes take the adiabatic condition in addition to heat exchanger and breaks, and there is no exchange of mass, momentum and energy between each volume in the rising channel and corresponding volume in downward ring. In the analysis, we also assume that the heat in the containment can only be transferred through natural circulation by passive containment cooling system. Furthermore, the break is supposed in the center of bottom of the containment. In this paper, the responses of the containment are predicted with the codes under large LOCA scenario. Under the same conditions, the characteristics of the natural circulation are also analyzed through the codes for the passive containment cooling system. The results can provide some references for the design of the passive containment cooling system.

In this paper, a closed loop concept, which is composed of two heat exchangers with same scale, pipes, valves and one tank, has been developed as a passive containment cooling system for a large dry concrete containment. The system is designed to maintain the containment integrity by taking the heat drained into the containment following a severe accident, e.g. LOCA or MSLB. Under different conditions in containment, the system may operate in single phase mode or two phase mode. According to the design limitation of containment, the fixed temperature boundary condition is applied to the system analysis. We have developed the codes for the analysis of the system by ourselves. The operating behaviors of the system are studied numerically from startup to long term operation. In the light of the fact that the fraction of steam in the containment may be changing during the accident scenario, it is reasonable that the heat transfer coefficient will be different. Therefore, the sensitivity analysis of the heat transfer coefficient is also performed. Based on the results and corresponding analysis, it can be concluded that the system may be utilized to meet the design purpose for the containment integrity requirement.