PIV measurement and numerical investigation on flow characteristics of simulated fast reactor fuel subassembly

Zhang, Cheng,Ju, Haoran,Zhang, Dalin,Wu, Shuijin,Xu, Yijun,Wu, Yingwei,Qiu, Suizheng,Su, G.H. Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.5

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

Prediction of flow boiling heat transfer coefficient in horizontal channels varying from conventional to small-diameter scales by genetic neural network

Jing Zhang,Yichao Ma,Mingjun Wang,Dalin Zhang,Suizheng Qiu,Wenxi Tian,Guanghui Su 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Three-layer back propagation network (BPN) and genetic neural network (GNN) were developed in this study to predict the flow boiling heat transfer coefficient (HTC) in conventional and small-diameter channels. The GNN has higher precision than BPN (with root mean square errors of 17.16% and 20.50%, respectively) and other correlations. The inputs include vapor quality x, mass flux G, heat flux q, diameter D and physical parameter φ, and the predicted flow boiling HTC is set as the outputs. Influences of input parameters on the flow boiling HTC are discussed based on the trained GNN: nucleate boiling promoted by a larger saturated pressure, a larger heat flux and a smaller diameter is dominant in small channels; convective boiling improved by a larger mass flux and a larger vapor quality is more significant in conventional channels. The HTC increases with pressure both in conventional and small channels. The HTC in conventional channels rises when mass flux increases but remains almost unaffected in small channels. A larger heat flux leads to the HTC growth in small channels and an increase of HTC was observed in conventional channels at a higher vapor quality. HTC increases inversely with diameter before dry out.

Preliminary design and assessment of a heat pipe residual heat removal system for the reactor driven subcritical facility

Wenwen Zhang,Kaichao Sun,Chenglong Wang,Dalin Zhang,Wenxi Tian,Suizheng Qiu,G.H. Su 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12

A heat pipe residual heat removal system is proposed to be incorporated into the reactor drivensubcritical (RDS) facility, which has been proposed by MIT Nuclear Reactor Laboratory for testing anddemonstrating the Fluoride-salt-cooled High-temperature Reactor (FHR). It aims to reduce the risk of thesystem operation after the shutdown of the facility. One of the main components of the system is an aircooled heat pipe heat exchanger. The alkali-metal high-temperature heat pipe was designed to meet theoperation temperature and residual heat removal requirement of the facility. The heat pipe modeldeveloped in the previous work was adopted to simulate the designed heat pipe and assess the heattransport capability. 3D numerical simulation of the subcritical facility active zone was performed by thecommercial CFD software STAR CCM þ to investigate the operation characteristics of this proposedsystem. The thermal resistance network of the heat pipe was built and incorporated into the CFD model. The nominal condition, partial loss of air flow accident and partial heat pipe failure accident weresimulated and analyzed. The results show that the residual heat removal system can provide sufficientcooling of the subcritical facility with a remarkable safety margin. The heat pipe can work under therecommended operation temperature range and the heat flux is below all thermal limits. The facilitypeak temperature is also lower than the safety limits

Airborne Infrared Scanning Imaging System with Rotating Drum for Fire Detection

Dalin Song,Jun Chang,Jiao Cao,Lifei Zhang,Yao Wen,Aman Wei,Jiang Li 한국광학회 2011 Current Optics and Photonics Vol.15 No.4

Airborne infrared techniques have been used in wild land fire management for decades. This paper describes a kind of infrared scanning system based on a rotating drum with a tilted porthole underside the plane nose. This design increases the stability of the mechanism system, reduces air resistance and protects inner parts. Aberration characteristics of a tilted ellipsoid porthole are analyzed and an effective solution is invented which makes the system achieve 30° field of regard. The system’s ultimate value of modulation transfer function is near the diffraction limit, which indicates that the performance of the rotating optical system meets the imaging requirements.

Numerical study of oxygen transport characteristics in lead-bismuth eutectic for gas-phase oxygen control

Wang, Chenglong,Zhang, Yan,Zhang, Dalin,Lan, Zhike,Tian, Wenxi,Su, Guanghui,Qiu, Suizheng Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.7

One-dimensional oxygen transport relation is indispensable to study the oxygen distribution in the LBE-cooled system with an oxygen control device. In this paper, a numerical research is carried out to study the oxygen transport characteristics in a gas-phase oxygen control device, including the static case and dynamic case. The model of static oxygen control is based on the two-phase VOF model and the results agree well with the theoretical expectation. The model of dynamic oxygen control is simplified and the gas-liquid interface is treated as a free surface boundary with a constant oxygen concentration. The influences of the inlet and interface oxygen concentration, mass flow rate, temperature, and the inlet pipe location on the mass transfer characteristics are discussed. Based on the results, an oxygen mass transport relation considering the temperature dependence and velocity dependence separately is obtained. The relation can be used in a one-dimensional system analysis code to predict the oxygen provided by the oxygen control device, which is an important part of the integral oxygen mass transfer models.

Assessment of ECCMIX component in RELAP5 based on ECCS experiment

Song, Gongle,Zhang, Dalin,Su, G.H.,Chen, Guo,Tian, Wenxi,Qiu, Suizheng Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.1

ECCMIX component was introduced in RELAP5/MOD3 for calculating the interfacial condensation. Compared to other existing components in RELAP5, user experience of ECCMIX component is restricted to developmental assessment applications. To evaluate the capability of the ECCMIX component, ECCS experiment was conducted which included single-phase and two-phase thermal mixing. The experiment was carried out with test sections containing a main pipe (70 mm inner diameter) and a branch pipe (21 mm inner diameter) under the atmospheric pressure. The steam mass flow in the main pipe ranged from 0 to 0.0347 kg/s, and the subcooled water mass flow in the branch pipe ranged from 0.0278 to 0.1389 kg/s. The comparison of the experimental data with the calculation results illuminated that although the ECCMIX component was more difficult to converge than Branch component, it was a more appropriate manner to simulate interfacial condensation under two-phase thermal mixing circumstance, while the two components had no differences under single-phase circumstance.

A Multicast Search Scheme Based on Bipartite Graph Matching Model

Yuan Yao,Zhang Dalin,Wang Qing,Shi Jinglin 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.11

This paper proposes an efficient multicast search scheme based on bipartite graph matching model, aiming at one of the most important problems in the multicast service, how can the wireless network track and locate the mobile uses in the idle state, under the tight bandwidth and delay constraints,. By quantifying the location uncertainty of mobile users with Shannon's entropy, the scheme adopts the LZ78 compression algorithm to design location update scheme and predict the location probability, in order to reduce the cost of location update. The multicast search system need to guarantee the maximum total probability that each user resides at the assigned paging area, for the purpose of an optimal performance on both expected paging delay and paging cost. Therefore, the bigraph-based multicast paging scheme (BMPS) firstly builds the bipartite graph model of multicast search problem, through converting the location probability into weight of the edge. BMPS decides the optimal allocation between the mobile users and location areas, which is mainly achieved by the maximum weight perfect matching in bipartite graph, while modifying the weights dynamically. Simulation results show that BMPS yields a low search delay as well as a low search cost, and reduces the impact of user collision.

Thermal-hydraulic research on rod bundle in the LBE fast reactor with grid spacer

Liu Jie,Song Ping,Zhang Dalin,Wang Shibao,Lin Chao,Liu Yapeng,Zhou Lei,Wang Chenglong,Tian Wenxi,Qiu Suizheng,Su G.H. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.7

The research on the flow and heat transfer characteristics of lead bismuth(LBE) is significant for the thermal-hydraulic calculation, safety analysis and practical application of lead-based fast reactors(LFR). In this paper, a new CFD model is proposed to solve the thermal-hydraulic analysis of LBE. The model includes two parts: turbulent model and turbulent Prandtl, which are the important factors for LBE. In order to find the best model, the experiment data and design of 19-pin hexagonal rod bundle with spacer grid, undertaken at the Karlsruhe Liquid Metal Laboratory (KALLA) are used for CFD calculation. Furthermore, the turbulent model includes SST k u and k ε; the turbulent Prandtl includes Cheng-Tak and constant (Prt ¼1.5,2.0,2.5,3.0). Among them, the combination between SST k u and Cheng-Tak is more suitable for the experiment. But in the low Pe region, the deviation between the experiment data and CFD result is too much. The reason may be the inlet-effect and when Pe is in a low level, the number of molecular thermal diffusion occupies an absolute advantage, and the buoyancy will enhance. In order to test and verify versatility of the model, the NCCL performed by the Nuclear Thermal-hydraulic Laboratory (Nuthel) of Xi'an Jiao tong University is used for CFD to calculate. This paper provides two verification examples for the new universal model

Impact of axial power distribution on thermal-hydraulic characteristics for thermionic reactor

Zhiwen Dai,Chenglong Wang,Dalin Zhang,Wenxi Tian,Suizheng Qiu,G.H. Su 한국원자력학회 2021 Nuclear Engineering and Technology Vol.53 No.12

Reactor fuel's power distribution plays a vital role in designing the new generation thermionic SpaceReactor Power Systems (SRPS). In this paper, the 1/12th SPACE-R's full reactor core was numericallyanalyzed with two kinds of different axial power distribution, to identify their impacts on thermalhydraulic and thermoelectric characteristics. In the benchmark study, the maximum error betweennumerical results and existing data or design values ranged from 0.2 to 2.2%. Four main conclusions wereobtained in the numerical analysis: a) The axial power distribution has less impact on coolant temperature. b) Axial power distribution influenced the emitter temperature distribution a lot, when the corepower was cosine distributed, the maximum temperature of the emitter was 194 K higher than that ofthe uniform power distribution. c) Comparing to the cosine axial power distribution, the uniform axialpower distribution would make the maximum temperature in each component of the reactor core muchlower, reducing the requirements for core fuel material. d) Voltage and current distribution were similarto the axial electrode temperature distribution, and the axial power distribution has little effect on theoutput power

Experimental study on the Influence of Heating Surface Inclination Angle on Heat Transfer and CHF performance for Pool Boiling

Chenglong Wang,Panxiao Li,Dalin Zhang,Wenxi Tian,Suizheng Qiu,G.H. Su,Jian Deng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.1

Pool boiling heat transfer is widely applied in nuclear engineering fields. The influence of heating surface orientation on the pool boiling heat transfer has received extensive attention. In this study, the heating surface with different roughness was adopted to conduct pool boiling experiments at different inclination angles. Based on the boiling curves and bubble images, the effects of inclination angle on the pool boiling heat transfer and critical heat flux were analyzed. When the inclination angle was bigger than 90°, the bubble size increased with the increase of inclination angle. Both the bubble departure frequency and critical heat flux decreased as the inclination angle increased. The existing theoretical models about pool boiling heat transfer and critical heat flux were compared. From the perspective of bubble agitation model and Hot/Dry spot model, the experimental phenomena could be explained reasonably. The enlargement of bubble not only could enhance the agitation of nearby liquid but also would cause the bubble to stay longer on the heating surface. Consequently, the effect of inclination angle on the pool boiling heat transfer was not conspicuous. With the increase of inclination angle, the rewetting of heating surface became much more difficult. It has negative effect on the critical heat flux. This work provides experimental data basis for heat transfer and CHF performance of pool boiling.