THREE-DIMENSIONAL COUPLED IMPELLER-VOLUTE SIMULATION OF FLOW IN CENTRIFUGAL PUMP AND PERFORMANCE PREDICTION

A three-dimensional turbulent flow through an entire centrifugal pump is simulated using k-ε turbulence model modified by rotation and curvature, SIMPLEC method and body-fitted coordinate. The velocity and pressure fields are obtained for the pump under various working conditions, which is used to predict the head and hydraulic efficiency of the pump, and the results correspond well with the measured values. The calculation results indicate that the pressure is higher on the pressure side than that on the suction side of the blade; The relative velocity on the suction side gradually decreases from the impeller inlet to the outlet, while increases on the pressure side, it finally results in the lower relative velocity on the suction side and the higher one on the pressure side at the impeller outlet; The impeller flow field is asymmetric, i.e. the velocity and pressure fields arc totally different among all channels in the impeller; In the volute, the static pressure gradually increases with the flow route, and a large pressure gratitude occurs in the tongue; Secondary flow exists in the rear part of the spiral.

Effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump

To study the effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump, guide vane outlet angle/34 is considered to be 20°, 15°, 10°, 5° and 3° respectively. Based on ANSYS Fluent, numerical results of pump head and efficiency are validated by exper/ment results, in which Xanthan gum solutions are used with concentration of 0.06 wt. % as working fluid. Then, the effects of/34 on pump performance and impeller radial force are discussed, the errors of head and efficiency between test and simulation are within 5%. The results a/so indicate that the pump performance and efficiency are much better than those of other angles when guide vane outlet angle/34 is 10°, and the maximum variations in head and efficiency are 1.9% and 2.2%, respectively. With/34 increasing, the pulsation of radial force decreases firstly and then increases, when/34 is 10°, the minimum pulsation is 0. 0392N, which is about 80% of the maximum pulsation amplitude.

Monitoring actual performance of ground source heat pump system using GPRS-based data transmission: A case analysis in Tangshan

The energy efficiency monitoring is an essential precondition for ground source heat pump system's controlling and energy saving operation. Based on the data monitoring applied in the school building, this work is focused on the parameters acquisition and operation analysis of the GSHP system in Tangshan. Results show the average COPs(coefficient of performance) are2.85 and 2.70 in summer and winter, respectively, and heat(cold) unbalance underground existed after whole year operation. The analysis of data also indicates that the direct borehole air-conditioning saved some power consumption obviously in the early stage of summer and energy saving of the GSHP system depended remarkably on its operation and management level. Besides the observation points of ground temperature are laid for a large-scale GSHP system, and the hydraulic balance of the pipes group needs to be concerned specially in safeguarding better reliability.

A Flexible Valve Based Piezoelectric Pump for High Viscosity Cooling Liquid Transportation

A piezoelectric pump with flexible valve has been developed to pump high viscosity cooling liquid in the nanosats thermal control system. The structure of the flexible valve is designed according to the characteristics of the human aortic shape with the aim to simulate the bionic pumping function of the human heart. Dynamic stress-strain features of the flexible valve are analyzed by the finite element method,and the results show that the proposed flexible valve is suitable and functional for the piezoelectric pump. Then the cylinder and diffuser/nozzle piezoelectric pumps based on flexible valves have been developed and fabricated. Experimental results of the output performance indicate that the maximum flow rate of the cylinder piezoelectric pump with flexible valve is 15.38 mL/min,170.77% higher than the diffuser/nozzle piezoelectric pump with flexible valve. The ability of the cylinder piezoelectric pump with flexible valve for transmitting high viscosity liquid has been validated. The piezoelectric pump with flexible valve has potential applications in the nanosats thermal control system.

Effects of rotational speeds on the performance of a centrifugal pump with a variable-pitch inducer

The centrifugal pumps usually work at various rotational speeds. The variation in the rotational speeds will affect the internal flow, the external performance, and the anti-cavitation performance of the pump. In order to improve the anti-cavitation performance of the centrifugal pumps, variable-pitch inducers are placed upstream of the impeller. Because the rotational speeds directly affect the flow and the performance of the pump, it is essential to characterize the performance of the pump with a variable-pitch inducer at various rotational speeds. In this paper, the simulations and the experimental tests of a centrifugal pump with a variable-pitch inducer are designed and carried out under various rotational speed conditions. Navier-Stokes equations, coupled with a Reynolds average simulation approach, are used in the simulations. In the experimental tests, the external and anti-cavitation performances of the pump are investigated in a closed system. The following results are obtained from the simulations. Firstly, the velocity in the passage of the inducer rises with the increase of the rotational speed. Secondly, the static pressure escalates on the inducer and the impeller with the increase of the rotational speed. Thirdly, the static pressure distribution on the inducer and the impeller is asymmetric. Fourthly, the anti-cavitation performance of the pump deteriorates with the increase of the rotational speed. Additional results are gathered from an analysis of the experiments. H-Q curves are similar parabolas at various rotational speeds, while η-Q curves are similar parabolas only when n ≤6 000 r/min. The anti-cavitation performance of the pump deteriorates with the increase of the rotational speed. Finally, the simulation results are found to be consistent with the experimental results.

The final limitation of receiver terminal performance with remotely pumped preamplifiers

In this paper, the performance of receiver terminals with remotely pumped preamplifiers (RPPAs) is analyzed by numerical simulation and experiment. Both simulation and experiment show that there is an optimal RPPA location and optimal pump power according to the highest performance. The amplified spontaneous Raman scattering (ASRS) self-oscillation caused by Rayleigh backscattering (RBS) and the lump reflector in transmission line are the final performance limitation.

Viscous Micropump Simulation by Particle/Continuum Methods

A novel viscous micropump consisting of a cylindrical rotor eccentrically placed inside a microchannel is simulated by the two Volume-CAD(V-CAD)framework-based flow solvers,i.e.,the direct simulation Monte Carlo(DSMC)package(named as V-DSMC)and the Navier-Stoke solver(named as V-Flow).V-DSMC is used in the case of the pump applied to gas,while V-Flow is applied to model the pump in the case of liquid working medium.The pumping performance curves under different liquid media with the variation of Reynolds number,as well as under different eccentricity factors are obtained.The performance and the flow filed characteristics are very sensitive to the tangential momentum accommodation coefficient in the case of gas medium.Three recirculations exist in the flow field,and the sizes of recirculation are different at the different operating points in a performance curve.

Systematical Experiment for Optimal Design of Vibrating Flow Pump with Jelly-fish Valve

The fundamental characteristics and the flow mechanism of a Vibrating Flow Pump （VFP） with a jelly-fish valve, which can be applied to a novel artificial heart, were studied theoretically and experimentally. By using water as the working fluid, the measurement methodology for the typical unsteady flow for VFP was developed here. The effects of the frequency, amplitude and inner diameter of the vibrating pipe, and thickness of the silicone rubber sheet of the jelly-fish valve on the basic per- formance of VFP were systematically investigated. A high-speed observation technique and simple theoretical model analysis were also introdueed for further detailed discussion. Quantitative contributions of the individual parameters to the pumping performance were shown through the experiment, which would give us essential knowledge for establishing design criteria of VFE The theoretical model, which agreed with the experiment and the high-speed observation, elucidated the pumping mechanism with respect to the role of inertia of the inner fluid.

Simulation of the flow and thermal breakthrough of a forced external circulation standing column well

The flow and thermal breakthrough phenomenon in a forced external circulation standing column well(FECSCW)directly affects heat transfer efficiency and load-carrying capacity.A numerical model for FECSCW is developed to analyze the migration of the temperature and velocity front under the flow and thermal breakthrough.The results indicated that thermal breakthrough began after simulation running 2.5 min and was completely formed after 12 min.The inlet water,which directly entered the production well without heat exchange with the aquifer,accounted for 12.8%.When the porosity of the backfill material decreased from 0.35 to 0,the coefficient of per-formance(COP)of the heat pump unit increased by 1.6%on average,and the thermal breakthrough strength decreased by an average of 45.3%within 25 min.Where seepage velocity near the well wall was greater than 1×10^(−3) m·s^(−1),faster velocity front migration was observed,while the migration advantage of the temperature front was more prominent outside of this region.Through quantitative analysis of flow and thermal breakthrough,temperature and velocity front migration,and COP change of heat pump unit,theoretical suggestions were pro-vided for the thermal transfer mechanism near the thermal well wall.The extended research in this study can be applied to the design and optimization of forced external circulation standing column well system.