真空集热管—水冷型太阳能吸附集热床的理论和实验研究

为提高太阳能吸附集热床的集热和散热性能,本文设计了一种新型真空集热管—水冷型太阳能吸附集热床。以活性炭纤维—甲醇为工质对,建立了吸附床非动态平衡吸附传热传质数学模型。以南京夏季典型一天的太阳辐射强度和温度为条件,模拟了吸附床内各点温度、压力、吸附率等随时间的变化规律。实验研究表明,在吸附阶段通水冷却可以迅速降低吸附床的温度,并验证了所建立数学模型的合理性,为系统的进一步优化设计提供了依据。

Controlling Nonlinear Dynamics in Continuous Crystallizers

Crystallization is used to produce vast quantities of materials. For several applications, continuous crystallization is often the best operation mode because it is able to reproduce better crystal size distributions than other operation modes. Nonlinear oscillation in continuous industrial crystallization processes is a well-known phenomenon leading to practical difficulties such that control actions are necessary. Nonlinear oscillation is a consequence of the highly nonlinear kinetics, different feedbacks between the variables and elementary processes taking place in crystallizers units, and the non-equilibrium thermodynamic operation. In this paper the control of a continuous crystallizer model that displays oscillatory behavior is addressed via two practical robust control approaches： （i） modeling error compensation, and （ii） integral high order sliding mode control. The controller designs are based on the reduced-order model representation of the population balance equations resulting after the application of the method of moments. Numerical simulations show good closed-loop performance and robustness properties

Numerical investigation of dynamic properties of plasma sheath with pitching motion

Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This paper investigates the dynamic properties of the plasma sheath by using the simplified conventional Burnett(SCB)equations and the Navier-Stokes(NS)equations with the thermochemical non-equilibrium effect.The eleven-species chemical kinetic models are applied to the comparison and there is verification of a dynamic plasma sheath simulation for the first time.After the introduction of vehicle pitching motion,the dynamic results are more consistent with the experimental data than the simulated results when treating it as static state.The plasma sheath characteristic parameters show periodic properties,whose changing period is the same as the pitching motion period.However,because of different velocities of the pitching motion,phase shifts exist in different positions of the vehicle.The enhancement of the rarefied effect weakens the disturbance to the plasma sheath.This research reveals the distribution and regularities of the dynamic plasma sheath.It is significant in solving the ionization blackout problem and the design of the reentry vehicle,and provides reliable data for further research on the dynamic plasma sheath.

Theoretical development for DSMC local time stepping technique

The direct simulation Monte Carlo(DSMC) method is the most mature and wildly used approach for nonequilibrium gas flow simulation.The phenomenological nature of this method brings flexibility to the computation algorithms.In this study,the theoretical foundations to decouple the molecular motion and collision within a time step are discussed in detail,which can be treated as criterions for the DSMC algorithms.Based on the theoretical developments,an improved local time stepping scheme is proposed,which specifies the movement time attribute and the collision time attribute for each representative particle.A free flow about a sphere body is considered as an example,which is compared with the calculations using the published local time stepping technique.The results show that the improved local time scheme is valid and is promising in realizing flow structures with strong variations.

Effect of Nozzle Inlet Shape on Annular Swirling Flow with Non-Equilibrium Condensation

Recently,by combining a swirl flow with non-equilibrium condensation phenomena of condensate gas generated in a supersonic flow,a separating and extracting techniques of condensate gas have been developed.This technique can reduce the size of the device and don't use chemicals.In the present study,by using a non-equilibrium condensation phenomenon of moist air occurred in the supersonic flow in the annular nozzle composed of an inher body and an outer nozzle with a swirl,the possibility of separation of the condensable gas and the effect of shape of nozzle inlet on the flow field were examined numerically.

Competition between attraction and diffusion in nanoscale non-equilibrium aggregation

The competition between attraction and diffusion determines the kinetics of non-equilibrium aggregation process.The formation of silver nanoclusters through non-equilibrium aggregation of silver atoms in solution was simulated by molecular dynamics as a model system to study the influence of the competition between attraction and diffusion on the aggregation process by varying concentration and temperature.It has been found that the aggregation time decreases monotonically with increasing concentration of silver atoms because of increasing attraction,while initially decreasing and then increasing with increasing temperature because of the competition between accelerated attractive motion and increasing diffusive motion of silver atoms.A mean field approximation was employed to develop a phenomenological model describing the mechanism of temperature dependence of aggregation time.

Methodology of non-equilibrium thermodynamics for kinetics research of CO_2 capture by ionic liquids

In this paper, the methodology of non-equilibrium thermodynamics is introduced for kinetics research of CO2 capture by ionic liquids, and the following three key scientific problems are proposed to apply the methodology in kinetics research of CO2 capture by ionic liquids: reliable thermodynamic models, interfacial transport rate description and accurate experimental flux. The obtaining of accurate experimental flux requires reliable experimental kinetics data and the effective transport area in the CO2 capture process by ionic liquids. Research advances in the three key scientific problems are reviewed systematically and further work is analyzed. Finally, perspectives of non-equilibrium thermodynamic research of the kinetics of CO2 capture by ionic liquids are proposed.