变浓度热泵实验系统自动控制研究

结合变浓度系统中的温度控制要求,对实验系统自动控制方案进行设计,并对控温程序采用LabVIEW7.0进行了编写.在软件设计的基础上进行了PID参数自整定调试及控温实验等.实验结果表明,冷凝器进水温度能准确地控制在设定温度的±0.1 ℃以内,蒸发器出口温度控制在设定温度的±0.3 ℃以内,从一个工况到另一个工况的过渡时间不大于15 min.控制程序可以较好地满足实验要求.     

变频多联机室外机在线高效自动测试技术研究

针对多联机室外机在线生产测试节拍要求快的现状,提出一种高效室外机开启故障判断的新方法,测试系统完全省去室内机,由气液短接管、辅助热气喷射、制冷剂充注量与气液短接管管径适宜匹配实现机组的正常运转,由自动化软件程序控制室外机主要部件的动作并与预分析状态进行有效对比。通过分析不同频率下压缩机吸气压力、排气压力、部件程序开启得出室外机装配是否正确。实证表明:相比传统测试方法(带辅助室内机),新型在线测试系统室外机在线测试耗时由传统测试方法的25分/台减少到5分/台左右,能耗大幅降低,生产效率也大幅提高。     

Performance optimization for a variable throat ejector in a solar refrigeration system

In a solar vapor ejector refrigeration system, the solar heat supply may vary because of variations in solar irradiation intensity, making it difficult to maintain a steady generator temperature. To improve ejector performance, this study proposes a variable throat ejector (VTEJ) and analyzes its performance using CFD simulations. The following conclusions can be drawn. An ejector with a greater throat area and larger solar collector allows a wider operating range of generator temperatures, but may be overdesigned and expensive. Conversely, decreasing the throat area limits the operating range of generator temperatures. Thus the ejector with a fixed throat area may be unsuitable to use solar energy as a heat source. For a VTEJ, this study derives a curve-fitting relationship between the optimum throat area ratio and the operating temperatures. Using this relationship to adjust the throat area ratio, the ejector can consistently achieve optimal and stable performances under a varying solar heat supply.     

Capacity control in ground source heat pump systems part II: Comparative analysis between on/off controlled and variable capacity systems

In the present paper, as the second part of two, modeling and simulation was carried out for a Ground Source Heat Pump (GSHP) system in the presence of all the most important interacting sub-systems such as building, ground heat source, electrical auxiliary heater, and the heat pump unit in order to make a fair and comprehensive comparison between the annual performance of on/off controlled and variable capacity systems. The annual modeling showed that dimensioning of the on/off controlled GSHP based on the peak heat demand of the building plays a significant role when the two control strategies are compared: if the on/off controlled GSHP is dimensioned to cover only 55% of the peak heat demand of the building, the electrical auxiliary, which then covers about 10% of the annual heating demand of the building, makes the SPF of the on/off controlled GSHP to be lower than the one of the variable speed system. On the contrary, when the on/off controlled system is dimensioned to cover more than 65% of the building’s peak heat demand, i.e. more than 95% of the annual heat demand of the building, there is no considerable difference between the SPFs of the on/off controlled and variable capacity systems.     

A mathematical model of variable displacement swash plate compressor for automotive air conditioning system

A mathematical model of control mechanism used in the variable displacement swash plate compressor (VDSC) is developed firstly based on the force balance equation, mass and energy conservation equation. The model of moving components dynamics is developed then by analyzing the forces and force moments acting on the pistons and the swash plate. The compression process model is obtained by fitting the data from our experiments. And finally, the steady-state mathematical model of VDSC is developed by combining the three sub-models above. In order to verify the mathematical model, a test bench for control mechanism and the test system for VDSC have been established, and the simulated results agree well with the experimental data. The simulation results show that, like the variable displacement wobble plate compressor, there are four operation modes for the VDSC, i.e. constant rotary speed and constant piston stroke length (PSL), variable rotary speed and constant PSL, constant rotary speed and variable PSL, variable rotary speed and variable PSL, which have included almost all operation modes of the refrigeration compressor in common use. And there is a hysteresis zone and multiple-valued relationship between the compressor parameters when PSL changes.     

变流量空调水系统稳定性的分析及试验研究

为了探讨压差控制的稳定性,提高该控制方式的节能效果,通过水力稳定度的计算,阐述了水力稳定度对水系统稳定性关系,并讨论了变流量空调水系统中压差设定值及定压点位置对各水力稳定度的影响.最后得出结论:定压点越靠近循环泵,系统总体稳定性越好,但这却降低了水泵的节能效果,压差设定值大小对水力稳定度没有影响.     

A hybrid method for refrigerant flow balancing in multi-circuit evaporators: Upstream versus downstream flow control

A hybrid method for optimizing refrigerant distribution in evaporators is presented that involves the use of small balancing valves in each circuit along with a primary expansion device to control the overall superheat from the evaporator. The flow balancing valves could be located upstream or downstream of the evaporator. This paper presents the results of a study to investigate the benefits of this hybrid scheme for both upstream and downstream flow balancing for the case of air flow mal-distribution. In order to perform this investigation, a simulation model was developed to consider evaporator flow mal-distributions for a 10.55 kW residential R410A heat pump and then validated through comparisons of predicted results with measurements. Simulation results show that there are significant benefits in controlling the superheat of each circuit of evaporators through the hybrid–individual superheat control method. Furthermore, the upstream refrigerant flow control consistently outperforms the downstream refrigerant flow control, and recovers most of the loss in cooling capacity and COP due to non-uniform air flow distribution.     

用于湿度独立控制的送风气流组织研究

利用计算流体力学（CFD）对5种不同的气流组织形式进行模拟分析，对每种气流组织下形成的空气含湿量分布进行研究。指出个性化送风和地板送风方式对于去除室内余湿较为有效，有可能作为适于湿度独立控制的送风气流组织形式。     

Use of ejectors in a multi-evaporator refrigeration system for performance enhancement

In this study, an improved cooling cycle for a conventional multi-evaporators simple compression system utilizing ejector for vapour precompression is analyzed. The ejector-enhanced refrigeration cycle consists of multi-evaporators that operate at different pressure and temperature levels. A one-dimensional mathematical model of the ejector was developed using the equations governing the flow and thermodynamics based on the constant-area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The energy efficiency and the performance characteristics of the novel cycle are theoretically investigated. The comparison between the novel and conventional system was made under the same operating conditions. Also, a comparison of the system performances with environment friendly refrigerants (R290, R600a, R717, R134a, R152a, and R141b) is made. The theoretical results show that the COP of the novel cycle is better than the conventional system.     

感应电机矢量控制系统仿真研究

针对基于空间矢量脉宽调制技术（SVPWM）和转子磁场定向控制原理的感应电机矢量控制系统,利用控制功能模块化的设计思想,在Matlab／Simulink中建立功能独立的子模块如矢量控制模块、速度控制模块、坐标变换模块、SVPWM子模块等,并将这些功能模块拼装组合,构建了电流、转速双闭环感应电机矢量控制仿真模型。仿真结果表明基于模块化设计的感应电机矢量控制仿真模型是有效可行的,为电机控制器的设计提供了一种途径。     

A modified drag model for power-law fluid-particle flow used in computational fluid dynamics simulation

A modified drag model for the power-law fluid-particle flow considering effects of rheological properties was proposed. At high particle concentrations (ε_s ≥ 0.2), based on the Ergun equation, the cross-sectional shape and the tortuosity of the pore channel are considered, and the apparent flow behavior index and consistency coefficient of the power-law fluid at the surface of the particles are corrected. At low particle concentrations (ε_s < 0.2), based on the Wen-Yu drag model, the modified Reynolds number for power-law fluid and the relational expression between drag coefficient for single particle and Reynolds number that considers the effect of the flow behavior index are adopted. Numerical simulations for the power-law fluid-particle flow in the fluidized bed were carried out using the non-Newtonian drag model. The effects of rheological parameters on the drag coefficient were analyzed. The comparisons of simulation and experiment show that the modified drag model predicts reasonable void fraction under different rheological parameters, particle diameters, and liquid velocities in both low particle concentrations and high particle concentrations. The increase in flow behavior index and consistency coefficient increases the drag coefficient between the two phases and decreases the average particle concentration within the bed.     

机载成像设备地面仿真系统的误差分析

依据多体系统理论和误差建模技术对构成机载成像设备地面仿真系统的13类(63项)误差进行了分析,建立了地面仿真系统误差的数学模型,运用所编制的MATLAB蒙特卡罗模拟程序进行了各项及各类误差的敏感度分析,最后依据分析结果进行了合理的误差分配。     

Instability of automotive air conditioning system with a variable displacement compressor. Part 2. Numerical simulation

A test system is built first in order to investigate the instability of the automotive air conditioning (AAC) system with a variable displacement compressor (VDC), and hunting phenomena caused by the large external disturbance in the AAC system with a VDC and a thermal expansion valve, and in the AAC system with a VDC and a fixed-area throttling device are investigated experimentally in part 1 of this paper. The experimental results indicate that there also exist the hunting phenomena in the AAC system with a fixed-area throttling device. The system stability is found to be dependent on the direction of the external disturbance, and the system is apt to cause hunting when the condensing pressure decreases excessively since it may cause two-phase state at the throttling device inlet and make a large disturbance to the system. The piston stroke length will oscillate only when the oscillation amplitudes of forces acting on the wobble plate are great enough, otherwise the piston stroke length will be kept invariable, and then the system instability rule is also suitable for the AAC system with a fixed displacement compressor. From the experimental results, it is concluded that the two-phase flow at the throttling device inlet or at the evaporator outlet is the necessary condition but not sufficient condition for system hunting. Finally, a new concept, conservative stable region, is proposed based on the experimental results and theoretical analysis.     

新疆某办公楼蒸发冷却空调系统应用及效益分析

本文旨为干燥地区办公建筑蒸发冷却空调系统的设计、设备选型、调试、运行的全过程提供基础理论支持,从系统设计、设备选型入手,对系统调试,应用情况及经济,节能效益进行分析。还提出了解决系统水流量异常的合理方案,且测得夏季室内温湿度符合设计要求时,温度应在24℃~27℃,湿度应在45%~70%,方可满足室内舒适性要求,维持良好的室内空气品质。本系统相较于传统空调系统,其初期投资高出10万元,但运行费用可节省32.20%,增量分析回收时间为2.04年;耗水量可节省60.29%,耗电量可节省27.4%,可节约标准煤35.84吨。     

切换流程空分设备切换系统的控制改进

介绍1#6000m3/h空分设备切换式换热器气动射流切换系统的不足,分析了将其改为PLC加电磁阀控制切换系统的方案设计、仪表选型、PLC编程及方案的实施和调试过程,减少了运行故障率。     

Material flow analysis and integration of watersheds and drainage systems: I. Simulation and application to ammonium management in Bahr El-Baqar drainage system

This paper is aimed at developing a systematic and generally applicable methodology for material flow analysis in drainage systems and watersheds. In particular, this research has focused on developing a mathematical framework and application for the management of nitrogenous species (primarily ammonium ions). Nitrogen compounds are among the most important species contributing to ecological cycles. Indeed, the environmental and biological aspects of water systems and their surrounding systems are highly impacted by nitrogen compounds as they contribute to the quality, nutrition, and toxicity of these systems. A material flow model was developed to deal primarily with the water phase while including pertinent information on the solid and air phases as they interface with the water medium. Both spatial and discrete temporal dimensions were included to account for nitrogen flow and transformation. The model includes the various environmental phenomena that influence the fate and transport of targeted species (e.g., volatilization, precipitation, sedimentation, uptake by biota, adsorption, chemical and biochemical reactions, etc.). Furthermore, the model includes material flow analysis operators (or transfer functions) that characterize the system inputs and outputs as they relate to the surroundings. The aforementioned material flow analysis tools were combined in a computer-aided modeling platform to provide a complete material flow analysis and yield useful insights on the transport and fate of targeted species. The simulation results shed light on the system performance. Actual data for an Egyptian drainage system (Bahr El-Baqar) along with the outfall to Lake Manzala were used to illustrate the usefulness and applicability of the developed model. Comparison with the measured data confirmed the validity and fidelity of the model.     

10000m~3/h空分设备分子筛纯化系统再生气流量控制方案的优化

由于分子筛纯化系统再生气流量控制方案不同,16300 m3/h空分设备的运行工况与10000 m3/h空分设备相比,上塔压力波动幅度更小,运行更稳定,制氩系统更易操作,于是对10000 m3/h空分设备的分子筛纯化系统再生气流量控制方案进行了优化。文章简介10000 m3/h空分设备分子筛纯化系统流程,分析2套空分设备分子筛纯化系统再生气流量的控制方案,详细阐述10000 m3/h空分设备分子筛纯化系统再生气流量控制流程的优化方案及取得的效果。     

Modeling and output feedback control of automotive air conditioning system

This paper presents an application of robust control theory to an automotive Air Conditioning (A/C) system. A control-oriented model built using moving-boundary method is validated against experimental data collected on a vehicle chassis dynamometer, at constant engine speeds as well as on driving cycles. Next, an H_∞ controller is synthesized by formulating an optimization problem whose solution requires appropriate weighting functions selection. Singular perturbation method is utilized to remove states associated with fast dynamics in both model and controller. Both full-order and reduced-order H_∞ controllers are verified by simulation results obtained using the nonlinear A/C system model. It is demonstrated that the designed controller is capable of tracking the reference output trajectories while rejecting disturbances introduced on the boundary conditions of the heat exchangers. Furthermore, a preliminary study is performed to reveal the opportunity of designing a gain-scheduled H_∞ controller for global output tracking.     

Evaluation of a hybrid method for refrigerant flow balancing in multi-circuit evaporators

A companion paper [Kim, J.-H., Braun, J.E., Groll, E.A., 2009. A hybrid method for refrigerant flow balancing in multi-circuit evaporators: upstream versus downstream control. International Journal of Refrigeration doi:10.1016/j.ijrefrig.2009.01.013 presented a hybrid approach for providing control of refrigerant flow distribution in evaporators that involves the use of small balancing valves in each circuit along with a primary expansion device to control the overall superheat from the evaporator. Furthermore, the companion paper demonstrated that the flow balancing valves should be located upstream rather than downstream of the evaporator in order to realize significant benefits. The current paper utilizes the model presented in the companion paper to more fully evaluate the effects of uneven air and refrigerant flow distributions and the benefits of upstream hybrid control in response to these effects.