全空气定风量空调系统变频变风量运行控制与仿真研究

分析了全空气定风量空调系统空调房间的特性,推导出变风量送风方式下空调房间的数学模型,构造PID控制器、模糊控制器和神经网络控制器三种控制器,并利用Matlab软件中的Simulink工具箱对三种控制器的性能进行比较。     

可变冷媒流量空调系统设计探讨

作者在多年从事设计工作的基础上,讨论了可变冷媒流量空调系统设计中需引起注意的几个问题。并总结了系统设计中的一些经验。     

Reliability evaluation of a port oil transportation system in variable operation conditions

The semi-Markov model of the system operation processes is proposed and its selected parameters are determined. The series ‘m out of k_n’ multi-state system is considered and its reliability and risk characteristics are found. Next, the joint model of the system operation process and the system multi-state reliability and risk is constructed. Moreover, reliability and risk evaluation of the multi-state series ‘m out of k_n’ system in its operation process is applied to the port oil transportation system.     

Steady‐state model of a variable speed vapor compression system using R134a as working fluid

This paper presents a steady‐state physical model for a variable speed vapor compression system. Its development and validation for a wide range of operating conditions are presented. The model requires as input parameters: compressor speed, static superheating degree and volumetric flow rates and temperatures of secondary fluids at the evaporator and condenser inlet. Using these input parameters, which can be easily obtained in this kind of facility, the model predicts the operating pressures, the temperature of secondary fluids at the evaporator and condenser outlet, the evaporator and condenser thermal capacities, the electric power consumed by the compressor and the coefficient of performance, COP. The experimental validation of the model has been carried out with 177 tests using R134a as working fluid, concluding that the model can predict the energetic performance of a variable speed vapor compression chiller with an error lower than ±10%. Copyright © 2009 John Wiley & Sons, Ltd.     

节能变风量空调系统探讨

以最常用的风量自动调节式节流变风量空调系统的自动控制为例，介绍了变风量空调控制中送风静压控制、送风流量控制的原理和应用。     

太阳能空调/热泵系统及运行分析

描述了位于北京天普集团工业园区的太阳能空调/热泵系统及其设计思路。系统以太阳能利用技术为主,热泵技术为辅,可以完全满足新能源示范大楼全年的空调、采暖及生活热水的需要。介绍了系统冬季运行的技术参数,并与其他几种传统的采暖方式进行了经济和环境效益方面的比较。     

Reliability and risk evaluation of a port oil pipeline transportation system in variable operation conditions

The semi-Markov model of the system operation processes is proposed and its selected characteristics are determined. A system composed on multi-state components is considered and its reliability and risk characteristics are found. Next, the joint model of the system operation process and the system multi-state reliability is applied to the reliability and risk evaluation of the port oil pipeline transportation system. The pipeline system is described and its operation process unknown parameters are identified on the basis of real statistical data. The mean values of the pipeline system operation process unconditional sojourn times in particular operation states are found and applied to determining this process transient probabilities in these states. The piping different reliability structures in various its operation states are fixed and their conditional reliability functions on the basis of data coming from experts are approximately determined. Finally, after applying earlier estimated transient probabilities and system conditional reliability functions in particular operation states the unconditional reliability function, the mean values and standard deviations of the pipeline lifetimes in particular reliability states, risk function and the moment when the risk exceeds a critical value are found.     

换热器性能对内容积可变空调系统性能的影响分析

文章针对常规空调在压缩机与冷凝器之间增加变容器的内容积可变容空调结构,建立了空调系统的稳态集中参数模型。基于给定的压缩机结构,研究了换热器性能对内容积可变空调系统性能的影响,提出了系统优化的方向。     

空调冷冻水变主流系统运行能耗分析

比较了单级泵、双级泵、变主流系统等三种冷冻水系统的特点 ,对其能耗进行了对比分析 ,认为变主流系统能耗低、系统简单 ,有广泛的应用前景     

Flow analysis and performance improvement of a radial inflow turbine with back cavity under variable operation condition of compressed air energy storage

Radial inflow turbine is an important working output device in compressed air energy storage (CAES) system. It influences the system's efficiency significantly. However, the investigation about effect of back cavity leakage flow on flow loss in radial unshrouded rotor is still needed, especially under variable operation condition of CAES system. Therefore, the performance of radial turbine with back cavity at different total expansion ratio is revealed in the present work. Results illustrate that the variation of labyrinth seal clearance in the original back cavity has limited impact on the leakage flow and the isentropic efficiency. The isentropic efficiency only reduced by 0.11%, and the leakage flow rate is only increased by 0.017 kg/s when labyrinth seal size varies from 0.09 to 0.20 mm. The fluid in back cavity intends to leak into the rotor channel and causes more flow loss; the isentropic efficiency under different total expansion ratio is thus decreased, and a maximum isentropic efficiency reduction of 1.5% is obtained when total expansion ratio is 2.89. To control the flow loss, a “rotor‐back cavity seal” is proposed, and a maximum isentropic efficiency increment of 1.12% is achieved when total expansion ratio is 2.89.     

Adaptive operation strategy of a polymer electrolyte membrane fuel cell air system based on model predictive control

The present article investigates a model predictive control-based operation strategy of an automotive fuel cell air system. For this purpose, a nonlinear model of a fuel cell system is derived, which is linearized and discretized around the current operation point during each time sample. This model is combined with a cost function taking into account power reference tracking and hydrogen minimization. Additional system constraints ensure a safe and robust operation. Subsequently, the adaptive and efficiency-optimal behavior of the model predictive controller is demonstrated based on a simulation study of different scenarios with varying power profiles. Furthermore, the thermal derating behavior of this control is studied using an exemplary situation with critical thermal conditions. Finally, the model predictive control approach is compared with a validated map-based operation strategy highlighting the potential of reducing the hydrogen consumption by 3% while decreasing the risk of harmful operation conditions.     

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

Based on the force balance equations, mass and energy conservation equations, a mathematical model of control valve used in the variable displacement wobble plate compressor (VDC) is developed firstly. The dynamic model of the moving components is developed then by analyzing the forces and force moments acting on the piston, piston rod, wobble plate, rotating journal and shaft sleeve. The compression process model is obtained by fitting the data from our experiments. And finally the steady-state mathematical model of VDC is developed by combining the three models above. In order to verify the mathematical model of compressor, a test bench for the control valve and the test system for the VDC have been established, and the simulated results agree well with the experimental data. The simulation results show that there are four operation modes for the VDC, 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.     

Novel operation and control of an electric vehicle aluminum/air battery system

The objective of this paper is to create a method to size battery subsystems for an electric vehicle to optimize battery performance. Optimization of performance includes minimizing corrosion by operating at a constant current density. These subsystems will allow for easy mechanical recharging. A proper choice of battery subsystem will allow for longer battery life, greater range and performance. For longer life, the current density and reaction rate should be nearly constant. The control method requires control of power by controlling electrolyte flow in battery sub modules. As power is increased more sub modules come on line and more electrolyte is needed. Solenoid valves open in a sequence to provide the required power. Corrosion is limited because there is no electrolyte in the modules not being used.     

洁净空调新风量的节能控制与运行

通过对洁净空调新风系统设计及运行的分析,探讨洁净空调变新风量的必要性和可行性,并利用自控相关理论,设计出在室内人员数量不定的情况下,通过实时监测室内二氧化碳浓度与余压状态来确定送入室内新风量的控制过程,最终达到系统节能的目的。     

空调闭式水系统多台水泵联合运行的工况分析

文中以某区域空调冷冻水系统为例,针对系统中水泵的串并联运行调节问题,通过绘制水泵性能曲线和管网特性曲线,分析了同级水泵并联时的台数切换问题以及多级水泵串联运行的扬程变化问题,结果表明:同级水泵并联时,在基于流量变化来改变水泵运行台数时,不能以单台水泵的额定流量为计算基准,应根据并联水泵的实际运行工况点来确定水泵的运行台数,否则会出现流量不足的问题;多级水泵串联时,不能以两台水泵的额定扬程之和为计算基准,应根据串联水泵的实际运行工况点来核定扬程,否则会出现扬程不足的问题。     

旁通型变风量集中空调系统的节能设计和运行研究

分析讨论了旁通型变风量集中空调系统的主要特点及在工程中的设计和运行调节方法,对所存在的不足之处提出了改进意见．     

Experimental study of an auto-controlled automobile air conditioning system with an externally-controlled variable displacement compressor

In this paper, an experimental study of an auto-controlled mobile air conditioning (MAC) system with an externally-controlled variable displacement compressor (EVDC) is performed and analyzed. A new displacement control method of EVDC is developed concerning about evaporator characteristics and in-car temperature fluctuation, which indicate the quality of the MAC system. Based on occupant’s thermal comfort, the wind-tunnel test results show that the MAC system with an EVDC can maintain the deviation of in-car temperature no more than 2 °C compared with the occupants’ desired one. This MAC system gives the occupants a good thermal comfort sensation in the rapid changing environment. The comparison shows that the discharge pressure changes of EVDC vary faster than that of the fixed displacement compressor, which reflects the effect of the internal climate changes.     

Experimental validation of the simulation module of the water-cooled variable refrigerant flow system under cooling operation

On the basis of EnergyPlus’s codes, the catalogue and performance parameters from some related companies, a special simulation module for variable refrigerant flow system with a water-cooled condenser (water-cooled VRF) was developed and embedded in the software of EnergyPlus, the building energy simulation program. To evaluate the energy performance of the system and the accuracy of the simulation module, the measurement of the water-cooled VRF is built in Dalian, China. After simulation and comparison, some conclusions can be drawn. The mean of the absolute value of the daily error in the 9 days is 11.3% for cooling capacity while the one for compressor power is 15.7%. At the same time, the accuracy of the power simulation strongly depends on the accuracy of the cooling capacity simulation.     

Exergetic performance assessment of a variable‐speed R404a refrigeration system

The goal of this study is to carry out exergy analyses for an experimental variable‐speed refrigeration system working with R404a in order to determine irreversibility rates and exergetic efficiencies of system components and the overall system. For this aim, an experimental refrigeration system was designed with a frequency inverter mounted on compressor electric motor. Controlling the rotational speed of the compressor with a frequency inverter is one of the best methods to vary the capacity of the refrigeration system. The experiments were made for different compressor electric motor frequencies. The results showed that at low‐frequency values, irreversibility rates of the system decreased and exergetic efficiencies were increased. In addition, the major irreversibility occurs in the compressor by 61.47–61.83% followed by condenser by 17.00–16.52%, evaporator by 12.39–13.73% and expansion valve by 6.24–6.76% for different compressor frequencies. Copyright © 2009 John Wiley & Sons, Ltd.