水冷螺杆冷水机组动态模型的改进算法及仿真

建立了壳管式换热器水冷螺杆冷水机组的动态模型.通过引入未知变量比焓,采用冷剂温度、压力、比热容和比焓的拟合关系求取矩阵系数,以及编写调用M-函数的方法,改进了模型算法,简化了模型状态方程系数的求导过程,提高了仿真速度和精度.基于R134a制冷剂的冷水机组的蒸发压力和温度等参数的动态仿真值与系统实测值基本吻合.对蒸发器和冷凝器总体采用分布参数模型,对具体的每一区采用集中参数模型,对压缩机和膨胀阀采用稳态的集中参数模型.动态模型和改进算法可用于机组的模拟器研发和控制策略.

Improved algorithm and simulation of the dynamic model of a water-to-water screw liquid chiller

We developed a dynamic model of a water-to-water screw liquid chiller with a shell tubular heat exchanger. In order to simplify calculations we introduced an unknown variable the enthalpy to evaluate the matrix coefficients of the state equation, using a poly-fitting relationship between temperature, pressure, specific heat capacity, and the enthalpy of the refrigerant. We then compiled the results and applied the M-function. In this way the usual algorithm was simplified, and simulation speed and accuracy were improved. In this study, we adopted a distributed parametric model for the evaporator and the condenser as a whole, but a concentrated parametric model for each small region. For the screw compressor and electronic expansion valve, we used a steady-state concentrated parametric model. Simulations showed evaporating pressure and temperature for a chiller with R134a refrigerant agreeing well with observed data from standard tests. The dynamic model and the improved algorithm can be used for research and development of simulators and control strategies.