高落差多分支管路结构对多联式空调系统能力影响的快速仿真

Fast Simulation of Influence of Significant Height Difference and Multiple Branch Pipeline Structure on Indoor Unit Performance in VRF System

大型高层建筑所采用的多联式空调系统中,室外机与室内机之间存在高落差、管路结构中存在众多分支,导致室内机能力的衰减。为了提高大型高层建筑中多联式空调系统室内机的能力,需要开发可以快速评估管路分支与落差对于室内机能力影响的仿真软件。本文建立了管路分布参数模型和基于流体网络理论的系统流量分配模型,以准确反映管路内制冷剂的流动特性;建立了室内机换热器分相模型和电子膨胀阀脉冲数快速计算模型,以快速反映室内机的运行状态;开发了分层迭代的求解算法,以提高软件计算的速度。同时采用已有数据进行模型验证,结果表明:各模型的误差均在±12%范围内;常见的多联机结构形式下仿真的计算时间均在1 min范围内。利用仿真软件的算例分析得到:室内机与室外机间的落差每增加20 m,室内机能力衰减2.7%~11.9%;管路中经过的分支个数每增加1个,室内机能力衰减0.4%~9.7%。

There are significant height differences between outdoor and indoor units and many branches in the pipeline structure for variable refrigerant flow(VRF)systems in high-rise buildings,resulting in the performance degradation of indoor units.A simulation software is needed to determine the influence of these factors to improve the capabilities of such VRF indoor units.In this study,a distribution parameter model for the pipeline and a flow distribution model for the system based on fluid network theory were established to accurately reflect the flow characteristics of the refrigerant in the pipeline.A multi-zone separation model for the indoor unit heat exchanger and a fast pulse number calculation model for the indoor unit electronic expansion valve were also established to quickly reflect the operating status of indoor units.In addition,a hierarchical iterative solution algorithm was developed to improve the calculation speed of the software.These models were validated using existing data,and the results showed that the errors for each model were<12%,while the calculation time for the VRF system with a common structure was<1 min.Further more,the calculated example using the simulation software showed that the indoor unit performance decreased by 2.7%-11.9%when the height difference between the indoor and outdoor units increased by 20 m and by 0.4%-9.7%when the number of branches in the pipeline increased by one.