磁悬浮冷水机组作为一项新兴的高效空调技术，近年来引起业内广泛关注，但其实际节能效果及技术经济性也存在一定争议，需要对磁悬浮冷水机组在实际工程中的可应用性进行客观评价，并且根据其特点合理应用，最大限度地发挥其性能优势，推动这一节能技术健康发展。本文在详细实测近年来国内不同城市磁悬浮冷水机组节能改造工程实际运行效果基础上，评价磁悬浮冷机运行能效现状，从节能运行的角度指出其急需改进的典型问题。实测数据表明，磁悬浮冷机在整个供冷季的平均运行能效高于相关国家标准规定的最高效率等级，远高于现有常规螺杆式或定速离心式冷水机组的整个供冷季实际运行能效。另一方面，现有磁悬浮冷水机组应用在公共建筑中，也存在多台冷机负荷分配不均、未能充分发挥其部分负荷率高效特点、输配系统水泵能耗偏高等问题，磁悬浮冷水机组冷站系统能效仍有很大提升空间。调查发现，磁悬浮冷水机组在替换吸收式冷水机组、高层或老旧公共建筑改造等方面优势突出，特别是施工安装便捷、占地面积小、可灵活布置，节能改造的效果和效益显著。本文通过大量实际运行数据，建立磁悬浮冷水机组运行能效和能耗模型，通过敏感性分析，发现相比于普通定速离心式冷水机组，蒸发温度的上升和冷凝温度的下降对磁悬浮冷机的能效提升非常明显，并且磁悬浮冷水机组的最高热力完善度工作点出现在部分负荷率和小压缩比工况下，即高效运行的“甜蜜点”并不在设备铭牌标称的“额定工况”附近。磁悬浮冷水机组的实际运行效率，外部受冷冻水供水温度设定值、冷却塔等冷却侧换热效果、多台冷机开启台数与负荷分配等因素影响，内部受压缩机转速和入口导叶开度的具体调节策略影响，因此必须在各种实际运行工况下因应变化而进行调节。本文针对磁悬浮冷水机组作为单一种类冷源或与定速离心式冷机组合这两种情景，研究系统高效运行调节策略；分析建筑物冷量需求特性，给出相应的磁悬浮冷机台数搭配设计方案。在此基础上，建立以磁悬浮冷水机组为主要设备的冷站模型，以冷站总电耗最低为目标，模拟分析磁悬浮冷机、冷冻和冷却水泵及冷却塔的全年运行策略，给出不同冷量需求、不同外界环境温度下冷却水泵及冷却塔节能控制策略，指出合理设计调节的变频输配系统与磁悬浮冷水机组结合，冷站全年运行能效比可超过5.0。
As a booming energy efficient technology, magnetic bearing centrifugal chillers with variable-speed control (so-called Oil-free Chiller as well) have drawn extensive attention in recent years. To survive in a strong competition in air-conditioning market and to contribute to the national energy efficiency target in China, it is essential to evaluate operational performance of the magnetic bearing variable-speed chiller and offer guidance to future applications.This thesis examines the actual operating performance of magnetic bearing centrifugal chillers in retrofitting projects in different cities, which is not only higher than the maximum efficiency level in national standards, but also defeats existing screw and centrifugal chillers. Some typical issues include uneven chiller load sharing and high energy consumption of pumps and fans. System energy efficiency still needs improvement. Magnetic bearing chillers have a significant advantage in retrofitting chiller plants with absorption chillers, and high-rise or old buildings chiller plant renovation.Magnetic bearing chillers adjust through the compressor speed and the inlet guide vane. If the load is high, the IGV is fully open, and magnetic bearing chillers adjust the compressor speed to change the cooling load and the compression ratio. If the load is low, the speed and IGV are jointly adjusted to prevent surge. Under such control, the maximum energy efficiency of magnetic bearing chiller appears under the partial load and small compression ratio conditions, ie the “sweet spot” where the chiller operates efficiently is not near the nominal “rated condition”. Through large amounts of actual operating data, establishes the magnetic bearing chiller model and analyzes the sensitivity of factors influencing its operating efficiency. Based on the chiller model, the design and operation strategies of the magnetic bearing chiller as a single cold source or combined with other types of chillers are studied respectively. A simple calculation method of building cooling load is used to decide the design number of magnetic bearing chillers under different cooling load profiles.Establishes chiller plant models equipped with magnetic bearing chillers; simulates and analyzes annual operation strategies with the goal of minimizing energy consumption. The control strategy of pumps and cooling towers under different cooling load and outside temperature conditions is given. Chiller plants with magnetic bearing chiller should also provide reasonable variable speed control for pumps and cooling tower fans, and therefore its annual energy efficiency can reach more than 5.0.
