区域供冷系统能效分析(2):功耗冷热比对系统能效的影响
Energy efficiency of district cooling systems (2): Influence of power consumption to heat supply ratio on system energy efficiency
摘要：
以功耗冷热比定义为出发点,结合现有规范与项目实践,针对典型功耗冷热比限值组合,通过分析各子系统功耗冷热比对系统能效的不同影响程度,为优化系统能效提供优化方法,明确了提高系统能效应重点关注子系统。在以功耗冷热比相似准则为变量的量纲一系统能效模型基础上,得到了各子系统功耗冷热比对系统能效影响率的数学模型,随着功耗冷热比的增大,区域供冷系统能效(COPDCS)以接近线性比例下降,下降斜率为制冷机能效(COPR)+1。这些模型可直接评估各子系统功耗冷热比对系统能效的影响,找出影响系统能效的瓶颈子系统。区域供冷系统外管网能耗对系统能效的影响幅度与站内冷却水系统等子系统对系统能效的影响幅度接近,外管网能耗不一定是区域供冷系统能效的主要限制因素。乙二醇系统功耗冷热比是影响冰蓄冷系统能效的瓶颈;降低各子系统功耗冷热比,是区域供冷系统与单体建筑制冷机房提高系统能效的共同路径。本文提出的子系统功耗冷热比对系统能效影响的数学模型可以作为区域供冷系统或单体建筑制冷机房设计与运行的优化依据。
Abstract：
Based on the definition of power consumption to heat supply ratio, the effects of power consumption to heat supply ratios on the system energy efficiency are analysed for the district cooling system (DCS) using the typical subsystem power consumption to heat supply ratio limit combinations of the existing standards and project practice. This paper provides optimization methods to optimize the system energy efficiency, and clarifies the bottleneck subsystems that should be focused on to improve the system energy efficiency. Based on the dimensionless system energy efficiency model with the power consumption to heat supply ratio similarity criterion as a variable, the mathematical model of the influence of the power consumption to heat supply ratio of each subsystem on the system energy efficiency impact rate is obtained. With the increase of the power consumption to heat supply ratio, the system energy efficiency of the DCS (COPDCS)decreases in a nearly linear proportion, and the decreasing slope is the energy efficiency of the chiller (COPR)+1. These models can directly evaluate the influence of each subsystem’s power consumption to heat supply ratio on the system energy efficiency, and identify the bottleneck subsystem affecting system energy efficiency. The influence magnitude of the external pipeline network energy consumption of the DCS on the system energy efficiency is close to that of the subsystems, such as the cooling water system inside the chiller plant, and the external pipeline network energy consumption is not necessarily the main limiting factor of the system energy efficiency of the DCS. The power consumption to heat supply ratio of the ethylene glycol system is the bottleneck affecting the energy efficiency of the ice storage chiller system, and reducing each subsystem’s power consumption to heat supply ratio is the common path to improve the system energy efficiency of the DCS and the chiller plants of individual buildings. The mathematical model of the influence of the subsystem’s power consumption to heat supply ratio on the system energy efficiency proposed in this paper can be used as an optimization basis for the design and operation of the DCS or chiller plants of individual buildings.
Keywords:district cooling system; system energy efficiency impact rate; mathematical model; power consumption to heat supply ratio; similarity criterion; traditional chiller system; ice storage chiller system; water storage chiller system