高载能供冷管路水力特征及其对热环境动态响应

Buildings consume around 40% of the primary energy worldwide each year and the percentage is even increasing. The problems of energy consumption and greenhouse gas emission caused by HVAC system in the buildings are extremely impressive. In order to improve building energy efficiency, developing innovative technologies in HVAC system becomes imperative. District cooling is acknowledged to be an advanced central air conditioning strategy. Nevertheless, the transport efficiency of cold supplying pipe system is not satisfactory. Hence, this project has proposed to investigate hydraulic characteristics of cold supplying pipe system with intensive-energy fluid, as well as their dynamic response to the thermal environment. Firstly, the coupled flow and concentration distributions of heterogeneous ice slurry flow are studied with granular kinetic and continuous medium theory. And the corresponding mathematical model on physical field prediction is established. Then, the thermal environment disturbance employed on pipe wall is analyzed. Based on the thermal boundary, the dynamic response mechanism of heterogeneous ice slurry flow will be obtained. Finally, considering the effects of heterogeneous flow and thermal environment disturbance, a quasi-two-dimensional flow resistance model is derived. Meanwhile, a multi-objective optimization method is developed, which concentrates on the transport capability and required pumping power of cold supplying pipe system. The successful implementation of this project will lay a theory foundation for improving the efficiency of cold supplying pipe system. Hopefully, the research effort will also realize the HVAC technical innovation in building energy conservation.

建筑每年消费的一次能源占全球总能耗的40%且呈增长态势，其中暖通空调系统的能耗和温室气体排放量极其可观，因此通过暖通空调技术创新引领建筑节能低碳发展势在必行。区域供冷作为一种先进的集中空调策略，其系统二次管网冷量输配效率亟待提升。为此，本项目提出开展冰浆高载能供冷管路水力特征及其对热环境动态响应的基础研究。拟应用颗粒动力学及连续介质理论，阐明供冷管路内冰浆非均质性流动的流场、浓度场耦合规律，建立相应的物理场预测模型。将热焓多孔介质与欧拉-欧拉方法相结合，协同外界热环境变化凝炼供冷管路壁面热边界，进而揭示场特征对热环境扰动的动态响应机制。基于冰浆的非均质性、热扰流动过程，构建供冷管路摩阻损失“准二维”量化模型；并以输送能耗和载冷能力为控制目标，发展高载能供冷管路多目标优化方法。本项目的成功实施将为提升二次输配管网载冷性能、实现区域供冷系统节能创新奠定理论基础。

全球范围内建筑运行能耗占社会终端能耗的平均比例高达30%，同时产生的温室气体和微细颗粒物引发的环境灾害愈发严重，因而超低能耗绿色建筑技术发展亟待加强。区域供冷作为一种先进的建筑能源供应策略，其系统二次管网冷量输配效率亟待提升。为此，本项目提出开展冰浆高载能供冷管路水力特征及其对热环境动态响应的基础研究。首先，将冰粒子间相互作用类比于稠密气体分子间相互作用，应用颗粒动力学和两相流连续介质理论研究了水平、垂直、倾斜管道内冰浆非均质性等温流动的场特征。其次，基于非牛顿流体力学和颗粒浓度扩散理论，建立了流场、浓度场解析模型与摩阻损失量化模型。而后，将热焓多孔介质与欧拉-欧拉方法相结合，构建了恒热流、恒壁温和对流换热三种边界下冰浆相变传热数值模型，阐释了冰粒子融化行为对冰浆热流动的影响机制。最后，搭建了实验测试平台并开展了相关的实验研究，进一步验证了所获得的理论模型。研究表明，随着流速的减小、冰粒子浓度的升高以及颗粒直径的增大，冰浆非均质性流动过程增强。分段流变模型和摩阻损失分相量化模型，能够准确刻画出冰粒子聚集对剪切应力的影响和各流体相所占的阻力份额。沿着管道流动方向冰粒子的相变使得冰浆的非均质性流动过程减弱，冰浆流动的摩阻损失降低。已建立的场特征、流变特性、摩阻损失相关模型的预测结果与实验测试结果取得了较好的一致性，其相对误差可基本控制在±20%内。本项目取得的理论研究成果，对于优化高载能介质管路输送设计与运行方法、实现区域供冷系统节能创新具有重大的科学价值，同时极有希望在城市地下轨道交通站冰浆集中供冷和高热害隧道降温工程领域得到应用。