【作者】 王磊；

【导师】 张建利； 展长虹；

【作者基本信息】 哈尔滨工业大学 ， 供热、供燃气、通风及空调工程， 2020， 博士

【摘要】 蒸发冷却技术是一种利用水对空气进行冷却的制冷模式,因此具有可再生和可持续发展的突出特点。目前蒸发冷却技术研究的主要方向包括提高蒸发冷却系统冷却效率,降低送风温度的同时增强显热处理能力等几个方面。但是不同蒸发冷却形式存在共同的弱点,即其送风参数和制冷能力在运行过程中会随室外环境空气参数不断波动而变化。由机械制冷辅助的蒸发冷却系统形成的复合空调系统,可以充分发挥各自系统的优点,避免其不足之处,应用前景非常广阔。本文首先针对传统普通蒸发冷却系统存在的不足之处,利用送风经露点间接蒸发冷却换热器处理后的温度在理想情况下趋于露点温度的特性,并且在对换热器的冷却性能、设备实用性、占地面积等实际因素综合考虑的基础上,提出了一种新型的逆流露点间接蒸发冷却换热器,并进行了深入的理论和实验研究。然后在上述研究的基础上,从实验和数值模拟方面对露点间接蒸发冷却与机械制冷复合空调系统开展了相关研究工作。本文的主要研究如下:首先通过合理的选取室外状态参考点和热力评价指标,并基于直接蒸发冷却换热器和间接蒸发冷却换热器的传热传质数学模型,分别提出了各自适用的?分析模型,并对六座典型城市在设计用室外气象参数条件下对比分析了它们的热力工况。通过研究发现干燥地区的乌鲁木齐、兰州的?效比最大,高等湿度地区的上海、广州的?效比最小。干燥地区露点间接蒸发冷却过程的?效比是普通间接蒸发冷却的1.8倍,是直接蒸发冷却的1.2倍。露点间接蒸发冷却换热器的送风有着最大的温降和最高的?效比,因此它具有更好的热力性能。第二,提出了一种新型的逆流露点间接蒸发冷却换热器,设计并建立了叉流露点间接蒸发冷却系统和逆流露点间接蒸发冷却系统的实验测试平台,基于我国不同地区气候条件的多样性,在选取的八种代表性气候条件下对两种系统的冷却性能开展了实验对比研究,分析了风量变化和二次空气与一次空气风量比变化对冷却性能的影响,同时也获得了八种典型气候条件下冷却性能的变化规律。在测试条件下,设计的逆流露点间接蒸发冷却换热器的露点效率为0.64-0.77,制冷量为673-1390W。第三,基于能量守恒和质量守恒方程,建立了描述逆流露点间接蒸发冷却换热器内部传热传质过程的数学模型,并通过实验数据对该数学模型的准确性进行了验证。基于建立的热力模型,在预设结构参数和运行参数条件下,计算并分别分析了进口空气干球温度及相对湿度、一次空气流速、二次空气与一次空气流量比、通道长度和通道高度对逆流露点间接蒸发冷却换热器的制冷量、?损失、露点效率和?效比的影响,得到了设计参数和运行参数合适的取值范围。在计算条件下,模拟结果表明当二次空气与一次空气流量比为0.3-0.4时,可以得到较大的制冷量和?效比;单通道高度的取值范围应该为3-5mm,通道长度的取值范围应该为1.0-1.5m。第四,分别建立了机械制冷系统仿真用的部件模型,在模型建立的过程中,制冷剂热力性质的计算选用适用于多种物质且形式简单的通用状态方程;压缩机热力模型采用集中参数稳态模型;毛细管模型采用近似积分技术进行计算;对于冷凝器和蒸发器,采用一维逆流分布参数数学模型。将上述数学模型与建立的露点间接蒸发冷却换热器数学模型相结合,建立通用的模拟仿真平台,并分析了室外气象参数变化对复合空调系统制冷量和COP的影响。通过搭建露点间接蒸发冷却与机械制冷复合空调系统的实验台,对模拟结果进行了一定的验证。第五,建立了露点间接蒸发冷却与机械制冷复合空调系统的TRNSYS仿真模型,对乌鲁木齐、哈尔滨、北京、上海及广州在供冷季(6月-9月)使用复合空调系统的经济性和节能性进行了研究。首先对乌鲁木齐、哈尔滨、北京、上海及广州的供冷小时数进行了统计分析,得到露点间接蒸发冷却系统的供冷小时数由多到少为:广州、上海、北京、乌鲁木齐、哈尔滨,在空调季每个月可提供33.9%-100%的冷量。然后,基于给出的露点间接蒸发冷却系统和机械制冷系统的初投资费用、年运行费用,得到了各城市使用复合系统的投资回收期及使用年限内的总节约费用。更多还原

【Abstract】 Evaporative cooling technology is a kind of cooling mode using water to cool air,which has the outstanding characteristics of renewable and sustainable development.At present,the main research directions of evaporative cooling technology include improving the cooling efficiency of evaporative cooling system,reducing the supply air temperature and enhancing the sensible heat treatment capacity.However,there is a common weakness in different forms of evaporative cooling,that is,the air supply parameters and cooling capacity will change with the fluctuation of outdoor ambient air parameters.The evaporative cooling system assisted with mechanical refrigeration system can maximize both their advantages and make up for their disadvantages.It therefore presents a promising future of application.Firstly,in view of the shortcomings of the traditional evaporation cooling system,the temperature of the supply air treated by the dew point indirect evaporative cooling heat exchanger tends to the dew point temperature under ideal condition,and based on the comprehensive consideration of the cooling performance,equipment practicability,floor area and other practical factors of the heat exchanger,a new type of counter flow dew point indirect evaporative cooling heat exchanger is proposed.It has been studied theoretically and experimentally.Then,based on the above research,the study on the dew point indirect evaporative cooling and mechanical refrigeration composite air conditioning system is carried out from the aspects of experiment and numerical simulation.The main content is as follows:Firstly,by selecting the reference point of outdoor state reasonably,the models for the analysis of direct evaporative cooling and indirect evaporative cooling heat exchangers are proposed,and the thermal conditions of six typical cities are analyzed.Through analysis,it is found that the exergy efficiency ratio is the largest in Urumqi and Lanzhou in dry areas,and the smallest in Shanghai and Guangzhou in high humidity areas.The exergy efficiency ratio of dew point indirect evaporative cooling in dry area is 1.8 times that of ordinary indirect evaporative cooling and 1.2 times that of direct evaporative cooling.Compared with other evaporative cooling heat exchangers,dew point indirect evaporative cooling heat exchanger has the largest temperature drop and the highest exergy efficiency ratio,so it has better thermal performance.Secondly,the experimental systems of cross flow dew point indirect evaporative cooling heat exchanger and counter flow dew point indirect evaporative cooling heat exchanger are designed and established.According to the change of air wet bulb temperature in different regions of China,eight typical climatic conditions are simulated by air pretreatment device.The cooling performance of the two systems is experimentally investigated,and the influence of intake air flow and working-to-intake air ratio on the cooling performance are analyzed.The cooling performance under eight typical climatic conditions is also obtained.Under the test conditons,the dew point effectiveness of designed counter flow dew point indirect evaporative cooling heat exchanger is 0.64-0.77,and the cooling capacity is673-1390 W.Thirdly,based on the energy and mass conservation equations,a mathematical model describing the heat and mass transfer process of the counter flow dew point indirect evaporative cooling heat exchanger is established,and the reliability of the model is verified.According to the above mathematical model,the effects of intake air dry bulb temperature and relative humidity,primary air velocity,secondary air to primary air flow ratio,channel length and channel height on cooling capacity,exergy destruction,dew point efficiency and exergy efficiency ratio are calculated and analyzed respectively,and the appropriate ranges of parameters are obtained.The results of numerical simulation show that the larger cooling capacity and exergy efficiency ratio can be obtained when secondary air to primary air flow ratio is 0.3-0.4,the channel height should be set to 3-5 mm,and the channel length should be in the range 1.0-1.5 m.Fourthly,component models for mechanical refrigeration system simulation are established.In the process of model establishment,the general state equations are used to calculate the thermodynamic properties of refrigerants,which is suitable for many substances and simple in form;the compressor thermodynamic model is a lumped parameter steady state model;the capillary model is calculated by approximate integration technology,and the condenser and evaporator are calculated by one-dimensional inverse method.Mathematical model of flow distribution parameters.Combining the above mathematical models with the dew point indirect evaporative cooling heat exchanger model,a general simulation platform is established,and the influence of outdoor meteorological parameters on the cooling capacity and COP of the composite air conditioning system is analyzed.The simulation results are verified by building the experimental platform of the composite air conditioning system.Fifthly,in the guidance of the above theories and methods,the economy and energy saving of composite air conditioning system in Urumqi,Harbin,Beijing,Shanghai and Guangzhou during the cold season(June-September)are studied.Firstly,the cooling hours of Urumqi,Harbin,Beijing,Shanghai and Guangzhou are analyzed.The results show that the cooling hours from more to less are Guangzhou,Shanghai,Beijing,Urumqi and Harbin,and in the air conditioning season,the dew point indirect evaporative system can provide 33.9–100% of cooling load for the selected cities.Then,the initial investment cost and annual operation cost of dew point evaporative cooling system and mechanical refrigeration system are given,and the payback period of investment and the total cost savings during the service life of the composite system in each city are obtained.更多还原