Study On The Flow Heat Transfer Characteristics Of Solar Collector Walls Based On Coupled Heat Transfer Between Microclimate And Multiple Air Ducts

Since the 21st century,China’s building energy consumption has been growing at a high rate in the context of rapid urbanization.According to the "China Building Energy Consumption and Carbon Emission Research Report[1]," the total energy consumption of the whole building process in 2019 was 2.233 billion tee,of which 1.03 billion tce was consumed in the building operation stage,which is nearly 50%of the total energy consumption,especially the carbon emission brought by this stage reached 2.13 billion t CO2,accounting for 21.6%of the total carbon emission in the country.In order to achieve the transformation from"double control" of energy consumption to "double control" of the total amount and intensity of carbon emissions,The application of renewable energy with solar energy as the main representative in the building operation stage is gradually changing to the dominant energy.The passive trombe wall technology,which is ideally matched with it,is one of them,and it is the key to future carbon peaking and carbon neutrality in the building sector.The heat collecting performance and thermal energy conversion efficiency of the trombe wall,as the primary heat collection component of solar building heating,have a direct impact on the building’s energy consumption level in the heating season.Under the restricted conditions of regional solar energy resources,the typical trombe wall has a small air heat transfer area and a single heat exchange mode,resulting in a considerable loss in heat collection efficiency and an increase in heating energy consumption.By combining the collector pipe bundle with the traditional trombe wall,a new multi-channel,multi-heat transfer mode trombe wall system-multi-channel solar trombe wall is proposed in this paper,and a series of in-depth studies on its thermal characteristics are carried out through theoretical analysis and numerical simulation.The thermal balance equation and the air flow equation in the collector tube in the multi-heat exchange mode of the wall are established in this study for the multiduct trombe wall system,and the joint equation is used to analyze several factors affecting the thermal process of the multi-duct trombe wall.Given that existing studies on traditional trombe walls is based on local typical meteorological year data,and the heat transfer process of the multi-duct trombe wall is significantly influenced by the microclimate of the building’s near wall surface,this project uses a typical high-rise residential building in Zhengzhou as the object,and takes the method of onsite measurement to determine the heat transfer process of the multi-duct trombe wall.The micro-environment parameter data of the building’s south-facing near wall in the heating season is gathered,and the primary change law and response relationship are described,which provides a data base for precisely modeling the system’s thermal performance in Zhengzhou.Based on the theory of heat transfer and fluid dynamics to analyze the thermal process characteristics of multi-duct solar trombe wall,and based on CFD technology with the existing measured data as the operating conditions,this project simulates and analyzes the relationship between multiple heat transfer modes,the number of collector tubes,the diameter of collector tubes,and the arrangement of collector tubes on the trombe wall heat collection performance.The results show that the coupled heat exchange mode(multi-duct solar collector wall)has an earlier start-up speed than the interlayer heat exchange mode(traditional collector wall),and the daily average collector efficiency and heat exchange can be increased by 27.8%and 36%,respectively,and the collector wall has the highest collector efficiency in the coupled heat exchange mode.When the number of branch pipes changed from 9 to 11,the daily average heat collection efficiency and daily average heat supply of multi-duct collector wall were not significantly improved,and its instantaneous heat collection efficiency was lower under higher solar radiation intensity,and the 9-tube multi-duct collector wall in the study showed a better effect in comprehensive aspects.The average daily heat collection efficiency of the collector wall is the highest when the tube diameter is 60mm,which can reach 70.3%,and the average daily heat collection efficiency and heat supply of the collector wall is the highest when the center distance of the middle five branches is twice the center distance of the other branches under the non-uniform distribution condition.This research establishes a technical and theoretical foundation for the thermal performance of multi-duct collector walls in northern metropolitan regions,as well as their passive heating and consumption reduction.