S355K2W
2011年5月4日 by admin
S355K2W
Solar energy collection on pavement and bridge is of solar energy collection of solid structure. The collecting energy can be stored into underground and used to melt snow and deice in winter. Composite system of collecting and storing solar energy in summer and melting snow and deicing in the winter is constructed, which will be applied in road traffic and construction of new energy technology in the future.Solar collecting on the solid structure is a key component of composite system of collecting and storing solar energy in summer and melting snow and deicing in the winter. According to new hot melt snow technology, theoretical analysis, simulation and experiment is combined to study some complex heat transfer problems in the solar energy collecting, underground energy storage and circulating fluid. By coupling of sub-model, heat transfer performance, energy usage and control methods and optimization methods in the solar energy collecting and storage dynamic process are studied. The research is the basis of the relevant technical theory to promote the technology and scientific progress.Supported by the National Natural Science Foundation of China （No.50776039）, a composite system is designed on the solid structure in this paper, which can collect solar energy and store energy in the underground in the summer, and melt away snow and deice in the winter. Heat transfer characteristics and operation performance of solar energy collecting system in the summer are studied. Influencing characteristics of different controlling methods in the process of solar energy collecting and energy storing are analyzed to work out the optimal controlling method. Simplized snow melting and deicing models are established and combined with solar energy collecting and energy storing process. Progress of solar energy collecting and storing and snow melting and deicing is simulated. Balance between energy collecting in the summer and energy using in the winter is analyzed accordingly.In the research of composite system of collecting and storing solar energy in summer and melting snow and deicing in the winter, an independent mathematic model and the corresponding module are established. Using heat collecting model, heat collecting characteristics and instantaneous influence effect of different influence factors, such as hydrolic fluid velocity, diameter and spacing of pipes buried in the solid structure, surface status, ambient wind velocity, ambient temperature and effect of cloud, are analyzed. The results show that with increasing of fluid velocity, heat collecting quantity per unit area increase, however, increasing extent will decrease. In the simulating range the optimal velocity is between 1m/s and 1.5m/s. Influence of pipe diameter and pipe spacing on heat collecting quantity and heat collecting temperature difference is reverse, so the relation should have an optimal range. Under reasonable heat collecting temperature, parameters of pipes should be chosen to make heat collecting quantity be maximized. Surface which has larger absorptance is in favor of heat collecting, but surface temperature will be higher. Wind and cloud reducing heat collecting quantity and are disadvantage factors. In addition, comparing with the above factors, effect of environmental temperature on the collector is smaller （when the ambient temperature rises 1℃, heat collecting quantity per unit area increases 23 W/m2）, thus its effects can be ignored in the actual construction of its operation.From the outdoor experimental system, it can be seen that large heat collecting quantity can be obtained by using solid structure as heat collecting slab. In the outdoor experiment the heat collecting quantity is about 150W/m2250W/m2 under natural conditions. At the same time the temperature of road can be reduced. Due to the larger heat capacity of solid structures, the change of surfaS355K2Wce temperature and heat collecting quantity is lagged behind that of radiation intensity. In addition, pipe layout and fluid flowing state has a great impact. With the increasing of circulating fluid flow, collection efficiency increases. Collecting efficiency is usually up to 30%. With pipe spacing reducing, heat collecting efficiency improves significantly. As shown in the results, pipe spacing reduces with 10mm, heat collecting efficiency increases by an average 5.5%, which indicates that surface solar radiation energy has been fully absorbed.Since some factors are difficult to be controlled, the outdoor experiments the impacting effect of some factors are also possible crossed, and it is difficult to determine the impacting effect of a particular factor. Therefore, in order to study influence of single factor on the heat collecting process in the solid structure, and indoor thermal radiation simulation experiment bench is built to explore heat collecting performance and laws in the solid structure such as bridge and road.The experiment results show that with the increasing of heat radiation intensity, the heat collecting capacity in the system increases linearly, while heat collecting efficiency reduces. Solid structures such as road and bridge have obvious thermal response lag. In addition, with increasing of wind speed, heat surface temperature and corrosion reduce, while temperature difference per pipe length and heat collecting quantity per unit area will reduce, which is not conducive to energy storage. When circulating hot fluid flow velocity increases, temperature difference per pipe length, heat collecting quantity per unit area and heat collecting efficiency will increase, while the temperature of road will rise accordingly to reduce the strength of pavement and be not conducive to road protection. In the experimental range, with the increasing of the circulating pipe spacing, the temperature difference per pipe length, heat collecting quantity per unit area and heat collecting efficiency will reduce. Comparing with the snake coil arrangement, the temperature difference per pipe length, heat collecting quantity per unit area and heat collecting efficiency is higher in the ellipse coil arrangement, which is helpful for energy storage. Reasonable pipe layout is conducive to solar energy collecting.In order to explore influencing characteristics of solar energy collecting and storage （SECS） in summer, instantaneous solar radiation module, solid structure collector module, storage water tank module and underground heat exchanger module are designed based on Matlab/Simlink platform, to established solar heat collecting and underground energy storage model. Heat transfer characteristics of SECS is simulated and studied accordingly. Different controlling methods of SECS are compared to work out the optimal one. From the research, it is found that temperature control method is optimal, which is controlled by opening and closing storage process and adjusting the fluid flowrate. This method can not only avoid the average temperature of road to be too low to make heat of underground loss, but also avoid the temperature around the underground heat exchanger to be higher and reduce heat collecting ability of solid structure to ensure that the solid structure heat collecting and storage system and the system performance. When the controlling teS355K2Wmperature difference changes, operating performance also changes. In the simulation cases, if the underground temperature rises 1℃, the decrement of controlling temperature difference will be about 0.5℃. In addition, the temperature difference switch control method in the solar collectors is an optimal one. Study also find that although under the conditions of clear sky solar switch control method is the best, the actual climatic conditions always changing, which will lead to operating system changing. Because there is no relation between the solar switch control and system changing, temperature difference switch control method should be chosen in the solar energy collector of solid structure.Finally, in order to study the operating performance of process of solar energy collecting and storing in the summer and snow melting and deicing in the winter. Using simplized snow melting and deicing models, combining with model of solar energy collecting and storing in the summer, heat transfer efficiency and energy usage of operating progress is studied. As shown in the results, when the collecting energy is too less or energy used in the melting snow and deicing is too much, so that energy does not make ends meet, underground temperature will be too low, and the system efficient will be too low.Comprehensive studies have shown that solar energy collection on the solid structures such as roads is a complicated heat transfer process. Coupling energy collecting with storage and couple energy storage and collecting wiht the process of melting snow and deice are more complex problems associated with heat transfer. In this study, theoretical analysis and simulation, combined with experimental studies are used to explore the mechanism and characteristics of heat and mass transfer. Thermal progress and control strategy in the energy underground storage and melting snow and deicing is revealed. The basic theory of solar energy collecting and underground storage and snow melting is developed and improved, which can be used to guide engineering applicationsS355K2W
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