Numerical Simulation Of The Heat Storage Device Based On The Flue Gas Heat Recovery

With the rapid development of industry and the improvement of human life, the demand for energy is growing. The problem of energy shortage caused by human mining unreasonably have appeared in most countries even the worldwide at present, but the situation of energy waste is still serious, it is necessary to adopt reasonable and effective way to reduce energy waste so that could improve energy efficiency.Solar energy, industrial waste heat and waste heat can be stored in the form of heat by energy storage technology. It solve the problems in difference space and the time between the supply and use of energy. So it became an effective means to improve energy efficiency. Two critical technologies for latent heat storage are the energy storage materials and the heat storage structure. Usually, the phase change materials have relatively poor heat conduction performance, which slow the storage /release heat during PCM's melting and the solidification process and limit the development of phase-change thermal storage technology. Therefore, it is necessary taking effective heat transfer enhancement to improve the heat transfer coefficient of phase change thermal storage.In this thesis, molten salt NaNO3-46KNO3 and LiNO3 and adipic acid are chosen as middle and the mid-high temperature latent heat thermal energy storage materials, to study the exothermic character of composite heat storage devices and heat transfer enhancement effect on the heat storage structure. For the problem of low thermal conductivity of gas in the flue gas heat recovery heat storage device. in order to improve the heat transfer efficiency of the system, the coil type heat storage device and bellows heat storage device are designed. The coil structure can extend the travel route of gas in a smaller size range, increasing contact time and increasing the heat transfer rate. Bellows structure can increase the contact area of heat transfer and fluid disturbance to enhance heat transfer, and the volume filling ratio of phase change material is bigger, cause to high material utilization.The physical and mathematical models of this coil heat storage device are established in this thesis. Using empirical formula based on the theoretical calculation, initially identified the characteristics and dimensions of the structural units, and established a 3D model after model sampling. Heat storage/exothermic process of the heat storage device are in numerical simulation studied by using Fluent software. Temperature field?Distribution of liquid rate?different measuring point temperature change rule and PCM heat/heat quantity are in simulated. In order to obtain universal results the HTF inlet velocity, the initial temperature of the heat storage devices and natural convection on the melting and solidification characteristics are carried out. The total heat storage for the coil heat storage device is 0.481 MWh or 0.508 MWh when the PCM is NaNO3-46KNO3 and LiNO3. Analysis of the structure according to the rationalization of related components, optimize the structure and size of each unit in heat storage devices, It provides reference basis for the application of the coil heat storage devices in the fields of the energy utilization.The two-dimensional mathematical model of a single tube in bellows heat storage device are established in this thesis, and the Heat storage/exothermic process are comparative analyzed with the appropriate size of the light pipe element model. Temperature field?Distribution of liquid rate?different measuring point temperature change rule and PCM heat/heat quantity are in simulated with pipe diameter of 25 mm, Impact of parameters such as node height and node spacing on heat effect were analyzed,the best design parameters of the two heat storage devices were determined. Eventually bellows heat exchanger structure was confirmed and total amount of stored heat is 66978 KJ.,this provide reference value in engineering applications.