Study Of Flow And Heat Transfer Performance And Design Of Molten Receiver In Solar Power Plants

With growing crisis in energy, solar energy is one of the most potential renewable energy sources. Researchers from all over the world are actively participating in concentrating solar power (CSP) technology. The total installed capacity of solar thermal power plants under construction will be17GW, including2.5GW in China. The thermal power technologies are in the primary phase in China, especially in researching on external tubular molten salt receiver.The thesis mainly researched on numerical investigation of flow and heat transfer performance in molten salt receivers and calculated its heat loss and proposed a method for molten salt receiver design based on its thermal strain of the receiver material and proposed optimal design for50MW molten salt receiver. The main work in the thesis was listed as follows:(1) Analyze fluid flow and heat transfer theory and some set of Fluent software as computational fluid dynamics tool, and give the data of molten salt temperature-dependent physical parameters including its density, specific heat capacity, thermal conduction, viscosity and thermal diffusivity, and then find physical parameters as a fit function of temperature.(2) Numerically investigate flow and heat transfer performance in molten salt receivers with uneven heat flux. Propose a flow and heat transfer performance grid model between molten salt and the receiver tube. And then analyze sectional temperature distribution of the receiver tube, axial temperature distribution of outer wall, inner wall and fluid. And through comparison of the simulated calculation, the Sieder-Tate equation, the Gnielinski equation and experimental result in a paper, it is found the Gnielinski equation is very suitable in molten salt receiver with uneven heat flux.(3) To calculate heat loss in the molten salt receivers, the thesis proposes a flow and heat transfer performance grid model between the air and the receiver. Give a data table of heat transfer performance between air and the receiver under different temperature of the receiver’s outer wall and environment, the velocity of the air.(4) Propose a method for molten salt receiver design based on its thermal strain of the receiver material. The thesis obtains the receiver optimal design to make the receiver’s efficiency maximal under some constraint conditions of the receiver’s shape, ratio of the receiver’s height and diameter, minimum thickness and resistance loss caused by the velocity molten salt. Through simulation and calculation, wall thickness and molten salt velocity of the receiver have much influence on its allowable heat flux, while tube inner diameter has little. Through comparison of the thermal efficiency of the receiver, good design of molten salt receiver should be thin, small tube and with large fluid velocity. Furthermore, minimum thickness and resistance loss caused by the velocity molten salt limit the receiver’s thickness and the velocity of molten salt respectively.Finally,50MW molten salt receiver’s thermal efficiency is86.8%for optimal design, its heat flux is519.5kW/m2and the velocity of molten salt is2.6m/s and its shape parameters are listed as follows: the receiver’s height and diameter are5.9m and5.2m respectively. Its whole area is96.2m2. The inside diameter and the thickness of the tube in the receiver are18.5mm and1.2mm respectively.