Research On Entropy Generation And Corrosion Of Heat Transfer Fluids For Concentrating Solar Power Plants

As a free,clean and easily accessible renewable energy source,solar energy is considered to have great potential to replace traditional fossil fuels for large-scale power generation in the future.Solar thermal power generation technology has a high energy utilization rate and can store heat to achieve continuous power supply.However,one of the main obstacles to the large scale application of solar thermal power plants is high temperature heat transfer fluids.Heat transfer fluid is an important part of concentrating solar power plants.Running a concentrating solar power plant requires a lot of heat transfer fluids,so choosing the right high temperature heat transfer fluid can minimize the cost and the amount to achieve the highest cycle efficiency.Molten salt has a wide working range,low vapor pressure and low viscosity,therefore is often used as a high temperature heat transfer fluid.The entropy generation corresponds to a drop in useful work.Therefore,the smaller the entropy generation of the high temperature heat transfer fluid,the better its figure of merit.The mathematical model of entropy generation was deduced in this paper.The entropy generation and the Carnot cycle efficiency of 9 kinds of molten salt mixtures as high temperature heat transfer fluids at 50 MW power plant capacity were compared.The capacity of the power plant between 100 MW and 400 MW was also compared.This model provides a fundamentally and effective method for concentrating solar power plants to evaluate the performance of different high temperature heat transfer fluids.The high temperature heat transfer fluid is also an important research direction for the corrosion of alloy materials.Most of the containers and pipes used to store the high temperature heat transfer fluid are alloys,and the salts are subject to higher corrosion at high temperatures.In this paper,the corrosion of four corrosion resistant alloys at a high temperature of 700 ?was studied for chloride mixtures,carbonate mixtures and fluorine-carbonate mixtures.SEM,EDS and XRD analyses were performed on the alloy samples after corrosion.The study found that all alloys in the chloride salt have higher corrosion,the alloy SS316,C276 and In718 have better corrosion resistance in the carbonate salt,and the corrosion resistance of the alloy SS316 and In718 in the fluorine-carbonate salt is better.In view of the problems faced by high temperature heat transfer fluids for concentrating solar power plants,this paper studies the performance of molten eutectic salt mixture as a high temperature heat transfer fluid and its compatibility with alloy materials.By using the entropy generation formula derived in this paper,the entropy generation under different working conditions is calculated,and the entropy generation is used as a unified figure of merit to make a reasonable comparison of the properties of all kinds of eutectic salt mixtures when used as high temperature heat transfer fluids.The compatibility of different eutectic salt mixtures and alloys can be measured by the gravimetric method in this paper,which can reveal the corrosion mechanism of different alloy by different eutectic salt mixtures and to determine the metal composition which is most easily affected by the eutectic salt mixture in the alloy.The research has important practicality for the development and application of concentrating solar power plants.