Design And Experimental Investigation Of Metal Foam-Solar Air Receiver

Thermal conversion efficiency of solar thermal power generation technology is directly related with the highest temperature of heat transfer medium. The higher the temperature is, the higher the thermal conversion efficiency is. The first-generation solar receiver takes heat transfer oil as heat transfer medium with a highest temperature of less than 400℃ while the second-generation solar receiver takes molten salt as heat transfer medium with a highest temperature of less than 600℃. Both are able to absorb and store heat. The generator of the system is steam turbine of which the highest efficiency is less than 43%. The heat transfer media of third-generation receiver are gases among which air and super-critical CO2 are research hotspots. Basically, there is no cap for temperature which depends on concentration ratio of concentrator and material. Advanced combined cycle is applied on the system. Theoretically, the efficiency can be as high as 60%.This study took solar air receiver as the research object, theoretically and experimentally investigated its design and heat transfer property. A metal foam-solar air receiver had been designed by utilizing metal foam as a heat absorption material and a method had been proposed to determine the size of the solar air receiver based on the system absorptivity of the cavity. Based on the design model of solar air receiver, a simplified heat transfer analysis model had been built to calculate heat loss and energy efficiency of solar air receiver. On this basis, performance test of the metal foam-solar air receiver had been done in the dish-type solar concentrator system. The test on the solar air receiver showed that the temperature difference reached 420℃ while outlet temperature of air was 463℃ and the energy efficiency was 81.5% when the inlet temperature was 43℃, and air mass flow rate stabilized around 2Nm3/min. The highest outlet temperature of air reached 528℃ while the energy efficiency was only 40%. There was a good agreement between results of test and results of simplified heat transfer analysis model, and cross verification of test and model was conducted. Furthermore, energy efficiency of other working conditions with higher inlet temperatures and higher outlet temperatures had been forecasted using the simplified heat transfer analysis model.In the end, due to the weakness of research of radiation heat transfer in metal foam, a two-dimensional simplified analytical model was proposed to predict the effective radiative conductivity of metal foam that used in solar air receiver. And then the reliability and accuracy of the abovementioned model had been verified with the experimental data in the references and the calculation results in a three-dimensional model.