Numerical Simulation of a Lab-Scale Molten-Salt External Solar Receiver and Its Experimental Validation

Abstract

In this work, a lab-scale external receiver with a xenon lamp set was designed to study optical and thermodynamic properties, and its benchmark was also introduced. Eighteen stainless-steel tubes were placed on the receiver to absorb radiant energy from the xenon lamps and achieve light-to-heat conversion. The indirect method was used to obtain the optical efficiency of the xenon lamp setup, and the heat-flux distribution on the surface of the receiver had an average heat flux of 99.4 kW/m2. Furthermore, the experimental method was used to study the temperature change of the receiver during the startup, stabilization, and shutdown of the receiver. A numerical simulation was conducted using commercially available software with the realizable k-ε model and the discrete ordinates model as the radiative transfer equation to valid the experimental result. The temperatures of the back and front of the receiver were obtained by thermocouples and an infrared thermal imager, respectively. The temperature of the back of the receiver rose rapidly after the lamps were turned on, and the temperature of the heat receiver remained unchanged when it was stable. The velocity of the molten salt was also studied, and the maximum speed was 1.9 m/s. The temperature increases of the experiment and simulation were approximately 4°C and 4.2°C, respectively, and the temperature of the tube wall was 40°C higher than that of the molten salt. The comparison of the experiment results indicate that the deviation between the receiver’s back temperatures in the simulation and experiment was basically within 5%, indicating consistency, and the thermal efficiency of the receiver was approximately 85%.