Experimental and Numerical Investigation of Spouted Bed Solar Receivers

Abstract

In this thesis, spouted bed solar receivers were investigated in both experimental and numerical methods. One of the emerging applications of spouted beds is its utilization as a thermal energy storage unit in concentrated solar power systems (CSP) systems. The potential advantages of spouted beds in CSP systems are high heat transfer rates and high charging/discharging efficiencies. Experimental and numerical modeling studies related to spouted beds used as thermal receivers in CSP systems are limited in the literature. Therefore, the main motivation of this study was to investigate the thermal energy storage characteristics of spouted beds using different particles in addition to creating a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model using an open-source software program called Multiphase Flow with Interphase Exchanges (MFIX). Throughout the experiments and the modeling, laboratory scale (15 cm cylindrical diameter, 60° conical angle) conical spouted beds were built and used. The solar power was simulated by a 2 kWe metal halide lamp in the thermal experiments. During the experiments CarboHSP (dp = 0.95 mm, p = 3630 kg/m3 ) and olivine (dp = 1.2 mm , p = 3195 kg/m3) materials which are common materials in CSP applications were used . In these experiments, minimum spouting velocity, bed pressure drop and interstitial gas velocity distributions, temperature charge/discharge and heat flux were measured. It was seen that minimum spouting velocity does not differ for both particles but more air tends to pass through the spout region with CarboHSP particles. On the other hand, CarboHSP particles had a better temperature charge efficiency although both particles reached the same maximum temperature. During the CFD-DEM simulations, it was observed that Coarse Grained Particle-Discrete Element Method (CGP-DEM) had a significant advantage in terms of computational time. Also, among the different DEM parameters tested, the restitution coefficient was the most sensitive one.

In this thesis, spouted bed solar receivers were investigated in both experimental and numerical methods. One of the emerging applications of spouted beds is its utilization as a thermal energy storage unit in concentrated solar power systems (CSP) systems. The potential advantages of spouted beds in CSP systems are high heat transfer rates and high charging/discharging efficiencies. Experimental and numerical modeling studies related to spouted beds used as thermal receivers in CSP systems are limited in the literature. Therefore, the main motivation of this study was to investigate the thermal energy storage characteristics of spouted beds using different particles in addition to creating a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model using an open-source software program called Multiphase Flow with Interphase Exchanges (MFIX). Throughout the experiments and the modeling, laboratory scale (15 cm cylindrical diameter, 60° conical angle) conical spouted beds were built and used. The solar power was simulated by a 2 kWe metal halide lamp in the thermal experiments. During the experiments CarboHSP (dp = 0.95 mm, p = 3630 kg/m3 ) and olivine (dp = 1.2 mm , p = 3195 kg/m3) materials which are common materials in CSP applications were used . In these experiments, minimum spouting velocity, bed pressure drop and interstitial gas velocity distributions, temperature charge/discharge and heat flux were measured. It was seen that minimum spouting velocity does not differ for both particles but more air tends to pass through the spout region with CarboHSP particles. On the other hand, CarboHSP particles had a better temperature charge efficiency although both particles reached the same maximum temperature. During the CFD-DEM simulations, it was observed that Coarse Grained Particle-Discrete Element Method (CGP-DEM) had a significant advantage in terms of computational time. Also, among the different DEM parameters tested, the restitution coefficient was the most sensitive one.