Monte Carlo Ray Tracing Coupled CFD Modelling and Experimental Testing of a 1 kW Solar Cavity Receiver Radiated via 7 kW HFSS

Abstract

Current state-of-the-art development of concentrated solar power (CSP) applications target cost-effective and highly efficient processes in order to establish commercialization of these technologies. The design of solar receivers/reactors and their respective flow configuration have a direct impact on the operational performance of the solar thermochemical processes. Thermal efficiencies, reaction kinetics and other key output metrics are the intrinsic result of the chosen configuration. Therefore, reactor design optimization plays a crucial role in the development of solar thermochemical applications. In this study a computational fluid dynamics (CFD) model of a directly-irradiated cavity receiver has been developed. The CFD-domain is coupled with incoming radiation that is obtained by using Monte Carlo Ray Tracing (MCRT). Experimental campaigns of the cavity receiver were carried out using a 7 kW High Flux Solar Simulator (HFSS) as radiative source. Temperature readings were obtained at different locations inside the cavity receiver for both wall and gas temperatures. In order to mimic naturally changing insolation conditions, the HFSS was run at different power levels. Heat flux at the aperture of the solar receiver was experimentally characterized. The acquired heat flux maps validated the intermediate results obtained with the MCRT method. The coupled computational model was validated against the measured temperatures at different locations inside the receiver. Computed temperature contours inside the receiver confirmed the experimentally observed non-uniformity of the axial temperature distribution. The validated analysis presented in this paper was then used as a baseline case for a parametric study. Design optimization efforts were undertaken towards obtaining temperature uniformity and achieving efficient heat transfer within the fluid domain. Enhanced flow circulation was achieved which yielded temperature uniformity of the receiver at steady state conditions. The outcome of this parametric analysis provided valuable insights in the development of thermal efficient solar cavity receivers. Hence, findings of this study will serve as a starting point for future solar reactor design. For example, it was found that reversing flow direction has an adverse effect on the temperature uniformity inside the receiver. Similarly, increasing the inlet angle does not positively affect the temperature distribution and hence should be chosen carefully when designing a solar reactor.

A numerical study on particle tracking and heat transfer enhancement in a solar cavity receiver

“…Following on the cold conditions fluid dynamics model, the energy and discrete ordinate radiation model are now accounted for. Extensive elaboration of the optical ray tracing model and its' coupling to the fluid domain has been described elsewhere [27]. The particle cloud in the present study will increase radiative absorption throughout the fluid domain as was previously illustrated in Figure 2.…”

“…More details on the geometrical specifications, thermocouple configuration and material properties can be found in Ref. [27]. The goal of the present study is to redesign this solar cavity receiver, starting with a validation of the numerical model.…”

“…In parallel with the model presented in Ref. [27], the following boundary conditions are assigned to the fluid domain:…”

“…[38] and Ref. [27]), details of this boundary condition and optical analysis are not described in the present study for the sake of brevity.…”

“…As a final stage of the numerical analyses presented in this study, the above-obtained results are utilized to improve upon the initial 1 kW receiver [27]. Three design iterations are presented and labelled as Solar In this way, residence time of the fluid and solid elements are similar, and the same amount of radiative power enters the cavity.…”