Solar Cavity Receiver Research Articles

Theoretical and experimental study on the effect of the heat shield on the trough solar cavity receiver in alpine areas

The large heat loss of the cavity receiver limits its application in parabolic trough collectors, matching the environmental factors in alpine areas, in this paper, adding a glass cover plate as a heat shield at the aperture of the trough inverted trapezoidal cavity receiver is investigated. To quantify the optimization of the system performance by adding, an analytical study is carried out for the cavity receiver using theoretical calculations of heat transfer and indoor experimental tests, while “thermal uniformity” is introduced as an indicator of the temperature distribution inside the cavity, and further verifies experimentally by the outdoor real-area environment. The findings indicate that adding a heat shield is significantly effective in reducing heat loss in windy areas. At the flow rate of 250 L/h and inlet temperature of 323 K, the maximum experimental heat loss value is significantly reduced by 70.01 % in the range of 1–5 m/s wind speeds compared to the one without a heat shield. When the wind direction is from −60° to 60°, the heat loss inside the cavity is small after adding, forming a stable stratified flow, and the thermal uniformity decreases by only 0.02, indicating that the stability of the temperature field inside the cavity is high. Furthermore, outdoor validation experiments demonstrate a slower change in heat loss rate with adding the heat shield compared to without, the growth rate of the former is close to 1/3 that of the latter, with a maximum suppressed heat loss rate of 23.49 %. This study provides the theoretical basis and data guidance for optimizing cavity receiver performance in alpine areas.

Heat transfer enhancement in pressurized solar cavity receivers with densely packed metallic wire mesh

Pressurized solar receivers are promising candidates as heat sources for integration with high-efficiency closed-loop air and supercritical carbon-dioxide based Brayton cycles. This paper focuses on the heat transfer enhancement of such a solar receiver using inline stacked wire mesh fibers in the heat transfer fluid flow path. The study involves modelling, characterization, and performance evaluation of a cavity-receiver with densely packed wire meshes. A new experimentally validated hybrid numerical approach is presented for modelling the inline stacked wire mesh layers. Initially, a direct numerical simulation at the pore scale on a representative elementary volume (REV) of the wire mesh geometry is performed for determining the hydrodynamic and thermal characteristics of the medium. Subsequently, these hydrodynamic and thermal properties are used to define a volume-averaged macroscopic porous medium. Experiments are performed using a rectangular channel stacked with stainless steel wire meshes, heated using a plate heater, and pressurized air supplied using a reciprocating compressor. Both numerical and experimental studies are performed for a Reynolds number range of 28 to 213 resulting in a Nusselt number range of 7.2 to 213. The porous medium model predictions for pressure gradient are within 17 %, while predictions for outlet air temperature are within 5 % of the experimentally obtained values. The study predicts a maximum heat transfer enhancement of five times in a channel stacked with wire meshes compared to the case of a clear channel, but incurring a peak pressure drop of only about 1.1 kPa.

Reducing convective losses in a solar cavity receiver VoCoRec by creating a controlled vortex of returned air

The efficiency of air-type solar towers influences the minimal cost of electricity/heat produced by them, which limits their use despite the widespread use of many forms of concentrated sun power plants. Nonetheless, the temperature potential of this kind of concentrated plant is the highest. To improve the efficiency of an air-type solar tower, a technique for reducing convective energy losses with return air is therefore suggested. In order to increase a cavity receiver's thermal efficiency, a little-known concept called vortex creation will be discussed in this work. The article models different ways of creating an air vortex inside the cavity receiver. Using the VoCoRec design as an example, cases are shown where the vortex increases and decreases the thermal efficiency of the receiver. The concept of Air Return Ratio (ARR) is used to determine the convective losses in a solar collector. This coefficient indicates the convective losses of the receiver due to buoyancy forces and has a direct proportional dependence on the convective efficiency coefficients of the receiver. The VoCoRec receiver, which incorporates the directional vortex inside the receiver, increased the air return coefficient by 4 % (at the same air mass flow rate). The dependence of the air return coefficient on different angles of the air outlet to the absorber plane, including in the radial direction, was also investigated. Increasing the angle of inclination of the air outlet to the main absorber increases the air return coefficient in all cases, but also increases the aerodynamic drag of the receiver (pressure drop).

Convective heat loss from a modified solar cavity receiver with vertical plate fins: An experimental assessment

AbstractExperimental investigations have been conducted to study the convective heat transfer from a cylindrical solar cavity receiver with vertical fins. The experiments were performed under varying surface heat flux levels and at seven inclination angles, ranging from −90° (upward facing) to +90° (downward facing) at 30° intervals. The impact of fins on the heat transfer process was studied by conducting experiments in two scenarios, namely, finned and unfinned cavities. The findings of the study showed that with an increase in cavity inclination, the magnitude of convective heat loss decreased in both finned and unfinned cavities, while the cavity surface temperature increased. At +90° inclination, the convective heat loss and Nusselt number were observed to have the lowest value, while the surface temperature had the highest value. For a downward‐facing cavity, the fins reduced convective heat loss, leading to an increase in cavity surface temperature. The finned cavity performed better for a vertically downward‐facing inclination (+90°) as it had a contribution of only 11% for convection heat loss compared with the unfinned cavity, which had a contribution of 21% for the same. Furthermore, an empirical model was developed based on the experimental results for the Nusselt number, which correlates experimental data with an error margin of ±15%. This model can be used to predict the Nusselt number for different inclination angles and surface heat flux levels. The presence of vertical fins in the cavity was found to be effective in reducing convective heat loss, especially for downward‐facing cavities. Understanding the influence of fin and cavity inclination on convective heat transfer can lead to enhanced efficiency and performance of solar receivers, thereby increasing the overall energy output of the system.

Solar cavity receiver for melting zinc metal

Concentrating solar power technologies can be applied to reduce the cost and carbon footprint of zinc melting processes. This study aims to improve the knowledge related to small-scale solar melting using a dish concentrator. This technology can be applied to zinc production as well as a range of small-scale applications, such as casting, recycling, galvanisation, and thermal storage. An experimental and analytical analysis of a rotating cylindrical cavity receiver for the indirect melting of zinc metal using concentrated solar power is presented. A multi-facet parabolic dish with an incident area of 2.85 m2 was considered together with a rotating cylindrical cavity receiver. The receiver had an aperture diameter of 0.2 m and the capacity for housing 17 kg of zinc. Five experimental test runs were executed, during which up to 73.5 % of the zinc inventory could be tapped from the receiver in its molten state, and average thermal efficiencies of up to 42 % were achieved. A predictive analytical model considering wind speed, wind direction, and direct normal irradiance was developed and validated against experimental data. A heat transfer efficiency factor was experimentally determined to account for voids in the zinc feedstock. The model was used to predict that approximately 41 kg of molten zinc could be tapped from the experimental setup throughout a typical day with a peak direct normal irradiance of about 900 W/m2 and an average wind speed below 2 m/s. A case study highlighted that energy savings of 0.6 kWh are achievable per kilogram of zinc processed by concentrated solar power rather than the conventional induction furnace.

Comparative analysis of entropy generation and heat transfer in a tilted partially heated square enclosure using the finite difference method

PurposeIn recent times, there has been a growing interest in buoyancy-induced heat transfer within confined enclosures due to its frequent occurrence in heat transfer processes across diverse engineering disciplines, including electronic cooling, solar technologies, nuclear reactor systems, heat exchangers and energy storage systems. Moreover, the reduction of entropy generation holds significant importance in engineering applications, as it contributes to enhancing thermal system performance. This study, a numerical investigation, aims to analyze entropy generation and natural convection flow in an inclined square enclosure filled with Ag–MgO/water and Ag–TiO2/water hybrid nanofluids under the influence of a magnetic field. The enclosure features heated slits along its bottom and left walls. Following the Boussinesq approximation, the convective flow arises from a horizontal temperature difference between the partially heated walls and the cold right wall.Design/methodology/approachThe governing equations for laminar unsteady natural convection flow in a Newtonian, incompressible mixture is solved using a Marker-and-Cell-based finite difference method within a customized MATLAB code. The hybrid nanofluid’s effective thermal conductivity and viscosity are determined using spherical nanoparticle correlations.FindingsThe numerical investigations cover various parameters, including nanoparticle volume concentration, Hartmann number, Rayleigh number, heat source/sink effects and inclination angle. As the Hartmann and Rayleigh numbers increase, there is a significant enhancement in entropy generation. The average Nusselt number experiences a substantial increase at extremely high values of the Rayleigh number and inclination.Practical implicationsThis numerical investigation explores advanced applications involving various combinations of influential parameters, different nanoparticles, enclosure inclinations and improved designs. The goal is to control fluid flow and enhance heat transfer rates to meet the demands of the Fourth Industrial Revolution.Originality/valueIn a 90° tilted enclosure, the addition of 5% hybrid nanoparticles to the base fluid resulted in a 17.139% increase in the heat transfer rate for Ag–MgO nanoparticles and a 16.4185% increase for Ag–TiO2 nanoparticles compared to the base fluid. It is observed that a 5% nanoparticle volume fraction results in an increased heat transfer rate, influenced by variations in both the Darcy and Rayleigh numbers. The study demonstrates that the Ag–MgO hybrid nanofluid exhibits superior heat transfer and fluid transport performance compared to the Ag–TiO2 hybrid nanofluid. The simulations pertain to the use of hybrid magnetic nanofluids in fuel cells, solar cavity receivers and the processing of electromagnetic nanomaterials in enclosed environments.

Improvement in the photothermal conversion performance of a solar cavity receiver with concave spherical windows

Photothermal conversion parameters are key indicators for measuring the operational performance of solar cavity receivers. By utilizing the redistributive ability of a functional surface in an optical concave lens to transmit solar radiation, previous studies have shown that installing a concave spherical quartz window at the front end of a solar cavity receiver can homogenize the flux distribution on the receiver wall. On this basis, research has been conducted on the impact of solar cavity receivers with concave spherical windows on their photothermal conversion performance. Based on the finite volume method, a coupling model for photothermal conversion in the receiver is established to calculate the heat transfer efficiency and temperature distribution of the receiver for different windows. The results indicate that, compared with a receiver with a flat quartz window, a receiver with a concave spherical quartz window can significantly reduce the peak temperature and peak temperature gradient of the spiral tube in the receiver, effectively improving the temperature distribution of the tube. When DNI = 1000 W/m2, the flow velocity at the inlet is 2.5 m/s, and the temperature at the inlet is 650 K. The receiver with a concave spherical quartz window has a reduced temperature peak from 868.09 K to 834.23 K and a temperature gradient from 2.46 K/mm to 1.27 K/mm relative to the receiver with a flat quartz window. This study provides ideas for the design of cavity receivers and improves their photothermal conversion performance.

Review of various solar cavity receivers of parabolic dish concentrators with design aspects and heat loss analysis

Review of various solar cavity receivers of parabolic dish concentrators with design aspects and heat loss analysis

Numerical investigation and comparison of tubular solar cavity receivers for simultaneous generation of superheated steam and hot air

Solar cavity receivers are a crucial technology to transform solar energy into easily usable thermal energy. Various cavity receiver structures employing helical absorber tubes were investigated to provide either superheated steam or hot air efficiently. However, few studies have focused on receivers that generate both hot fluids simultaneously. The simultanoues generation can lead to a more compact and cheaper system, and can be used for applications such as a high-temperature electrolysis to produce green hydrogen or syngas. In our study, three different tubular solar cavity receivers were proposed and numerically investigated. Each receiver consists of three different processes: (1) water evaporation, (2) superheating steam, and (3) heating air. The 1D-3D model developed in our previous study was used to investigate the various aspects such as lamp-to-thermal (solar simulator was used as a light source) and exergy efficiencies. The numerical results have proven that the receiver employing both cylindrical and conical helical tubes can obtain the highest lamp-to-thermal (67.0%) and exergy efficiencies (46.9%). A parameter study was also conducted based on the chosen optimal receiver. The obtained results can become a basis for further implementation, and especially the use in high-temperature electrolysis could become crucial in a future energy system.

Experimental Test Setup of an Airwall to Reduce the Convective Heat Loss in Solar Thermal Cavity Receivers

An experimental setup is presented which allows to experimentally determine the thermal heat losses from a heated solar cavity receiver with an airwall. The setup is a ‘near-full-scale’ replica of a receiver, which ensures that the characteristic fluid dynamic numbers are in a range relevant for practical industrial applications. The executed tests show that – at ideal configuration – the airwall can reduce the overall thermal losses by 7±2%. The reduction of the convective losses amounts to 32±11%, which is in line with the known predictions from CFD simulations.

Directly irradiated liquid metal film in an ultra-high temperature solar cavity receiver. Part 2: Coupled CFD and radiation analysis

A novel solar cavity receiver was proposed in Part 1 to facilitate operation at ultra-high temperatures (>1300 K). The concept featured enclosing a directly irradiated liquid metal film inside a window-sealed cavity containing an inert protective fluid. The receiver’s technical performance was evaluated using a quasi-steady-state analysis based on various assumptions, which were used to enable analytical modelling of the involved energy transfer mechanisms. This paper describes a Computational Fluid Dynamics (CFD) solution developed to verify the conclusions of Part 1 and furtherly investigate the technical performance of the proposed receiver. The solution combined the Volume Of Fluid (VOF) and Discrete Ordinates Model (DOM) methods to simulate the volumetric radiation absorption by the liquid metal film while accounted for the transient flow developments of the gravity-driven film and buoyancy-driven cavity fluid. Analytical models were verified, showing improved performance for the absorptive cavity configuration. Film flow disintegration was mitigated by using surface corrugations, which were found to significantly influence the fluid dynamics and heat transfer performance of the receiver. Finally, a steady-state thermal analysis was presented for the proposed ceramic window, which indicated that active cooling is indispensable for protecting the window against thermo-mechanical fatigue.

Directly irradiated liquid metal film in an ultra-high temperature solar cavity receiver. Part 1: Concepts and a quasi-steady-state analysis

Solar thermal energy has the theoretical potential to deliver heat at ultra-high temperatures (>1300 K), which can enable integration with state-of-the-art thermal energy storage systems and unlock new applications, including advanced power cycles and thermal processes. Liquid metals are prospective heat transfer fluids for such systems, given their favourable thermo-physical properties, while their aggressive corrosiveness is shown to be mitigated using compatible refractory containment materials. The conventional approach of collecting concentrated solar energy typically involves intermediate solid absorbers, in form of tubes or porous structures, which are prone to thermomechanical and chemical failure under high solar radiation. This paper investigates the use of directly irradiated liquid metal (tin) film, operating between 800 and 1673 K, in two possible cavity configurations: A ‘reflective cavity’ and an ‘absorptive cavity’. The former employs cavity walls as internal reflectors to entrap radiation by secondary reflections until directly absorbed by the liquid metal. In the latter, the directly irradiated film is used to moderate the initial shot of concentrated solar radiation before diffusively reflecting them to the absorptive cavity walls, which perform as a radiative heat exchanger used to preheat the liquid metal. The concept performance is evaluated using an approximate quasi-steady-state energy model of the receiver. The reflective cavity performance is found strongly dependent on the optical properties of its internal surfaces, which resulted in poor efficiencies (<40 %) without special treatments. The absorptive cavity demonstrated higher efficiencies (>70 %) with greater insensitivity to the optical properties, hence, promoting its consideration in future developments of this concept.

Performance assessment and Pareto front mapping of a novel truncated elliptic cavity solar receiver

Cavity-shaped receivers are new alternative heat collection elements for parabolic trough collectors that aim to reduce longwave thermal radiation. This study proposes a novel truncated elliptic receiver with front transparent and back opaque insulation for competitive performance without a vacuum. A novel analytical model, coupled with a ray tracing tool, is introduced to assess and maximize the performance of a standard-scale collector by varying the cavity’s depth, width, truncation fraction, and eccentricity, as well as the tube’s diameter ratio and eccentricity. The results show that the optical efficiency is driving the overall collector’s performance and the ellipse’s aspect ratio and truncation fraction should be set to around 1.5 and 0.42, respectively. The maximum energy and exergy efficiencies are 81.59 and 33.17 % for optical and thermal efficiencies of 90.90 and 89.76 %, respectively. These efficiencies are achieved when the cavity’s half-depth, half-height, truncated fraction, and eccentricity are 55.89 mm, 37.06 mm, 0.395, and 1.0, with tube eccentricity and diameter ratio of 0.16 and 1.063, respectively. The PTC’s energy and exergy efficiencies decrease by increasing the depth of the cavity and the two eccentricities and increase by increasing the truncated fraction and the tube diameter. The two efficiencies increase by 1.69 and 2.54 % when increasing the irradiance level and by 7.40 and 5.65 %, respectively, as the flow rate increases. As the ambient temperature increases, the energy efficiency enhances by 0.7 %, whereas the exergy efficiency degrades by 10.74 %. In contrast, the energy efficiency decreases by 11.59 %, and the exergy efficiency increases by 52.1 % as the inlet fluid temperature increases from 150 to 350 °C.

Contactless thermal mapping of high-temperature solar receivers via narrow-band near-infrared thermography

We present the design, construction, and successful proof-of-principle demonstration of a thermal camera capable of seeing through glass and other radiatively participating media, and apply the device to map the temperature distribution of a steam-filled windowed solar cavity receiver operating at temperatures up to 1400 °C. This “glass piercing” thermal camera utilizes a narrow bandpass filter with a center wavelength of 772 nm to effectively see through glass and similar optical glazing materials, as well as infrared-active radiatively participating media, to allow direct contactless measurement of the inner surfaces of windowed cavity receivers. By utilizing a standard optical CMOS sensor, the device achieves much higher resolution at a lower cost than traditional thermal cameras operating in the mid-infrared. Using a calibrated photometry sphere, we experimentally determined the device sensitivity (grayscale value per spectral radiance value), which allows the spectral radiance and ultimately temperature to be determined from a simple grayscale image. The calibrated device was then applied to both a blackbody source operating at above 1000 °C, and a high-temperature solar cavity receiver operating above 1400 °C. The results serve as an experimental proof-of-concept for glass-piercing and radiatively-participating-gas-piercing thermography.

Performance Investigation of Cylindrical Cavity Receiver Using Roughened Surfaces

Solar cavity receiver is an integral part of the solar parabolic dish collectors used for absorbing concentrated solar irradiation. The performance of the receivers can be enhanced utilizing different types of heat transfer fluids (HTF) and modified geometries. The thermal performance of a redesigned cavity receiver with solid semi-circular tube attached to its surface was investigated using CFD three-dimensional simulation. The influence of operating and geometric parameters (i.e., inlet mass flow rate and inlet temperature) were investigated. The results obtained shows that, redesigned solar cavity receiver has thermal efficiency of 8.49-10.27% higher than a normal cavity receiver with an inlet flow rate of 0.01-0.04 kg/s under the same environmental and operating conditions. The temperature of outlet of HTF increases with increases in inlet temperature for Therminol66 oil. The comparison of thermal performance using different HTF (i.e., Therminol66, Ethylene Glycol, Water) is also conducted and it is found that Therminol66 oil gives 9% and 17% higher outlet temperature than ethylene glycol and water respectively at intake flow rate of 0.02 kg/s.

Thermal Performance Improvement of Modified Hemispherical Cavity Receiver with Air Curtain

Heat losses from solar cavity receivers degrade the efficiency of solar parabolic dish collector system. Specifically, increased convection losses emulate a significant contribution in decreasing the performance of the modified solar cavity receiver and hence, reducing these convection losses has become a matter of great concern. The Air curtain plays a crucial role in minimizing the convection losses. This work proposes an air curtain-based modified cavity receiver wherein a plane nozzle is placed on the face of receiver to produce air curtain effect. Air curtain will prevent hot air from escaping the modified cavity receiver and increase the stagnation zone inside it to reduce natural convection on the surfaces. Numerical analyses are performed considering different air velocities and receiver orientations to evaluate the effect of air curtains on the convection losses. The impact of plane air nozzle parameters like outlet temperature, inclination, and outlet velocity of the nozzle on convection losses are shown and these parameters’ optimal value is evaluated. Our results state that the air curtain attached to the modified solar cavity receiver significantly improves performance by reducing the convection losses.

Numerical and experimental studies on a pressurized hybrid tubular and cavity solar air receiver using a Scheffler reflector

• Coupled optical and thermal model of a pressurized tubular and cavity solar air receiver. • Modelled the dynamic variation of concentrated solar radiation input to the receiver cavity surface. • Three-dimensional CFD analysis is performed on the hybrid receiver model. • Validation with on-sun experimental results using a Scheffler dish. • Natural convection and radiation heat loss estimation. In this study, a pressurized tubular and cavity solar air receiver is analyzed numerically, and the results are validated experimentally using a Scheffler fixed focus concentrator. Transient numerical analyses for periods similar to experimental testing duration allows realistic performance prediction of new receiver designs and help in understanding the dominant heat loss mechanisms, thus mitigating or reducing them. A coupled optical and thermal model is developed for analyzing the receiver with a novel method of capturing the spatial and temporal variation in the heat input to the receiver. The concentrated heat flux input to the receiver is defined as the product of two separate functions. The first function defines the incident radiation to the receiver as a spatially resolved flux profile on the cavity inside surface, obtained from the ray tracing algorithm. The second function captures the transience in heat input by curve-fitting the measured direct normal irradiation variation with time corresponding to the experimental testing period. Receiver heat loss modelling involves natural convection heat loss from the inside cavity surface estimated using an existing correlation, while radiation heat loss is estimated by prescribing the surface emissivity and computing the ambient view factor. A three-dimensional transient CFD analysis is performed on the hybrid receiver model under identical heating conditions as experiments to predict the flow heat transfer. The result from the numerical model is subsequently compared with on-sun experimental results obtained using a test rig equipped with a Scheffler dish for heat input and supply of compressed air as the heat transfer fluid through the receiver. The deviation between numerical and experimental results are less than 16 °C for air outlet temperature and less than 9% for the receiver thermal efficiency, thus proving the effectiveness of the coupled optical and thermal model. To account for the transient nature of the receiver heating during the on-sun experiments, the receiver thermal efficiency definition has been modified to include the thermal inertia of the receiver material. It is also observed that natural convection is the dominant heat loss mechanism for the present configuration and can significantly reduce the overall thermal efficiency of a receiver. The present numerical model incorporating an optical model of the solar field and as-measured variation of solar radiation input can be effectively used for optimizing the design of any generic concentrator-receiver system with high-pressure heat transfer fluid, with the objective of minimizing thermal losses.

Nusselt Number Prediction for Oil and Water in Solar Tubular Cavity Receivers

In this study, a numerical model was developed for prediction of Nusselt number in solar cavity receivers. Thermal oil and water were used as the working fluid. A dish concentrator with different shapes of the cavity receiver, including hemispherical, cylindrical, and cubical, was investigated. The different shapes of cavity receiver were studied under the same operating conditions for prediction of the internal heat transfer coefficient correlation for each cavity receiver. The system is investigated under the variation of solar radiation, flow rate, and inlet temperature of solar working fluids. The developed thermal model is validated based on the experimental data for the cylindrical cavity receiver using thermal oil. The results reveal that the hemispherical cavity receiver had the highest cavity heat gain, heat transfer coefficient, and Nusselt number values compared to two other cavity receivers. It could be concluded that the cavity heat gain, and heat transfer coefficient, and Nusselt number amounts had improved with increasing solar radiation, increasing flow rate, and decreasing inlet temperature of the working fluid. Some equations were suggested for prediction of Nusselt number with the variation of solar radiation, flow rate of the working fluid, and inlet temperature of working. It was concluded that application of thermal oil had resulted in higher Nusselt numbers than the use of water as the solar working fluid. Consequently, the application of oil is suggested for high-temperature systems.

Energy performance of a solar cavity receiver with neural output flow regulation under controlled conditions

This article presents the theoretical and experimental performance of a Solar Cavity Receiver (SCR) which operates under controlled conditions of radiation and flow regulation using an Artificial Neural Network (ANN); the objective of this application of neural networks is to obtain the maximum temperature of a fluid in an open hydraulic circuit that presents variations in pressure and temperature of the inlet fluid. The SCR is evaluated for two cases: In the first case, inlet fluid presents a constant temperature and pressure variations of 62–96 kPa, and in the second case, the system presents variations in pressure 55–89 kPa and temperature 29 °C to 31 °C; it was found that an ANN presents a response with a varied range of 2–14%, with average temperature variations lower than 6% respect to the set-point, with the advantage of being self-regulated through ANN training.

Discrete particle modelling of buoyant convective particle-laden air flow in solar cavity free-falling particle receivers

A coupled computational fluid dynamics and discrete particle method numerical model is developed to provide a systematic analysis of buoyant convective particle-laden air flow and heat losses from a solar cavity receiver with free-falling particles. The fundamental mechanisms of heat loss from a solar cavity particle receiver are poorly understood and difficult, if not impossible, to obtain experimentally. Studies on particle-laden air flow and heat transfer mechanisms in a solar cavity free-falling particle receiver are extremely limited. As such, this study is the first attempt to unravel the convective heat transfer mechanisms of a solar cavity particle receiver while considering the influence of the entrained air, air recirculation patterns, and solid–gas thermal dynamics. Furthermore, the receiver efficiency due to air recirculation and particle transport in addition to the relative losses due to heat exiting the receiver aperture and outlet ports is investigated. It is found that the particle mass flow rates have profound implications on the air recirculation patterns, entrained air, and heat fluxes of the solar receiver. The heat losses at the particle outlet greatly increase with increasing particle mass flow rate due to the higher thermal mass of the entrained air. An increase in the particle injection rate from 100,000 pps to 3,000,000 pps leads to an increase in the net heat by 48.6% although the aperture heat loss decreases by 24.4%. This is linked to the high entrained air velocities which recirculates much of the heated air in the cavity thereby reducing the aperture heat loss. This also infers a linear increase in the thermal efficiency and exponential decrease in exit loss ratios of the solar cavity receiver. It is also found that a competition exists between the various flow intensities of the particle curtain, the ambient air, and the entrained air velocities, which is quantified by the dimensionless thermal energy. Scientists and engineers can further optimize the geometric morphologies of solar cavity receivers after gaining a solid comprehension of the flow structures and thermal efficiencies of the solar receiver. To this end, a modified receiver geometry is proposed to mitigate convective heat losses. The modified receiver is about 26% efficient than the original receiver, which is linked to the 45° plate which impedes the velocity of the particle curtain at the outlet and reduces the entrained air velocity and heat losses from the cavity. Furthermore, a high particle initialization velocity greatly amplifies the heat losses at the particle outlet port. This high thermal mass at the outlet port amplifies the entrained air velocity regardless of the geometric morphology of the solar receiver. The results from the validated numerical model can be used by engineers and scientists to better optimize geometric morphologies of solar particle receivers.