A design method of a volumetric solar carbon dioxide receiver

Abstract

The application discloses a design method of a volumetric solar CO2 receiver, which combines geometric parameters porosity, pore diameter and length with heat transfer parameters volume convection coefficient, effective solid phase thermal conductivity coefficient and optical thickness, so as to combine and optimize them. The optimization target is the combination of large volume convection coefficient, large effective solid phase thermal conductivity coefficient and optimal optical thickness. The corresponding parameter combination is small pore diameter, small length and moderate porosity. According to the standard, the optimal combination is 0.4 mm pore diameter, 4 mm length and 0.85 porosity; and the corresponding thermal efficiency is 71.5%. The combination of the developed method is consistent with the combination of the exhaustive method, but the optimization complexity of the developed method is reduced by more than two dimensions. The method provides quantitative guidance for the design of a porous volumetric solar receiver.

Description

Technical Field

[0001] This invention belongs to the field of solar receiver technology, specifically relating to a design method for a volumetric solar carbon dioxide receiver. Background Technology

[0002] Greenhouse gas emissions from fossil fuel use are increasingly drawing global attention. Concentrated solar power (CSP) is a crucial technology for mitigating the greenhouse effect, with the solar receiver being a key component. Current receivers rely on molten salt heat transfer fluids. However, due to high-temperature stability and corrosion issues, the operating temperature of molten salts is limited to below 600°C. For example, commercially available HITEC salts can only operate below 454°C. Porous volumetric solar receivers using supercritical carbon dioxide as the heat transfer fluid represent the next generation of CSP technology. They can generate carbon dioxide at temperatures above 700°C, thus promising not only efficient generation of solar thermal energy but also the valuable utilization of carbon dioxide.

[0003] Existing designs are obtained by optimizing each individual parameter independently, i.e., through a computationally intensive exhaustive method. Therefore, a more comprehensive quantitative design method is needed to fill this knowledge gap. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0005] As one aspect of the present invention, the present invention provides a design method for a volumetric solar carbon dioxide receiver: using silicon carbide as the skeleton material of the volumetric solar carbon dioxide receiver, calculating the volumetric convection coefficient, effective solid thermal conductivity and optical thickness, and performing combination optimization according to formula (1) to obtain the optimized porosity, pore size and length parameters.

[0006] The formula (1) is:

[0007]

[0008] In formula (1), The receiver's thermal efficiency is A, where A is the receiver's volumetric absorptivity, and E is the receiver's internal thermal efficiency at the highest temperature (T). s,max The volume emissivity at (h) is given by τ, where τ is the optical thickness. v It is the volumetric convection coefficient, λ se Φ is the effective solid-phase thermal conductivity, d is the porosity of the receiver, L is the pore size of the receiver, and L is the length of the receiver.

[0009] in,

[0010] (2)

[0011] In formula (2), T s It is the solid-state temperature, I b The receiver's internal temperature at its highest (T) s,max Blackbody thermal radiation at time ), C is the ratio of the concentrated radiation energy density per unit area to the incident energy density; I sun It is solar irradiance;

[0012] (3)

[0013] (4).

[0014] As a preferred embodiment of the design method for the volumetric solar carbon dioxide receiver described in this invention: the calculation of the volumetric convection coefficient, effective solid-phase thermal conductivity, and optical thickness includes simulating a porous volumetric solar receiver, and setting the simulation conditions as follows: ignoring the effects of buoyancy, hydrodynamic dispersion, viscous dissipation, and thermal expansion; assuming that the thermophysical properties of the solid are independent of temperature; and that the thermophysical properties of the fluids are different, thus obtaining the continuity equation:

[0015] (5)

[0016] And the momentum equation:

[0017] (6)

[0018] (7)

[0019] In formula (5) ~ formula (7), It is surface velocity. It is fluid pressure. It is the fluid density. It is fluid viscosity. It is the source term generated by porous media;

[0020] Furthermore, the temperature distribution of the fluid and solid phase within the receiver is obtained using a local thermal non-equilibrium model, leading to the energy equations for the fluid and solid phases:

[0021] (8)

[0022]

[0023] In formulas (8) and (9), It is the specific heat of the fluid. It is the fluid temperature. It is the effective thermal conductivity of the fluid. It is the effective thermal conductivity of the solid phase.

[0024] in,

[0025] (10)

[0026] (11)

[0027] And, the volumetric convection coefficient is expressed as:

[0028] (12)

[0029] The source term is obtained by solving the radiative transfer equation. :

[0030] (13)

[0031] The radiative transfer equation is:

[0032]

[0033] In formula (14), It is optical thickness. It is the scattering albedo. It is a specific location and the radiation intensity at direction X, It is temperature Thermal radiation of the lower blackbody; ,in It refers to the scattering direction and the forward direction. The angle between them;

[0034] Optical thickness and scattering albedo:

[0035] (15)

[0036] (16)

[0037] In formulas (15) and (16), , and These are the extinction coefficient, absorption coefficient, and scattering coefficient, respectively; among which,

[0038] (17)

[0039] (18)

[0040] (19)

[0041] This represents the surface reflectivity of a solid phase. It is the scattering phase function, where the scattering phase function is:

[0042] (20).

[0043] As a preferred embodiment of the design method for the volumetric solar carbon dioxide receiver described in this invention, it further includes analyzing the volumetric reflection loss of the receiver:

[0044] (twenty one)

[0045] In formula (21), A is the volumetric absorptivity of the receiver. It is the incident solar energy flow.

[0046] As a preferred embodiment of the design method for the volumetric solar carbon dioxide receiver described in this invention: the simulated porous volumetric solar receiver has the following boundary conditions: the sidewalls of the receiver are insulated, the surface of the receiver receives concentrated solar radiation, and solar energy flows... As a uniform incident energy flow, the receiver inlet mass velocity is 0.592~0.85 kg m. -2 s -1 The inlet fluid temperature is 300 K, the outlet wall is an ideal reflector, and the gauge pressure is 0 Pa.

[0047] As a preferred embodiment of the design method for the volumetric solar carbon dioxide receiver described in this invention: the silicon carbide has a density of 3210 kg m³. -3 The thermal conductivity is 80 W / m. -1 K -1 Specific heat capacity is 750 J kg -1 K -1 .

[0048] As a preferred embodiment of the design method of the volumetric solar carbon dioxide receiver described in this invention: In the simulated porous volumetric solar receiver, solar energy flows to the front surface of the receiver and is transported axially into the receiver volume, where high-temperature carbon dioxide is generated when carbon dioxide passes through.

[0049] As a preferred embodiment of the design method of the volumetric solar carbon dioxide receiver described in this invention, the optimal porosity of the volumetric solar carbon dioxide receiver is 0.85.

[0050] As a preferred embodiment of the design method of the volumetric solar carbon dioxide receiver described in this invention, the optimal aperture of the volumetric solar carbon dioxide receiver is 0.4 mm.

[0051] As a preferred embodiment of the design method of the volumetric solar carbon dioxide receiver described in this invention, the optimal length of the volumetric solar carbon dioxide receiver is 0.004 meters.

[0052] The beneficial effects of this invention are as follows: This invention proposes a unique design method that combines geometric parameters (porosity, pore size, and length) with three heat transfer parameters (volume convection coefficient, effective solid-phase thermal conductivity, and optical thickness) for combined optimization. The optimization objective is a combination of large volume convection coefficient, large effective solid-phase thermal conductivity, and optimal optical thickness. The corresponding parameter combination is small pore size, small length, and moderate porosity. According to this criterion, the optimal combination is a pore size of 0.4 mm, a length of 4 mm, and a porosity of 0.85; the corresponding thermal efficiency is 71.5%. This combination of the developed method is consistent with the combination of the exhaustive method, but the optimization complexity of the developed method is reduced by more than two dimensions. This provides quantitative guidance for the design of porous volumetric solar receivers. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0054] Figure 1 This is a schematic diagram of a porous volumetric solar carbon dioxide receiver.

[0055] Figure 2 This is a comparison between the receiver temperature distribution simulated in this invention and the results in the references.

[0056] Figure 3 Thermal efficiency for different combinations of porosity, pore size, and length.

[0057] Figure 4 The effect of volumetric convection coefficient on receiver efficiency.

[0058] Figure 5 The effect of effective solid-phase thermal conductivity on receiver efficiency.

[0059] Figure 6 The percentage of volumetric reflection loss varies with pore size when the porosity is 0.85 and the length is 0.004 meters.

[0060] Figure 7 The percentage of volumetric reflection loss varies with porosity when the aperture is fixed at 0.4 mm and the length is 0.004 m. Detailed Implementation

[0061] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0062] The present invention provides a design method for a volumetric solar carbon dioxide receiver, which uses silicon carbide as the skeleton material of the volumetric solar carbon dioxide receiver, calculates the volumetric convection coefficient, effective solid thermal conductivity and optical thickness, and performs combination optimization according to formula (1) to obtain the optimized porosity, pore size and length parameters.

[0063] The formula (1) is:

[0064]

[0065] In formula (1), The receiver's thermal efficiency is A, where A is the receiver's volumetric absorptivity, and E is the receiver's internal thermal efficiency at the highest temperature (T). s,max The volume emissivity at (h) is given by τ, where τ is the optical thickness. v It is the volumetric convection coefficient, λ se Φ is the effective solid-phase thermal conductivity, d is the porosity of the receiver, L is the pore size of the receiver, and L is the length of the receiver.

[0066] in,

[0067] (2)

[0068] In formula (2), T s It is the solid-state temperature, I b The receiver's internal temperature at its highest (T) s,max Blackbody thermal radiation at time ), C is the ratio of the concentrated radiation energy density per unit area to the incident energy density; I sun It is solar irradiance; the first term of formula (2) represents volumetric reflection loss, and the second term represents volumetric thermal radiation loss; the volumetric absorptivity A is determined by the optical thickness τ, which is a function of the receiver porosity, aperture, and length. Therefore, we can conclude that:

[0069] (3)

[0070] In addition to τ, the solid phase temperature T s The distribution of solar energy also determines the volumetric emissivity E. According to energy balance analysis, absorbed solar energy is carried away through thermal radiation, fluid volumetric convection, and solid-phase heat conduction. The volumetric convection coefficient h... v It is a function of porosity, pore size, and length, while the effective solid-phase thermal conductivity λ se It is a function of the receiver porosity. Therefore, we can conclude that:

[0071] (4).

[0072] Numerical verification was performed on the combined design method developed in this invention. Figure 1 shows the two-dimensional axisymmetric geometry used in this invention. Solar energy flow ( The carbon dioxide is collected on the front surface and transported axially into the receiver volume, where it generates high-temperature carbon dioxide as it passes through.

[0073] Governing equations: The simulation requires the following assumptions: (i) The thermophysical properties of solids are independent of temperature, while the thermophysical properties of fluids vary. (ii) The effects of buoyancy, hydrodynamic dispersion, viscous dissipation, and thermal expansion are neglected. Based on these assumptions, the continuity equation can be derived:

[0074] (5)

[0075] And the momentum equation:

[0076] (6)

[0077] (7)

[0078] In formula (5) ~ formula (7), It is surface velocity. It is fluid pressure. It is the fluid density. It is fluid viscosity. It is the source term generated by porous media;

[0079] To accurately obtain the temperature distribution of the fluid and solid phase within the receiver, a local thermal nonequilibrium (LTNE) model was employed. The energy equations for the fluid and solid phases are expressed as follows:

[0080] (8)

[0081]

[0082] In formulas (8) and (9), It is the specific heat of the fluid. It is the fluid temperature. It is the effective thermal conductivity of the fluid. It is the effective thermal conductivity of the solid phase.

[0083] in,

[0084] (10)

[0085] (11)

[0086] And, the volumetric convection coefficient is expressed as:

[0087] (12)

[0088] The source term is obtained by solving the radiative transfer equation. :

[0089] (13)

[0090] The radiative transfer equation is solved using the discrete ordinal method, and its expression is as follows:

[0091]

[0092] In formula (14), It is optical thickness. It is the scattering albedo. It is a specific location and the radiation intensity at direction X, It is temperature Thermal radiation of the lower blackbody; ,in It refers to the scattering direction and the forward direction. The angle between them;

[0093] Optical thickness and scattering albedo:

[0094] (15)

[0095] (16)

[0096] In formulas (15) and (16), , and These are the extinction coefficient, absorption coefficient, and scattering coefficient, respectively; among which,

[0097] (17)

[0098] (18)

[0099] (19)

[0100] This represents the surface reflectivity of a solid phase. It is the scattering phase function, where the scattering phase function is:

[0101] (20).

[0102] Boundary conditions. The receiver's sidewalls are thermally adiabatic. The front surface receives concentrated solar radiation. As a uniform incident energy flow, the inlet mass velocity is 0.592 kg m.-2 s -1 The ratio of incident solar radiation power to fluid velocity was the same as under experimental conditions. The front surface was set as a pseudo-surface with the same porosity as the volumetric porosity. The inlet fluid temperature was 300 K. The outlet wall was an ideal reflector with a gauge pressure of 0 Pa.

[0103] Material properties. Silicon carbide was used as the receiver framework in this study. The density of silicon carbide is 3210 kg m³. -3 The thermal conductivity is 80 W / m. -1 K -1 Specific heat capacity is 750 J kg -1 K -1 .

[0104] Model validation. Simulations were performed using FLUENT. The dominance equations were solved using the SIMPLE algorithm and the second-order upwind method. The residual convergence criterion for the energy and radiative transfer equations was set to 10. -6 The residual convergence criterion for the remaining equations is set to 10. -3 To verify the reliability of our model, we performed simulations using the same parameters and material properties as Kribus et al., as well as the same energy and radiation transfer models (LTNE and discrete ordinal models). The structured mesh had 12,800 elements. The absolute value of the thermal efficiency calculated with 12,800 elements differed by only 0.3% from that calculated with 51,200 elements, therefore 12,800 elements were used. Figure 2 The results show that the receiver temperature distribution we simulated is in excellent agreement with the results in the references, with a maximum deviation of less than 5%. Therefore, the model and method used in this study are reliable.

[0105] The exhaustive method yielded the following results: Considering current porous structure manufacturing technology, porosity is typically between 0.7 and 0.95, pore density between 5 and 65 PPI, and the corresponding minimum pore diameter is approximately 0.4 mm. Therefore, if an exhaustive method is used to find the optimal receiver, simulations are needed for 90 conditions: six porosities (0.7, 0.75, 0.8, 0.85, 0.9, and 0.95), five pore diameters (0.4, 0.8, 1.2, 1.6, and 2.0 mm), and three receiver lengths (0.004, 0.008, and 0.016 m). The simulation results are shown in Figure 3. The optimal receiver has a porosity of 0.85, a pore diameter of 0.4 mm, and a length of 0.004 m.

[0106] Figure 3The thermal efficiency is shown for different combinations of porosity, pore size, and length. (a) L = 0.004 m, (b) L = 0.008 m, (c) L = 0.016 m. Figure 3a shows that, under the condition of L = 0.004 m, for a specific porosity, the thermal efficiency increases with decreasing pore size across the entire pore size range. When the pore size is less than 1.2 mm, the thermal efficiency increases with increasing porosity and then decreases. When the pore size is greater than 1.2 mm, the thermal efficiency decreases monotonically with increasing porosity. Figure 3b shows that the trend under the condition of L = 0.008 m is the same as that under the condition of L = 0.004 m. However, Figure 3c shows that, under the condition of L = 0.016 m, the thermal efficiency still increases with decreasing pore size, but for a specific pore size, the thermal efficiency decreases with increasing porosity across the entire pore size range. Therefore, there is currently no clear and reliable criterion for improving thermal efficiency applicable to exhaustive calculations under all operating conditions. Furthermore, the exhaustive method involves a large amount of computation. Therefore, this invention addresses this issue by calculating the volumetric convection coefficient h. v Effective solid-state thermal conductivity λ se The study of optical thickness τ guides the design of receivers.

[0107] h v and λ se Impact on receiver thermal efficiency: To verify the effectiveness of the combined design method, we first demonstrated that a larger volumetric convection coefficient and a larger effective solid-phase thermal conductivity are required to improve thermal efficiency.

[0108] First, to demonstrate the positive correlation between thermal efficiency and volumetric convection coefficient, we calculated and analyzed the variation of thermal efficiency with volumetric convection coefficient under the same optical thickness and effective solid-phase thermal conductivity. The results under six sets of operating conditions—same porosity, same pore length ratio, and different pore diameters—are shown in Figure 4. It can be seen that the larger the volumetric convection coefficient, the higher the thermal efficiency. Therefore, an efficient receiver should possess a large volumetric convection coefficient.

[0109] Secondly, Figure 5 shows the thermal efficiency for different effective solid-state thermal conductivity at τ = 6. The results indicate that for a given volumetric convection coefficient, the higher the effective solid-state thermal conductivity, the higher the thermal efficiency. Therefore, an efficient receiver should have a large effective solid-state thermal conductivity.

[0110] Equation (12) shows that a large volumetric convection coefficient is obtained when the pore size and length are small and the porosity is large. However, equation (11) shows that a large effective solid thermal conductivity is obtained when the porosity is small. Therefore, to obtain both a large volumetric convection coefficient and a large effective solid thermal conductivity, a receiver with a small pore size and length should be designed, and a suitable porosity should be further optimized.

[0111] The effect of optical thickness on receiver thermal efficiency:

[0112] We have demonstrated that an optimal optical thickness is required to improve thermal efficiency.

[0113] First, we considered five cases with a fixed porosity of 0.85, a length of 4 mm, and pore diameters of 0.4, 0.8, 1.2, 1.6, and 2.0 mm. Table 1 lists the optical thickness, volumetric convection coefficient, and effective solid-phase thermal conductivity under various conditions. As shown in Table 1, among the three key heat transfer parameters under the five conditions, only the optical thickness varies significantly, while the effective solid-phase thermal conductivity remains constant, and the volumetric convection coefficient changes slightly. Table 1 shows the heat transfer parameters and thermal efficiency of the receiver when the porosity is fixed at 0.85 and the length is 0.004 m.

[0114] Table 1

[0115]

[0116] The results show that when the optical thickness decreases to τ < 4.5, the thermal efficiency decreases rapidly with increasing aperture. To understand this, we analyzed the volumetric reflection loss of the receiver, which is expressed as:

[0117] (twenty one)

[0118] In formula (21), A is the volumetric absorptivity of the receiver. It is the incident solar energy flow.

[0119] Figure 6 shows the percentage of volumetric reflection loss as a function of pore size under the conditions of a porosity of 0.85 and a length of 4 mm. The results show that in the range of τ < 4.5, reducing the optical thickness leads to a significant increase in volumetric reflection loss.

[0120] Secondly, we considered four conditions with a fixed aperture of 0.4 mm, a length of 0.004 m, and porosities of 0.7, 0.75, 0.8, and 0.85 mm. Table 2 lists the optical thickness, volumetric convection coefficient, and effective solid-phase thermal conductivity under various conditions. As shown in Table 2, among the three key heat transfer parameters under the four conditions, the volumetric convection coefficient varies relatively little, while the optical thickness and effective solid-phase thermal conductivity differ by a factor of two. Table 2 shows the heat transfer parameters and thermal efficiency of the receiver with a fixed aperture of 0.4 mm and a length of 0.004 m.

[0121] Table 2

[0122]

[0123] The results show that when τ > 4.5, even if the effective solid-phase thermal conductivity increases by a factor of two, the thermal efficiency decreases with decreasing porosity. This indicates that when τ > 4.5, the thermal efficiency decreases with increasing optical thickness. Figure 7 shows that when τ > 4.5, both volumetric absorptivity and volumetric reflection loss reach a peak. Furthermore, with increasing optical thickness, more solar energy is absorbed near the inlet surface, resulting in greater volumetric thermal radiation loss and a corresponding decrease in thermal efficiency.

[0124] Combining Tables 1 and 2, it can be seen that τ = 4.5 is the optimal optical thickness. This optimal optical thickness should be satisfied when optimizing the porosity of the receiver.

[0125] In summary, it can be seen that when optimizing the receiver design, (i) a receiver with a smaller pore size and length should be designed to obtain a larger volumetric convection coefficient. (ii) a receiver with moderate porosity should be designed to balance the volumetric convection coefficient and the effective solid-phase thermal conductivity. (iii) the porosity design should satisfy the requirement that the optical thickness of the receiver is close to τ = 4.5. Guided by these criteria, within the achievable parameter range of porous structures, the optimal combination is a pore size of 0.4 mm, a length of 4 mm, and a porosity of 0.85, corresponding to a thermal efficiency of 71.5%.

[0126] To further demonstrate the versatility of this design method, we conducted supplementary simulations, changing the inlet mass velocity to 0.85 kg m / s². -2 s -1 Furthermore, the supercritical carbon dioxide was changed to an ambient pressure fluid. The results show that the optimal combination remains 0.4 mm pore size, 4 mm length, and 0.85 porosity, which simultaneously achieves a large volumetric convection coefficient, a large effective solid-phase thermal conductivity, and an optimal optical thickness τ = 4.5.

[0127] The optimal combination obtained by the combined design method of this invention is consistent with the combination obtained by the exhaustive method used in the literature. This proves the reliability of our developed design method and the provided guidelines. Secondly, for the exhaustive method used in the literature, optimization requires scanning every combination of aperture, length, and porosity, resulting in a large computational load. However, for the combined design method, optimization only requires scanning the porosity within a small range limited by optical thickness. Therefore, the optimization complexity of the design method of this invention is reduced by two dimensions compared to the prior art.

[0128] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A design method for a volumetric solar carbon dioxide receiver, characterized in that: Using silicon carbide as the skeleton material of a volumetric solar carbon dioxide receiver, the volumetric convection coefficient, effective solid thermal conductivity and optical thickness were calculated. The optimized porosity, pore size and length parameters were obtained by combining and optimizing according to formula (1). The formula (1) is: ； In formula (1), The receiver's thermal efficiency is given by A, where A is the receiver's volumetric absorptivity, and E is the receiver's internal thermal efficiency at the highest temperature T. s,max Volume emissivity at time; τ is optical thickness, h v It is the volumetric convection coefficient, λ se Φ is the effective solid-phase thermal conductivity, d is the porosity of the receiver, L is the pore size of the receiver, and L is the length of the receiver. in, （2）； In formula (2), T s It is the solid-state temperature, I b The receiver's internal temperature at its highest point, T. s,max Blackbody thermal radiation at time; C is the ratio of the concentrated radiation energy density per unit area to the incident energy density; I sun It is solar irradiance; （3）； （4）。 2. The design method of the volumetric solar carbon dioxide receiver according to claim 1, characterized in that: The calculation of volumetric convection coefficient, effective solid-phase thermal conductivity, and optical thickness includes simulating a porous volumetric solar receiver. The simulation conditions are set as follows: buoyancy, hydrodynamic dispersion, viscous dissipation, and thermal expansion are ignored; the thermophysical properties of the solid are assumed to be independent of temperature; and the thermophysical properties of the fluids vary, resulting in the continuity equation: （5）； And the momentum equation: （6）； （7）； In formula (5) ~ formula (7), It is surface velocity. It is fluid pressure. It is the fluid density. It is fluid viscosity. It is the source term generated by porous media; Furthermore, the temperature distribution of the fluid and solid phase within the receiver is obtained using a local thermal non-equilibrium model, leading to the energy equations for the fluid and solid phases: （8）； ； In formulas (8) and (9), It is the specific heat of the fluid. It is the fluid temperature. It is the effective thermal conductivity of the fluid. It is the effective thermal conductivity of the solid phase. in, （10）； （11）； And, the volumetric convection coefficient is expressed as: （12）； The source term S is obtained by solving the radiative transfer equation. r : （13）； The radiative transfer equation is: ； In formula (14), It is optical thickness. It is the scattering albedo. It is the scattering phase function. It is a specific location and the radiation intensity at direction μ, It is temperature Thermal radiation of the lower blackbody; ,in It refers to the scattering direction and the forward direction. The angle between them; Optical thickness and scattering albedo: （15）； （16）； In formulas (15) and (16), , and These are the extinction coefficient, absorption coefficient, and scattering coefficient, respectively; among which, （17）； （18）； （19）； Indicates the surface reflectivity of a solid phase. It is the scattering phase function, where the scattering phase function is: （20）。 3. The design method of the volumetric solar carbon dioxide receiver according to claim 2, characterized in that: This also includes analyzing the volumetric reflection loss of the receiver: （21）； In formula (21), A is the volumetric absorptivity of the receiver. It is the incident solar energy flow.

4. The design method of the volumetric solar carbon dioxide receiver according to claim 2, characterized in that: The simulated porous volumetric solar receiver has the following boundary conditions: the receiver's sidewalls are insulated, the receiver's surface receives concentrated solar radiation, and solar energy flows... As a uniform incident energy flow, the receiver inlet mass velocity is 0.592~0.85 kg m. -2 s -1 The inlet fluid temperature is 300 K, the outlet wall is an ideal reflector, and the gauge pressure is 0 Pa.

5. The design method of the volumetric solar carbon dioxide receiver according to any one of claims 1 to 4, characterized in that: The silicon carbide has a density of 3210 kg m³. -3 The thermal conductivity is 80 W / m. -1 K -1 Specific heat capacity is 750 J kg -1 K -1 .

6. The design method of the volumetric solar carbon dioxide receiver according to claim 2, characterized in that: In the simulated porous volumetric solar receiver, solar energy flows to the front surface of the receiver and is transported axially into the receiver volume. High-temperature carbon dioxide is generated when carbon dioxide passes through.

7. The design method of the volumetric solar carbon dioxide receiver according to any one of claims 1 to 4, characterized in that: The optimal porosity of the volumetric solar carbon dioxide receiver is 0.

85.

8. The design method of the volumetric solar carbon dioxide receiver according to any one of claims 1 to 4, characterized in that: The optimal aperture of the volumetric solar carbon dioxide receiver is 0.4 mm.

9. The design method of the volumetric solar carbon dioxide receiver according to any one of claims 1 to 4, characterized in that: The optimal length of the volumetric solar carbon dioxide receiver is 0.004 meters.

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