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CN-117131690-B - Design method of volumetric solar carbon dioxide receiver

CN117131690BCN 117131690 BCN117131690 BCN 117131690BCN-117131690-B

Abstract

The invention discloses a design method of a volumetric solar carbon dioxide receiver, which combines the geometrical parameter porosity, aperture and length with the heat transfer parameter volumetric convection coefficient, the effective solid phase heat conduction coefficient and the optical thickness, thereby carrying out combination optimization on the two. The optimization objective is a combination of large volumetric convection coefficient, large effective solid phase thermal conductivity coefficient, and optimal optical thickness. The corresponding parameter combinations are small pore size, small length and moderate porosity. According to this criterion, the best combination is a pore size of 0.4 mm, a length of 4 mm and a porosity of 0.85, with a corresponding thermal efficiency of 71.5%. This combination of developed methods is consistent with the combination of exhaustive methods, but the optimization complexity of the developed methods is reduced by more than two dimensions. Providing quantitative guidance for the design of the porous volumetric solar receiver.

Inventors

  • LIU DONG
  • NI XUEWEI
  • FENG HAO
  • ZHANG YING
  • LI QIANG

Assignees

  • 南京理工大学

Dates

Publication Date
20260512
Application Date
20230830

Claims (9)

  1. 1. A design method of a volumetric solar carbon dioxide receiver is characterized in that silicon carbide is taken as a framework material of the volumetric solar carbon dioxide receiver, the volumetric convection coefficient, the effective solid phase thermal conductivity and the optical thickness are calculated, and the combination optimization is carried out according to a formula (1), so that the optimized porosity, aperture and length parameters are obtained; the formula (1) is: ; In the formula (1), Is the thermal efficiency of the receiver, A is the volumetric absorptivity of the receiver, E is the volumetric emissivity of the interior of the receiver at the highest temperature T s,max , τ is the optical thickness, h v is the volumetric convection coefficient, λ se is the effective solid phase thermal conductivity, Φ is the porosity of the receiver, d is the aperture of the receiver, and L is the length of the receiver; Wherein, the (2); In equation (2), T s is the solid phase temperature, I b is the blackbody thermal radiation at the highest temperature T s,max inside the receiver, C is the ratio of the concentrated radiant energy density per unit area to the incident energy density, I sun is the solar irradiance; (3); (4)。
  2. 2. the method for designing a volumetric solar carbon dioxide receiver according to claim 1, wherein calculating the volumetric convection coefficient, the effective solid phase thermal conductivity, and the optical thickness comprises simulating a porous volumetric solar receiver, and setting simulation conditions such that effects of buoyancy, hydrodynamic dispersion, viscous dissipation, and thermal expansion are ignored, and a continuity equation is obtained assuming that the thermophysical properties of the solid are independent of temperature and the thermophysical properties of the fluid are different from each other: (5); Momentum equation: (6); (7); in the formulas (5) to (7), Is the surface velocity of the object to be inspected, Is the pressure of the fluid and, Is the density of the fluid which is to be measured, Is the viscosity of the fluid and, Is a source item generated by the porous medium; and obtaining the temperature distribution of the fluid and the solid phase in the receiver by adopting a local thermal non-equilibrium state model, and obtaining an energy equation of the fluid and the solid phase: (8); ; In the formula (8) and the formula (9), Is the specific heat of the fluid and, Is the temperature of the fluid and, Is the effective thermal conductivity of the fluid, Is the effective thermal conductivity of the solid phase, Wherein, the (10); (11); And, the volume convection coefficient is expressed as: (12); the source term S r is derived by solving the radiation transport equation: (13); the radiation transmission equation is: ; in the formula (14) of the present invention, Is the optical thickness of the film, Is the scattering albedo of the light, Is a function of the scattering phase and, Is of a specific position And the intensity of the radiation in the direction mu, Is the temperature Heat radiation of the lower black body; wherein Is the scattering direction and the forward direction An included angle between the two; The optical thickness and scattering albedo are: (15); (16); in the formulas (15) and (16), , And Respectively an extinction coefficient, an absorption coefficient and a scattering coefficient, wherein, (17); (18); (19); Indicating the surface reflectivity of the solid phase, Is a scattering phase function, wherein the scattering phase function is: (20)。
  3. 3. The method for designing a volumetric solar carbon dioxide receiver according to claim 2, further comprising analyzing volumetric reflection loss of the receiver: (21); in equation (21), a is the volumetric absorption rate of the receiver, Is the incident solar energy flow.
  4. 4. The method for designing a volumetric solar carbon dioxide receiver according to claim 2, wherein the simulated porous volumetric solar receiver is characterized by a sidewall of the receiver being insulated with a surface of the receiver receiving concentrated solar radiation, a solar stream As a uniform incident energy flow, the receiver inlet mass velocity was 0.592 to 0.85 kg m -2 s -1 , the inlet fluid temperature was 300K, the outlet wall was an ideal reflector, and the gauge pressure was 0 Pa.
  5. 5. The method for designing a volumetric solar carbon dioxide receiver according to any of claims 1-4, wherein the silicon carbide has a density of 3210 kg m -3 , a thermal conductivity of 80W m -1 K -1 and a specific heat capacity of 750J kg -1 K -1 .
  6. 6. The method of designing a volumetric solar carbon dioxide receiver according to claim 2, wherein the solar energy flows are concentrated on the front surface of the receiver and are transported axially into the receiver volume to generate high temperature carbon dioxide as it passes through.
  7. 7. The method for designing a volumetric solar carbon dioxide receiver according to any of claims 1-4, wherein the volumetric solar carbon dioxide receiver has an optimal porosity of 0.85.
  8. 8. The method for designing a volumetric solar carbon dioxide receiver according to any of claims 1-4, wherein the volumetric solar carbon dioxide receiver has an optimal aperture of 0.4 mm.
  9. 9. The method for designing a volumetric solar carbon dioxide receiver according to any of claims 1-4, wherein the volumetric solar carbon dioxide receiver has an optimal length of 0.004 m.

Description

Design method of volumetric solar carbon dioxide receiver Technical Field The invention belongs to the technical field of solar energy receivers, and particularly relates to a design method of a volumetric solar carbon dioxide receiver. Background Greenhouse gas emissions from the use of fossil fuels are increasingly becoming a worldwide concern. Concentrated solar power generation (CSP) is an important technology for mitigating the greenhouse effect, with solar receivers being a key component. Current receivers rely on molten salt heat transfer fluids. However, due to high temperature stability and high temperature corrosion problems, the operating temperature of the molten salt is limited to below 600 ℃. For example, commercial HITEC salts can only operate at temperatures below 454 ℃. Porous volumetric solar receivers using supercritical carbon dioxide as a heat transfer fluid represent the next generation CSP technology. The solar energy heat pump can generate carbon dioxide at the temperature of more than 700 ℃, so that the solar energy heat pump is expected to efficiently generate solar heat energy, and the valuable utilization of the carbon dioxide is expected to be realized. The prior art designs are obtained by independent optimization of each single parameter, i.e. by computationally intensive exhaustion methods, and therefore a more comprehensive quantitative design approach is needed to fill this knowledge gap. Disclosure of Invention This section is intended to outline some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. Taking silicon carbide as a framework material of the volumetric solar carbon dioxide receiver, calculating a volumetric convection coefficient, an effective solid phase thermal conductivity and an optical thickness, and carrying out combination optimization according to a formula (1) to obtain optimized porosity, aperture and length parameters; the formula (1) is: In the formula (1), Is the thermal efficiency of the receiver, A is the volumetric absorptivity of the receiver, E is the volumetric emissivity of the interior of the receiver at the highest temperature (T s,max), τ is the optical thickness, h v is the volumetric convection coefficient, λ se is the effective solid phase thermal conductivity, Φ is the porosity of the receiver, d is the pore size of the receiver, and L is the length of the receiver; Wherein, the (2) In equation (2), T s is the solid phase temperature, I b is the blackbody thermal radiation at the highest temperature (T s,max) inside the receiver, C is the ratio of the concentrated radiant energy density per unit area to the incident energy density, I sun is solar irradiance; (3) (4)。 The method for designing the volumetric solar carbon dioxide receiver comprises the steps of calculating the volumetric convection coefficient, the effective solid phase thermal conductivity and the optical thickness, simulating the porous volumetric solar receiver, and setting simulation conditions such that the influence of buoyancy, hydrodynamic dispersion, viscous dissipation and thermal expansion is ignored, and a continuity equation is obtained assuming that the thermophysical properties of solids are irrelevant to temperature and the thermophysical properties of fluids are different from each other: (5) Momentum equation: (6) (7) in the formulas (5) to (7), Is the surface velocity of the object to be inspected,Is the pressure of the fluid and,Is the density of the fluid which is to be measured,Is the viscosity of the fluid and,Is a source item generated by the porous medium; and obtaining the temperature distribution of the fluid and the solid phase in the receiver by adopting a local thermal non-equilibrium state model, and obtaining an energy equation of the fluid and the solid phase: (8) In the formula (8) and the formula (9), Is the specific heat of the fluid and,Is the temperature of the fluid and,Is the effective thermal conductivity of the fluid,Is the effective thermal conductivity of the solid phase, Wherein, the (10) (11) And, the volume convection coefficient is expressed as: (12) obtaining source terms by solving radiation transmission equations : (13) The radiation transmission equation is: in the formula (14) of the present invention, Is the optical thickness of the film,Is the scattering albedo of the light,Is of a specific positionAnd the intensity of the radiation in the direction mu,Is the temperatureHeat radiation of the lower black body; wherein Is the scattering direction and the forward directionAn included angle between the two; The optical thickness and scattering albedo are: (15) (16) in the formulas (15) and (16), ,AndRespectively an extinction coefficient, an absorption coefficient and a scattering coefficient, wherein, (17) (18) (19) Indicating the surface reflectivity of the solid phase.Is a scattering phase function, wherein the scattering phase function is: (20)。 as a preferable scheme of the