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a b s t r a c tStoring excess thermal energy in a storage media, that can later be extracted during peak-load times is one of the better economic options for nuclear power in future. Thermal energy storage integration with light-water cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different options. Various choices of storage media considered in this study include molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. Due to limitations of complex process conditions and safety requirements there are only few combinations which have potential integration possibilities. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. This study identifies, examines, and compares different energy storage options for integration with modular NPPs, with the calculated values of energy density and exergy efficiency. The thermal energy storage options such as synthetic heat transfer fluids perform well for light-water cooled NPPs, whereas liquid storage salt show better performance with advanced NPPs as compared to other options.

In this paper, the lattice Boltzmann equation (LBE)-based framework is used to obtain the solution for the linear radiative or neutron transport equation. The LBE framework is devised for the integrodifferential forms of these equations which arise due to the inclusion of the scattering terms. The interparticle collisions are neglected, hence omitting the nonlinear collision term. Furthermore, typical representative examples for one-dimensional or two-dimensional geometries and inclusion or exclusion of the scattering term (isotropic and anisotropic) in the Boltzmann transport equation are illustrated to prove the validity of the method. It has been shown that the solution from the LBE methodology is equivalent to the well-known P(n) and S(n) methods. This suggests that the LBE can potentially provide a more convenient and easy approach to solve the physical problems of neutron and radiation transport.

The Laplace transform (LT) is a widely used methodology for analytical solutions of dual phase lag (DPL) heat conduction problems with consistent DPL boundary conditions (BCs). However, the inversion of LT requires a series summation with large number of terms for reasonably converged solution, thereby, increasing computational cost. In this work, an alternative approach is proposed for this inversion which is valid only for time-periodic BCs. In this approach, an approximate convolution integral is used to get an analytical closed-form solution for sinusoidal BCs (which is obviously free of numerical inversion or series summation). The ease of implementation and simplicity of the proposed alternative LT approach is demonstrated through illustrative examples for different kind of sinusoidal BCs. It is noted that the solution has very small error only during the very short initial transient and is (almost) exact for longer time. Moreover, it is seen from the illustrative examples that for high frequency periodic BCs the Fourier and DPL model give quite different results; however, for low frequency BCs the results are almost identical. For nonsinusoidal periodic function as BCs, Fourier series expansion of the function in time can be obtained and then present approach can be used for each term of the series. An illustrative example with a triangular periodic wave as one of the BC is solved and the error with different number of terms in the expansion is shown. It is observed that quite accurate solutions can be obtained with a fewer number of terms.

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Summary Present work encompasses developing a new methodology to incorporate the heat transfer characteristics of the evacuated space (vacuum) in the annulus region between the absorber tube and glass cover and the effect of selective coatings on the steel absorber tube for a 3‐dimensional computational fluid dynamics model of a parabolic trough solar collector (PTSC) receiver. In the present work, glass cover has been modeled semitransparent to the incoming solar flux, which has been applied on the glass cover. Wavelength‐dependent absorption properties of glass cover material also has been modeled. In the current work, the direct normal irradiation and the mass flow rate of heat transfer fluid (HTF) has been varied to check their individual effect on the performance of PTSC absorber tube. Circumferential temperature distribution of absorber tube and glass cover has been found out; heat transfer to HTF and pressure drop of HTF in the absorber tube have also been calculated. A comparative study has been undertaken to highlight the relative contribution of the vacuum and selective coating on the receiver performance. The value of circumferential temperature difference at mid‐length of absorber tube was found to be 14.78 K for 750 W/m2, which increases to 19.70 K for direct normal irradiation of 1000 W/m2. When vacuum is replaced by air in the annulus region, PTSC absorber performance decreases by 4.82%. Similarly, because of use of selective coating, the thermal efficiency of the receiver increased by 34.59%.

Recently developed lattice Boltzmann equation (LBE) framework [1, 2] for radiation transport is extended to solve time-dependent non-equilibrium radiative and neutron tranport problems. Dynamics of radiation and material energy exchange is modeled by coupling radiation transport equation with the material energy equation in a one-dimensional isotropically scattering homogenous medium. The LBE solutions are compared against the existing semi-analytical P 1 benchmark and show good agreement for different times. Furthermore, a two-dimensional D 2 Q 8 lattice Boltzmann method is proposed for solving the neutron transport equation in a heterogenous media (e.g., checkerboard lattice with pure scattering and absorbing cells). The results obtained with LBE are in good agreement with the existing discrete ordinate method results for the benchmark problem.