Introduction The receiver of space-based solar-thermal power systems (solar dynamics) is a critical component which must absorb incoming concentrated solar energy, store part of it for release during eclipse, and deliver a near constant thermal power for both the solar insolation and eclipse parts of low earth orbit. These requirements have led to latent energy storage using phase-change materials (PCM's) which involve comparatively massive containment canisters [1,2,3], Advanced PCM concepts strive to reduce the canister weights [2,4], whereas investigations of advanced sensible-heat concepts have suggested heat pipes and control logic [5], carbon-fiber/carbon composites [6] and use of Fast Fourier Transforms [7] with axial-flow designs. In this investigation a sensible-heat receiver concept is introduced in which the effect of the orbital periodic input solar flux is attenuated by thermal conduction along the length of the absorber, with heat removal at the base of the absorber, as shown in figure 1. Since the largest heat flux occurs near the "top" of the absorber this attenuation results in reduced amplitude of the fluid outlet temperature at the base. The principle whereby increased energy is stored through attenuation (or amplitude interference) is illustrated in Appendix A where a lumped one-mass system is compared to a lumped two-mass system with internal resistance; it is shown that for the same boundary conditions, internal resistance exists which reduces the required mass for the same energy storage. For the analysis of the Figure 1 concept the input flux is separated into average (steady) and variable (oscillating) components, as previously [7], so that constraints on these components may be applied separately. This includes the average power input and fluid temperature rise, the receiver steady efficiency for the average component, and the amplitude of the fluid outlet oscillating temperature for the variable component. The model assumptions include one-dimensional conduction in the absorber cylinder and radiative losses from its surfaces. Solid/fluid heat transfer at the base is modeled through a heat exchange effectiveness. The steady component is solved numerically, subject to specified receiver efficiency and boundary conditions; the variable component is linearized and solved analytically in the transform space, and inverted using the Fast Fourier Transform (FFT) algorithm [8], For direct comparisons, the thermal conditions of the Space Station Freedom phase-change design [9], are considered as a benchmark reference. The results of the present analysis are applied to several materials, which indicates improved performance (reduced mass) compared to the benchmark phase-change results and the axial-flow sensible-heat results [7],
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