1992-08-03

FFT Analysis of Sensible-Heat Solar-Dynamic Receivers 929451

Solar Dynamic receiver designs are investigated and evaluated for possible use with sensible energy storage in single-phase materials. The designs are similar to previous receivers having an axial distribution of concentrated solar input flux, and an axial flow of the working fluid. The objective is to study the feasibility of single-phase designs which have comparable weight and thermal performance to existing two-phase designs.
Linearized heat transfer equations are formulated for the storage of sensible heat in the receivers. The periodic input solar flux is represented as the sum of steady and oscillating distributions, which results in steady and oscillating components in the one-dimensional, time-dependent thermal model.
The steady component is solved analytically to produce the desired receiver steady outlet gas temperature. For the oscillating components the Fast Fourier Transform algorithm (FFT) is applied, and the resulting one-dimensional equations solved analytically in the transform space. The complex transfer function of the receiver is obtained and evaluated as a filter for the input spectrum. Convolution of the source and the transfer function, and inverse transformation, results in the amplitudes and mode shapes of the oscillating solid and gas temperatures. By adjustment of design parameters, the amplitude of the oscillating component of the outlet gas temperature is limited to an acceptable magnitude.
The overall result of the investigation is that sensible-heat receiver designs exist with comparable performance to present state-of-the-art two-phase receivers. As these designs also offer improvements in cost reduction and reliability they warrant further detailed investigation.

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