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Research Papers

# Heat Transfer Analysis of a Novel Pressurized Air Receiver for Concentrated Solar Power via Combined Cycles

[+] Author and Article Information
I. Hischier, D. Hess

Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland

W. Lipiński

Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455

M. Modest

School of Engineering, University of California, Merced, CA 95343

A. Steinfeld1

Department of Mechanical and Process Engineering, ETH Zurich, Zurich 8092, Switzerland; Solar Technology Laboratory, Paul Scherrer Institute, Villigen 5232, Switzerlandaldo.steinfeld@ethz.ch

The solar flux concentration ratio $C$ is defined as the ratio of the solar flux intensity achieved after optical concentration to the incident beam normal insolation. It is a dimensionless number, usually reported in units of “suns.”

1

Corresponding author.

J. Thermal Sci. Eng. Appl 1(4), 041002 (May 19, 2010) (6 pages) doi:10.1115/1.4001259 History: Received May 15, 2009; Revised November 19, 2009; Published May 19, 2010; Online May 19, 2010

## Abstract

A novel design of a high-temperature pressurized solar air receiver for power generation via combined Brayton–Rankine cycles is proposed. It consists of an annular reticulate porous ceramic (RPC) bounded by two concentric cylinders. The inner cylinder, which serves as the solar absorber, has a cavity-type configuration and a small aperture for the access of concentrated solar radiation. Absorbed heat is transferred by conduction, radiation, and convection to the pressurized air flowing across the RPC. A 2D steady-state energy conservation equation coupling the three modes of heat transfer is formulated and solved by the finite volume technique and by applying the Rosseland diffusion, $P1$, and Monte Carlo radiation methods. Key results include the temperature distribution and thermal efficiency as a function of the geometrical and operational parameters. For a solar concentration ratio of 3000 suns, the outlet air temperature reaches $1000°C$ at 10 bars, yielding a thermal efficiency of 78%.

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## Figures

Figure 1

Solar receiver concept featuring an annular RPC foam bounded by two concentric cylinders. Concentrated solar radiation absorbed by the inner cylindrical cavity is transferred by conduction, radiation, and convection to the pressurized air flowing across the RPC.

Figure 2

Heat fluxes at the boundaries of the computational domain. The axis of symmetry is indicated at r=0.

Figure 3

Reference case temperature distribution in °C as a function of the radial and axial positions for an air outlet temperature of 1000°C obtained by applying P1 approximation. Gray lines indicate the boundaries between the CAV, RPC, and INS cylindrical components.

Figure 4

Radiative source term within the RPC in the radial direction at z=0.008 m obtained by P1, MC, and Rosseland approximations

Figure 5

Efficiencies as a function of the solar power input for the reference case with constant Tf,outlet=1000°C

Figure 7

Deviation from the reference case efficiency as a function of the relative change in the dominating material properties

Figure 6

Thermal efficiency as a function of the air outlet temperature in °C for constant power inputs in kW (solid lines) and constant mass flow rates in g/s−1 (dotted lines). The reference case is indicated by the star.

Figure 8

Deviation from the reference case efficiency as a function of the relative change in the geometrical dimensions

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