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Author Miller, Fletcher John
Title Radiative heat transfer in a flowing gas-particle mixture
Descript 200 p
Note Source: Dissertation Abstracts International, Volume: 50-04, Section: B, page: 1614
Chairman: Ralph Greif
Thesis (Ph.D.)--University of California, Berkeley, 1988
A gaseous suspension of small particles is considered as a medium to directly absorb concentrated sunlight to yield a high temperature gas for electricity production or industrial processes. A receiver employing a directly irradiated gas-particle mixture has several advantages over conventional blackened tube solar receivers. The primary benefit is the much improved heat transfer between the incident radiation and the gas. The more effective heat transfer results in lower receiver wall temperatures, and permits higher incident fluxes allowing smaller, more efficient receivers. To determine the temperatures and efficiencies attainable with such a receiver it is necessary to solve the equation of radiative transfer together with the energy equation. This work examines the optical characteristics of a carbon particle mixture, and the ensuing temperature profiles when the flowing mixture is radiantly heated
Single particle absorption and scattering efficiencies and phase functions are calculated from Mie theory for different particle sizes and carbon indices of refraction. These properties are utilized to determine the absorption and scattering coefficients and phase function of a mixture composed of many particle sizes. Experimental measurements of the extinction coefficient at 0.633$\mu$m and the phase function at 0.442$\mu$m of a carbon particle aerosol, along with a determination of the particle size distribution from scanning electron microscopy and the mass loading from filtration, allowed comparison with the Mie calculations. The experiments showed somewhat less scattering and more absorption than was calculated. The calculations also revealed that small particles can act as strong selective absorbers, and that an optimum particle size minimizes the mass of the particles required. Agglomeration of particles was shown to be a limiting factor in achieving high absorption coefficients with small particles, and criteria for minimizing the mixture emission were established
A four-flux radiative transfer model was developed and solved simultaneously with the energy equation. Temperature profiles were calculated for a gas-particle mixture flowing in a pipe irradiated by light through a window at one end. Cocurrent and countercurrent flow directions were investigated for various particle loadings. An experimental system was built and the temperature profiles were measured in this cylindrical system. Comparisons between theoretical and experimental results are presented, and several experimental problems are identified
School code: 0028
DDC
Host Item Dissertation Abstracts International 50-04B
Subject Engineering, Mechanical
0548
Alt Author University of California, Berkeley
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