Reduction of heat loss from solar thermal collector by diminishing natural convection with high-porosity porous medium

Shigeki Hirasawa, Ryohei Tsubota, Tsuyoshi Kawanami, Katsuaki Shirai

研究成果: Article査読

30 被引用数 (Scopus)

抄録

We studied the reduction of natural convection heat loss from a solar thermal collector by placing a high-porosity porous medium above the collector plate in a solar thermal collector system. It is known that natural convection can be diminished in a porous medium. In order to use a porous medium in a solar thermal collector, it is necessary to minimize the shading effect of solar radiation caused by the porous medium. In this work, we used a series of offset wire screens made of fine nylon fishing lines of 0.05. mm in diameter with 2-mm pitch and a porosity of 0.999. The experimental apparatus consisted of a copper 300. mm. ×. 300. mm collector plate with a selective absorption film on the surface. We measured the reduction rate of the convection heat loss from the collector plate and the shading effect for actual sun radiation by changing the condition of the porous medium, the temperature of the collector plate, and the inclined angle of the collector plate. Experimental results of the Nusselt number of natural convection in the high-porosity porous medium agreed with the equation proposed by Gupta et al. The effect of the inclined angle on the Nusselt number was small. The net reduction rate of natural convection heat loss was 7% by placing the high-porosity porous medium above the collector plate when the temperature of the collector plate was 100. °C.

本文言語English
ページ(範囲)305-313
ページ数9
ジャーナルSolar Energy
97
DOI
出版ステータスPublished - 2013 11
外部発表はい

ASJC Scopus subject areas

  • 再生可能エネルギー、持続可能性、環境
  • 材料科学(全般)

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