Heat transfer process on rice husk layer as an insulation material for long-term snow storage Part 2: heat balance on the surface and simulation of heat conduction inside the rice husk layer

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  • KAMIMURA Seiji
    Department of Mechanical Engineering, Nagaoka University of Technology
  • SAKASHITA Akiko
    Graduate school of Engineering, Nagaoka University of Technology,
  • HOSHINO Shingo
    Graduate school of Engineering, Nagaoka University of Technology,

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Other Title
  • 貯雪用断熱被覆材としての籾殼の伝熱過程　第2報：内部熱伝導および表面熱収支モデル構築の試み
  • 貯雪用断熱被覆材としての籾殻の伝熱過程(第2報)内部熱伝導および表面熱収支モデル構築の試み
  • チョセツヨウ ダンネツ ヒフクザイ ト シテノ モミガラ ノ デンネツ カテイ ダイ 2ホウ ナイブ ネツ デンドウ オヨビ ヒョウメン ネツ シュウシ モデル コウチク ノ ココロミ

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Abstract

The aim of this research is to investigate the advantages of rice husk as an insulation material for long-term snow storage. This paper describes the heat balance model of the rice husk surface and the heat conduction analysis of the rice husk layer based on the open-air snow pile storage experiment and measurements of the properties in the first report (Kamimura et al., 2007). Measurement of the net radiation shows the following results : approximately 25% of the maximum solar radiation of 800 Wm -2 on a sunny day is reflected directly from the surface into the air, and the same amount of energy is emitted as long-wave radiation into the air. The average surface albedo of rice husk is 0.75 and increases with time, ranging from 0.65 to 0.85 . The energy of of the net radiation is absorbed at the surface, released into the air by sensible and/or latent heat transfer, and the remaining 8-10% flows into the snow pile through the rice husk layer. The temperature profile of the rice husk layer was simulated by using one-dimensional, non-steady heat conduction analysis, and it was found to agree well with the temperature profile observed outside the experiment. Since the surface temperature estimated by the calculation of heat conduction is 15℃ below that recorded by a radiation meter, it is considered that another heat transfer phenomenon, which cannot account for the heat conduction model, occurs at the neighboring surface layer. Long-term simulations of the decrease in the height of the snow pile agree well with the observation results. Further, it is shown that the heat transferred by rain may not contribute toward the deformation of the snow pile but toward the creation of holes.

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