查詢結果分析
來源資料
頁籤選單縮合
題 名 | Flow Instability of Open Loop Solar Thermosyphon Water Heaters=開路式自然循環太陽能熱水系統穩定性分析 |
---|---|
作 者 | 杜旭純; | 書刊名 | 龍華學報 |
卷 期 | 8 1991.06[民80.06] |
頁 次 | 頁115-136 |
分類號 | 446.56 |
關鍵詞 | 太陽能; 自然循環; 開路式; 熱水系統; 穩定性分析; |
語 文 | 英文(English) |
中文摘要 | 過去懷疑,在自然循環式太陽能熱水系統常見的逆流現象是由於系統的不穩定所產生。本文以理論推導的方式來討論此問題。藉著一維模式的推導,及線性微擾分析,本文推得太陽能熱水系統的動態模式透過系統轉移函數,將輸入輻射微擾與輸出流量擾動運上關係。接著以Nyquist穩定性分析方法來討論系統特徵方程式的穩定性。系統的穩定性可由穩定性參數M來表示,而此參數是其它13個無因次設計,操作參數的函數。結果發現,在實際運作的系統,都在穩定操作範圍,並不會發生不穩定的現象。主要是因為,實際的箹統阻力都較高,而自然界的太陽輻射強度並不足以引起系統產生不穩定現象。另外一個原因,乃是由於儲水槽內大量的水,形成一很大的阻尼器,所有擾動在此很容易被衰減,而使系統不容易產生不穩定現象。因此,太陽能熱水系統所發生的逆流現象,並不是由於箹統不穩定所引起,而是由其它因素所造成,例如飽和現象所引起。 |
英文摘要 | Reverse flow has been observed very often in thd solar thermosyphon water heaters and is suspected to be due to flow instability. A theoretical analysis is thus carried out in the present study. The analyses use a 1-D approach and linear perturbation method to derive a system dynamic model. A transfer function, which treats solar irradiation as the system input and flow rate as the system output, is derived to describe the dynamic behavior of solar thermosyphon water heaters. A characteristic equation is then derived from this dynamic model and the Nyquist criterion is used to examine the flow instability. It is found that there are 14 dimensionless parameters governing the flow instability and that the stability maps can be expressed and constructed by using the critical values of stability parameter M. The variations of flow instability with the system parameters are then studied. It is found that flow instability is almost impossible to occur in most of open loop solar thermosphon water heaters. This is due to the facts that the water mass in the tank is large enough to damp all the perturbations, the loop friction in the practical design of solar water heaters is high and the solar irradiation in field operation is limited and not intense enough to cause flow instability. |
本系統中英文摘要資訊取自各篇刊載內容。