同向流式螺旋管加熱爐的性能分析

The Analysis of Performance for a Parallel Flow Type Combustion Furnace with Helically Coiled Tube

姜庭隆(Ting-Lung Chiang) ； 黃惟泰(Wei-Tai Huang) ； 羅詩傑(Shih-Chieh Lo)

《燃燒季刊》 80期 (2013/02) Pp. 64-76

https://doi.org/10.30041/CQ.201302_(80).0006

摘要

內部以螺旋式環管（helically coiled tube）做為液體預先加熱（或冷卻）的同向流式（parallel flow）加熱爐在化工與石油相關產業中是被廣泛運用的。因為此種熱交換爐可以使用煉製某種原料過程中所產生的多種可燃性氣體做為加熱目的使用，不須再付出額外的成本去購買燃料。此種將原須排除的副產品再回收、利用之做法除了有利環保，亦可增加經濟效益。然而此類加熱爐之傳統設計往往面臨的類似問題是：供應給環管之燃燒熱使用的效率不高，以致燃燒完後排出至大氣中之廢氣溫度過高，造成熱汙染。然而若要在此種高溫環境下，以實驗方式進行研究有其實際的困難度，且難以完整的了解加熱爐內發生的所有現象，因此本文之目的在於利用藉著電腦輔助設計中的計算流體力學方法（Computational Fluid Dynamics）去分析加熱爐內的熱流現象，找出問題所在，然後才有可能於未來提出改善的方法。為簡化分析，以二維軸對稱模型做為分析的模型。本研究使用Gambit 軟體建構模型與網格，泛用型計算流體力學軟體Fluent 模擬解析加熱爐內之火焰燃燒特性，以及熱與流場的詳細資料，包含輻射與對流兩種效應。分析的結果顯示藉著計算流體力學方法可以將爐體內部高溫燃氣的流動特性顯現出，達成所預期的目標。 未來則有可能以此方法，將爐體幾何形狀依照火焰傳遞與高溫燃氣的流動特性加以適當的改善，就能達成增加給熱效率，同時降低排出廢氣溫度的目標。

關鍵字

螺旋式環管 ； 加熱爐 ； 火焰與高溫燃氣 ； 計算流體力學方法

並列摘要

Parallel flow type heat exchanger/furnace with helically coiled tube is frequently used in the traditional chemical engineering industries. In most of the times, it is used to pre-heat some fluid flowing in the coiled tube. Usually, the fuel burned in the furnace will be a by-product of a certain chemical operation. Therefore, the fuel is free and good for environmental reasons, and that is why this kind of furnace is so popular used today. However, a common problem of this furnace is its low efficiency and the exhaust gas temperature is too high, which creates the thermal pollution. Since it is difficult to solve the problem with experimental methods, it is quite nature to switch to the help of numerical methods. Computational fluid dynamics (CFD) methods is used in this research project, to demonstrate the flame propagation and combustion process inside the furnace. Both the flow field and thermal field can be revealed, and heat transferred to the fluid in the coiled tube can be calculated. A decoupled scheme is used to calculate the temperature increment in each section of the coiled tube. Commercial software Gambit is used to build the model and the following mesh system, and the thermal/ flow solution is acquired by apply the software Fluent. To simply the problem, a 2D/axisymmetric furnace model is adopted in the analysis.

並列關鍵字

Computational fluid dynamics ； helically coiled tube ； flame propagation