强化传热在锅炉对流受热面中的应用_热能与动力工程.doc

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  • 更新时间:2016-06-09
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摘 要:热量传输一般通过导热、对流或辐射三种方式来实现。显然,强化传热技术的研究和发展也要从这三种传热过程的增强来进行,而其中涉及面最广和研究得最多的是对流传热的强化。本文主要针对强化传热讨论了以下问题。

肋片管能大幅度地扩展受热面积,减小锅炉对流受热面的布置空间和重量,目前已广泛用之于锅炉省煤器部分。实践证明,它对提高锅炉安全、经济性有重要意义。论文对螺旋肋片管省煤器进行了设计计算。省煤器由于烟气侧和水侧的换热系数相差悬殊(水侧的换热系数比烟气侧的换热系数大1-2个数量级),由此可见气--液传热效果主要取决于烟气侧的换热系数,为了减少所占空间,制造商往往采取提高烟速来提高烟气侧的对流换热系数,从而导致在运行中省煤器的磨损加剧,降低了机组的使用寿命。论文讨论了省煤器的磨损问题;锅炉过热器的工作条件和省煤器不同,因而限制了肋片管技术在过热器中的应用,论文针对中压锅炉和具有类似工作条件的余热锅炉,讨论了肋片管应用于过热器的使用条件以及应当注意的问题;当需要强化一个传热过程时,应当首先判断哪一种传热环节的热阻大,针对这一传热分热阻采取强化措施收效最显著. 论文在理论上讨论了传热学问题;锅炉空气预热器,普遍存在低温腐蚀和堵灰现象,其结果是漏风增加,引风机出力不足。热管空气预热器可以解决低温腐蚀问题。论文讨论了热管空气预热器比传统的列管式和回转式空气预热器相比其特点如何。

关键词:强化传热,锅炉,对流受热面,肋片

 

Abstract:Generally, the heat transfer are achieved by three ways of conduction, convection or radiation. Clearly, enhanced heat transfer technology, research and development have increased from three kinds of heat transfer process to proceed, which involves the most extensive and most studied is the convective heat transfer enhancement. This article discusses the enhanced heat transfer for the following questions.

   Heating surface can be significantly extended by finned tube, reducing the layout of space and weight of the boiler heat transfer surface, it now has been widely used on the boiler economizer section. Practice has proved that it is important in improving boiler safety and economy. Spiral Tube economizer has been designed and calculated in this paper; Because the heat transfer coefficients of traditional fluorescent tubes economizer between flue gas side and water side are significant differences (water side heat transfer coefficient is more 1-2 orders of magnitude than the gas side heat transfer coefficient), we can see that the effect of gas - liquid mass heating transfer depends on the heat transfer coefficient of flue gas side, in order to reduce the occupied space, manufacturers tend to increase the speed to improve the convective heat transfer coefficient of the flue gas side, resulting in the increased wear and tear of economizer operation and reducing the life of the unit. This Paper discusses the problem of wear economizer; the working conditions of super-heater and economizer are different, thus it was limited in application of the finned tubes in super-heater. For boiler of media pressure and waste heat boiler with similar working conditions, the paper discussed the terms of using finned tubes in super-heaters and what should pay attention; When it is need to strengthen a heat transfer process, which should first determine is the thermal resistance of heat transfer of which part is large and it is the most effective measure to for strengthen significantly in this resistance of the heat transfer. The paper discusses heat transfer problems in theory; the air pre-heater of boiler, generally has the phenomenon of low temperature corrosion and blocked ash, which resulting in increased air leakage and lack of fan output. Heat pipe air pre-heater can solve the problem of low temperature corrosion. The paper discusses the characteristics of the heat pipe air pre-heater tube compared to the conventional rotary air pre-heater.

Keywords: heat transfer enhancement, boiler, convection heating surface, fin

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