基于煤矿乏风热氧化的填充床内置换热器取热特性

Heat extraction characteristic of packed bed embedded heat exchanger based on thermal oxidation of coal mine VAM

基于煤矿乏风热氧化取热过程,搭建了填充床内置换热器稳态取热实验台,取热率最大相对误差为2.50%,实验研究了床层内取热区两侧及取热区内填充蜂窝陶瓷对换热器取热的影响,结果表明:取热区两侧空间填充的蜂窝陶瓷通过增大床层气体物理流速、辐射换热面积、扰动换热器背风侧流场而强化换热器取热,当气体质量流速0.15 kg/(s·m2),温度从613 K升高到1 113 K时,取热区两侧蜂窝陶瓷的存在使换热器取热率比空床增大了2.20%~14.84%,而当气体质量流速增至0.30 kg/(s·m2),温度同样从613 K升高到1 113 K时,取热区两侧蜂窝陶瓷则使换热器的取热率比空床增大了4.92%~10.61%;取热区内填充的蜂窝陶瓷对换热器取热率影响的矛盾两面性决定了取热区内填充的蜂窝陶瓷不会对换热器取热率产生较大影响,也并不总是强化换热器取热,甚至会削弱换热器取热,当气体质量流速为0.15 kg/(s·m2)、温度从613 K升高到1 113 K时,取热区内蜂窝陶瓷的存在使得换热器取热率比空床变化了-1.92%^+4.47%;采用换热器外壁镀银的方法,研究了填充床内置换热器取热过程中传热方式的贡献,结果表明气体质量流速0.15 kg/(s·m2),温度为1 113 K时,换热器取热率中已经有55%的贡献来自辐射,随着温度进一步升高,辐射成为填充床内置换热器取热的主要方式。

Based on the heat extraction process of coal mine VAM thermal oxidation,the steady state heat extraction experimental platform was built. Using the experimental platform,the role of packed honeycomb ceramic in bed on heat extraction of heat exchanger was studied. The maximum relative error of heat extraction rate of heat exchanger was2. 50%. The experimental results show the packed honeycomb in both sides of heat extraction zone increases the gas physical velocity in the bed and the radiation heat transfer area of heat exchanger and disturbs the leeward flow field of heat exchanger,so that can always strengthen heat extraction of heat exchanger. For example,when gas mass velocity is0. 15 kg /( s·m2) and its temperature is raised to 1 113 K from 613 K,the packed honeycomb ceramic in the space of heat extraction zone two sides makes the heat extraction rate of heat exchanger increased by 2. 20% to 14. 84%than empty bed,and when gas mass velocity is increased to 0. 30 kg /( s·m2),gas temperature is also increased to1 113 K from 613 K,the packed honeycomb ceramic in the same space makes the heat extraction rate of heat exchanger increased by 4. 92% ~ 10. 61% than empty bed; The role of packed honeycomb ceramic in heat extraction zone onheat extraction of heat exchanger shows contradictory two sides,which determines the honeycomb ceramic will not have an obvious effect on the heat extraction rate and may strengthen and may also weaken heat extraction of heat exchanger. For example,when gas mass velocity is 0. 15 kg /( s·m2) and its temperature is 613 K,the packed honeycomb ceramic in heat extraction zone makes the heat extraction rate of heat exchanger decreased by 1. 92% than empty bed,when gas temperature is 1 113 K,the packed honeycomb ceramic in heat extraction zone makes the heat extraction rate of heat exchanger increased by 4. 47% than empty bed; Using the method of plating silver on the outer surface of heat exchanger,the roles of heat transfer modes are studied in the heat extraction process of heat exchanger,the experimental results show the 55% contribution of heat extraction rate of heat exchanger is from radiation when gas mass velocity is 0. 15 kg /( s·m2) and gas temperature is 1 113 K,with the further increase of gas temperature,radiation will become the main mode of heat exchanger heat extraction.