Research Of The Heat Transfer Characteristics Of Oxidation-bed With Embedded Heat Exchanger

China is a country whose main energy is coal,in order to ventilate for coal mine,a large quantity of methane is exhausted into the atmosphere together with VAM and results into environment pollution and energy waste,therefore,treatment and utilization of coal mine VAM becomes one of the most important Twelfth Five-Year Plan topics in China.Currently the technology that realizes methane zero emission in VAM is relatively mature.Therefore the industrial ceramic honeycomb which having good storage,heat radiation performance and the smaller the flow resistance can be used as the core components of the regenerative burner,as the means for thermal oxidation unit countercurrent process VAM.Methane may be oxidized into thin water and carbon dioxide.The heat released during the oxidation removal means to maintain their operation and the excess heat externally output through a heat exchanger.The heat exchanger placed inside the regenerative burner,then it constitutes a heat exchanger combustion which has compact structure and large power adjustment rang.Domestic and foreign scholars have done a lot of research on it,But they mainly focus on the point of combustion and start around its operating characteristics.Most of them study burner internal temperature distribution or emission of pollutants,which considers the effect of heat on combustion.At present,research on heat transfer mechanism is lacked.When the heat exchanger embedded in honeycomb ceramics,the momentum transfer of flow in the vertical direction is limited and the development of the boundary layer is also limited when the flue gas flow around the wall,limited the development of the boundary layer,thereby it results in the traditional convective heat transfer calculation formula which is flowing around cylinder is not suitable for combustion heat exchanger.In this paper,it gets the model which is flowing around the cylinder by simplifying and abstracting the serpentine tube heat exchangers that on the test of Coal Mine Ventilation Air Methane oxidation unit.Taking the limitations of the ceramic honeycomb structure into account,it gets the cellular ceramic model after improving.Based on the experimental verification of the mathematical model effective,study the influence of heat exchanger embedded in honeycomb ceramics honeycomb ceramic on the flow and convective heat transfer characteristics,when Re was 692、1646、2594、3540.Details are as follows:1)A pair of small vortexes would be formed at the back of the heat exchanger which is embedded in honeycomb ceramics,and the separation point move forward than that in free space because of the limitation of the honeycomb ceramics.There is no Karman vortex street behind heat exchanger embedded in honeycomb ceramics within the research scope.And the stress on the heat exchanger is stable.It means that the existence of honeycomb ceramics can effectively avoid the phenomenon of flow induced vibration.Compared with flow around cylinder in free space,flow speed near the wall of the heat exchanger embedded in honeycomb ceramics is higher under the condition of the same inlet velocity,and the greater the inlet velocity is,the greater the difference is.2)The results show that when the size of the ceramic honeycomb placed is 80mm ×80mm,the boundary layer thickening process is hindered due to the existence of honeycomb ceramic,furthermore the flow of fluid micelles on heat exchanger surface becomes no chapter and disturbances intensely,so it strengthens the convection heat transfer process.And Deal with the simulated data,it gets the simple mathematical expressions of flowing around the heat exchanger embedded in honeycomb ceramics.3)When the pace size of Honeycomb ceramic formed is different,found that the greater the size on the vertical to the flow direction is,the thicker the boundary layer is,the greater the overall size is,the more complete the vortex is,which on the back surface of heat exchanger;When the space size is 60mm×60mm、70mm×70mm、80mm×80mm,the Nu decreases with space size increasing;When the space size is 50mm×60mm、50mm×80mm,the greater the space size is,the greater the heat transfer ability is.The other,if the speed is invariable,the position of separation point will not change.