Research On Heat Transfer Characteristics Of Millimeter-scale Fine Channel Pulsed Asynchronous Buffer Regenerator

According to the topic of “micro-energy system” in the National 973 Program,the research group carried out research on multi-field multi-scale coupling mechanism of key components of micro-energy power system,and proposed a multi-cavity micro-swing engine with heat recovery.Effectively improve the efficiency of the micro power system.There are two characteristics in the micro regenerator: the heat exchange channel is a millimeter-scale small channel,and the flow guiding effect is serious;due to the working characteristics of the micro pendulum engine,the flow of hot and cold gas in the regenerator is small and the flow is Intermittent pulse flow.In this paper,the flow-guided thermal phenomena and the intermittent flow and heat transfer of hot and cold gas existing in the millimeterscale fine channels existing in the micro regenerator are analyzed.The main work and conclusions are as follows:Aiming at the flow conduction thermal effect existing in the millimeter-scale fine channel,the influence of the size factor and the thermal conductivity of the heat transfer material on the effectiveness of the casing regenerator is investigated.The influence of the flow guide heat on the heat transfer is measured by the M number.The results show that if the heat exchange wall material is a high thermal conductivity material,the thinner the solid wall,the weaker the heat transfer effect;if the heat exchange wall material is a low thermal conductivity material,the M number is below 0.05,and the flow guiding thermal effect can be ignored.When the hot and cold gas flows intermittently,it is necessary to comprehensively consider the heat effect of the flow guiding,the heat storage of the heat exchange wall and the heat conduction capacity of the solid wall surface,and select the heat transfer wall material with the best efficiency and the wall thickness.Finally,the data is fitted according to the numerical analysis results to obtain the heat transfer law in the millimeter-scale fine channel.According to the working characteristics of the miniature pendulum engine,the influence of the intermittent pulse flow of the millimeter-scale small channel under the laminar flow condition,the intake frequency f and the Reynolds number Re change on the heat transfer effect are investigated.In the millimeter-scale small channel cold-hot gas intermittent pulse flow,the same Reynolds number Re increases with the intake frequency f,and the heat exchange efficiency increases.This is because the small-channel small-channel cold-hot gas intermittent heat exchange,the channel The volume remains unchanged.With the increase of the intake frequency f,the hot and cold gas can exist in the channel at the same time,establishing effective heat exchange.With the infinite increase of the intake frequency,the flow can be made under unsteady conditions.The gas is close to the steady working conditions and has a favorable effect on the heat transfer.In order to solve the intermittent flow of cold and hot fluid in the regenerator,a buffered regenerative structure is adopted to increase the residence time of the gas in the regenerator,and to solve the problem that the heat exchange time in the channel is short and the heat exchange efficiency is short.The low problem is to change the residence time of the gas in the channel by changing the pipe length and the pipe diameter of the channel,taking into account the heat transfer effect of the channel and the flow loss.The optimized micro-tube type regenerator has better flow characteristics under constant working conditions,the total pressure recovery coefficient of hot and cold air flow is higher,the total pressure loss is less than 8%,and also has good heat transfer characteristics.The heat exchange efficiency is 83%;when the hot and cold gas flows intermittently,it also has good heat transfer characteristics,the heat exchange efficiency is 81%,and the decrease rate is 2.5% compared with the fixed condition micro regenerator.The results of the analysis and design of the single casing regenerator are similar.