Ledinegg Instability Study And Safety Analysis Of Microchannels With Different Corrugated Walls

The morphology of the microchannel heat exchange wall has a significant effect on the heat transfer enhancement and Ledinegg instability.Ledinegg instability is one of the common causes of microchannel heat exchangers.Therefore,the influence of the heat transfer wall of different corrugated structures on the instability of Ledinegg on the fine channel and the safety of Ledinegg instability in the application of microchannels are studied.The research content mainly includes the following points:(1)Ledinegg instability study of microchannels with different corrugated walls.The effects of heat flux,system pressure and inlet subcooling on the pressure drop-flow characteristic curves of different corrugated wall microchannels are analyzed.Based on the characteristic equations of parallel multi-channels,the stability of Ledinegg in parallel multi-channels is studied.The criteria were applied to the experimental analysis.The results show that the increase of heat flux density or the decrease of system pressure makes the negative slope of the characteristic curve of each microchannel steeper,which increases the probability of Ledinegg instability.The negative slope of the characteristic curve of inlet subcooling for each microchannel The area has less impact.The negative slope region of the fine channel of the corrugated wall is steeper than that of the ordinary smooth microchannel,so the fine channel of the corrugated wall is more prone to Ledinegg instability than the ordinary smooth microchannel.Increasing the heat flux density or reducing the inlet subcooling degree causes the OFI(Onset of Flow Instability)point to move toward the direction of increasing mass flux,which increases the occurrence of microchannel flow from supercooled boiling to saturated boiling drift.Probability;system pressure has less effect on the OFI point.(2)Study on heat transfer characteristics of microchannels with different corrugated walls.The heat transfer characteristics,boiling heat transfer curve,saturation boiling heat transfer coefficient and pressure drop of different corrugated wall microchannels were analyzed.The modified Qu-Mudawar model was used to predict the two-phase frictional pressure drop of each microchannel.The results show that the corrugated wall has good heat transfer enhancement performance.At low heat flux density,the heat transfer efficiency of the triangular corrugated wall is enhanced by 39.6% compared with the ordinary smooth microchannel;the heat transfer efficiency ratio of the sinusoidal corrugated microchannel Ordinary smooth microchannels are enhanced by 36.8%.The composition of the total pressure drop of the fine channels of different corrugated walls is similar,and the frictional pressure drop accounts for the highest proportion,which is 63.7%~74.6%.Under the same working conditions,the total pressure drop of the microchannel of the corrugated structure wall is larger than that of the ordinary smooth microchannel,and the total pressure drop of the microchannel of the triangular corrugated wall is about 1.3 times larger than that of the ordinary smooth microchannel;the total pressure drop of the sinusoidal corrugated microchannel It is about 1.27 times larger than the ordinary smooth microchannel.(3)Analysis of the hazards caused by Ledinegg instability in practical applications.Parallel analysis of parallel using FMECA(Failure Mode,Effects and Criticality Analysis)method and improved FMECA method based on fuzzy VIKOR(Vlse Kriterijumska Optimizacija I Kompromisno Resenje)Common failure modes of flow evaporators and their harmful effects.It was found that Ledinegg instability is the main cause of failure modes in parallel flow evaporators,and proactive and passive measures to suppress Ledinegg instability are given.