Study On The Flow And Heat Transfer Characteristics Of The Interrupted Micro-channel Heat Sink With Ribs

The concentrating photovoltaic system with its unique advantages had broad application prospects in the field of photovoltaic power generation,but it had higher requirements for the cooling system of CPV cells.The shortcoming of traditional microchannel heat sinks could not meet requirements for the heat dissipation,result from the working fluid had larger temperature gradient and pressure gradient along the flow direction.Therefore,it was of great significance to the design and explore new microchannels including interrupted microchannel heat sinks with ribs?IMCHS-R?and investigatived deeply the enhanced heat transfer mechanism and flow and heat transfer characteristics of interrupted microchannel heat sinks with ribs.In this thesis,a 3-D physical model of interrupted microchannel heat sinks with ribs using water as a working fluid in a silicon substrate was established.The mathematical model of interrupted microchannel heat sinks for the fully developed laminar flow was determined.The grid is performed.It was proved that the model was reliable through comparing the numerical results and experimental results.Heat transfer enhancement mechanism was revealed by comparing the flow and heat transfer characteristics of IMCHS-R and conventional microchannel heat sinks?MCHS?and interrupted microchannel heat sinks?IMCHS?.The effect of the flow parameters?Re?and the ribs structure parameters?the dimensionless width of ribs W₂/W₁,the dimensionless length of ribs L₂/L₁,the dimensionless position of ribs S/L₁?of IMCHS-R on flow and heat transfer characteristics were investigated.The results show that the regions of high Nu_local and f_local were distributed in the head of the ribs and the entrance of the second part of the microchannel.In both regions,the fluid violently hited the wall result in strong disturbance;for L₂/L₁=0.5,S/L₁=0.5,when Re is less than 300,the comprehensive heat transfer coefficient?PEC?of W₂/W₁=0.5 was the largest,while Re is greater than 300,PEC of W₂/W₁=0.3 was the largest;for W₂/W₁=0.5,S/L₁=0.5,when Re is less than 500,PEC of L₂/L₁=0.5 was the largest,and when Re is greater than 500,PEC of L₂/L₁=0.7 was the largest;for W₂/W₁=0.5 and L₂/L₁=0.5,the IMCHS-R of S/L₁=0.5 had the largest PEC.Based on the convective heat transfer entropy production model,the local and average heat transfer and viscous dissipation entropy generation characteristics were numerically investgated.The local entropy generation characteristics in the boundary layer proved accurate of the distribution of Nu_local and f_local in Chapter 3.Average heat transfer entropy generation sorted:IMCHS>MCHS>IMCHS-R,average viscous dissipation entropy generation sorted:IMCHS-R>MCHS>IMCHS,average Be_aveve sorted:IMCHS>MCHS>IMCHS-R.The average heat transfer entropy generation and average Be_ave decreased with the increase of Reynolds number,the dimensionless width of ribs,the dimensionless length of ribs,and the increase of the asymmetry of the ribs.The average viscous dissipation entropy generation increased with the increase of Reynolds number,the dimensionless width of ribs,the dimensionless length of ribs,and the increase of the asymmetry of the ribs.Accrrding to the above research,the shape of the ribs was optimized.The results showed that when the offset angle???was 45°,with the dimensionless head width of ribs??/W₂?increases,the flow transition becomed more violent after the fluid impinges on the ribs,the disturbance was more violent,the area of high Nu_local and high flocal increased,the average heat transfer performance increased,and the average resistance became larger.The optimal PEC value correspond to the dimensionless head width of ribs was?/W₂=2/3;When?/W₂=1/3,the offset angle?increases after the fluid hited the ribs,the flow transition was smoother,the disturbance was smaller,and the area of the high Nu_localocal and high f_local areas decreased.The thermal performance was weakened and the average resistance was reduced.The optimal PEC value corresponding to the offset angle was:when Re<800,it was?=45°,while Re>800,it was?=60°.