Numerical Simulation Of Flow-thermal Coupling Of Microchannel Heat Sink With Complex Internal Structure

Cooling of microelectronic components with high power density is a frontier theme in scientific and technological development,and cooling of high heat flux microprocessors has become a key limitation in the future development of high performance integrated circuits.Micro-channels can be used to provide effective heat dissipation,and microchannel heat sinks have great potential for cooling high performance devices including supercomputers.Based on the finite volume method(FVM),the effect of the internal structure of the microchannel on the pressure drop and heat transfer performance under the little Reynolds number is investigated by numerical simulation,with structural optimization and analytical evaluation of the integrated pressure drop and heat transfer efficiency.The research results can provide some reference for the heat dissipation of high heat microelectronic components.With reference to the existing studies,three different microchannel internal structures are firstly proposed and compared with the common rectangular micro-channels under the same conditions.The results show that the internal structure of three microchannels increases the pressure drop,but the thermal performance is enhanced.Under the same inlet Reynolds number,ordinary rectangular micro-channels have the smallest pressure drop due to the smooth inner wall surface.Micro-channels with diamond-shaped structure have a certain effect on pressure drop due to the periodic contraction and expansion of fluid inside,but the fluid flow rate rises.The micro-channels with triangular structure as well as trapezoidal structure have larger heat sink pressure drop and greater heat transfer performance improvement.The microchannel with trapezoidal structure at Re=648 increases the pressure drop by about 13%-22%,the bottom surface temperature decreases by 4-9°C and 5-10°C,the thermal resistance decreases by about 8.8%-14.4%,and the Nu number increases by about 8.4%-12.6%compared with the ordinary rectangular microchannel.When the pumping power is low,the overall thermal resistance is high and the pumping power required to reach the same thermal resistance is close,however,the overall thermal resistance can reach lower values when the pumping power is high,but the pumping power required to reach the same thermal resistance differs greatly.The optimal structure was analyzed by the thermal transfer enhancement coefficient(PEC).In the low Reynolds number region(Re<648),the micro-channels with triangular structure had the largest PEC and the strongest heat transfer performance,in the higher Reynolds number region(Re>648),the micro-channels with trapezoidal structure had the largest PEC and the largest increase in overall thermal performance,and the micro-channels with diamond structure had the smallest increase in heat transfer performance in the whole study range(216<Re<1080)have the smallest increase on the heat transfer performance.When choosing the internal structure of the microchannel,it is necessary to analyze the inlet Reynolds number according to the actual application and then make a choice.For the above three microchannel internal structures,we optimize the design and analyze the effect of different radial distances(S_x)on the heat transfer performance.The results show that:WhenS_x=0 mm,the pressure drop in the microchannel is the lowest,the internal structure has a weak effect on the pressure distribution in the microchannel,and the bottom temperature distribution is similar to that of the rectangular microchannel.As the radial distance increases,the internal structure invades the main channel of the microchannel and cuts the fluid,and the pressure drop increases,the pressure drop of the three structures at S_x=0.3 mm increases by more than 34%compared with that at S_x=0 mm.The temperature at the bottom of the microchannel heat sink decreases with increasing radial distance,the trapezoidal structure microchannel temperature reduction is the largest,the average temperature in the middle can be reduced by 12.85%-30.33%of the temperature rise of the heat sink under the same conditions,the diamond structure microchannel is the second,the average temperature change rate at the bottom is more uniform,but the initial increase is not obvious,the average temperature reduction in the middle region is about 4.89%-29.71%,the triangle structured micro-channels performed the worst,with a temperature reduction of about 11.46%-27.78%.Comprehensive hydraulic and thermal performance,the thermal transfer enhancement coefficient(PEC)was used to assess the enhancement of heat transfer performance.In a certain radial distance range,increasing the radial distance has a greater enhancement of the overall heat transfer performance,and the trapezoidal structure micro-channels have the largest PEC in a certain Reynolds number range.The triangular structure microchannel obtains the maximum heat transfer enhancement atS_x=0.2 mm,and whenS_x>0.2 mm,increasing the radial distance can reduce the overall thermal resistance,but cannot increase the thermal transfer enhancement coefficient.As for trapezoidal structure micro-channels,the maximum enhanced heat transfer coefficient is obtained at S_x=0.25 mm.The diamond structure microchannel is more special.When S_x≤0.15 mm,the increase in the radial distance cannot enhance or even weaken the overall heat transfer performance.When S_x>0.15 mm,the heat transfer performance can be significantly enhanced,and as the radial distance increases,the increase is more obvious,then reached the maximum value at S_x=0.3 mm.Comparing the PEC curves of the three structures with the maximum heat transfer enhancement,the trapezoidal structure microchannel has the largest PEC in the low Reynolds number region(216<Re<486),and the diamond structure microchannel has the largest increase in heat transfer performance in the higher Reynolds number region(486<Re<1080).In conclusion,the current study investigates the effect of microchannel internal structure on the hydraulic and thermal characteristics through numerical simulation,proposes three different microchannel internal structures,optimizes each of the three structures,and compares the three structures using the thermal transfer enhancement coefficient(PEC)to arrive at a more suitable design.