Research On Cooling Power Of L-type Heat Exchanger Based On Multi-inlet And Multi-outlet Effect

Due to the rapid development of information technology,the development trend of modern electronic devices in recent years has gradually moved toward the direction of intelligence,integration and miniaturization,resulting in greater energy consumption and heat flux density of electronic chips.Therefore,the heat dissipation in various applications,such as electronic chips,has increasingly stimulated people's interest in electronic thermal management.Among them,ensuring the temperature uniformity of the electronic chip is the most important task to ensure its efficient and normal operation,and is also the key to the heat dissipation design.At present,many cooling channels can effectively reduce the temperature of electronic equipment,and the temperature uniformity has been improved.However,the traditional structural design can no longer meet the high heat flow requirements of chips.On this basis,combining with the basic theory of thermal design,the structure is innovating and optimized.An L-type heat exchanger based on multi-inlet and multi-outlet effect is put forward.The relevant flow and heat transfer characteristics are studied and analyzed from two aspects of steady state and transient state.At the same time,the experimental analysis and verification are carried out.The specific work results are as follows:First,numerical simulation of flow and heat transfer characteristics of L type heat exchangers with different inlet and outlet conditions under laminar flow condition(Re=200~1600)is carried out through ANSYS Fluent 15 simulation software.The velocity,the average Nusselt number,the pressure drop,the temperature uniformity and total thermal resistance are analyzed concretely.The results show that type 1(the long axis enters and the short axis gets out),type 2(the short axis enters and the long axis gets out)and type 3(the long axis and the short axis enters and gets out alternately)start from the short axis flow path to the end of the long axis flow path,and the speed on the centerline generally shows a trend of decreasing first and then increasing.High temperature hot spots are distributed in the four corners of the heat exchanger,but the temperature gradient on the bottom plate is relatively small,and the substrate temperature uniformity of type 3 is the best.The average Nusselt number of type 2 is the largest,and the heat transfer effect is the best,while the pressure drop is not significantly affected by the changes in import and export.The total thermal resistance of type 1 and type 2 is not significantly different,while the total thermal resistance of type 3 is higher than that of the two types mentioned above.Secondly,the experimental platform of the L type heat exchanger proposed in this paper is set up,and the experimental data are recorded and analyzed.And the experimental results are compared and verified with the simulation results.The results show that the maximum error of Nusselt number is 4.34%,and the maximum error of pressure drop is 5.66%,which indicates that the experimental and simulation data are in good agreement.In addition,through uncertainty analysis,the maximum uncertainty of Re is 3.01%,and the maximum uncertainty of Nu is 4.37%.Finally,through the numerical simulation method,the research and analysis of the enhanced heat transfer under the pulsating flow of the L-type radiator are carried out.The fluid flow and heat transfer in the heat exchanger channel are discussed mainly from three different parameters:different pulsation frequency f,the amplitude A_u and the Reynolds number Re.The results show that when Re=800,Au=0.5,there is a pulsating critical frequency(0.01Hz).When f<0.01Hz,compared with the steady state,the pulsating flow weakens the heat transfer effect,and when f>0.01Hz,the heat exchange is enhanced.When the Reynolds number Re=800 and the frequency f=0.02Hz,compared to the steady state,the heat transfer enhancement effect is the best when the amplitude Au is equal to0.25.When the frequency f=0.02Hz and amplitude Au=0.25,the larger the Reynolds number Re,the Nusselt number Nu also increases correspondingly,and the heat transfer effect is continuously enhanced.Finally,the relationship and influence between different frequency,amplitude and field synergy angle are analyzed by the synergy principle between velocity and temperature gradient and pressure gradient three fields,and the mechanism of heat transfer enhancement is further elaborated.