Study On Heat Transfer Performance Of Single-phase And Two Phase Flow In A Throttle Microchannel

Microelectronic technology has now been widely used in many fields,such as space,military,biochemistry,medical and other fields,because of its precision,precision and flexibility.While the microelectronic devices are popular in use,the high heat flux produced by the microelectronic devices affects their service life.The microchannel heat exchanger has high heat transfer ability,which has become the focus of the research of electronic element radiator parts.In many cases,in order to solve the problem of practical application,it sometimes has to design the micro channel of the sudden expansion and throttle structure.In order to study the flow and heat transfer performance of the throttle structure,the characteristics of the flow and heat transfer are studied from the single phase and the gas-liquid two phase angle respectively.In this paper,the effects of the characteristics of thermal resistance,heat flow,heat transfer,resistance and pressure drop on the flow and heat transfer are mainly discussed with pure water and nitrogen as the experimental working fluid.The study shows that the thermal resistance characteristics are greatly influenced by the flow rate.With the increase of flow rate,the convection heat resistance decreases,and the ratio of thermal conduction resistance to convective thermal resistance increases.For heat flow characteristics,when the heat flux is constant,the larger the flow rate is,the more obvious the increase of pressure difference.The input heat flux and mass flow rate are directly proportional to the heat transfer coefficient.The convective heat transfer coefficient in the whole channel increases with the increase of the flow rate,and the heat transfer coefficient of the single phase liquid flow is smaller than that under the same experimental condition.For the resistance characteristic,the friction coefficient of the single phase flow is inversely proportional to the mass flow,and the friction coefficient decreases with the increase of the flow.When the fluid flows from the large channel into the small channel,the irreversible loss of the fluid in the microchannel increases with the turbulence of the two phase flow and increases with the flow rate.The coefficient of friction resistance decreases.The pressure of the inlet and outlet of the micro channel is mainly determined by the flow rate.When the input heating power is certain,the large pressure difference will gradually increase with the increase of the flow rate.The pressure ratio of the inlet and outlet increases with the increase of the volume of nitrogen.