An Experimental Study on the Flow Boiling of HFE-7100 in a Rectangular Parallel Microchannel

Abstract

With the rapid development of microelectronic technology, the integration and power of chip are increasing. Heat dissipation with high heat flux in limited space has become a bottleneck problem restricting the efficient and stable operation of the microelectronic devices. Flow boiling in microchannel heat sinks is one of the most essential candidates for solving this problem. It has shown remarkable high heat transfer performance due to the liquid to vapor change process, which would dissipate a large amount of heat from a small area. In addition, dielectric fluorinated fluids, such as HFE-7100, HFE-7200, FC-72 etc., are especially suitable for cooling microelectronic devices since their excellent safety and environmental characteristics. However, dielectric fluorinated fluids have relative poorer thermophysical properties compared to water. Thus, the flow boiling heat transfer characteristics of dielectric fluorinated fluids could be different from those of water. In this paper, an experimental investigation on flow boiling heat transfer and flow characteristics of HFE-7100 in a rectangular parallel microchannel is carried out. The tests are conducted at mass fluxes from 88.9 to 277.8 kg∙m^-2∙s^-1, inlet subcooling temperature from 20.5 to 35.5°C and effective heat flux from 12 to 279 kW∙m^-2 near atmospheric pressure. The effects of mass flux, inlet subcooling temperature, effective heat flux and vapor quality are examined and analyzed. Additionally, flow visualization is also obtained during the experiments to explain the heat transfer mechanism. The results show that the boiling hysteresis is observed for HFE-7100 at low inlet subcooling temperature, and the increasing inlet subcooling temperature and mass flux could delay the onset of nucleate boiling. The increases of inlet subcooling temperature and mass flux could enhance the two-phase heat transfer coefficient. And the two-phase heat transfer coefficient is significantly dependent on the inlet subcooling temperature in the slug flow, while it is significantly dependent on the mass flux in the annular flow. The two-phase pressure drop increases drastically as the effective heat flux increases. And the two-phase pressure drops with different mass flux at constant vapor quality are obvious different in the slug and annular flow. Furthermore, the experimental data were compared with four predicted values of the literature correlations. It’s found that the correlation of Lockhart has the best statistical agreement with a MAE of 19.6% and over 85% of points in the deviation bandwidth of ±30%. The results in this paper offer valuable theoretical guidance for the design and optimization of heat dissipation equipment for microelectronic devices. By utilizing HFE-7100 as the coolant and microchannel heat sinks in flow boiling, it is possible to enhance the stability and reliability of the electronic devices. Additionally, the heat transfer performance associated with different heat flux can be improved by regulating the inlet subcooling and mass flow rate. At last, the two-phase pressure drop correlation proposed by Lockhart can be employed to predict the pump power for heat dissipation equipment.