Comprehensive evaluation of graphene/R141b nanofluids enhanced heat transfer performance of minichannel heat sinks

Abstract

Flow boiling heat transfer of minichannel heat sinks with nanofluids is an ideal solution for cooling high-power electronics. Nevertheless, the flow boiling performance of nanofluids in a minichannel heat sinks is usually evaluated separately by the heat transfer coefficient or the pressure drop, limiting the application of nanofluids in minichannel heat sinks. Herein, graphene/R141b nanofluids with graphene mass fractions in the range of 0.01% to 0.1% were prepared, and the flow boiling heat transfer characteristics in a minichannel heat sinks were investigated. Furthermore, we report an innovative comprehensive evaluation method based on entropy analysis for the evaluation of the flow boiling heat transfer performance. The results obtained using the conventional evaluation method demonstrate that graphene nanosheets can significantly enhance the heat transfer performance of R141b. The maximum heat transfer coefficient of R141b with 0.025 wt% graphene increases by is 75% higher than that of pristine R141b, and the lowest pressure drop of R141b transportation in minichannels is achieved for R141b with a graphene content of 0.035 wt%. In contrast, by comprehensive combination analysis of the operating parameters of a minichannel heat sinks with the optimal heat transfer performance and minimum energy consumption according to the scoring method, the weights of the influence of the nanofluids on the heat transfer coefficient and pressure drop of the heat sinks were found to be 0.509 and 0.491, respectively. The best heat transfer enhancement is achieved for the optimal graphene mass concentration of 0.015 wt%, and the optimal heat transfer coefficient and minimum energy consumption for the minichannel heat sinks are 1.98 kW/(m2·K) and 2.56 kPa, respectively. Furthermore, a comparison was made between the experimental data and other investigation's data. The results show that the results of the work are reliable and that the comprehensive evaluation method has a good universal applicability for evaluating the flow boiling heat transfer performance of minichannel heat sinks.