Experimental study on pool boiling heat transfer enhancement in reduced graphene oxide nanofluid
HUANG Xiaoli1, CHEN Zeliang1, GUI Nan1, YANG Xingtuan1, TU Jiyuan1,2, JIANG Shengyao1
1. Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China; 2. School of Engineering, RMIT University, Melbourne VIC 3083, Australia
Abstract：[Objective] Continuous enhancement of energy efficiency is an essential element of China's green development plan to meet the peak carbon dioxide emission target by 2030 and carbon neutrality objective by 2060. Boiling heat transfer, being one of the most effective methods for phase-change heat transfer, is crucial for heat-energy transfer and conversion in various industries. Therefore, improved boiling performance can increase the efficiency, safety, and cost-effectiveness of energy systems. Graphene, a novel material discovered at the turn of the 21st century, has exceptional properties in numerous fields and can be used as nanoparticles for enhancing the heat transfer of base fluids. This research study aims to enhance boiling heat transfer by examining the effects of the heating surface and working fluids, specifically with graphene nanofluids.[Methods] Reduced graphene oxide (RGO) nanofluid, which is a product of graphene preparation via the redox method, was utilized as the working fluid. The experimental investigation aimed to examine the heat-transfer characteristics of RGO-nanofluid saturated pool boiling at atmospheric pressure. The experimental data were collected and analyzed using a high-speed camera to record the morphology of vapor bubbles during boiling. The research study also used a pool-boiling experiment with a pure copper heating surface and distilled water as the working fluid to provide benchmark data to compare with the RGO nanofluid experiment.[Results] The results indicated that the RGO nanofluids had a significant impact on the critical heat flux (CHF) of pool boiling, which reached 1 684.22 kW/m2, increased by 49.2% compared to distilled water. However, the nanofluids did not significantly affect the heat transfer coefficient (HTC) of pool boiling, which reached 73.87 kW/(m2·K), only increased by 2.3% compared to distilled water. At a constant heat-flow density, the effect of RGO nanofluids on the superheated wall was insignificant. Further analysis of the experimental data revealed that the RGO deposition layer formed by the RGO nanofluids on the heated surface during boiling was the core factor contributing to the increase in CHF. The deposition layer changed the wettability and vaporization core number of the surface, reduced the detachment diameter of vapor bubbles on the heated surface, and increased the detachment frequency, which delayed the appearance of CHF. This was supported by the measurement of the contact angle of the heated surface, surface observation of the heated surface after boiling, and analysis of the vapor bubble visualization images.[Conclusions] In conclusion, this study demonstrated that the use of RGO nanofluids can significantly improve the critical heat flux of pool boiling, which can contribute to the efficiency, safety, and cost-effectiveness of energy systems. The results also provide insights into the mechanism of heat transfer enhancement through the use of RGO nanofluids, specifically through the formation of a deposition layer on the heated surface during boiling. These findings can have practical implications in various industrial applications, including nuclear reactors, electronic cooling systems, and heat exchangers. However, further research is necessary to optimize the use of graphene nanofluids in various industrial applications and to assess their long-term effects on energy systems.
黄潇立, 陈泽亮, 桂南, 杨星团, 屠基元, 姜胜耀. 还原氧化石墨烯纳米流体池沸腾强化换热实验[J]. 清华大学学报（自然科学版）, 2023, 63(8): 1291-1296.
HUANG Xiaoli, CHEN Zeliang, GUI Nan, YANG Xingtuan, TU Jiyuan, JIANG Shengyao. Experimental study on pool boiling heat transfer enhancement in reduced graphene oxide nanofluid. Journal of Tsinghua University(Science and Technology), 2023, 63(8): 1291-1296.
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2023, Vol. 63 
