Experimental study on subcooled pool boiling heat transfer of sodium dodecyl sulfate surfactant solution

To improve the critical heat flux (CHF) in boiling heat transfer, an idea of triggering three-dimensional mixed boiling was proposed, and the corresponding surface with an extended thin film (ETFS) was designed by adding a film structure on the plain surface (PS). With ethanol as working fluid, experiments were conducted to explore mixed boiling heat transfer and CHF enhancement mechanisms on ETFS. The results demonstrate that ETFS induces spatially uneven temperatures on the boiling surface, which triggered mixing boiling in the spatial dimension—the coexistence of nucleate and film boiling—leading to a significant CHF enhancement. Nucleate boiling in the falling liquid along the extended surface is the key to stabilizing the surface temperature during the formation of dry spots on the base surface. Compared with PS and the traditional pin–fin surface, ETFS increased CHF by approximately 110% and 45%, respectively. Analysis indicated that mutual interference between nucleate boiling and film boiling effectively inhibits heat transfer deterioration caused by the deactivation of nucleating points. Through decoupling analysis of the mutual interference process in mixed boiling, it is shown that at heights of 2.0, 4.0, 6.0, and 8.0 mm, the contributions of extended film to total heat transfer are 12%, 64%, 37%, and 24%, respectively, indicating an optimal extended film height of 4.0 mm for maximum boiling heat transfer performance. This novel boiling surface with extended film structure not only improves CHF, but also reduces design costs, offering valuable guidance for radiator design purposes.

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Effects of heterogeneous nucleation model on computational fluid dynamics simulation of flow boiling heat transfer in the mini-channel

Chen,

Ji,

Gao

et al. 2023

Physics of Fluids

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Bubble nucleation is the initial stage of flow boiling and plays an important role in boiling heat transfer. However, bubble nucleation occurs at a microscopic scale, rendering it challenging for the macroscopic computational fluid dynamics method to realistically simulate this intricate process. In this paper, based on the coupled volume-of-fluid and level set method, a heterogeneous nucleation model is improved and conducted to simulate the subcooled flow boiling in a rectangular mini-channel, considering these conditions both in the presence and absence of a microlayer. The coefficient of the original heterogeneous nucleation model is adjusted across a range from 0.1 to 10.0 times its previous value to establish multiple new nucleation models for illustrating their effects on flow patterns and heat transfer characteristics. For flow boiling without a microlayer, when the coefficient of the original heterogeneous nucleation model is halved, the nucleate boiling intensity upstream of the channel diminishes, resulting in a reduction in the heat transfer coefficient. Nevertheless, this alteration mitigates the formation of slug flow and the appearance of dry patches near the channel outlet, consequently averting a sharp increase in outlet wall superheat. Quantitatively, relative differences of 23.83% and 90.48% in average and local maximum wall superheat are observed, respectively. In contrast, the presence of a very thin microlayer beneath the growing and slipping bubble in flow boiling with a microlayer is notable. This microlayer quickly evaporates, dissipating more than 77% of the input heat flux and substantially expanding the bubble volume. Consequently, under identical wall superheat conditions, the influence of variations in the number of activated bubbles induced by different heterogeneous nucleation models on heat transfer and flow patterns in flow boiling is significantly attenuated. Specifically, when the difference in nucleus site density remains within a tenfold range, the differences in the average and maximum wall superheat are limited to just 16.78% and 33.86%, respectively. Concerning flow boiling in a mini-channel featuring a microlayer, the simulation results verify that large deviations in the activated bubble number have few effects on the flow pattern and wall superheat, greatly reducing heterogeneous nucleation model requirement and promoting the numerical study of flow boiling.

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Experimental study on subcooled pool boiling heat transfer of sodium dodecyl sulfate surfactant solution

Cited by 4 publications

References 41 publications

The hydrodynamic aspect mechanism of the effect of surfactant on boiling heat transfer

The hydrodynamic aspect mechanism of the effect of surfactant on boiling heat transfer

Three-dimensional mixed boiling: A strategy for critical heat flux enhancement

Effects of heterogeneous nucleation model on computational fluid dynamics simulation of flow boiling heat transfer in the mini-channel

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