Philip John, Shima P D, Raj Baldev
Nanotechnology. 2008 Jul 30;19(30):305706. doi: 10.1088/0957-4484/19/30/305706. Epub 2008 Jun 16.
The unusually large enhancement of thermal conductivity (k/k(f)∼4.0, where k and k(f) are the thermal conductivities of the nanofluid and the base fluid, respectively) observed in a nanofluid containing linear chain-like aggregates provides direct evidence for efficient transport of heat through percolating paths. The nanofluid used was a stable colloidal suspension of magnetite (Fe(3)O(4)) nanoparticles of average diameter 6.7 nm, coated with oleic acid and dispersed in kerosene. The maximum enhancement under magnetic field was about 48φ (where φ is the volume fraction). The maximum enhancement is observed when chain-like aggregates are uniformly dispersed without clumping. These results also suggest that nanofluids containing well-dispersed nanoparticles (without aggregates) do not exhibit significant enhancement of thermal conductivity. Our findings offer promising applications for developing a new generation of nanofluids with tunable thermal conductivity.
在含有线性链状聚集体的纳米流体中观察到的热导率异常大幅增强（k/k(f)∼4.0，其中k和k(f)分别为纳米流体和基础流体的热导率），为热量通过渗流路径的高效传输提供了直接证据。所使用的纳米流体是平均直径为6.7纳米的磁铁矿（Fe(3)O(4)）纳米颗粒的稳定胶体悬浮液，表面包覆油酸并分散在煤油中。磁场下的最大增强约为48φ（其中φ为体积分数）。当链状聚集体均匀分散且无团聚时观察到最大增强。这些结果还表明，含有充分分散的纳米颗粒（无聚集体）的纳米流体不会表现出显著的热导率增强。我们的发现为开发具有可调热导率的新一代纳米流体提供了有前景的应用。
