Effect of the hotter groove on the capillary flow enhancement with nanofluids in a microgrooves wick

Abstract

This work studied the capillary flow enhancement with Fe3O4-water nanofluids in a microgrooves wick when the groove is hotter than the fluid. Capillary-rise experiment was conducted to derive three parameters, ∆Pcap∙K, capillary pressure and Poiseuille number for evaluating the flow on flow driving force and resistance. Results show that the hotter groove promotes the enhancement by making it easier for the nanofluids to induce friction reduction. When the temperature difference between the groove and liquid pool, ∆T is about 15 °C, the nanofluids lead to a 76% increase in ∆Pcap∙K and 42% decrease in Poiseuille number on average, which is 30 and 15 percentage points larger than that for ∆T of zero respectively. Furthermore, it requires optimizing the concentration and ∆T for raising the enhancement with the nanofluids. However, the capillary pressure is slightly affected by the nanofluids when the groove is hotter. At the optimal concentration, the capillary pressure even becomes almost independent of ∆T. The mechanism is explained with how the hotter groove can change the particle migrations that exist in the groove cross-section and determine the wetting and friction reduction of a nanofluid.