Flow and heat transfer behaviour of nucleating agent-enhanced nanofluids through manifold mini-channels

Abstract

Improving the thermal performance of mini-channels is crucial. The nature of working nanofluids and the mini-channel structure can have a significant impact on the thermal efficiency of mini-channels. This study investigated the flow and heat transfer characteristics of a manifold mini-channel heat sink (MCHS) structure. The working fluids were composite nano-phase change emulsions (NPCE), which were prepared from eicosane, eicosanol, and metal oxide particles (nano-MgO). They possess low supercooling, high thermal conductivity, and high stability. Using these NPCEs, convective heat transfer studies were conducted in the two mini-channels. The impacts of the channel type, NPCEs, and Re on the heat transfer characteristics, flow characteristics, and overall performance were investigated. The results showed that the prepared NPCE can improve the heat transfer coefficient in mini-channels compared to water. The incorporation of nano-MgO particles effectively enhanced the heat transfer capacity with the highest enhancement (17.7%) in the heat transfer coefficient compared to water. The addition of alcohol further enhanced the heat transfer performance. A mixture of 6 wt% eicosane + 1 wt% nano-MgO + 0.6 wt% eicosanol yielded the highest enhancement in the heat transfer coefficient of 29.7%. In addition, a manifold mini-channel was found to have a better comprehensive performance than a rectangular mini-channel. The maximum reductions in pressure drop and thermal resistance of the manifold MCHS were 51.2% and 53.9%, respectively, compared to the rectangular mini-channel. Overall, the evaluated performance indicators of the manifold MCHS with composite nanofluid were 17.9% higher than those of the rectangular MCHS.