Mechanistic insights into surface contribution towards heat transfer in a nanofluid.

Ajit Singh,Chirodeep Bakli,Chandan Bera,Naimat Kalim Bari,Ramanujam Lenin

doi:10.1039/d0na00452a

Abstract

Nanofluids play a very important role in thermal management and heat exchange processes and for a stable nanofluid, a surfactant is a salient material. There are many contrasting reports on the thermal conductivity of nanofluids and the associated heat transport mechanism in nanofluids. In this article, four different types of nanoparticles are synthesized using citric acid and oleic acid as surfactants, followed by the assessment of their thermal conductivities. For a nanofluid of 3 wt% nanoparticles, coated with citric acid in water 67% reduction in thermal conductivity is observed, and on the other hand a 4% enhancement in thermal conductivity is observed for oleic acid-coated nanoparticles in toluene. This anomaly in the thermal transport behaviour of the nanofluid can be related to the surface properties of nanoparticles and the polarity of the base fluid. Theoretical calculation based on molecular dynamics simulations shows that the reduction in long-range interaction and fluid structuration reduce the thermal conductivity in a polar fluid with a polar surfactant coated nanoparticle.

Highlights

Nano uids have diverse applications in thermal management, thermal insulation and thermal exchange
In hyperthermia applications of magnetic nanoparticles, understanding of the heat exchange mechanism between nanoparticles and tissues is important for clinical applications and the heat transfer mechanism holds the key for drug delivery applications using nanoparticles
The thermal transport mechanism in nano uids is investigated by experiment and theoretical analyses

Summary

Introduction

Nano uids have diverse applications in thermal management, thermal insulation and thermal exchange. They have gained tremendous attention for biological and clinical applications, where heat transfer plays a critical role. The thermal conductivity of Fe3O4 nano uids has been reported by several groups;[1] there is a lack of systematic understanding of the heat transfer mechanism on the thermal conductivity of nano uids. Different mechanisms are proposed to explain the thermal transport properties of nano uids such as interfacial resistance,[8] Brownian motion,[9,10,11,12] liquid layering particle–liquid interface, and nanoparticle clustering.[13,14,15,16] Theoretical models in most of the cases are not aligned with the experimental observation.[17,18] A few reports of

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Results

Conclusion