Media thermal conductivity is important in various heat-transfer processes. Many conventional
fluid conductors suffered low conductivity and environmental issues. Therefore, research was
active in finding out alternative systems, mostly relying on aqueous liquids that are low-cost and
ecofriendly. After the emergence of carbon nanotubes (CNTs), with their many special structural,
electrical and thermal properties, they have been examined for many applications, including heattransfer
processes. Adding CNTs to water yields CNT aqueous nanofluids that have been widely
investigated as heat-transfer media. The literature shows that CNT addition improves water thermal
conductivity and other water properties, such as viscosity, surface tension, freezing point and boiling
point. The literature also shows that nanofluid thermal conductivity improvement is affected by CNT
type and concentration, in addition to other factors such as surfactant addition. All these subjects
were widely described in literature, focusing on experimental, modelling and theoretical accounts.
Despite the wide literature, there exist inconsistencies and discrepancies between reports that need to
be justified. In addition to technical papers, many reviews were published on various aspects of the
subject including experimental results and mathematical modeling. However, the very basic question
here is as follows: Why does adding CNT to water affect its thermal conductivity? In spite of the
wide published literature, this issue was not targeted in a simple qualitative approach. This review
provides a clear understanding of how CNTs improve thermal conductivity of aqueous nanofluids.
A qualitative model is presented to explain mechanisms behind improvement as presented in the
literature. CNT type effects are discussed with other factors such as aspect ratio, Reynold number,
dispersion quality, composition, temperature and additives. CNT functionalization is described.
Relations to estimate nanofluid thermal conductivity are discussed. The model will help specialists
to tailor CNT aqueous nanofluid characteristics as desired by varying types and concentrations of
CNT and surfactant, and other factors.

العنوان

Processes

الناشر

MDPI

بلد الناشر

سويسرا

Indexing

Thomson Reuters

معامل التأثير

3,5

نوع المنشور

Both (Printed and Online)

المجلد

12

السنة

2024

الصفحات

834