A Survey of Measurements, Models, and Explanations of the Effect of Nanoparticles on the Specific Heat of Various Nanofluids

Abstract

A survey was conducted to determine if any unified models and/or explanations exist that adequately predict the change in specific heat of a nanofluid as a function of concentration of nanoparticles.

The papers and previous studies about the specific heat of nanofluids were collected and reviewed. The existing models and experimental data were summarized and compared. Through the investigation, only four different models were discovered, and two types of experimental result of the specific heat of nanofluids were found. Then, the four models were used to predict the change of the specific heat of nanofluids and compare with different selected sets of experimental result. This was intended to determine if the models are suitable for predicting the results of different sets of published results. The published results can be categorized into two types: a decrease in specific heat resulted from the addition of nanoparticles; and an initial increase in specific heat as nanoparticles were added followed by a decrease as the concentration of particles was increased above a particular value. The comparisons showed that there is no unified model that can predict or theory that can explain all the experimental results.

The mechanisms of the enhancement of the specific heat of nanofluids were presented. The results indicated that the enhancement of the specific heat of nanofluids was caused by the high specific surface area of nanoparticles. The specific surface area is a property of a material which is the total surface area of a material per unit of mass. A higher specific surface area of a material results in an increase of the heat transfer velocity between the material and surroundings.

Further, two novel explanations of the change in the specific heat at a nanoscale level have been proposed. Additionally, suggestions at a nanoscale level for future research of the specific heat of nanofluids have been recommended.