In this paper, a review of the impact of most common nanoparticles on the Leidenfrost temperature T _Leid in heat transfer applications is delivered. Moreover, a simple economic analysis of the nanoparticles use is proposed. When coolant is distilled water, T _Leid can range 150–220 °C; occasionally, it can even amount to over 400 °C. When the base liquid is modified by additives, considerable changes in the character of heat transfer are observed. Out of five nanofluids under consideration in this study, the best thermal effect (up to 50%) is obtained when Al₂O₃ nanofluid having particle sizes ~39 nm and volume concentration of 0.1% is used. Conversely, the fluid containing TiO₂ particles, 20–70 nm in size, seems to be the worst of the analysed fluid, giving only 7% heat transfer enhancement in comparison with water. However, when TiO₂ nanoparticles are far smaller, very good thermal effects are obtained (23–25%). In a majority of the cases analysed, the temperature that marks the onset of film boiling is inversely proportional to concentrations of nanoparticles, which is relevant from the economic standpoint.

Currently; the transfer of new technologies makes it necessary to also control heat transfer in different industrial processes—both in practical and research—applications. Not so long ago water and ethylene glycol were the most frequently used media in heat transfer. However, due to their relatively low thermal conductivity, they cannot provide the fast and effective heat transfer necessary in modern equipment. To improve the heat transfer rate different additives to the base liquid are sought, e.g., nanoadditives that create mono and hybrid nanofluids with very high thermal conductivity. The number of scientific studies and publications concerning hybrid nanofluids is growing, although they still represent a small percentage of all papers on nanofluids (in 2013 it was only 0.6%, and in 2017—ca. 3%). The most important point of this paper is to discuss different ways of stabilizing nanofluids, which seems to be one of the most challenging tasks in nanofluid treatment. Other future challenges concerning mono and hybrid nanofluids are also thoroughly discussed. Moreover, a quality assessment of nanofluid preparation is also presented. Thermal conductivity models are specified as well and new representative mono and hybrid nanofluids are proposed.

This article discusses the evaluation of three methods of static contact angle measurements of de-ionized (DI) water and TiO2 nanofluid droplets with three concentrations (0.5%, 1%, and 5%) that evaporate on the substrate of three different temperatures. To compare the discussed approximation methods, the differences between the results of the mean contact angles were identified; the highest standard deviation was recorded for the Young–Laplace and circle methods, such as for the nanofluid TiO2–DI with 1% at 50 °C, it is 3.21°, while the lowest value was obtained for TiO2–DI with 5% at Tenv, SD = 0.04°, by comparing the contact angle results using the ellipse and circle methods. Research shows that circular shape approximation is not to be excluded for contact angle determination in the angular range of 0°–75°.