“…• conventional models specified for mono nanofluids do not apply in the case of hybrid nanofluids; what's more there are no unequivocal experimental results or agreement regarding available models and characteristics among researchers involved in this subject, • the relative viscosity and density of a hybrid nanofluid is directly proportional to the concentration of nanoparticles and inversely proportional to the temperature, • thermal conductivity and heat capacity increase with temperature, • with rising temperature and concentration of nanoparticles, the thermal properties improve until the critical point is reached-a visible deterioration of nanofluid thermal properties is observed beyond this point, • the thermal conductivity ratio, viscosity, density, heat capacity, pressure drop and friction factor of a hybrid nanofluid are slightly higher than for the base fluid and mono nanofluid, and they grow directly proportionally to the concentration of nanoparticles, • dispersion of nanoparticles in the base fluid is a problem frequently during stabilisation, and suspension stability time is relatively short (up to 60 days [35]), • Brownian motion of nanoparticles and micro-convection effect, clustering and pH values strongly affect the thermal parameters of hybrid nanofluids (which is very rarely discussed in the literature) [36], • coagulation and clustering of multi-sized nanocomposites in a nanofluid strongly affect its thermal properties [37,38], • there are quite a few valuable papers examining from a statistical point of view of mono and hybrid nanofluid preparation, stabilization and evaporation in specific systems [39,40].…”