## 2 Thermal Properties  
Determining the properties of NFs is complex, and several groups have obtained different results due to the large number of variables involved in the process and difficulty in relating cause and effect in the variations of parameters [5; 37]. Furthermore, the general thermal transfer properties of each system are determined by the characteristic of the solid liquid interface [38]. The main thermal properties of NFs are presented below, together with the means by which they can be obtained. Thermal conduction has its value affected by several parameters such as concentration, shape, size, temperature and thermal conductivity of NPs, type of base fluid, pH, sonication, and preparation technique [3; 5]. Among recent techniques for measuring thermal conductivity, one can mention [PERSON] et al. [39], who implemented and improved a Steady Flow Method (SFM) based on the theory of heat transfer in laminar flow under uniform heat flow. With this, the authors could reduce the influence of natural convection in the measurement process. Other techniques that can be mentioned are the transient hot-wire approach, which consists of a thin metallic wire that works as a thermometer and heat generator simultaneously. The wire is then immersed in the fluid and the rate of temperature change indicates the conductivity [40]. The parallel plate technique consists of placing small samples of NFs between two parallel copper plates (purity greater than 99%) connected to thermocouples. Thermal conduction is defined by the temperature variation of the plates when one of them is subjected to a heat source [41]. [PERSON] et al. [42] evaluated the impact of the Graphene Quantum Dot on the stability and thermal properties of a water-based solution. The results showed a significant increase in thermal conductivity when a very low concentration of NPs was placed. Although it is of great importance, there is limited research concerning specific heat in articles concerning the physical properties of NFs [3]. The most common way to measure specific heat is through DSC (Differential Scanning Calorimetry). This test measures the difference in the amount of heat needed to increase the temperature of the analyzed material and is compared to reference material at the sequence [43]. There are derivations of this method that have brought some advances, such as the case of Temperature Modulated Differential Scanning Calorimetry (TMDSC) that varies the temperature with slight sinusoidal disturbances. Combined with a mathematical treatment, the method allows for greater sensitivity and the observation of other phenomena such as metastable melting [44] and Quasi-isothermal TMDSC varies the temperature at an insignificant rate [45]. [PERSON] et al. [43] used the Quasi-isothermal TMDSC method to determine the specific heat of Ethylene glycol-containing NPs from AIN, Si\({}_{3}\)N\({}_{4}\), TiN. The author observed a large variation of the specific heat by increasing the concentration of particles without their size having a great influence. Density influences Nusselt and Reynolds number, friction factor, and pressure loss [46]. As it is an easy parameter to obtain, it is measured by dividing the measured mass by a known volume or using a densimeter that works with these same principles. [PERSON] and [PERSON] [47] determined the carbon density of quantum dots NFs using a densimeter. Dynamic viscosity is the fluid's resistance to shear stress, being one of the most important properties of the fluid as it demonstrates its behavior close to the limits of a solid body. The viscosity directly affects the pumpability and pressure of the system [48]. One way to measure viscosity is through a capillary viscometer, where a tube with a short internal diameter (about 2.5 mm) comes vertically into contact with the NF, whose viscosity is determined by the variation in pressure and volumetric rate through Poieuille's law [49].