*2.2. Experimental Methodologies*

This study was carried out at an inlet temperature of 30 ◦C; the basic thermophysical properties such as dynamic viscosity and thermal conductivity should be determined initially. The tools of KD2 Pro and Anton Paar Rheometer were used to evaluate thermal conductivity and dynamic viscosity, respectively [26]. In the meantime, for the density readings, a density meter was used at an accuracy level of <sup>±</sup>10−<sup>4</sup> g/cm<sup>3</sup> . Lastly, a Differential Scanning Calorimeter (data accuracy = ±1.0%) was used to capture the specific heat of the samples. SEM-EDX analysis was conducted to study morphology and elemental structures of the prepared nanomaterials using VEGA3 tool (Tescan, Brno, Czechia).

Experimental model is schematically depicted in Figure 2. The flow loop parts include a magnetic flow meter, a storage tank, a pump, a test section, and a differential pressure

transmitter. Each working fluid is driven from a 12 L capacity stainless steel by a magnetic drive pump at the flow rate range of 0–10 LPM. Uncertainties of the flow rate and pressure loss measures were ±0.5% and ±0.075%, respectively. *Nanomaterials* **2022**, *12*, x FOR PEER REVIEW 4 of 21

**Figure 1.** Schematic illustration for the different nanofluids preparation process. **Figure 1.** Schematic illustration for the different nanofluids preparation process.

**Figure 2.** Diagram of the adopted experimental set-up.

*2.3. Data Processing*

**Figure 2.** Diagram of the adopted experimental set-up. The test section is a square heated pipe (length = 1.4 m, inner width = 10 mm, outer The test section is a square heated pipe (length = 1.4 m, inner width = 10 mm, outer width = 12.8 mm). It was heated by a 900 W flexible tape heater attached to a transformer

width = 12.8 mm). It was heated by a 900 W flexible tape heater attached to a transformer and a power meter. Then, a high-temperature epoxy glue was used for installing 5 T-type

maximum heat loss was about 7.2%. This low heat loss rate was thought to have no sig-

Two RTD (PT-100) sensors (uncertainty = ±0.1 °C) were immersed into the pipe to measure the inlet and outlet temperatures. All temperature measurements were collected

In the current study, primary data were collected from an experimental setup and handled using very well-known procedures, as described in earlier studies [27]. The present laboratory analysis focused on evaluation of the heat transfer enhancement and hydrodynamic effectiveness under the condition of fully developed turbulent flow. The approximate heat flux, heat transfer coefficient, average Nusselt number, friction factor,

> × 4ℎ

" −

ℎ<sup>ℎ</sup> 

[ −]), the

(1)

(2)

(3)

by Graphtec (LOGGER GL240). After using the formula ( = = ̇

nificant impact on the entire process of heat transfer estimation.

Reynolds number, and Prandtl number; are presented as follows:

Heat flux (*q"*)

Heat transfer coefficient (*h*)

Nusselt number (*Nu*)

and a power meter. Then, a high-temperature epoxy glue was used for installing 5 T-type thermocouples (uncertainty = ±0.1 ◦C) to measure the surface temperature.

Two RTD (PT-100) sensors (uncertainty = ±0.1 ◦C) were immersed into the pipe to measure the inlet and outlet temperatures. All temperature measurements were collected by Graphtec (LOGGER GL240). After using the formula (*Q* = *VI* = . *mCp*[*Tout* − *Tin*]), the maximum heat loss was about 7.2%. This low heat loss rate was thought to have no significant impact on the entire process of heat transfer estimation.
