Enhanced effectiveness of nanofluid based natural circulation mini loop

• Thermal performance is enhanced by using nanofluids.
• A non-dimensionalized effectiveness factor was defined.
• The effectiveness factor provides more concrete results than temperature differences.
• Nanofluid provides elevated operation temperatures than the base fluid.
• Nanofluid based SPNCmL have a potential to be used for high heat dissipation devices.

The goal of this study is to investigate experimentally the thermal performance of a single-phase natural circulation mini loop (SPNCmL). The experiments were carried out with de-ionized water (DIW) with different particle concentration (1–3 % vol.) and size (10 and 30 nm) of Al2O3–DIW nanofluids. During the study, the operating parameters such as applied power to the heater (10–50 W), heat sink temperature (10 °C and 20 °C) and inclination angle (0°, 30°, 60° and 75°) of the loop were varied. To interpret the thermal performance of SPNCmL, a non-dimensionalized effectiveness factor was used. It was found that the effectiveness of the system is enhanced by the increase of particle concentration and inclination angle for all samples at full power range. Moreover, the results indicate a remarkable thermal performance enhancement (effectiveness factor increased to 30%) with using Al2O3–DIW nanofluids as a working fluid at inclined conditions which was achieved for the first time in a nanofluid based SPNCmL.