Thermal performance of natural circulation loop filled with Al۲O۳/Water nanofluid

Natural Circulation Loop (NCL) which is also called as a thermosyphon system is the heat transfer loop which uses no pump or external device to drive the loop fluid. In the present paper, a comparative study on thermal characteristics of two loop fluids viz. water and Al۲O۳/water nanofluid is made. Experiments are conducted on in-house designed test rig. Thermo-hydraulic behaviour of loop fluid is presented. Two parameters such as heat input, nanofluid concentration are varied in order to study their individual and combined effects. It is concluded that Al۲O۳/water nanofluid as loop fluid results in higher mass flow rates as compared to the water. Different derived quantities such as Nusselt number and Grashof number are calculated. Quantitative comparison is made between water and Al۲O۳/water nanofluid. Time to reach steady state is reduced by ۲۲ % using Al۲O۳/water nanofluid as loop fluid when compared with water. Mass flow rate and Grashof number of the Al۲O۳/water nanofluid based NCL are enhanced by ۶.۷۵% and ۲۶% respectively, when compared with water-based NCL at ۱۰۰۰W heat input. At the heater, the temperature gradient is reduced by ۳۰.۲% due to the improved thermal and transport properties of Al۲O۳/water nanofluid when compared with water at ۱۰۰۰ W heat input. As particle concentration increases from ۱% to ۵%, Nusselt number increases from ۱۰.۱ to ۲۰.۱, for the heat input of ۱۰۰۰W.

Keywords:

Grashof Number , Heat transfer enhancement , Nanofluid , NCL , Nusselt number , Thermal performance