Influence of nanofluid on heat transfer in a loop heat pipe

Experiments are conducted to investigate heat transfer characteristics of using nanofluid in a Loop Heat Pipe (LHP) as a working medium for heat input range from 20 W to 100 W. The experiments are carried out by manufacturing the LHP, in which the setup consists of a water tank with pump, a flat evaporator, condenser installed with two pieces of fans, two transportation lines (vapor and liquid lines), copper pipe sections for attachment of the thermocouples and power supply. The uniqueness of the current experimental setup is the vapor and liquid lines of LHP which are made of transparent plastic tube to visualize the fluid flow patterns. In this study, the LHP performance using silica (SiO2-H2O) nanofluid with particle volume fraction of 3% which was used as a coolant is examined. The experimental results are verified by simulation using Finite Element Method (FEM). The LHP performance is evaluated in terms of transient temperature distribution and total thermal resistance (Rt). Rt is estimated for both LHP using SiO2-H2O nanofluid and pure water cases under a steady state condition. The results reveal the average decrease of 28%-44% at heat input ranging from 20 W to 100 W in total thermal resistance of LHP using SiO2-H2O nanofluid as compared with pure water. Therefore, the presence of nanoparticles could greatly enhance the cooling of LHP. The experimental and simulation results are found in good agreement.