Development of a design for measurement the thermal conductivity of nanofluids

The energy problem is a significant engineering challenge today, both in terms of energy losses and the efficiency of energy obtained. Thermal systems, which are gaining increasing importance in industry and daily life, are encouraging efforts to improve heat transfer. In this context, there is great interest in the development of heat transfer fluids. In recent years, nanofluids with higher thermal conductivity have started to be used instead of traditional fluids. However, uncertainties in the stability of nanofluids lead to various errors in thermal conductivity measurements. This study aims to develop a new design for measuring the thermal conductivity of nanofluids. The new design is the cylindrical copper tube design. In this design, thermal conductivity measurement is based on measuring the time-dependent changes in the temperature of the fluid inside the copper tube resulting from heating a resistance wire wrapped around the tube. The study compares the cylindrical copper tube design developed in this thesis with the widely used Transient Hot Wire (THW) method for measuring the thermal conductivity of nanofluids. First, the calibration of the experimental setup was performed using deionized water. Subsequently, thermal conductivity measurements of the nanofluid obtained from synthesized Fe3O4@ZnO nanoparticles were conducted. The results show that due to natural convection and heat losses, the cylindrical copper tube design has a higher margin of error compared to the THW method. It is anticipated that after design improvements, the cylindrical copper tube design will become more reliable and will make significant contributions to further research and investments in this area. These findings shed light on the development of more effective and cost-efficient methods for accurately measuring the thermal conductivity of nanofluids.