Characterization of Local Nano-Heat Transfer Fluids for Solar Thermal Collection

Abstract

Performance of organic oils in solar thermal collection is limited due to their low thermal conductivity when they are compared to molten salt solutions. Extraction of organic oils from plants can be locally achieved. 'e purpose of this study was to investigate the effect of use of copper nanoparticles in some base local heat transfer fluids (HTFs). Addition of volume fraction of 1.2% of the copper nanoparticles to oil-based heat transfer fluids improved their thermal conductivity as deduced from the thermal heat they conducted from solar radiation. 'e oil-based copper nanofluids were obtained by preparation of a colloidal solution of the nanoparticles. Impurities were added to increase the boiling point of the nano-heat transfer fluids. Stabilizers were used to keep the particles suspended in the oil-based fluids. 'e power output of the oil-based copper nano-heat transfer fluids was in the range of 475.4 W to 1130 W. 'e heat capacity of the steam in the heat exchanger was 93.7% dry and had a thermal capacity of 5.71 × 10 3 to 89.1 Js kJ. 'e heat rate of flow of the oil-based copper nano-heat transfer fluids was an average of 72.7 Js −1 −1 ·kg −1 −1 . 'e thermal efficiency for the oil-based copper nano-heat transfer fluids ranged from 0.85 to 0.91. 'e average solar thermal solar intensity was in the range 700 Wm ·kg . 'e heat exchanger used in this study was operating at 4.15 × 10 −2 −2 to 1180 Wm 3 kJ and a temperature of 500.0 ° C. 'e heat transfer fluids entered the exchanger at an average temperature of 381 ° C and exited at 96.3 ° C. 'e average temperatures of operation ranged between 394.1 C and their heat coefficient ranged between 290.1 Wm −2 ° −2 ° C and 254.1 Wm ° C and 219.7 ° C with respective temperature efficiencies ranging between 93.4% and 64.4%. It was established that utilization of copper nanoparticles to enhance heat transfer in oil-based local heat transfer fluids can mitigate energy demand for meeting the world’s increasing energy uses, especially for areas inaccessible due to poor land terrain.