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. The 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. The 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. The power output of the oil‐based copper nano‐heat transfer fluids was in the range of 475.4 W to 1130 W. The heat capacity of the steam in the heat exchanger was 93.7% dry and had a thermal capacity of 5.71 × 103 kJ. The heat rate of flow of the oil‐based copper nano‐heat transfer fluids was an average of 72.7 Js−1·kg−1 to 89.1 Js−1·kg−1. The thermal efficiency for the oil‐based copper nano‐heat transfer fluids ranged from 0.85 to 0.91. The average solar thermal solar intensity was in the range 700 Wm−2 to 1180 Wm−2. The heat exchanger used in this study was operating at 4.15 × 103 kJ and a temperature of 500.0°C. The heat transfer fluids entered the exchanger at an average temperature of 381°C and exited at 96.3°C and their heat coefficient ranged between 290.1 Wm−2°C and 254.1 Wm−2°C. The average temperatures of operation ranged between 394.1°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.
Highlights
Solar thermal collectors are used for solar thermal collection and some of their various applications include heating and cooling of houses, drying agriculture food materials, and water desalination processes. e heat collected by the oilbased nanofluids passing through the absorber was exchanged between the oil-based nano-heat transfer fluids (HTFs) and a secondary fluid in the heat exchanger
A volume of 2.0 × 10−1 m3 of the oil-based copper nano-heat transfer fluids was passed through the parabolic trough solar collector of area of 32 m2 which was connected to a heat exchanger [17]. e transfer of solar thermal heat to form steam took place in the heat exchanger [18]. e steam expanded in the turbine and propelled the blades. e steam turbine was coupled to a 1500 W generator that converted the mechanical energy into electrical power. e hot oil-based copper nano-heat transfer fluids flowed through coiled copper tubes in the heat exchanger. e water on the pressurized shell side conducted the solar thermal heat from the hot oil-based copper nano-heat transfer fluids and turned into steam
Performance of Oil-Based Copper Nano-Heat Transfer Fluids. e oil-based copper nanofluids conducted solar thermal heat energy which was in turn conducted away by the water flowing through the pressurized side of the shell of exchanger
Summary
Solar thermal collectors are used for solar thermal collection and some of their various applications include heating and cooling of houses, drying agriculture food materials, and water desalination processes. e heat collected by the oilbased nanofluids passing through the absorber was exchanged between the oil-based nano-HTFs and a secondary fluid in the heat exchanger. Solar thermal collectors are used for solar thermal collection and some of their various applications include heating and cooling of houses, drying agriculture food materials, and water desalination processes. E heat collected by the oilbased nanofluids passing through the absorber was exchanged between the oil-based nano-HTFs and a secondary fluid in the heat exchanger. E particles enhance certain properties of the fluid such as thermal conductivity and further study can reveal the nature of the observed enhanced conductivity. The copper nanoparticles in oil base gave a large volume-tosurface-area ratio for thermal transfer. It was established that nanoparticles can be prepared in onestep process such as in the case of one-step synthesis system of preparing carbon/water nanofluid by use of plasma arch welding equipment [3]. Carbon nanotube nanoparticles can achieve thermal conductivity of 3000 W/mK and 2000 aspect ratio. Suspended nanoparticles enhanced the intended thermal conduction which led to superior performance due to their low momentum and improved mobility. e heat
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