Browsing by Author "Millien, Kawira"

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  • Publication
    Publication
    Characterization of Local Nano-Heat Transfer Fluids for Solar Thermal Collection
    (Advances in Materials Science and Engineering, 2020-07-07) Millien, Kawira
    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.
  • Publication
    Publication
    Characterization of Local Nano-Heat Transfer Fluids for Solar Thermal Collection
    (Hindawi, 2020) Millien, Kawira
    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.
  • Publication
    Publication
    Prototype Steam Turbine for Solar Power Production
    (Advances in Materials Science and Engineering, 2020-07-20) Millien, Kawira
    Fabrication of a prototype direct drive steam turbine using locally available materials provides a means to supply power and process heat for off-grid areas, which are not accessible due to rugged terrain. The use of solar power technologies to provide clean power and heat will mitigate environmental pollution and global warming that are caused by combustion of fossil fuels and other carbon-based power sources. The energy density of fossil fuels is higher than that of nonconcentrated solar power, which makes them a better option compared to nonconcentrated solar power sources. The high cost of steam thermal turbines and the limited technical skills on utilization of local materials for steam turbine construction have hampered the realization of potential of producing both small- and large-scale power in Africa. The design of the single-stage blade wheel system solar thermal turbine was done using AutoCAD 2010. The blades were made from encapsulated rice husk particle boards, and the steam casing was made from 0.0015 galvanized black iron sheet. Compensation for more stages was done by sending the fluid exiting from the turbine into the solar collector for reheating. It was coupled to a single-phase generator and gearbox. The rotor was made of galvanized iron tube. The turbine’s average efficiency was obtained as 61.6% and average isentropic efficiency was 55.3%. The combined gearbox and generator approximate efficiency was 54.7%. Locally available heat transfer fluids were used for solar thermal collection. The prototype turbine was designed to produce 500 W of power. It had a heat rate ratio of 0.08. The turbine inlet conditions were as follows: average temperature of 112.8°C, average pressure of 2.7 × 105 Nm−2, average enthalpy of 3156 kJ/kg, and average steam flow rate of 243.3 kg/hr. Outlet conditions were as follows: outlet average temperature of 97.3°C, average steam flow rate of 102.0 kg/hr, average pressure of 1.20 × 105 Nm−2, and enthalpy of 2103 kJ/kg. With use of 6 M sodium chloride solution, the turbine inlet conditions were as follows: enthalpy of 3789.1 kJ/kg at a pressure of 3.0 × 105 Nm−2 and its enthalpy at exit was 2346.3 kJ/kg at a pressure of 1.05 × 105 m−2 which can provide process heat and power for off-grid areas.
  • Publication
    Publication
    Prototype Steam Turbine for Solar Power Production
    (Hindawi, 2020) Millien, Kawira
    Fabrication of a prototype direct drive steam turbine using locally available materials provides a means to supply power and process heat for off-grid areas, which are not accessible due to rugged terrain. The use of solar power technologies to provide clean power and heat will mitigate environmental pollution and global warming that are caused by combustion of fossil fuels and other carbon-based power sources. The energy density of fossil fuels is higher than that of nonconcentrated solar power, which makes them a better option compared to nonconcentrated solar power sources. The high cost of steam thermal turbines and the limited technical skills on utilization of local materials for steam turbine construction have hampered the realization of potential of producing both small- and large-scale power in Africa. The design of the single-stage blade wheel system solar thermal turbine was done using AutoCAD 2010. The blades were made from encapsulated rice husk particle boards, and the steam casing was made from 0.0015 galvanized black iron sheet. Compensation for more stages was done by sending the fluid exiting from the turbine into the solar collector for reheating. It was coupled to a single-phase generator and gearbox. The rotor was made of galvanized iron tube. The turbine’s average efficiency was obtained as 61.6% and average isentropic efficiency was 55.3%. The combined gearbox and generator approximate efficiency was 54.7%. Locally available heat transfer fluids were used for solar thermal collection. The prototype turbine was designed to produce 500 W of power. It had a heat rate ratio of 0.08. The turbine inlet conditions were as follows: average temperature of 112.8°C, average pressure of 2.7 × 105 Nm−2, average enthalpy of 3156 kJ/kg, and average steam flow rate of 243.3 kg/hr. Outlet conditions were as follows: outlet average temperature of 97.3°C, average steam flow rate of 102.0 kg/hr, average pressure of 1.20 × 105 Nm−2, and enthalpy of 2103 kJ/kg. With use of 6 M sodium chloride solution, the turbine inlet conditions were as follows: enthalpy of 3789.1 kJ/kg at a pressure of 3.0 × 105 Nm−2 and its enthalpy at exit was 2346.3 kJ/kg at a pressure of 1.05 × 105 m−2 which can provide process heat and power for off-grid areas.