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The effect of solar irradiation on the temperature of an electronic device attached to a heat sink is studied. Heat sinks with different surface treatments are considered for this study. The contribution of absorbed solar heat by the Al2O3 coated fin surface varies from 2.1% to 12.4% of the heat generated by the electronic devices and it reveals that the amount of solar heat absorbed by the black painted heat sink is almost equal to the heat generated by the electronics system. It is also found that the percentage of heat transfer by radiation varies from 6.2% to 11.0% for commercial finish heat sinks and is as high as 58.7% for a black painted heat sink. The combined effect of emissivity and solar absorptivity is studied to optimize the heat sink. For 10 mm fin height, the black painted heat sink illustrates better performance and for 20 mm and 30 mm fin height, the Al coated heat sink exhibits better performance. The temperature of the electronic device increases when the base area of the heat sink is increased beyond 700 cm², which is the optimum base area. When the fin height is increased to 20 mm, the optimum base area for the black painted and Al2O3 coated heat sink is also increased to 780 cm² and 850 cm², respectively, thus reducing the device temperature further. The CFD results are validated with the temperature measurement conducted on the heat sink exposed to solar irradiation. [ABSTRACT FROM AUTHOR]

Since carbon dioxide (CO2) has a more substantial impact on climate change, it must be recycled to slow down global warming. In this work, wet impregnation (at a 3 wt.% concentration), drying, and calcination processes were used to synthesise calcium oxide-loaded carbon beads (CaO/CB). In order to produce Ca/CB (catalyst) from the CaO/CB, hydrogen gas was employed for the reduction process. Then, the obtained Ca/CB were used in a packed bed reactor (PBR) to produce carbon monoxide (CO) as a fuel gas from CO2 by thermocatalytic gasification process. The experiments were conducted with non-catalysed CB and the Ca/CB catalyst from 100 to 900 °C and 100 to 300 °C, respectively. The current study reveals that Ca reactive sites on Ca/CB have significantly higher gasification activity than the non-catalysed CB for CO2 reduction. The samples (CB and CaO/CB) were thoroughly characterised by N2 adsorption and desorption isotherms, FESEM with EDX, XRD, TG-DSC, and FTIR spectroscopy. Also, gas chromatography was used to verify the reactant and product species qualitatively and quantitatively. Compared with regular CB, Ca/CB has a maximum CO2 conversion and CO yield of 50.7% at 150 °C. In contrast, CO formation began to occur above 300 °C using regular CB. For this, the PBR was operated with CO2 on a CB-filled and catalyst-filled (Ca/CB) reactive zone at a 100 mL/min flow rate under the same circumstances. These findings lead to the hypothesis that the kinetic barrier for converting CO2 to CO can be overcome by Ca/CB. [ABSTRACT FROM AUTHOR]

This contemporary work was mainly focused on the application of ANN model and RSM optimization tool for analyzing the performance and exhaust emissions of a single-cylinder Compression Ignition (CI) engine operating with acetylene and diesel on dual fuel mode. Experiments were performed in a 3.5 kW Kirloskar TV1, water-cooled engine with various flow rates (2, 4, and 6 liters per minute) of acetylene gas, variations in the Compression Ratio (CR) (16, 18, and 20), Injection Timing (IT) (19ºbTDC, 23ºbTDC, 27ºbTDC) and Injection Pressure (IP) (200, 220, and 240 bar). Multi-objective optimization was conducted using the RSM, while the central composite design was chosen as the design matrix. The desirability approach was employed to find optimum operating conditions. High flow rate of acetylene injection of 6 lpm, higher IP of 240 bar, CR of 18 and IT of 23ºCA bTDC were arrived as the optimum operating conditions with 0.649 desirability value.The ANN model was developed based on experimentaldata to forecast the brake thermal efficiency (BTH), hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx) and smoke. ANN was trained using Levenberg-Marquardt Algorithm for predicting output parameters. To analyze theStatistical error,measuring tools Normalized Root Mean Square Error (NRSME) and Mean Absolute Percentage Error (MAPE) were used in the proposed ANN model.NRSME and MAPE values for the developed ANN model were 0.00908–0.047516 and 0.014502–0.118807 respectively. Regression coefficients (R), Coefficient of determination (R2) were implemented to validate the proposed model. The range of values obtained for R and R2were 0.998742–0.999953, 0.997487–0.999906 correspondingly. The low range of error and closeness of R and R2 values nearest to 1 confirms that the proposed model can predict the output parameters with acceptable limits of error. [ABSTRACT FROM AUTHOR]

To improve the efficiency of solar flat-plate collectors further, a study had been carried out wherein the conventional working fluid was replaced by nanofluids. A 25-L/day solar flat-plate water heater with collector area of 0.5 has been designed and fabricated. The thermosyphon system of the solar water heater was monitored at 15 locations using T-type thermocouples. Alumina and CuO nanoparticles were synthesized and characterized using Brunauer-Emmett-Teller and X-ray diffraction techniques and dispersed using ultrasonic mechanism. To stabilize the system at an optimum level, the collector is operated with volume fractions of 0.2% and 0.4% of synthesized Al 2O 3 and CuO nanoparticles mixed with distilled water and used in the solar flat-plate collector. The temperature profile was compared with different volume fractions of the nanoparticles in the flowing medium. Enhanced heat transfer was observed in the solar flat-plate collector using nanoparticles, and hence, it is inferred that addition of nanoparticles improves the efficiency of the solar water heaters. This paper details the temperature profile observed in the collectors, variation of insolation over the day, and change in efficiency both on the primary side (collector) and on the secondary side (storage tank) of the solar water heater. [ABSTRACT FROM AUTHOR]

Two collectors with the same area of 945×420mmhave been designed and fabricated: one flat plate collector with internally grooved fins inserted inside the riser tubes and the other one with plain riser tubes. Provisionswere made for inserting the T-type thermocouples at six different locations to monitor temperature variations inside the riser tubes of the collector. The two identical systems of collectors (finned and unfinned tube) were initially run with base working fluid (water) and then with Al2O3 nanoparticles with a size of 40 nm for diffierent weight fractions of 0.2%and 0.4%in incremental order to study the effect on the efficiency of collectors. Mixing of nanoparticles in water thus improves the efficiency of the collector. Results show the efficiency of finned tube collector using the nanoparticles and water is substantially higher when compared to that of unfinned riser tubes collector. [ABSTRACT FROM AUTHOR]