Abstract: This article presents a thermodynamic energy and exergy analysis to optimize a cascade refrigeration system to be used for biomedical cold-storage application. An azeotrope mixture carbon dioxide and ethane–propane (R744+R170–R290) cascade system has been promoted as a prospective alternative solution to the use of HFC refrigerants. A novel multilinear regression analysis was employed to develop mathematical expressions for maximum COP, optimum evaporating temperatures of the R290 cycle, and an optimum mass flow ratio in terms of evaporating temperature, condensing temperature and temperature differences in the system’s cascade condenser.

Abstract: The upcoming stringent emission regulations and the depletion of oil resources have led to the development of alternate energy sources. In the present study the performance and emission characteristics of a single- cylinder direct- injection diesel engine under neat diesel operation and blends of alternative fuels with pure diesel are examined. The hot outlet water from the engine was circulated in the heat exchanger and the final temperature was raised by heating coil inside the heat exchanger. Thus the use of heat exchanger improves the performance of the diesel engine under pure diesel mode as well as blends of alternative fuels. A net gain in brake thermal efficiency with heat exchanger was observed to be 7.33 percent. The results show that the variations in the peak cylinder pressures of all the blends at full load are marginal. The results also indicate that the alternative fuels have lower concentrations of nitrogen dioxide and particulate matter, although emissions of sulfur dioxide and carbon deposits are higher as compared to neat diesel. An increasing trend of emissions is also observed with an increase in brake mean effective pressure. A marginal variation in the engine speed was observed when the engine was run under blends of alternative fuels.

Abstract: Fly ash particles are potentially used in metal matrix composites, since they are low-cost, low-density and available in large quantities as a waste by-product in thermal power plants. The addition of fly ash into aluminum as reinforcement can potentially reduce the production cost and density of aluminum. However, mechanical properties of fly ash reinforced aluminum matrix composite (MMC ALFA) have some limitations due to the characteristic of fly ash. In this study, a carbothermal reduction process of fly ash with activated carbon powder was performed prior to produce MMC ALFA. The carbothermal reduction process was carried out in a furnace at 1300 oC in vacuum condition. The product was analyzed by XRD with Cu-Ka radiation. The synthesis product was subsequently used as reinforcement particle. Aluminum powder and 5, 10 and 15 % wt of carbothermally reduced powder were mixed and then uni-axially compacted at pressure of 300 MPa. Green body was sintered for 2 hours in argon atmosphere at temperature of 550 and 600 oC. Hardness, wear resistance and density of MMC ALFA’s product were tested using Brinell hardness test, ogoshi high speed universal wear testing machine and Archimedes method respectively. The results of this study shows that the reinforcement of carbothermally reduced of fly ash in general can improve the hardness and wear resistance of MMC ALFA. From XRD analysis, it shows that the synthesis process can produce SiC powder