Abstract Six Sigma is an organized and systematic method for strategic process improvement that relies on statistical and scientific methods to reduce the defect rates and achieve significant quality up-gradation. Six Sigma is also a business philosophy to improve customer satisfaction, a tool for eliminating process variation and errors and a metric of world class companies allowing for process comparisons. Six Sigma is one of the most effective advanced improvement strategies which has direct impact on operational excellence of an organization. Six Sigma may also be defined as the powerful business strategies, which have helped to improve quality initiatives in many industries around the world. With the use of Six Sigma in casting industries, rejection rate is reduced, customer satisfaction is improved and financial benefits also increased. Six Sigma management uses statistical process control to relentlessly and rigorously pursue the reduction of variation in all critical processes to achieve continuous and breakthrough improvements that impact the bottom-line and/or top-line of the organization and increase customer satisfaction. In this paper author reviewed some of the significant previous published papers and focused on the general overview of publication in casting industries.

Abstract The cross wire projection welding of wires (Al 5182, =4 mm) performed using the conventional (i.e. pneumatic) electrode force system was subjected to thorough numerical analysis. Calculations were performed until one of adopted boundary conditions, i.e. maximum welding time, maximum penetration of wires, the occurrence of expulsion or the exceeding of the temperature limit in the contact between the electrode and the welded material was obtained. It was observed that the ring weld was formed within the entire range of welding parameters. The process of welding was subjected to optimisation through the application of a new electromechanical electrode force system and the use of a special hybrid algorithm of electrode force and/or displacement control. Comparative numerical calculations were performed (using SORPAS software) for both electrode force systems. Technological welding tests were performed using inverter welding machines (1 kHz) provided with various electrode force systems. The research also involved the performance of metallographic and strength (peeling) tests as well as measurements of welding process characteristic parameters (welding current and voltage). The welding process optimisation involving the use of the electromechanical force system and the application of the hybrid algorithm of force control resulted in i) more favourable space distribution of welding power, ii) energy concentration in the central zone of the weld, iii) favourable (desired) melting of the material within the entire weld transcrystallisation zone and iv) obtainment of a full weld nugget.

Abstract Application of nanoparticles have been proven to aid heat transfer in engineering systems. This work experimentally investigated the performance of a domestic refrigerator under the influence of Al 2 O 3 nanoparticles dispersed in mineral oil based lubricant at different charges (40, 60 and 80 g) of LPG refrigerant. The performance of the system was then investigated using test parameters including: power consumption, evaporator air temperature (pull-down time), to attain the specified International Standard Organisation (ISO) requirement for standard evaporator air temperature with small refrigerator size. Results showed improved pull down time and steady state evaporator air temperatures for the nano-lubricant based LPG. Improvement of about 11.79% in coefficient of performance (COP) was obtained with Al 2 O 3 -lubricant based LPG at 40g charge on the refrigerator system, while reduction of about 2.08% and 4.41% in COP were observed at 60 and 80 g charge of LPG based on Al 2 O 3 -lubricant respectively. Furthermore, reduction of about 13.4% and 19.53% in the power consumption of the system were observed at 40 and 60g charges of Al 2 O 3 -lubricant based LPG, whereas at 80 g, an increase of about 1.28% was recorded. Using Al 2 O 3 -LPG nano-refrigerant in domestic refrigerators is economical  and also a better alternative to pure LPG.

Abstract Heat recovery is one of the measures proposed for the appropriate use of ammonia in tropical countries. This article analyzes a heat recovery system installed in an industrial refrigeration plant.  B ased on comparative readings of operating parameters of the installation, determined the effectiveness of the heat exchange, the increase in the efficiency of the refrigeration system, as well as the fuel saved by heating water in the industry. The results obtained reported that the thermal design based on heat exchange in annular spaces allows a significant saving of resources and a high rate of thermal utilization.

Abstract This work presents the results of the continuity of the research process carried out in the Energy Studies Center belonging to the Faculty of Technical Sciences of the University of Matanzas, which involves the establishment of a dimensionless model to determine the average condensation heat transfer coefficient of Air Coleed Condenser (ACC) systems in straight and inclined tubes. The research consists in obtaining in an analytical way the solution of the differential equation of the velocity profile, considering that condensation is of pellicular type, finally the empirical condition of Roshenow is combined with the theoretical solution to generate a numerical expression that allows obtaining with a 15.2% of deviation in 2,192 tests, a value of the average coefficient of heat transfer by condensation very similar to the one obtained with the use of the most referenced model in the consulted literature, the empirical model of Chato.