Rotary regenerative heat exchangers or rotary regenerators are used for various heat recovery applications in order to fulfil the energy requirements. Rotary air preheater is a rotary regenerative heat exchanger which is widely used in thermal power plants to recover heat energy from exhaust flue gases. Several numerical works are being carried out to improve the performance and reduce the cost of the rotary air preheater. However, the accurate modelling of the internal structure of the matrix demands a lot of CPU power and is a big challenge for researchers. To overcome this problem, the rotary matrix of the preheater can be modelled using a porous media approach. But a thorough investigation is required to evaluate its performance. In this work, rotary air preheater simulations were carried out by applying a porous media approach. The effects of different operating conditions, such as speed of rotor, the mass flow rate of incoming fluids, material of matrix, and inlet temperature of hot fluid on the performance of rotary air preheater were investigated. Simulation results were validated with the results obtained from the experimentation performed in-house. The effect of fluid flow rates on pressure drop was also studied. It has been observed that the rotational speed of the rotor significantly affects the performance of the preheater, while the inlet temperature of hot fluid has a negligible effect on performance.
Semisolid metal (SSM) casting or thixoforming is a technique used to produce near net-shaped products. The process is used with non-ferrous metals, such as aluminium, copper and magnesium. Furthermore, it has advantage over conventional casting due to suppression of dendrite growth. In the present work, the semisolid casting of A319 aluminium alloy has been carried out by using an inclined plate with different melt pouring temperatures (620, 625, 630 and 635 °C). A319 alloy melt undergoes partial solidification when it flows down on an inclined plate. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed or fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. The prepared castings were checked for their mechanical properties like tensile, hardness and impact strength. The results obtained were compared with that of alloy prepared from conventional sand casting. It was found that there is an enhancement in mechanical properties due to shearing off columnar dendrites.
Methyl ester as biodiesel is one clean energy sources for fueling diesel engines. The adverse effects of the conventional fossil fuels and rise in fuel price have made researchers to carry out their researches on various sources of biodiesels. The process of producing biodiesel from vegetable oil is not so economical due to cost of the raw materials though there are reductions in emission gases from automobile exhaust. The cooking oil as waste is not eco-friendly and difficult to dispose. The same can be used as a part substitute to diesel to run internal combustion engine to economize the fuel cost, reduce environmental pollution, ameliorate the difficulties of unburnt cooking oil disposal. Recent study envisages an attempt to convert the waste cooking oil to fatty acid methyl ester (FAME) as a supplement to diesel. An internal combustion engine was run with different proportion by substituting with FAME acquired from cooking oil waste. The analyses of the noxious gases released have been conducted to find the concentration of noxious gasses by using Exhaust Gas Analyzer. The percentage of toxic gasses exhausted on running the internal combustion engines with extracted biodiesel at 10%, 20% and 30% mix were analyzed. The results revealed that the percentage of emitted gases like Hydrocarbon (HC), and Monoxide of Carbon (CO) were reduced and it was found optimum at a blend of 20% of biodiesel when added with 80% conventional diesel but need further work on it.
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