• Energy Research

Solar air heating devices have been employed in a wide range of industrial and home applications for solar energy conversion and recovery. It is a useful technique for increasing the rate of heat transfer by artificially creating repetitive roughness on the absorbing surface in the form of semicircular ribs. A thermo-hydraulic performance analysis for a fully developed turbulent flow through rib-roughened solar air heater (SAH) is presented in this article by employing computational fluid dynamics. Both 2-dimensional geometrical modeling and numerical solutions were performed in the finite volume package ANSYS FLUENT. The renormalization-group (RNG) k-ε turbulence model was used, as it is suitable for low Reynolds number (Re) turbulent flows. A thermo-hydraulic performance analysis of an SAH was carried out for a ranging Re, 3800–18,000 (6 sets); relative roughness pitch (RRP), 5–25 (12 sets); relative roughness height (RRH), 0.03–0.06 (3 sets); and heat flux, 1000 W/m2. The numerical analysis revealed that with an RRP of 5 and an RRH of 0.06, the roughened duct produces the highest augmentation in average Nur in the order of 2.76 times that of a plain duct at an Re of 18,000. With an RRP = 10 and RRH = 0.06, the roughened duct was found to provide the most optimum thermo-hydraulic performance parameter (THPP). The THPP was determined to have a maximum value of 1.98 when the Re is equal to 15,000. It was found that semi-circular ribs which have a rib pitch = 20 mm and a rib height = 2 mm can be applied in an SAH to enhance heat transfer.

Abstract This research work is focused on the regeneration of used lubricating oils which are simply thrown out to the environment. It is evident from the past research outcome that there is an acute shortage of petroleum oils and regeneration of fuels from used lubricating oils can be potential substitute of fossil fuels. But due to some drawback such as higher viscosity and density it cannot be used as a single fuel. In this regard the distillation of used lubricating oil has been carried out with. Further, this distilled used lubricating oil (DULO) was blended in different proportions with Jatropha biodiesel (JB) which has excess oxygen by about 10%. The aim of the current study is to investigate the performance and emission characteristics of a DI diesel engine run on these blends and comparison with base fuel diesel. The behavior of the engine was evaluated in terms of brake thermal efficiency, brake specific fuel consumption, exhaust gas temperature, carbon monoxide emission, hydrocarbon, nitric oxide emission and smoke opacity. The test result revealed that, the behaviour of the engine run on the JBDULO20 (i.e. 80% JB and 20% DULO) blend was better than other blends considered in the study.