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Harpreet Singh ¹, Harpreet Singh ¹, S. S. Sehgal ¹

Affiliations
1 Mechanical Department, Chandigarh University, Gharuan, Mohali - 140413, Punjab, IN

Abstract

Objectives: The aim of present work is to find out the thermal performance of solid and perforated heat sink with various perforated designs (Rectangular, Circular and Slotted). Methods/Statistical Analysis: The CFD analysis was performed to investigate the thermal performance of different perforation design. The test has been conducted in a horizontal rectangular duct equipped with forced draft fan. The data was obtained by varying flow velocities of air from 2, 5 and 8m/sec and maintaining constant heat input 100 Watt taken over a period of time. Findings: In this computational analysis we calculate the Heat transfer coefficient, Reynolds number and Nusselt number and obtain the result. The results show the heat transfer coefficient is more in circular perforated fin as well as more Nusselt number as compared to slotted and rectangular Perforation. Application/Improvements: Electrical component, higher-power lasers, refrigerator, air condition, Computers etc.

Keywords

Air, Heat Source, Heat Sink, Wind Tunnel.

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A. Sharma ¹, S. S. Sehgal ², H. Sandhu ³

Affiliations
1 Thermal Engineering, Chandigarh University Gharuan – 140413, Punjab, IN
2 Mechanical Engineering, Chandigarh University Gharuan – 140413, Punjab, IN
3 Chemical Engineering, Chandigarh University Gharuan – 140413, Punjab, IN

Abstract

Objectives: Utilization and minimization of premature washout of active microbes from the bioreactor and providing better microbe-substrate contact through suitable modification in existing bioreactor models for enhancing biogas production. Methods / Statistical Analysis: A large bioreactor (15000ml) used as control was compared for gas production and pH with two sets3 smaller bioreactors each with capacity 1/3^rd of the larger one. One set of three bioreactors were arranged in parallel fashion and the other set was connected in series. This experiment was repeated twice keeping all the considerable aspects same. The gas production patterns obtained were quite similar thus their mean is presented in the results. Findings: Gas production both from the set up in series as well as parallel was found to be 11 to 15% higher in comparison to larger bioreactor used as control. Reactors in series were producing highest biogas during first 7 days but 8^th day onwards there was rapid decrement in production due to low pH of the leading tank in the series connection. On the other hand parallel set-up was stable throughout and its gas production pattern was although higher but similar to control. The subdivision method used here for the bioreactor design with arrangement of the sub units in series and parallel has enhanced biogas production, which has made good case for bioreactor optimization in terms of minimizing microbial loss and stabilization of influential parameters like pH, organic loading rate, hydraulic retention time etc. through proper combinations of series-parallel arrangements. Application / Improvements: If series parallel combination is properly chosen as per feed substrate, such a design can properly utilize washed out microbes and undigested organic material in the effluent thus increasing biogas yield.

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Daniel Mulugeta Soma ¹, Saurabh Chhabra ¹, S. S. Sehgal ¹

Affiliations
1 Department of Mechanical Engineering, Chandigarh University, Mohali – 140413, Punjab, IN

Abstract

Background/Objectives: Porous medium burners are presented as an alternative technology in order to improve the thermal efficiency and emission characteristics of domestic cooking stoves. In this paper CFD analysis of a 90mm top diameter porous medium burner (PMB) which is made of two different sections, namely pre-heating and combustion section is considered. Methods/Statistical Analysis: Silicon carbide foam having a thickness of 25mm and 10ppi porosity in the combustion section and 6.5mm diameter steel balls in pre-heating section was used. The variation in the model was due to different measurement values of centre pipe length and fluid inlet diameter. The centre pipe length was 27.5mm, 55mm, 110mm and 220mm each, whereas the fluid inlet diameter was 15mm, 20mm and 25mm. The mass flow rate of air and fuel were 0.05kg/m³ and 0.009kg/m³ with temperature of air 300k and fuel 285k respectively. Wall temperature was taken as 300k and 5% turbulence intensity at all inlet and outlet. Air and LPG are used as oxidizer and Fuel. Findings: ANSYS Fluent was used to simulate the mixing and reaction of Fuel and Oxidizer through a two layer porous burner. The burner was evaluated considering turbulence model and Species Model. Total six 3D models are considered for simulation and results are taken as Contours of Temperature. It was found that porous burner having centre pipe diameter of 27.5mm and 25mm fluid inlet diameter gives the maximum surface temperature of 2250k. Increasing the centre pipe length by half (27.5mm – 55mm) caused a slight drop of surface temperature which is almost negligible. Furthermore, from the temperature contours, it was observed that increasing the center pipe length above 55mm reduced the surface temperature by 300k. From the four models considered the minimum surface temperature was 2087k, for porous burner model having 110mm centre pipe length and 25mm fluid inlet diameter. Based on the insight obtained from the CFD simulation, increasing the center pipe length above the range of 27mm to 55mm, might increase the chance of flashback. Considering the fluid inlet diameter, increasing the fluid inlet diameter by 5mm caused an increase of surface temperature by about 300k. Improvements/Applications: Porous medium combustion has been center of interest amongst researchers due to its higher thermal efficiencies and lower emission of Nox and CO gases. They are employing a porous media for various applications, such as: IC engines, heat exchangers, gas turbine and propulsion, hydrogen production and cooking applications.

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