International Journal of Emerging Technology and Advanced Engineering Volume 3, Special Issue 3: ICERTSD 2013, Feb 2013, pages 126-130 An ISO 9001:2008 certified Int. Journal, ISSN 2250-2459, available online at www.ijetae.com Presented at International Conference on Energy Resources and Technologies for Sustainable Development, 07-09 February 2013, Howrah, India. ICERTSD2013-XX-XXX © IJETAE2013 Performance Tests on Medium-Scale Porous Radiant Burners for LPG Cooking Applications N. K. Mishra, P. Muthukumar*, Subhash C. Mishra Department of Mechanical Engineering Indian Institute of Technology Guwahati, Guwahati – 781039. *Email: pmkumar@iitg.ernet.in ABSTRACT The principle of operation of the porous radiant burner (PRB) is based on porous medium combustion (PMC) in which the combustion of fuel and air mixture takes place inside a matrix of open cavities in the presence of an inert solid surface. Since the porous matrix has high thermal conductivity and high emissivity, the contributions of conduction and radiation in the PMC are significant. In the present paper, performance tests on PRB used for medium - scale cooking applications of capacity 5-10 kW are presented. The PRB chosen for the study is SiC-based porous burner of diameter 120 mm and 90% porosity. Liquefied petroleum gas (LPG) is used as a fuel. Effects of different heat inputs in the range of 5 - 10 kW on the thermal efficiency and emission levels of PRB are investigated. For the conventional LPG burner of 5-10 kW capacity, the measured value of thermal efficiencies is in the range of 30-40%, and the CO and NOx are in the range of 350-1145 ppm and 40 - 109 ppm, respectively. These emissions levels are well above the world health organization standards. Within range of parameters tested, the SiC- based PRB yields the maximum thermal efficiency of about 50%, which is about 25 % higher than the conventional stoves. The measured emission levels are also much lower than the conventional stoves. Keywords: Combustion, LPG cooking stove, Porous radiant burner, Energy saving 1. INTRODUCTION The conventional combustion devices are characterized by a free flame, where the convection is the only mode of heat transfer. Thus, the poor heat transport makes the conventional combustion devices less efficient and result in increased CO and NOx emissions. The LPG cooking gas burner is one such device that goes well with this category of high emission levels and low thermal efficiency. In order to overcome these difficulties of the free flame combustion, another means of combustion was discovered known as porous medium combustion (PMC).The principle of operation of the porous radiant burner (PRB) is based on PMC. PMC offers high power density, high power dynamic range and very low NO and CO emissions, owing to the high levels of heat capacity, conductivity and emissivity of the solid matrix, compared to a conventional combustion devices. The improvement in the living standard of the mankind and the rapid industrial growth demand the abundant use of fossil energy which leads to the diminution of fossil fuel resources and also cause environmental pollution. The issues related to the environmental pollution can be minimized by improving the efficiency of the combustion devices. The thermal efficiencies of the current LPG commercial stoves (5-10 kW thermal load range) available in the Indian market are in the range of 30 - 40% and at the same time the CO (350 - 1145 ppm) and NO x (40 - 109 ppm) emissions levels are above the world health organization standards. Pantangi et al. [1] implemented the idea of the PMC in a liquefied petroleum gas (LPG) cooking stove for the improvement in thermal efficiency. They investigated the efficiency, emission and energy cost for the conventional domestic LPG cooking stoves with and without the usage of various porous media likes metal balls, pebbles and metal chips. With the usage of porous media, the maximum thermal efficiency of the stove was found to be 73% which was 8% higher than conventional burner. They reported energy saving of about 10%. With LPG as a fuel, Dongbin et al. [2] investigated the combustion phenomenon in a porous ceramic stove doped with rare earth elements. The increased emissivity due to the addition of rare earth elements to porous ceramic was attributed to the special valence shell of rare earth elements. Akbari et al. [3] carried out a study to investigate the lean flammability limits of the burner and the unstable flash-back/blow-out phenomena. Flame stability showed that the inlet firing rate and matrix porosity were two main parameters which influence the lean flammability limit of a porous burner. Mujeebu et al. [4]