VOL. 12, NO. 21, NOVEMBER 2017 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences ©2006-2017 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 6164 MODELLING AND ANALYSIS OF WATER HEATING USING RECOVERED WASTE HEAT FROM HOT FLUE GASES OF CHULHA Saravanna J. Y., Rahul Kantamnen, Nizvan Fasil, Seralathan Sivamani, Hariram V., Micha Premkumar T. and Mohan T. Department of Mechanical Engineering, School of Mechanical Sciences, Hindustan Institute of Technology and Science Padur, Tamil Nadu, India E-Mail: siva.seralathan@gmail.com ABSTRACT The study on heating water for domestic applications by using low grade waste heat recovered from the exhaust flue gas of Chulha is analyzed theoretically as well as experimentally. Two different material combinations are considered for the hot fluid domain (shell) and cold fluid domain (pipe). Theoretical analysis is carried out to estimate the time required to heat the water from its room temperature to 75 o C by transfer of heat energy. Numerical investigations are carried out to validate the findings obtained theoretically. Time required in raising the water temperature from its room temperature of 27 o C to 75 o C is 8 hr for a stainless steel shell - stainless steel pipe combination WHRS. This heating time is reduced by around 4 hr using stainless steel shell - copper pipe combination WHRS. Using biogas as a fuel for the Chulha, the cost of heating the water is reduced to 1.90 Paisa per kg and the cost saved per year on biogas by a typical Indian household is estimated to be 3580 in Indian rupees. Numerical simulation showed a good agreement between the simulation results and theoretical analysis. This WHRS can be used to recover the low grade waste heat released through chimney exhaust flue gas by domestic applications like fireplace, domestic water heating boiler thereby reducing the conventional energy consumption as well as minimizing the environmental degradation. Keywords: waste heat recovery, flue gas, water, heat transfer, chulha, CFD. INTRODUCTION Chulha is a hindi word spoken widely in India which means cook stove or fireplace. Cook stoves that uses biomass such as dried animal dung cake, agricultural waste, saw dust cake and firewood as a fuel are known as biomass stoves. These biomass stoves cater to the cooking needs of nearly seventy three percent of India's 1.25 billion populations. The fixed Chulha with smoke removal facility is referred to as smokeless Chulha and these are modified versions of the traditional Chulhas. These are designed to save fuel consumption through better combustion by shielding the fire with provision for air supply and removal of exhaust flue gases and smoke through chimney. The thermal efficiency of these Chulhas are high with values around 25% to 35% and also consumes 40% to 60% lesser fuel than traditional Chulhas. These types of Chulhas are promoted actively by MNRES, Government of India under National Biomass Cookstoves Programme, KVIC, OREDA, various State Government agencies as well as by non-governmental organizations in the context of concerns over health, climate change and energy security [1]. Fireplace is also used for heating the room. These are a structure made up of metal, stone or brick. Modern fireplaces have variable heat efficiency based on their superiority of the design. Figure-1 shows the typical Chulha / fireplace used in India. In a developing country like India, the demand for energy is growing day by day. With growing climatic concerns across the globe along with soaring energy costs, innovative, cost effective and accessible solutions with the aim in reducing energy consumption and improving its efficiency has to be developed. Waste heat recovery system (WHRS) is one such solution to capture the low grade waste heat carried away by the fluids such as gases and fluids from the systems like boiler, fireplace, Chulha, cooking stove, internal combustion engines, etc. Otherwise, these low grade waste heat energy would have been lost to the surroundings without any productive use raising only the environmental concerns [2-7]. Apart from using electrical heaters, in rural India, fossil fuel is the most predominant energy source used for heating the water for domestic purposes. The environmental issues and its drawbacks can be solved by using WHRS for these purposes. It is understood that nearly 65% to 75% of the heat produced by the Chulha is lost up through the chimney. Therefore, innovative waste heat recovery systems are to be evolved in order to recover this waste heat from the flue gases of Chulha being sent to the atmosphere through chimney. Several studies were carried out theoretically, experimentally as well as numerically on recovering the low grade waste heat from the flue gases involving different industrial / domestic applications. Mahmoud Khaled et al. [5] experimentally investigated a WHRS by using the chimney exhaust gas for heating the water in the residential building. The heat input was varied and the gas flow rates through the pipes were noted. The temperatures at different locations of WHRS were measured. The results showed that the water temperature increased by 68 o C by one hour. This was due to the radiation and convection heat transfer of flue gases at the bottom side of WHRS which caused high heat transfer rate to the water.