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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 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 75oC 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 27oC to 75oC 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.