Numerical Estimation of Heat Recovery within a Distributed Incinerator Using Water and Hydrocarbons as Working Fluids

The potential of a cogeneration system combined with a small combustion furnace was investigated in this study. The heat transfer between the exhaust gas and working fluid flowing in a spiral tube heat exchanger was estimated numerically and the amount of vapor generated was predicted. The combustion chamber had a 0.49 m3 inside volume with a chimney height of 2.5 m and an inner diameter of 0.28 m. A uniform gas side temperature condition that was referenced from the results of a preliminary experiment and a computational fluid dynamics simulation were adopted to simplify calculations and clarify the effects of working fluids. The amounts of heat recovery when utilizing water and other types of working fluids (Pentane, Butane) were compared. The most effective tube length considering pressure drop and phase change was also predicted. Isentropic theoretical thermal efficiency and T-s diagrams are analyzed to evaluate the vapor-power conversion rate using waste heat. As a result, a potential the heat recovery rate of approximately 100 kW at a 150 kg/h mass flow rate is expected.