Simulation of a heat pump system for total heat recovery from flue gas

• An OAHP system is analyzed to improve heat recovery from natural gas flue gas.
• OAHP system models are presented and analyzed.
• The key factors influencing the OAHP systems are analyzed.
• The OAHP system is most efficient for most cases compared with other systems.
• The OAHP system is more economic than other systems.

This paper introduces an approach of using an open-cycle absorption heat pump (OAHP) for recovering waste heat from the flue gas of a gas boiler with a system model. And equivalent energy efficiency is used to evaluate two other heat recovery systems that integrate an electric compression heat pump (EHP) or an absorption heat pump (AHP) with a boiler. The key factors influencing the systems are evaluated. The OAHP system efficiency is improved by 11% compared to the base case. And the OAHP system is more efficient than the AHP or the EHP systems, especially when the solution mass flow rate is only a little less than the cold water mass flow rate. The energy efficiency comparison is supplemented with a simplified economic analysis. The results indicate that the OAHP system is the best choice for the current prices of electricity and natural gas in Beijing.