Thermodynamic analysis of heat pump heating system based on flue gas waste heat recovery

Abstract A lot of waste heat has not been recycled from exhaust gas of gas-fired condensing boilers. By enhancing boiler’s thermal efficiency, condensation latent and heat sensible heat should be deeply utilized. This article uses a heat pump to recover the waste heat from boiler flue gas to improve the heating efficiency of the unit. Taking an example of boiler unit, to illustrate the function of the thermodynamic capability, this article create a new heating system by installing a flue gas condenser and a low-temperature economizer, and a thermodynamic model. The experimental results show that if gas is cooling from 130° C to90° C and coefficient of performance( C op ) is set by 1.746, by setting a low-temperature economizer, 20.87 MW can be obtained from waste heat, which decrease water consumption of desulfurization tower 28.792 t / h ; due to that the heat pump use the condenser, waste heat can be recovered to 10.10 MW and condensed water can be recovered to13.654 t / h . When heat network’s return water increases, C op decreases, but efficiency will increases in network; when outlet water in condenser increases, C op and network efficiency decrease, but heat pump system increases in efficiency.