Research On The Application Of Heat Pump Technology In Condensing Wall Mounted Gas Boiler

The exit flue gas temperature of conventional wall mounted boiler is above120℃.Great amount of sensible heat and latent heat of water vapor is contained in the flue gas,can be recovered by some methods, which will lead to a significant improvement of theboiler thermal efficiency. For the sake of its energy saving and environmental protection,the condensation technology of wall mounted boiler is gaining more and more attention inrecent years, which becomes a new development direction of wall mounted boiler heatingindustry. In this dissertation, according to the characteristics of wall mounted boilerexhaust and heat pump operation, a condensing heat recovery system by heat pump isproposed, and is compared with the waste heat of flue gas recovery system byconventional heat exchanger. Also, the energy saving and economy of the two systems isanalyzed.This thesis takes wall mounted boiler heating as the object. First of all, the methodsof flue gas heat recovering have been reviewed, and the shortcomings about the wallmounted boiler heating are analyzed. For the condensing heat of flue gas recovery systemby heat pump, its organization forms are discussed, including the compression heat pumpand the absorption heat pump.Secondly, the characteristics of natural gas combustion and the calculation methodsof the exit heat loss are analyzed. Therefore, curves how the exit gas temperature and airrelative humidity affect the condensing heat of flue gas recovery system by heat pumpsystem and waste heat of flue gas recovery system by conventional heat exchanger havebeen obtained. Lower the exit gas temperature, higher the system efficiency. And higherthe air relative humidity, higher the efficiency of the combining heat pump system.Compared to the two systems, condensing heat of flue gas recovery system by heat pumpis more energy efficient.Finally, from the perspective of investment and income, the static payback period andcumulative life cycle cost savings of the two systems under different exhaust temperaturesis analyzed on the basis of the energy-saving analysis. From the point view of the paybackperiod, the optimal exhaust gas temperature is100℃for the waste heat of flue gas recovery system by conventional heat exchanger, whose payback period is0.71years.And the optimal exhaust gas temperature is35℃for the condensing heat of flue gasrecovery system by heat pump, whose payback period is1.82years. In the view ofcumulative cost savings, for both systems, lower the exit gas temperature, higher thecumulative cost savings, but the rate of increase slows.