Performance Research On Combustion And Heat Transfer Of Wall Mounted Gas Boiler Under The Climate Condition Of Lhasa Area

Tibet autonomous region is belongs to the heating area. Due to the economic,energy and transportation and other limiting factors, Lhasa city has not been formedwith the scale of the heating facilities and reasonable and efficient way of heating. Andthere is no uniform heating development planning. In recent years, along with the partyand the state paying attention to the standard of living and the economic development,the Tibet autonomous region will launch city heating construction energetically bytaking Lhasa city as the pilot unit in the "Twelfth Five-Year Plan" period. Along withthe Tibet autonomous district heating project, large heating project will use awall-mounted gas boiler as heat source. But Lhasa is located in Qinghai-Tibet Platean,annual mean atmospheric pressure is equivalent to64%per cubic meter in plain area,the oxygen content in the air is only equivalent to62%to65.4%in the plain area, whichrestrict the promotion and use of the wall-mounted gas boiler in LhasaIn this paper the combustion and heat transfer performance of the wall-mountedgas boiler under the climatic condition of Lhasa area were studied, And chapter2,3,4and5are the main chapters.The second chapter introduces the system structure of the wall-mounted gas boiler.Analysis the combustion and heat transfer processes of the wall-mounted gas boilertheoretically. And analysis the impact on primary air rate, excess air coefficient,combustion temperature, combustion speed, pollutant emissions in flue gases, heattransfer coefficient due to low atmospheric pressure and low oxygen concentration inthe air.The third chapter selects two wall-mounted gas boilers which have the same brandand different thermal power. Performance test under the rated heat input condition andpart (30%) heat input are both taken in the plain area and Lhasa area. In rated heat inputcondition, the average heat output power of wall-mounted gas boiler which rated outputpower are18kW and28.1kW in three kinds of supply and return water temperature(80/60℃,55/45℃,50/40℃) in Lhasa climate condition were decreased by23.6%and27.3%, the average thermal efficiency were decreased by1.1%and3.2%; in part of theheat input conditions, the average heat output power were decreased by26.2%and31%,the average thermal efficiency were decreased by0.8%and0.7%. The difference ofthermal efficiency of wall-mounted gas boiler under the same weather and different supply and return water temperature conditions is very small. This explained the Lhasaarea climate is mainly through the influence of combustion chamber gas combustionprocess which affects the performance of wall-mounted gas boiler. As the fuel gas andthe air mass flow rate change, the influence on the combustion chamber temperature forLhasa climate conditions is reduced, thereby reducing the discharged into theatmosphere and the content of NO in flue gas.The fourth chapter analysis the gas burning process in combustion chamber ofwall-mounted gas boiler using the fluid dynamics Fluent numerical calculationsoftware.The average temperature, maximum temperature and the outlet flue gastemperature of the combustion chamber of wall-mounted gas boiler under Lhasa climatewere obviously decreased, and the thermal power of wall-mounted gas boiler effectshould be significantly larger than the thermal power unit, and the combustion chamberof a gas burning space required no significant impact.The fifth chapter takes a test which increase gas quality flow method by increasingpressure of the gas entrance. Test results show that the thermal efficiency of the meetthe basic requirements of the premise, can make the rated thermal output reachednameplate value, but a plain flue gas discharge (CO) can increase somewhat. Theadjustment method is feasible on the whole.