Condensing boiler was first applied in the western developed countries.The first condensing boiler in the world appea red in Nether［andsin the 1970s. Benefiting from the energy saving and environmentalprotection which are highlighted in its practical use, condensing boilerhas gotten ra pid deveiopment in North America and Eu rope. At present,the penetration rate of condensing boilers is70% in Netherlands andSwitzerland, 30% in Germany, 30% in Austria and 25% in British.However, condensing boilers have the fastest growing and the highestpenetration rate in some Asia countries such as South Korea and China.Along with the economic development of our country, the improvementof energy consumption and more and more attention to the problemsof environmental protection, the utitization of high efficiency energysaving technology and clean energy is pa rticu［arly important. Th roughthe anaiysis of the heat loss of boilers, Yuntian Boiler deeply studieson the relationship between the boiler exhaust temperatu re and thethermal efficiency of the boiler, and developsWNS series condensingfuel oi［ (gas) boilers. The relation curves between the heat Ioss ofthe boiler exhaust and the exhaust temperatu re, the coefficient ofthe excess air and air humidity and temperature for combustion areobtained t:hrough experiments. The thermal efficiency of boiiers isimproved th rough reasonable decorations of heating su rface, theoptimization of the back pressure of boilers, making full use of theexplicit heat in high temperatu re flue gas and iatent heat of vaporizationof water vapor in flue gas to provide water for the heating boiler or gas
for the combustion.