A note on calculation of efficiency and emissions from wood and wood pellet stoves

[摘要] In recent years, national laws and international regulations have introduced strict limits on efficiency and emissions from woody biomass appliances to promote the diffusion of models characterized by low emissions and high efficiency. The evaluation of efficiency and emissions is made during the certification process which consists in standardized tests. Standards prescribe the procedures to be followed during tests and the relations to be used to determine the mean value of efficiency and emissions. As a matter of fact these values are calculated using flue gas temperature and composition averaged over the whole test period, lasting from 1 to 6 hours. Typically, in wood appliances the fuel burning rate is not constant and this leads to a considerable variation in time of composition and flow rate of the flue gas. In this paper we show that this fact may cause significant differences between emission values calculated according to standards and those obtained integrating over the test period the instantaneous mass and energy balances. In addition, we propose some approximated relations and a method for wood stoves which supply more accurate results than those calculated according to standards. These relations can be easily implemented in a computer controlled data acquisition systems.

[发布机构] Ravelli S.r.l., Via Kupfer 31, Palazzolo sull'Oglio, BS; 25036, Italy^1;Dipartimento di Ingegneria Meccanica Ed Industrials, Universitá Degli Studi di Brescia, via Branze 38, Brescia; 25123, Italy^2

[效力级别] 力学 [学科分类] 力学，机械学

[关键词] Certification process;Data acquisition system;Flue gas temperatures;Fuel burning rate;International regulations;Mass and energy balance;Standardized tests;Wood pellet stove