DEVELOPMENT OF A NEW TEST METHOD OF DEFINING A REAL LIFE THERMAL HEAT OUTPUT OF FIREWOOD STOVES

摘要

The market for firewood stoves with low thermal heat output is increasing due to new technologies forrnheat provision in buildings of low heating demands. However, definition of thermal heat output according to therncurrent standard type testing method (EN 13240) does not sufficiently respect real life combustion conditions, forrninstance the cold conditions at beginning of heating operation as well as the heat storage capacity of the stove. Withinrnthe project “Ofenprüfung 2020” (coordinated by BIOENERGY 2020+ GmbH) a new testing method was developedrnin order to reflect real life conditions. Thereby a method for a Real Life Thermal Heat Output Range was defined,rnwhich includes a maximum, mean and minimum thermal heat output. In the present study the objective is to evaluaternthis approach and consequently to define the most appropriate method for testing a Real Life Thermal Heat Output.rnHence, the net heat energy release of a stove was measured using a calorimeter room. Then the approach of Real LifernThermal Heat Output Range was applied. The results show that for the particular stove tested 60 % of the producedrnheat is still dissipated after the last batch in the cooling down phase. Therefore, especially the mean and minimumrnthermal heat output would be appropriate values for estimating the Real Life Thermal Heat Output. The maximumrnthermal heat output does not respect the cooling down phase and therefore overestimates the overall performance ofrnthe stove. The minimum thermal heat output was found to be 60.2 % lower than the maximum thermal heat output inrnaverage. User behavior surveys of “Ofenprüfung 2020” showed that in most cases only three batches are conducted.rnHence, the minimum THO is most suitable for reflecting real life operations. Finally, the new approach seems to be arnvalid method for defining a Real Life Thermal Heat Output since the heat storage capacity of a stove significantlyrninfluences the thermal heat release. However, for better evaluation more tests with stoves providing different heatrnstorage capacities have to be done.