An emissions-based fuel mass loss measurement for wood-fired hydronic heaters

Regulations that standardize the evaluation of wood-fired hydronic heaters (WHH) use mass loss as an important variable to compute energy input. Generally, mass loss is measured by placing the entire appliance on a scale and measuring the system mass change. This method suffers from resolution problems since the change in mass of the fuel during a run is much smaller than the total mass of the empty appliance. This experimental study provides a higher-resolution measurement of mass loss by measuring the concentration of flue gas emissions in addition to the flow rate of air into the WHH. Three fuels (red oak, cherry, and pine) are independently tested, and measurements of the emissions are made using both a Testo gas analyzer and tunable diode laser absorption spectroscopy. A simultaneous direct measurement of the mass loss is performed using a hanging basket inside the WHH, and the average percent difference between the two methods are 5.4% for red oak, 5.4% for cherry, and 8% for pine, indicating that the emissions-based method is suitable for mass loss measurements.