The briquette porosity is a quality characteristic known to be important for combustion analysis, heat and mass transfer processes during combustion stages, determination of effective thermal conductivity or other related properties. This paper describes a method to quantify the briquette porosity by some surface roughness parameters that can be useful for alternative, inexpensive and at hand evaluations. Porosity of briquettes manufactured with a hydraulic press from waste wood from secondary processing was calculated with three methods suggested in the literature for wood; of these, one was adapted here for a wet porosity model (called "general relation") proposed for wood briquettes. Briquettes density was obtained by using two stereometric methods and a liquid displacement method. Correlations were examined between porosity, surface roughness parameters and density of briquettes. Very strong correlations with surface roughness were identified for porosity calculated with all three methods, when density was measured by one of the stereometric methods. These correlations can serve as a method to indirect evaluation of the briquettes porosity by measuring the surface roughness.
Statement of noveltyPorosity is important for the analysis of briquettes combustion; therefore it would be interesting to see if this property can be indirectly evaluated by another method, such as by measuring some roughness parameters of the briquette surface in connection with briquette density. Based on previous studies carried out on wood, it can be assumed that both porosity and roughness parameters are properties depending on density. Porosity and density were determined in the present study by using three different methods. The experimental data contribute to the existing literature on briquettes properties by adding the surface roughness. The novelty of the present paper consists in extending the applicability of the porosity models originally developed for wood, to the wood briquettes. To the best knowledge of the present authors, the wet porosity model applied to briquettes has not been reported before.