Härdens utformning och dess påverkan på rökkanalens dimensionering

Abstract

During a literature review on open fireplaces and their technical characteristics, a gap in the existing literature was identified regarding the design of the hearth and its potential influence on the flue area required to prevent smoke spillage during operation. This study investigates whether the required flue area can be reduced by modifying the hearth geometry, specifically by angling the side walls outward from the back wall toward the fireplace opening. An experimental open fireplace was constructed in which a damper, with an opening corresponding to the full cross-sectional area of the flue, was installed at the flue outlet. During firing experiments, the damper was gradually closed to determine the point at which smoke began to enter the room. At this point, the damper opening was measured and used to calculate the effective flue area at the onset of smoke spillage. Three different hearth configurations were tested. The results showed that the flue area could be reduced by up to 70% during combustion in configuration A, 80% in configuration B, and 85% in configuration C before smoke spillage occurred. However, the reduction of the flue area was only possible during ongoing combustion. During ignition, the fireplace required the damper to remain fully open—regardless of hearth configuration—to prevent smoke from entering the room.