Low-temperature heating in existing Swedish multi-family houses—An assessment of the significance of radiator design and geometry

Abstract

The current study evaluates the impacts of radiator designs and geometries. The aim was to map the thermal efficiency and performance differences of studied radiator types. A typical Swedish low-rise, multi-family house was selected to present the analysis. A Swedish climate was employed to evaluate the applicability. The on-site measurements, analytical model, and real-life performance data from radiator manufacturing were applied for the modeling work. Radiator Type 21 (1.2 × 0.4 m) showed the highest exergy efficiency; Type 11 (1.2 × 0.45 m), the lowest. There is no evidence that Type 22 (adding more convector plate) has a higher thermal efficiency than Type 21, from an engineering perspective, within the climate range of −20°C to 15°C. Baseboard radiators showed a 34% higher exergy performance than the most efficient conventional radiator, with the same surface area, at mean outdoor temperatures during an average heating season in Sweden (−1.3°C). The results also suggest that Type 21 would have higher efficiency than Type 11 during 50% time of the heating season, in severe climate conditions. In the climate of Stockholm, this efficiency advantage was 20%. For the mild climate, Type 11 and Type 21 performed almost the same over the entire heating season.