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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.
Nomenclature
| Acronyms | ||
| BR | = | baseboard radiator |
| CR | = | conventional radiator |
| DHW | = | domestic hot water |
| Hradiator | = | height of radiator |
| HP | = | heat pump |
| Lradiator | = | length of radiator, m |
| LTH | = | low-temperature heating |
| Type 11 | = | hydronic radiator with one panels and a single convector plate |
| Type 21 | = | hydronic radiator with two panels and a single convector plates |
| Type 22 | = | hydronic radiator with two panels and two convector plates |
| Ex | = | specific exergy, W/m2 |
| = | hydronic mass flow in the radiators, kg/s | |
| cp, water | = | Specific heat capacity of water (as a function of mean water temperature), J/(Kg °C) |
| Tsupply | = | supply water temperature, Kelvin |
| Treturn | = | return water temperature, Kelvin |
| Treference | = | reference temperature (average outdoor temperature in this study), Kelvin |
| Qdemand | = | Heating demand of the building, W |
| θsupply | = | supply temperature, °C |
| θreturn | = | return temperature, °C |
| q | = | specific heat output of baseboard radiator, W/m |
| H | = | height of baseboard radiator, m |
| Δθ | = | excess temperature (mean temperature difference between radiator and room air), °C |
| Φpanels | = | Specific power from panels, W/m2 |
| Φfins | = | specific power from fins, W/m2 |
| P radiator | = | power of radiator, W |
| (A/V)radiator | = | area to volume ratio of a radiator (compactness), m2/m3 |
Acknowledgments
The authors would like to acknowledge the building owners and manufacturing firms that contributed valuable information and empirical documents for this project.
Funding
The authors are grateful to Formas in Nordic Built, Nordic Innovation, SBUF (Swedish Construction Industry Development) and the Swedish Energy Agency for providing financial support.
Additional information
Notes on contributors
Qian Wang
Qian Wang, PhD, is a Researcher. Adnan Ploskić, PhD, is a Researcher. Sture Holmberg is a Professor.
Adnan Ploskić
Qian Wang, PhD, is a Researcher. Adnan Ploskić, PhD, is a Researcher. Sture Holmberg is a Professor.
Sture Holmberg
Qian Wang, PhD, is a Researcher. Adnan Ploskić, PhD, is a Researcher. Sture Holmberg is a Professor.