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Improving the thermal performance of ventilation radiators: The role of internal convection fins
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.ORCID iD: 0000-0003-1882-3833
2011 (English)In: International journal of thermal sciences, ISSN 1290-0729, Vol. 50, no 2, 115-123 p.Article in journal (Refereed) Published
Abstract [en]

This paper deals with heat output optimization of a ventilation radiator by varying the distribution of vertical longitudinal convection fins. A ventilation radiator, which combines ventilation air supply and heat emission to the room, has a higher driving force on air in between the radiator panels compared to traditional radiators and can for this reason have more heat transferring surfaces to improve thermal efficiency. Improving the thermal efficiency means a lower water temperature is required for heating and energy can be saved in production and distribution of heat in systems with heat pumps, district heating or similar. The investigation was made using Computational Fluid Dynamics (CFD) simulations while analytical calculations were used for verification of different flow and heat transfer mechanisms. Results showed that heat transfer can be increased in the section where ventilation air is brought into the room by slightly changing the geometry of the fins, decreasing the fin to fin distance and cutting off a middle section of the fin array. This change in internal design could mean considerable increase in thermal efficiency for the ventilation radiator as a whole.

Place, publisher, year, edition, pages
2011. Vol. 50, no 2, 115-123 p.
Keyword [en]
Ventilation radiator, Convection fins, CFD simulation, Exhaust ventilation, Thermal comfort, Energy consumption, Low-temperature heating
National Category
Other Civil Engineering
URN: urn:nbn:se:kth:diva-30542DOI: 10.1016/j.ijthermalsci.2010.10.011ISI: 000286082300001ScopusID: 2-s2.0-78649639757OAI: diva2:401671
QC 20110303Available from: 2011-03-03 Created: 2011-02-28 Last updated: 2011-03-29Bibliographically approved
In thesis
1. Potential of Ventilation Radiators: Performance evaluation by numerical, analytical and experimental means
Open this publication in new window or tab >>Potential of Ventilation Radiators: Performance evaluation by numerical, analytical and experimental means
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy consumption for heating and ventilation of buildings is still in 2011considered far too high, but there are many ways to save energy and construct lowenergy buildings that have not been fully utilised. This doctoral thesis has focused onone of these - low temperature heating systems. Particular attention has been given tothe ventilation radiator adapted for exhaust-ventilated buildings because of itspotential as a low energy consuming, easily-operated, environmentally-friendlysystem that might also ensure occupant health and well-being.

Investigations were based on Computational Fluid Dynamics (CFD) simulations andanalytical calculations, with laboratory experiments used for validation.

Main conclusions:

  • Low and very low temperature heating systems, such as floor heating, in general createan indoor climate with low air speeds and low temperature differences in the room, whichis beneficial for thermal comfort. A typical disadvantage, however, was found to beweakness in counteracting cold down-flow from ventilation air supply units in exhaustventilatedbuildings.
  • with ventilation radiators, unlike most other low temperature systems, it was found thatthe risk of cold draught could be reduced while still maintaining a high ventilation rateeven in cold northern European winters.
  • ventilation radiators were found to be more thermally efficient than traditional radiators.
  • design of ventilation radiators could be further modified for improved thermal efficiency.
  • at an outdoor temperature of -15 °C the most efficient models were able to give doublethe heat output of traditional radiators. Also, by substituting the most efficient ventilationradiators for traditional radiators operating at 55 °C supply water temperature, it wasfound that supply water temperature could be reduced to 35 °C while heat outputremained the same and comfort criteria were met.
  • lowering the supply water temperature by 20 °C (as described above) could givecombined energy savings for heating and ventilation of 14-30 % in a system utilising aheat pump.
  • supply water temperatures as low as 35 °C could increase potential for utilising lowtemperature heat sources such as sun-, ground-, water- or waste-heat. This would beparticularly relevant to new-built “green” energy-efficient buildings, but severaladvantages may apply to retrofit applications as well.
  • Successful application of ventilation radiators requires understanding of relevant buildingfactors, and the appropriate number, positioning and size of radiators for best effect.Evaluation studies must be made at the level of the building as a whole, not just for theheating-ventilation system.

This work demonstrated that increased use of well-designed ventilation radiatorarrangements can help to meet regulations issued in 2008 by the Swedish Departmentof Housing (Boverket BBR 16) and goals set in the Energy Performance of BuildingsDirective (EPBD) in the same year.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 63 p.
Ventilation radiator, thermal comfort, exhaust ventilation, CFD, energy saving, convection fin, low temperature heating
National Category
Building Technologies
urn:nbn:se:kth:diva-31813 (URN)978-91-7415-940-0 (ISBN)
Public defence
2011-04-18, F3 (Flodis), Lindstedtsvägen 26,, 114 28 Stockholm, 16:12 (English)
STEM Projektnummer:30326-1 Energieffektiva lågtemperatursystem i byggnader
QC 20110328Available from: 2011-03-29 Created: 2011-03-25 Last updated: 2011-04-05Bibliographically approved

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