International Scientific Journal

Thermal Science - Online First

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Experimental analysis of radiators' thermal output for heat accounting

Radiators represent the most spread heating body (installed since late 1800s) and in the last decades different radiators typologies have been proposed on the market, characterized by different materials, sizes, shapes, etc. Recent EU Directive on energy efficiency (EED) has set the obligation to install individual meters for space heating in building served by a central heating source. To this aim, when direct heat meters are not technically feasible, indirect systems like heat cost allocators are applied on each radiator in a dwelling and the knowledge of single radiators' thermal output is essential for an accurate and fair heat cost sharing. The EN 442:2014 describes a method for radiators' thermal output measurement whose expanded uncertainty is lower than 1% in reference laboratory conditions. However, radiators' thermal output is strongly dependent on installation and boundary conditions. Thus, to get radiators' thermal output at operating conditions "characteristic equations" are available but, unfortunately, they do not include any possible actual operating condition among which: i) installation position with respect to the wall and the floor; ii) presence of grid/shelf/niche or an obstruction (e.g. caused by curtains); iii) thermo-fluid-dynamic condition variations (inlet flow rate and temperature); iv) hydraulic connections. In this paper, the experimental results of thermal output measurement of different radiators typologies (cast iron, aluminium) at different installation conditions are presented, together with an analysis of the associate technical-economic effects on space heating cost sharing. Reductions of radiators' thermal output up to 15% due to hydraulic connections and between 10% and 20% due to flow-rate variations have been found. Furthermore, different installation conditions showed deviations between operating and standard radiators' thermal output between 5% and 15%.
PAPER REVISED: 2017-07-03
PAPER ACCEPTED: 2017-07-10
  1. DIRECTIVE 201227/EU, 25 October 2012.
  2. L. Celenza, et al., Heat accounting in historical buildings, Energy and Buildings, 95 (2015), pp. 47-56.
  3. A. Ferrero, R. Marchesi, The Fundamentals of the Measurement Technique, NATO Handbook of measurements, 2002, pp. 9-17.
  4. F. Arpino, et al., Influence of Installation Conditions on Heating Bodies Thermal Output: Preliminary Experimental Results, in: Energy Procedia, 2016, pp. 74-80.
  5. S. Peach, Radiators and other convectors, J. Inst. Heating Ventil. Eng., 39 (2) (1972), pp. 239-253.
  6. EN 442-1, Radiators and convectors - part 1: technical specification and requirements, (2014).
  7. EN 442-2, Radiators and convectors - part 2: test methods and rating, (2014).
  8. UNI 10200, Impianti termici centralizzati di climatizzazione invernale e produzione di acqua calda sanitaria - Criteri di ripartizione delle spese di climatizzazione invernale ed acqua calda sanitaria, 2013.
  9. L. Brady, M. Abdellatif, J. Cullen, J. Maddocks, A. Al-Shamma'a, An investigation into the effect of decorative covers on the heat output from LPHW radiators, Energy Build.,133 (2016), pp. 414-422.
  10. Embaye, R.K. AL-Dadah, S. Mahmoud, Numerical evaluation of indoor thermal comfort and energy saving by operating the heating panel radiator at different flow strategies, Energy and Buildings, 121 (2016), pp. 298-308.
  11. Calisir, T. et al., Experimental investigation of panel radiator heat output enhancement for efficient thermal use under actual operating conditions, EPJ Web of Conferences, 92 (2015). EFM14. - Experimental Fluid Mechanics 2014.
  12. EN 834, Heat Cost Allocators for the Determination of the Consumption of Room Heating Radiators. Appliances with Electrical Energy Supply, 2013.
  13. S.M.B. Beck, et al., A novel design for panel radiators, Applied Thermal Engineering, 24 (8-9) (2004), pp. 1291-1300.
  14. I.C. Ward BSc, Domestic radiators: performance at lower mass flow rates and lower temperature differentials than those specified in standard performance tests, Building Serv. Eng. Res. Technol., 12 (3) (1991), pp. 87-94.
  15. R. Marchesi, La camera termostatica di riferimento europeo, La Termotecnica, 2 (1998), pp. 75-89.
  16. R. Marchesi, Calibration of test systems for determining the thermal output of radiators and convectors, SMT4 CT96-2127 Final Report, in, Brussels, 1999.
  17. R. Marchesi, et al., Test room specifications on the basis of the research program carried out at Dipartimento di Energetica del Politecnico di Milano, CEN TC-130, doc. n. 45, 1989.
  18. L. Celenza, et al., Economic and technical feasibility of metering and sub-metering systems for heat accounting, International Journal of Energy Economics and Policy, 6 (3) (2016), pp. 581-587.
  19. G. Ficco, et al., Experimental comparison of residential heat accounting systems at critical conditions, Energy and Buildings, 130 (2016), pp. 477-487.
  20. EN 1434-1, Heat Meters - Part 1: general requirements, (2015).
  21. H.W. Coleman, W.G. Steele, Experimentation and Uncertainty Analysis for Engineers, 2nd, USA, 1999.
  22. G. Betta, et al., Experimental design techniques for optimising measurement chain calibration, Measurement: Journal of the International Measurement Confederation, 30 (2) (2001), pp. 115-127.
  23. M. Dell'Isola, G. Ficco, F. Arpino, G. Cortellessa, L. Canale, A novel model for the evaluation of heat accounting systems reliability in residential buildings, Energy and Buildings, 150(2017), pp. 281-293.
  24. M. Saidi, R.H. Abardeh, Air pressure dependence of natural-convection heat transfer, Worlds Congress on Engineering WCE2010, London, U.K., 2010.