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Daniel A DAMOVSKÝ , Martin K NY

University centre for energy efficient buildings CTU in Prague, Třinecká 1024, Buštěhrad , daniel.adamovsky@fsv.cvut.cz. Daniel A DAMOVSKÝ , Martin K NY. Influence of airflow on thermal comfort in an energy-saving house. Introduction.

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Daniel A DAMOVSKÝ , Martin K NY

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  1. University centre for energy efficient buildings CTU in Prague, Třinecká 1024, Buštěhrad, daniel.adamovsky@fsv.cvut.cz Daniel ADAMOVSKÝ, Martin KNY Influence of airflow on thermal comfort in an energy-saving house

  2. Introduction • New or refurbished buildings are designed as energy saving buildings. • High quality of envelope insulation. • Expectation of low energy consumption. • Are we designing buildings for occupants or for energy labels..? • What conditions of thermal comfort we may expect in today buildings? • How is it with „old school“ rules about location of heating bodies? • What about a risk of draught in such buildings? • Many new and old challenges arises. 1208

  3. Methodology • 3 electric heating bodies - radiant panel, underfloor heating and ceiling heating (500 W each). • Experiments in a cabin with a controlled ambient environment. • Heat transfer coefficients (W/(m2.K)) are 0.13 for floor, 0.11 for ceiling, 0.13 for walls and 1.2 for window. • Air temperature inside maintained at 19, 20, 21, 22 and 25 °C. • Air temperature outside maintained at 5 and -12 °C. • Verification of measuring conditions in 4 heights besides the manikin; • ankles at 0.1 m, belly of a sitting person at 0.6 m, head of a sitting person at 1.1 m and head of a standing person at 1.7 m. 4.4 m Adiabatic wall 3.1 m 1208

  4. Methodology • A seated person with low activity - 36 zones thermal manikin. • Thermal resistance of clothing 0.132 m2.K/W (0.85 clo). • Analysis of air flow was performed by particle image velocimetry 325 mJlaser, two cameras and theflow seeded with Expancel particles (0.03 mm). • Data analysis by EN ISO 7730 (PMV, PPD) and EN ISO 14505-2 (equivalent temp.). 1208

  5. Experiment results • Reference state - Heatingsystemattenuation • Outside air temperature -12°C. • Heating setpoint reached • Due to the low temperatures of the sill and floor surfaces, this airflow is slowed down very slowly above the floor and these conditions can be perceived by the user as a slight draft. Up to 0.17 m/s 1208

  6. Experiment results • Radiant heating panel • Outside air temperature -12°C. • Maximum surface temp. 82 °C, 50 to 55 % of radiation of total heat flux. • Panel beneath the window. • 7 states from cold to maximum. • At 33 °C surface temp. direction of descending air flow changes. • Air velocity above floor was about 0.075 m/s. The top of radiant panel 1208

  7. Experiment results • Floor (and ceiling) heating • Outside air temperature 5 °C (-12 °C state in thepaper). • Surface temperature of the sill 21.6 °C, floor surface temperature 26.9 °C. • Air temperature above heating floor almost do not change with the distance and outside air temperature. 22.7 °C Manikinfeet at 1.5 m 0.125 m/s 23.2 °C 23.5 °C 22.8 °C ≈30 cm 1208

  8. Resulting conditions of thermal comfort • The most sensitive to conditions in the cabin are feet of a sitting person. • At room air temperature 21 °C PMV values of all systems fall to range ‹-0.9,-1.5› from slightly cool to cool. • From the worst to the best - ceiling heating, radiant panel and floor heating. • Optimal temperature for neutral thermal sensation is22.65 °C for floor heating, 22.72°C for radiant panel and 23.18 °C for ceiling heating CEILING HEATING RADIANT PANEL FLOOR HEATING PMV scale, sensation of thermal comfort: -3 cold /-2 cool / -1 slightly cool / 0 neutral / +1 slightly warm / +2 warm / +3 hot 1208

  9. Discussion • The most significant for thermal comfort is air flow caused by the window with U-value over 1 W/(m2.K) • important for renovations, • tall windows with low sill. • The problem of descending air flow is significant in case of floor and ceiling heating. • Radiant panel - old school rule of heating body length equal to 0.8 of window length is still valid today. • Consider operation of a control system (when turn off the heating body). 1208

  10. Discussion • How to prevent draft in thescenario of floor and ceiling heating? • To reverse descending air around window sill, another heat source is necessary. • 60 W electric heating filmfor outsideair temperature -12°C. • The speed drops below 0.1 m/s at a distance of about 1 m. 1208

  11. Conclusion • Could modern residential buildings offer improved conditions of thermal comfort? • YES. This is due to better technical properties of the envelope and more efficient heating systems. • BUT. It is important to keep well known rules about location of a heating bodies. • ESPECIALLY for floor and ceiling heating systems attention to windows parametres must be paid. • Otherwise low activity person seated person may recognize descending air as slightly cooling his feet. • Supporting solution may be supplementary little heating body integrated in vertical position into the window sill. 1208

  12. Daniel Adamovsky daniel.adamovsky@fsv.cvut.cz 1208

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