Abstract
Experimental studies on internal convective (CHTC) and radiative (RHTC) heat transfer coefficients are very rarely conducted in real conditions during the normal use of buildings. This study presents the results of measurements of CHTC and RHTC for a vertical wall, taken in a selected room of a single-family building during its everyday use. Measurements were performed using HFP01 heat flux plates, Pt1000 sensors for internal air and wall surface temperatures and a globe thermometer for mean radiant temperature measured in 10 min intervals. Measured average CHTC and RHTC amounted to 1.15 W/m2K and 5.45 W/m2K, compared to the 2.50 W/m2K and 5.42 W/m2K recommended by the EN ISO 6946, respectively. To compare with calculated CHTC, 14 correlations based on the temperature difference were applied. Obtained values were from 1.31 W/m2K (given by Min et al.) to 3.33 W/m2K (Wilkes and Peterson), and in all cases were greater than the 1.15 W/m2K from measurements. The average value from all models amounted to 2.02 W/m2K, and was greater than measurements by 75.6%. The quality of models was also estimated using average absolute error (AAE), average biased error (ABE), mean absolute error (MAE) and mean bias error (MBE). Based on these techniques, the model of Fohanno and Polidori was identified as the best with AAE = 68%, ABE = 52%, MAE = 0.41 W/m2K and MBE = 0.12 W/m2K.
Highlights
Heat transfer by convection and radiation plays an important role in numerous applications from nanoscale [1,2,3] to large industrial installations [4]
In addition to the aforementioned methods, various computer-based techniques have been developed, and simulation tools used, in convective heat transfer analyses [41,42,43,44,45]. Despite their abilities to deal with complex problems that are not possible to solve analytically, they are used for proving experimental results rather than to formulate mathematical relationships to obtain convection heat transfer coefficients in building applications
radiative heat transfer coefficients (RHTCs) and convective heat transfer coefficients (CHTCs) are computed in the present study indirectly from formulas given by Equations (4) and (5), respectively
Summary
The measured internal air temperature varied from 20.44 ◦ C (at 16:40 on 3 February) to 23.40 ◦ C (at 22:10 on 30 January), with an average of 21.98 ◦ C. It was higher than that of the wall surface (Figure 7) This difference varied from 1.54 ◦ C (at 13:10 on 7 February) to. It was higher than that 13 ofof the wall surface (Figure 7) This difference varied from 1.54 °C (at 13:10 on 7 February) to the wall surface (Figure 7). The EN ISO 6946 standard gives the value hc = 2.5 W/m2K for the internal surface of the wall.
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