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Measurement of the overall heat transfer coefficient in existing building walls using in-situ guarded hot box metho.

Number: pap. n. 5

Author(s) : BADRAN A., ABUEED M.

Summary

A miniaturized guarded hot box apparatus was built and tested in order to measure the overall heat transfer coefficient of walls in existing buildings in situ. The apparatus consists of three main parts; the metering box, the guard box and the cold box. The metering box containes an electric heater as a source of energy with an effective area of (0.5m*0.5m) 0.25 m2. The guard box (0.8m*0.8m) prevents any heat transfer outside the metering box that is fully located inside the guard, these two parts act as one pressed against one part of the wall. The cold box is a refrigerator pressed against other side of the wall. Also, there are three fans included in apparatus distributed as a fan for each of the above parts. In addition, a simulation program was developed to investigate the theoretical results of temperature distribution for analytical and numerical solutions using Matlab software. This done to prove that approximation from two to one dimensional analysis can be used. The U-value of three types of wall was calculated theoretically based on codes, and the experimental U-values were measured using the miniaturized guarded hot box under steady state conditions. For un-insulated wall specimen, the value of the theoretically calculated U-value was obtained as 2.45 W/m2.K, while the value of experimental one was 2.6 W/m2.K with deviation of 8% with about 3.5% uncertainty in measurement. Also, it took 24 hours to reach steady state condition in this case. The theoretically calculated U-Value of insulated wall specimen was obtained as 1.04 W/m2.K while the experimental one was 1.17 W/m2.K with about 14% deviation with about 2% uncertainty in measurement. The time needed to reach steady state conditions for insulated wall was 48 hours. In the actual wall case, the theoretically calculated U-value was obtained as 3.45 W/m2.K while the value of the experimental one was 3.7 W/m2.K with 7% deviation in this case with less than 7% uncertainty in measurement. It took less than 7 hours to reach steady state conditions.

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Pages: 14 p.

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Details

  • Original title: Measurement of the overall heat transfer coefficient in existing building walls using in-situ guarded hot box metho.
  • Record ID : 30014715
  • Languages: English
  • Source: 5th Jordanian IIR International Conference on Refrigeration and Air Conditioning. Proceedings: Aqaba, Jordan, March 8-10, 2015.
  • Publication date: 2015/03/08

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