6. Conclusion

from in situ measurements to characterise heat transfer at both the interior and exterior surfaces 14. Inferring the thermal resistance and effective thermal mass of a wall using frequent temperature and heat flux measurements

In the case of using hot plate data and ISO standard calculation results as true reference values, after using different methods to perform U-value measurements on the same sample wall to obtain a certain amount of data and refer to other research materials, according to the results, it can be concluded that when the in-situ measurement is aimed at fast and efficient, IRT is the most suitable Methods. IRT does not need to install many instruments, and the experiment time is the shortest. When the goal is to get the closest true reference value (calculate according to ISO standard), HFM can have smaller errors than IRT, although HFM is the longest time-consuming method. The dynamic method has the advantages of both short time and high enough accuracy. When the n-situ measurement has high-level personnel with enough ability to finish more complex calculations, the dynamic method can complete the experiment within a few hours and obtain a sufficiently accurate value. It can be observed in multiple tests that the heat flux can have a very large impact on the Uvalue calculation results, especially in the HFM test, when the temperature difference between the two sides of the hot box stabilizes, the uncertainty of U-value is mainly caused by unstable heat flux readings. In IRT testing and dynamic methods, temperature also affects the experimental results. In dynamic testing, some suspected wrong temperature data will cause the simulation results to be very different from the actual measured values. In addition, some experimental equipment problems should not be ignored, such as the poor performance and optional functions of the IR thermometer 2. Mistakes in some experiments also have an impact on the experiment, causing the experiment to fail or increase the error. Two HFM control experiments proved that a higher temperature difference can effectively reduce the uncertainty of the experimental results. It is not yet confirmed whether it will also affect U-value and other methods.

Due to the shortage of manpower and time, some tests cannot be further explored, such as IR test and dynamic test with higher temperature difference. The thermal mass required in the dynamic experiment should be measured with a special instrument. If the estimated thermal mass is correct, it should be checked whether the formula used in the simulation software is correct and the PT100 can correctly measure the surface temperature of the sample wall. The heat flux sensor needs also further calibration to ensure the data from it is correct and accurate. If the temperature and heat flux are corrected, then the hot box should be checked to exclude any influence from gaps or

57

holes that may exist. In the IR tests, the IR thermometers can be switched to another side to verify the pervious data is correct, especially for the cold side sample wall surface temperature. If possible, the IR thermometer should use the power cord as the energy supply method instead of the battery. It is not possible to use the battery IR thermometer for a long time at high temperatures.

58