ESTIMATION OF THE LOCAL HEAT TRANSFER COEFFICIENT IN COILED TUBES: COMPARISON BETWEEN TIKHONOV REGULARIZATION METHOD AND GAUSSIAN FILTERING TECHNIQUE

Most of passive techniques for heat transfer enhancement (e.g. rough surfaces, swirl-flow devices and coiled tubes) origins an irregular distribution of the heat transfer coefficient at the fluid wall-interface along the wall perimeter. This irregular distribution could be critical in some industrial applications but most of the available research papers, mainly due to the practical difficulty of measuring heat flux on internal wall surface of a pipe, presents the results only in terms of Nusselt number averaged along the wall circumference. The application of inverse heat conduction problem solution techniques overcomes this limitation because they enable to estimate the local convective heat transfer coefficient starting from the temperature distribution acquired on the external wall surface. In this work, two different techniques were considered and compared: Tikhonov Regularization Method (TRM) and Gaussian Filtering Technique (GFT). They were tested considering a particular problem within passive heat transfer enhancement techniques: estimating the local convective heat transfer coefficient in coiled tubes. The comparison, performed both by synthetic and experimental data, revealed that the TRM performs better than the GFT if the signal is affected by low noise level while, for higher noise value, their efficiency is comparable. ICIPE2014 8th International Conference on Inverse Problems in Engineering, May 12–15, 2014, Poland Eds: I. Szczygieł, A.J. Nowak, M. Rojczyk 3