@article{GundermannRaabRaabetal.2021, author = {Gundermann, Michael and Raab, Florian and Raab, Daniel and Botsch, Tilman}, title = {Investigation of the heat transfer coefficient during the condensation of small quantities of water vapour from a mixture with a high proportion of non-condensable gas in a horizontal smooth tube}, series = {International Journal of Heat and Mass Transfer}, volume = {170}, journal = {International Journal of Heat and Mass Transfer}, publisher = {Elsevier BV}, issn = {0017-9310}, doi = {10.1016/j.ijheatmasstransfer.2021.121016}, pages = {15}, year = {2021}, abstract = {During heat recovery of exhaust gas energy in a shell and tube heat exchanger, the exhaust gas is cooled down and the water vapour content may condense when the corresponding temperature is reached. In this case, a condensation heat exchanger allows recovering the latent heat in addition to the sensible heat and is therefore beneficial for a preferably high heat recovery. The database and algorithms for the design of this kind of apparatus are still nowadays quite week because only little experimental work is realized with condensation of water vapour from a mixture with a very high proportion of non-condensable gas in horizontal tubes. The actual research work improves this database with a considerable amount of experimental data and proposes a correlation for the prediction of the heat transfer coefficient in an exhaust gas heat exchanger in which parts of the gas humidity condense. All experiments were carried out under conditions, which are typical for this kind of heat exchangers, hence the presented results can be used for the design of condensation heat exchangers in industrial heat transfer systems. A gas inlet temperature of 120 °C, a range of the air-steam mixture Reynolds number 11,000 Re 31,000, three tube lengths between 1.87 m and 3.04 m, water vapour volume fractions of 7 \% to 14.5 \% as well as tube diameters of 22 mm and 28 mm were selected to derive the correlation. Furthermore, additional tube lengths (0.574 m, 0.973 m, 1.373 m) were investigated to determine the parameters influencing the condensation rate and comprehensive location profiles over the tube length. A correlation for a correction factor is derived, which enables to calculate the increase of the heat transfer coefficient due to condensation from the dry heat transfer coefficient without condensation. This dry heat transfer coefficient is calculated by the measured values in the inlet and outlet for a purely dry air-steam mixture cooling without condensation. The correction factor depend on the water vapour volume fraction, the Reynolds number and the geometry ratio between the inner diameter and the tube length.}, language = {en} } @incollection{RaufeisenBreuerKumaretal.2007, author = {Raufeisen, A. and Breuer, M. and Kumar, V. and Botsch, Tilman and Durst, F.}, title = {LES and DNS of Melt Flow and Heat Transfer in Czochralski Crystal Growth}, series = {High Performance Computing in Science and Engineering '06}, booktitle = {High Performance Computing in Science and Engineering '06}, publisher = {Springer}, address = {Berlin, Heidelberg}, isbn = {9783540361657}, doi = {10.1007/978-3-540-36183-1_20}, pages = {279 -- 291}, year = {2007}, abstract = {In the present work, computations of flow and heat transfer in an idealized cylindrical Czochralski configuration are conducted using Large Eddy Simulation (LES) with the flow solver FASTEST-3D developed at LSTM Erlangen. The results match well with DNS data from the literature. However, detailed data for analysis of turbulent quantities are not available. Therefore, DNS computations are conducted using the code LɛSOCC, employing explicit time marching. Preliminary simulations show the high efficiency of the solver on the NEC SX-8. Furthermore, from a study of the velocity profiles at the wall, the resolution requirements had to be corrected such that the computational grid will now consist of approximately 8 × 106 control volumes. The present run of the DNS took more than 540 hours of walltime on 8 processors. With the results, the LES computations will be thoroughly validated so that appropriate models and parameters can be chosen for efficient and accurate simulations of practically relevant cases.}, language = {en} } @incollection{RaufeisenBotschKumaretal.2007, author = {Raufeisen, A. and Botsch, Tilman and Kumar, V. and Breuer, M. and Durst, F.}, title = {Prediction of Flow and Heat Transfer in a Czochralski Crucible using LES with Interface Tracking}, series = {Springer Proceedings in Physics}, booktitle = {Springer Proceedings in Physics}, publisher = {Springer}, address = {Berlin, Heidelberg}, isbn = {9783540326021}, doi = {10.1007/978-3-540-32603-8_59}, pages = {289 -- 292}, year = {2007}, language = {en} }