Herwig, HeinzHeinzHerwig2017-08-282017-08-282016-05-20Entropy 18 (2016), 5: 198http://tubdok.tub.tuhh.de/handle/11420/1420The often used Nusselt number is critically questioned with respect to its physical meaning. Based on a rigorous dimensional analysis, alternative assessment numbers are found that in a systematic way separately account for the quantitative and qualitative aspect of a heat transfer process. The qualitative aspect is related to the entropy generated in the temperature field of a real, irreversible heat transfer. The irreversibility can be quantified by referring it to the so-called entropic potential of the energy involved in the transfer process.The often used Nusselt number is critically questioned with respect to its physical meaning. Based on a rigorous dimensional analysis, alternative assessment numbers are found that in a systematic way separately account for the quantitative and qualitative aspect of a heat transfer process. The qualitative aspect is related to the entropy generated in the temperature field of a real, irreversible heat transfer. The irreversibility can be quantified by referring it to the so-called entropic potential of the energy involved in the transfer process.en1099-43002016Multidisciplinary Digital Publishing Institutehttps://creativecommons.org/licenses/by/4.0/dimensional analysisenergy devaluationentropic potentialPhysikJournal Article2017-08-24urn:nbn:de:gbv:830-882w0222610.15480/882.141711420/142010.3390/e1805019810.15480/882.1417Journal Article