%0 Journal Article %1 San2010 %A San, J.-Y. %D 2010 %J Energy %K heat-exchanger 2010 SLA %N 5 %P 1936 - 1945 %R 10.1016/j.energy.2010.01.007 %T Second-law performance of heat exchangers for waste heat recovery %U http://dx.doi.org/10.1016/j.energy.2010.01.007 %V 35 %X Exergy change rate in an ideal gas flow or an incompressible flow can be divided into a thermal exergy change rate and a mechanical exergy loss rate. The mechanical exergy loss rates in the two flows were generalized using a pressure-drop factor. For heat exchangers using in waste heat recovery, the consumed mechanical exergy is usually more valuable than the recovered thermal exergy. A weighing factor was proposed to modify the pressure-drop factor. An exergy recovery index (etaII) was defined and it was expressed as a function of effectiveness (var epsilon), ratio of modified heat capacity rates (C*), hot stream-to-dead-state temperature ratio, cold stream-to-dead-state temperature ratio and modified overall pressure-drop factor. This etaII-var epsilon relation can be used to find the etaII value of a heat exchanger with any flow arrangement. The etaII-Ntu and etaII-Ntuh relations of cross-flow heat exchanger with both fluids unmixed were established respectively. The former provides a minimum Ntu design principle and the latter provides a minimum Ntuh design principle. A numerical example showed that, at a fixed heat capacity rate of the hot stream, the heat exchanger size yielded by the minimum Ntuh principle is smaller than that yielded by the minimum Ntu principle.

@article{San2010, abstract = {Exergy change rate in an ideal gas flow or an incompressible flow can be divided into a thermal exergy change rate and a mechanical exergy loss rate. The mechanical exergy loss rates in the two flows were generalized using a pressure-drop factor. For heat exchangers using in waste heat recovery, the consumed mechanical exergy is usually more valuable than the recovered thermal exergy. A weighing factor was proposed to modify the pressure-drop factor. An exergy recovery index ([eta]II) was defined and it was expressed as a function of effectiveness ([var epsilon]), ratio of modified heat capacity rates (C*), hot stream-to-dead-state temperature ratio, cold stream-to-dead-state temperature ratio and modified overall pressure-drop factor. This [eta]II-[var epsilon] relation can be used to find the [eta]II value of a heat exchanger with any flow arrangement. The [eta]II-Ntu and [eta]II-Ntuh relations of cross-flow heat exchanger with both fluids unmixed were established respectively. The former provides a minimum Ntu design principle and the latter provides a minimum Ntuh design principle. A numerical example showed that, at a fixed heat capacity rate of the hot stream, the heat exchanger size yielded by the minimum Ntuh principle is smaller than that yielded by the minimum Ntu principle.}, added-at = {2011-01-19T18:07:26.000+0100}, author = {San, J.-Y.}, biburl = {https://www.bibsonomy.org/bibtex/2dd62ed80e80a1fb69a4b218b2ef35a27/thorade}, description = {ScienceDirect - Energy : Second-law performance of heat exchangers for waste heat recovery}, doi = {10.1016/j.energy.2010.01.007}, interhash = {36545c5049a6ebd605303645e93b76c7}, intrahash = {dd62ed80e80a1fb69a4b218b2ef35a27}, issn = {0360-5442}, journal = {Energy}, keywords = {heat-exchanger 2010 SLA}, number = 5, pages = {1936 - 1945}, timestamp = {2011-01-19T18:07:26.000+0100}, title = {Second-law performance of heat exchangers for waste heat recovery}, url = {http://dx.doi.org/10.1016/j.energy.2010.01.007}, volume = 35, year = 2010 }