1. ICE/HT/FORTH and Department of Chemical Engineering, University of Patras, P.O. Box 1414, 265 00 Patras, Greece, School of Science and Technology, Hellenic Open University, 262 22 Patras, Greece, and CPERI/CERTH and Department of Mechanical and Industrial Engineering, University of Thessaly, Pedion Areos, 383 34 Volos, Greece