Prof. Hjertager has published over 200 papers at international conferences and in international journals on fluid flow, heat transfer, combustion, gas explosions and chemical reactors. In addition he has authored and coauthored over 75 reports during his affiliation with NTH, NUI, CMI, HiT-TF/Tel-Tek and AAUE.
He has Professor competence in the following areas: Engineering Thermodynamics, NTH, 1984; Fluid Mechanics, Technical University of Denmark (DTH), 1987; Process Engineering, Telemark Institute of Technology (HiT-TF), 1988; Industrial Mathematics (Modeling and simulation), HiT-TF, 1988 and Chemical Process Engineering, AAUE, 1996.
Prof. Hjertager is also listed in Who's Who in Frontier Science and Technology.
He has been adviser to Royal Norwegian Council for Scientific and Industrial Research, NTNF's, committees on 1) Multiphase flow transport and 2) Explosions and Fires and he was member in the permanent Commission for Diving accidents set up by the Royal Norwegian Ministry of Justice. He has been Board member of DANSIS - the Danish Society for Industrial Fluid Mechanics. He has also been appointed "assessor" for the Australian Research Council (ARC), "evaluator" for the EU commission and for the Research Council of Norway as well as "reviewer" for Science & Engineering Research Council (SERC) in Singapore.
He has been member of numerous doctoral committees in Norway, England, Sweden, Denmark, The Netherlands, Finland, Spain and Australia and he has supervised 21 succesful Dr.Ing./PhD candidates in Norway and Denmark.
He has also participated in numerous evaluation committees for applicants for professorships at Universities in Norway, Denmark and Sweden.
He has been reviewer for many international conferences and international journals including the bi-annual Int. Symposia on Combustion, Int. J. for Multiphase Flow, Chemical Engineering Science, Combustion Science and Technology, Int. J. for Heat and Mass Transfer, Powder Technology, Industrial & Engineering Chemistry Research, Chemical Engineering Communications, AIChE Journal, Process Safety and Environmental Protection, Int. J. of Chemical Reactor Engineering, International Conference on Multiphase Flow (ICMF), Computers and Fluids, Reviews in Chemical Engineering.
He has also consulted for numerous industrial companies in Europe as well as in Australia and the USA.