Identification of the Most Effective Heat Exchanger for Waste Heat Recovery

Laboratory of Energy Intensive Processes placed in the building of NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology, is a research laboratory focused on increasing efficiency of industrial plants. Current research in the laboratory focuses on improving of the energy efficiency of industrial laundries. That can be achieved for example by recovery of the heat produced in the process. A microturbine is used as a power source. It produces flue gas with temperature approximately 300 °C. This flue gas is currently leaving into ambient air without utilization of its heat. Temperature this high enables utilization of the waste heat for preheating the combustion air or for heating water for various purposes. In this article, an evaluation procedure of several types (both conventional and special) of heat exchangers that are suitable for utilization of flue gas’ waste heat and the possibilities of their intensification will be described. It will be shown that heat exchangers with enhanced surfaces are more suitable for the application than exchangers with plain tubes. For heat exchange intensification it is possible to use various types of finned tubes or inserts. This enhancement increases turbulence and thereby heat exchange but also pressure loss. It is therefore, necessary to find suitable solution that will meet the condition of maximal allowed pressure loss while size of the device will be acceptable at the same time. Different types of heat exchangers with various possibilities of intensification and their influence on the heat transfer and pressure loss will be described in the article. The overall suitability of each type of heat exchanger for the current application will be briefly discussed. Selected types of exchangers will be made and tested in the above mentioned laboratory.