Waste heat is a common challenge in industries requiring high temperatures. With the help of heat exchangers, waste heat can be recovered and channelled to other processes within the same facility. But corrosive exhaust gases and high temperatures pose critical challenges to engineers when they try to extract thermal energy from flue gases. In 2017, ten companies and institutes from across Europe joined forces within ETEKINA project to develop and test a new type of heat pipe heat exchanger (HPHE) for energy-intensive industries. Heat pipes are hermetically sealed metal tubes that contain a working fluid. They transfer thermal energy passively from a hot to a cold stream by a boiling condensation cycle inside the tube. In this way, heat from the hot area can be transferred efficiently to a cold part of the pipe.
In the ETEKINA project, engineers have arranged many such heat pipes and created a heat exchanger design according to the specific needs of each of the production plants involved in the project: three factories producing aluminium, steel, and ceramics, respectively.
The hot production steam passes at the bottom of a container to heat the liquid inside the many tubes working together in parallel. At the other end of the heat exchanger cool air, water or thermal oil flows along, absorbing the heat of the condenser sections. This heated air or water can now be transported to parts of the production line where it can be re-used to preheat combustion air, treat automotive parts, or dry clay for example. The heat pipe heat exchanger concept developed during this project is highly scalable and can be adapted to any type of industrial exhaust in a wide range of temperatures for different heat sinks (hot air, hot water, pressurised water, thermal oil etc.). The estimated lifetime of an ETEKINA HPHE is 10 – 20 years.
