HoVAG

The industry's transformation to a climate-neutral economy is necessary to achieve the climate targets for combating climate change. One task here is the climate-neutral provision of heat for industrial processes and district heating networks. High-capacity (high-temperature) heat pumps, also known as large heat pumps with heating capacities of 0.5 MW and above, are suitable for this purpose.

Due to regulatory requirements, most of the refrigerants used to date will no longer be available. Climate-damaging refrigerants such as R245-fa or R134a are gradually being replaced by the F-Gas Regulation. There is also significant uncertainty regarding the newer HFOs used as substitute refrigerants. The EU plans to ban these substances as part of the PFAS ban. Only "natural refrigerants" such as ammonia, water, CO2 and hydrocarbons are considered future-proof. Ammonia and ammonia/water mixtures are particularly interesting as refrigerants for the temperature and output range of industrial processes and heating networks.

Large heat pumps generally use shell and tube heat exchangers as evaporators. After the compressor, the heat exchangers account for the largest share of the investment costs of large heat pumps and makeup between 35% and 50% of the total costs. For ammonia, the state of the art is using smooth tubes. For other refrigerants, high-performance tubes optimized for evaporation are used in shell and tube heat exchangers, which can multiply the output per tube. Due to the material properties of ammonia and the required pipe materials, these high-performance pipes are currently unavailable. In this project, new types of high-performance tubes for the spray evaporation of refrigerant ammonia are to be developed and tested in shell and tube heat exchangers. The aim is to increase the efficiency of shell and tube heat exchangers, reduce the investment cost and achieve a 50% reduction in the filling quantity compared to previous tube bundles.

IGTE:

Subproject: Investigation of tube bundles made of high-performance tubes

Wieland-Werke AG:

Development of heat exchangers with high-performance tubes for ammonia

• Definition of the application conditions (heat source temperatures, boiling pressures, pressure losses) and case study
• Design, construction and commissioning of a tube bundle test rig
• Experimental investigation of tube bundles made from high-performance tubes
• Experimental investigation of various spray devices
• Development of design guidelines for the structure of the tube bundle

October 2024 – March 2028

The HoVAG project is funded by the Federal Ministry for Economic Affairs and Climate Action (BMWK) based on a decision of the German Bundestag via Project Management Jülich (PtJ) under grant number 03EN4095A. The authors would like to sincerely thank the German Bundestag for their support and take responsibility for this publication.