Experimental characterization and simulation of a fin-tube latent heat storage using high density polyethylene as PCM

Polymers have rarely been used as storage materials in latent heat storages up to now. Thus, we systematically screened all polymers available on a large-scale, selected promising ones based on their theoretical properties and experimentally tested more than 50 candidates. We found that polyethylene, polyoxymethylene and polyamides are promising even as recycled material. Especially high density polyethylene (HDPE) turned out to be suitable as was shown by detailed thermophysical characterization including more than 1000 heating and cooling cycles for INEOS Rigidex HD6070EA. We built a storage with 170 kg HDPE and a total mass of 600 kg based on a fin-tube heat exchanger and characterized its energy capacity, power characteristics and temperature profiles using a thermal oil test rig. A 3-dimensional model was implemented in ANSYS Fluent achieving excellent agreement between experiment and simulation. By analyzing the internal heat transfer contributions, temperature distributions and flow conditions, we were able to propose an optimized design and operation for future polymer latent heat storages.