Experimental and simulative characterization of a fin and tubes heat exchanger with PCM for process heat applications

Thermal storage is one option to make solar or conventional process heat applications more efficient. Phase change material (PCM) storages offer the potential to keep constant temperatures for different time periods. In this paper a fin and tubes heat exchanger filled with the sugar alcohol D-mannitol was characterized regarding its usability as PCM storage in the temperature range between 100 and 250 °C. D-mannitol melts at ca. 166 °C. Different heating and cooling experiments were carried out. The specific heat capacity of the PCM as well as the latent heat was determined. The heat flow into the storage was determined at different mass flow rates for heating and cooling processes. During the measurements thermal losses to the ambient were very high leading to high uncertainties. Due to the viscosity of D-mannitol natural convection between the fins seems to have no significant influence on heat transfer during melting of the PCM. Some results led to the assumption that the heat distribution in the heat exchanger was not even. A simulation model was created and a first validation was carried out. Geometry improvement with the aim of more even heat distribution and higher charge and discharge power will be carried out by using the simulation model and further measurements.