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Characterization of melting and solidification in a real-scale PCM–air heat exchanger: Experimental results and empirical model

Dolado, Pablo, Lazaro, Ana, Marin, Jose M., Zalba, Belen
Renewable energy 2011 v.36 no.11 pp. 2906-2917
air, air flow, air temperature, ambient temperature, drying, energy, heat exchangers, melting, models, prototypes, solidification, thermal properties
This paper describes the experimental studies carried out to test thermal cycling of a real-scale PCM–air heat exchanger at ambient temperatures. To achieve this goal an experimental setup previously designed and used for testing real-scale prototypes of PCM–air heat exchangers is modified. The PCM used is commercially available, organic, and paraffin based. The total energy exchanged during melting and solidification, as well as the time elapsed until total melting/solidification are determined from the power curves experimentally obtained. The influence of the inlet air temperature and air flow is studied, and results show that the continuous thermal cycling of the unit is a repetitive process: running experiments with similar conditions leads to the same thermal behavior, no degradation in the PCM properties is noticed. Pressure drop is measured for different air flows. Depending on the inlet air temperature, full solidification of the PCM could be achieved in less than 3h for an 8°C temperature difference between the inlet air and the average phase change of the PCM. Average thermal powers of up to 4.5kW and 3.5kW for 1h are obtained for melting and solidification stages, respectively. An empirical model is developed from the experimental results, which could be a useful designing tool for applications that use such technology: green housing, curing and drying processes, plant production, HVAC, and free-cooling.