EXPERIMENTAL IMPROVEMENTS OF HEAT-TRANSFER IN A LATENT-HEAT THERMAL-ENERGY STORAGE UNIT WITH EMBEDDED HEAT-SOURCES

An experimental study was conducted in order to improve the heat trans fer in a single layer latent heat thermal energy storage unit with emb edded electrical heat sources. This study is motivated by the need to increase the performance of a more complex multi-layer latent heat the rmal energy storage system used for smoothing daily electrical load pr ofiles. In the first part, it is-shown that melting from discrete heat sources may be substantially enhanced by a careful distribution and/o r by activating the sources at different times. These strategies rende r the natural convection flows in the melt more efficient for melting the PCM and preventing overheating of the heat sources. In the second part of the study, passive air side heat transfer augmentation techniq ues are examined in order to improve heat recovery. It is found that a ugmented channels prolong the heat recovery period while maintaining t he outlet temperature in a comfortable zone. Wire coiled channels prov ed to be very efficient for air flow Reynolds number Re above 1000. Fo r Re = 1700, the heat transfer coefficient increased by 190%, while th e pressure drop increased by only 60%. (C) 1998 Elsevier Science Ltd. All rights reserved.