A variable effectiveness model for indirect thermal storage devices

A. M. Boies, K. O. Homan, J. H. Davidson, Wei Liu

Research output: Chapter in Book/Report/Conference proceedingConference contribution

12 Scopus citations


The performance of indirect thermal storage systems is critically dependent on the degree of thermal contact between the energy storage medium and the energy transfer medium. For liquid-liquid systems, he energy transfer occurs across a heat exchanger for which the overall effectiveness is determined by both tube-side and storage-side convection coefficients. While the tube-side convection is essentially constant throughout a draw at a constant flow rate, the storage-side convection process depends intimately on the natural convection flow driven by the temperature difference between the two fluids. This temperature difference is inherently transient during the discharge process. In the present work, analytical models are developed which predict system behavior for constant and variable heat exchanger effectiveness. The accuracy of each model is quantified in relation to empirical data obtained by Liu et al. [1, 2] in a physical system motivated by application to integral collector storage (ICS) solar water heating devices. From analysis of the empirical data, discharge-averaged val jes in the constant effectiveness model and in the variable effectiveness model are determined for a range of empirical conditions. The results show that the initial flow transients generated by the start of the discharge process are flow rate dependent and have a significant impact on the observed overall heat transfer coefficients.

Original languageEnglish (US)
Title of host publicationProceedings of the ASME Summer Heat Transfer Conference, HT 2005
Number of pages9
StatePublished - 2005
Event2005 ASME Summer Heat Transfer Conference, HT 2005 - San Francisco, CA, United States
Duration: Jul 17 2005Jul 22 2005

Publication series

NameProceedings of the ASME Summer Heat Transfer Conference


Other2005 ASME Summer Heat Transfer Conference, HT 2005
Country/TerritoryUnited States
CitySan Francisco, CA


  • Heat exchanger
  • Natural convection
  • Thermal storage
  • Water heating


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