What is the best solution to improve thermal performance of storage tanks with immersed heat exchangers: Baffles or a divided tank?

Aaron D. Wade, Jane H Davidson, Julia F. Haltiwanger

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

Abstract

Prior studies of indirect water storage tanks that employ an immersed heat exchanger to discharge the stored energy have identified two potential methods of improving the rate of energy extraction: 1) an internal baffle to increase the velocity across the heat exchanger, and 2) a divided storage compartment to achieve thermal stratification. Thermal performance of these two options is compared to that of a conventional cylindrical tank during transient discharge. Each tank has a storage volume of 350 liters and a 10 m long, 0.3 m2 coiled tubular heat exchanger. For the specific configurations evaluated, the baffled heat exchanger provides the highest energy delivery rates and heat exchanger outlet temperatures. An analytic model shows the advantage of the divided storage depends on the NTU of the immersed heat exchanger. The heat exchanger employed in the present study is too small to realize the potential benefit of a divided storage. Both options, if used in the appropriate system, can improve thermal performance as measured by the rate and quality of delivered energy. The baffle is most appropriate when storage-side natural convection is the largest thermal resistance of the heat exchanger. The divided tank is useful when the NTU of the heat exchanger exceeds three.

Original languageEnglish (US)
Title of host publication2008 Proceedings of the 2nd International Conference on Energy Sustainability, ES 2008
Pages551-559
Number of pages9
Volume2
StatePublished - Oct 19 2009
Event2008 2nd International Conference on Energy Sustainability, ES 2008 - Jacksonville, FL, United States
Duration: Aug 10 2008Aug 14 2008

Other

Other2008 2nd International Conference on Energy Sustainability, ES 2008
CountryUnited States
CityJacksonville, FL
Period8/10/088/14/08

Keywords

  • Heat exchanger
  • Hot water
  • Storage

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  • Cite this

    Wade, A. D., Davidson, J. H., & Haltiwanger, J. F. (2009). What is the best solution to improve thermal performance of storage tanks with immersed heat exchangers: Baffles or a divided tank? In 2008 Proceedings of the 2nd International Conference on Energy Sustainability, ES 2008 (Vol. 2, pp. 551-559)