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Nondimensional convection numbers modeling thermally stratified storage tanks: Richardson's number and hot-water tanks

Journal Article · · Renewable and Sustainable Energy Reviews
 [1];  [2];  [2];  [2];  [3];  [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Texas A & M Univ., College Station, TX (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Texas A & M Univ., College Station, TX (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Thermally stratified storage tank studies have spanned over 50 years to increase the thermal storage efficiency and accurate prediction of the outlet temperature particularly for solar applications. The studies have reviewed and modeled the jet and plume flow phenomena inside the tank due to the inlet mixing and stratification level. Kelvin–Helmholtz and Rayleigh–Taylor instabilities are the major drivers of the mixing in these tanks. Momentum jets deflecting off walls at the bottom of the tank also create significant mixing. Reviewing Richardson models shows that the categorization was based on the range of Reynolds numbers at the inlet. Unfortunately, the use of superficial velocity in calculating the Richardson number results in critical values in the literature ranging from below 0.25 to 100. The most used length scale associated with these flows is an inertial scale based on the tank height or diameter although the mixing can occur at a relatively smaller scale. The various inlet devices and a large span of flow rates experienced in thermally stratified storage tanks requisite the use of the Reynolds number in combination with a convection number for accurate one dimensional models that predict performance over the long-term. The evaluation of peak shifting of electric loads leveraging renewable sources for applications, including residential hot-water tanks, commercial water tanks, and large-scale chilled water storage tanks, require these models. Finally, this paper is focused on establishing the significance of the convection numbers in conjunction with the Reynolds number for modeling the thermal stratification in storage tanks.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1808398
Journal Information:
Renewable and Sustainable Energy Reviews, Journal Name: Renewable and Sustainable Energy Reviews Vol. 150; ISSN 1364-0321
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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