Measurement and simulation of flow rate in a water-in-glass evacuated tube solar water heater

G. L. Morrison*, I. Budihardjo, M. Behnia

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

149 Citations (Scopus)


This paper evaluates the characteristics of water-in-glass evacuated tube solar water heaters including assessment of the circulation rate through single ended tubes. A numerical model of the heat transfer and fluid flow inside a single-ended evacuated tube has been developed assuming no interaction between adjacent tubes in the collector array. Flow measurement using Particle Image Velocimetry (PIV) has been undertaken to validate the numerical model. The experimental rig consists of a single full-scale tube coupled to a storage tank. A non-dimensional correlation has been developed of the circulation rate through a single evacuated tube mounted at 45° inclination over a diffuse reflector. Simulation results show that the natural convection flow rate in the tube is high enough to disturb the tank's stratification and that the tank temperature strongly affects the circulation flow rate through the tubes. Circumferential heat distribution was found to be an important parameter influencing the flow structure and circulation rate through the tube, hence a separate correlation needs to be developed if a concentrating reflector is incorporated into the collector.

Original languageEnglish
Pages (from-to)257-267
Number of pages11
JournalSolar Energy
Issue number2
Publication statusPublished - Feb 2005
Externally publishedYes


  • Evacuated tube
  • Natural circulation
  • Water-in-glass


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