Optimal passage size for solar collector micro-channel and tube-on-plate absorbers

Roger Moss, Stan Shire, Paul Henshall, Phillip Eames, Farid Arya, Trevor Hyde

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)
232 Downloads (Pure)


Solar thermal collectors for buildings use a heat transfer fluid passing through heat exchange channels in the absorber. Flat plate absorbers may pass the fluid through a tube bonded to a thermally conducting plate or achieve lower thermal resistance and pressure drop by using a flooded panel or microchannel design. The pressure drop should be low to minimise power input to the circulating pump.A method is presented for choosing the optimum channel hydraulic diameter subject to geometric similarity and pumping power constraints; this is an important preliminary design choice for any solar collector designer. The choice of pumping power is also illustrated in terms of relative energy source costs.Both microchannel and serpentine tube systems have an optimum passage diameter, albeit for different reasons. Double-pass and flooded panel designs are considered as special microchannel cases. To maintain efficiency, the pumping power per unit area must rise as the passage length increases. Beyond the optimum pumping power the rise in operating cost outweighs the increase in collector efficiency.
Original languageEnglish
Pages (from-to)718-731
Number of pages14
JournalSolar Energy
Early online date20 Jun 2017
Publication statusPublished (in print/issue) - 1 Sept 2017


  • Solar collector
  • solar absorber
  • single pass
  • double pass
  • thermal
  • flat panel
  • heat transfer
  • laminar
  • turbulent
  • microchannel
  • serpentine
  • pressure drop
  • pumping power
  • optimisation


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