wind mill vs box mill

i need to know in which the efficeincy is more in wind mill or in wind mill which is covered with a closed path and a opening near fan like ventilator

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: wind mill vs box mill

    In theory, yes an Diffuser Augmented Horizontal Axis Wind turbine in more efficient.

    In practice--The measured air flow predictions did not hold up to theory:

    Comments on the Vortec Diffuser Augmented Turbine


    Attachment not found.

    Vortec 7 DAWT Summary of Test Results
    Vortec 7 DAWT Summary of Test Results
    In 1997 Vortec installed 7.3 meter diameter DAWT prototype. Developers claimed that the Vortec 7 was the first full-scale DAWT ever built. It didn’t go well, though Vortec raised a lot of money before they went defunct—with the money.
    This summary reflects my view at the time. Key participants were acknowledging the technical failure of Vortec 7, but they couched their failure in arcane technical language at arcane conferences.
    I came across this paper while researching DAWTs for an upcoming book.
    Unlike the hype leading up to the “demonstration” of the turbine, the damning conclusions seldom garner any press. By then it’s all to late.
    Aerodynamic analysis and monitoring of the Vortec 7 diffuser-augmented wind turbine by Derek Grant Phillips, Trevor Nash, et al, paper presented at the 1998 IPENZ.

    Selected conclusions with emphasis added.
    • Simplified one-dimensional arguments lead to predictions of speed-ups of about 2 and power augmentations of about 4, but such power levels have not been observed to date.
    • The velocity profile across the blade plane showed lower speeds closer to the hub, and a high speed region beyond the blade tips. As a consequence, power measurements were not as high as predicted by Foreman [Grumman Aerospace contractor to DOE], who assumed uniform velocity across the blade plane as measured beyond the blade tips.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: wind mill vs box mill

    Excellent item in latest Home Power mag (June/July, issue 161) on various wind turbines etc. It appears that ducted types don't work so well because - - the wind finds much easier paths out around the whole thing than to actually get funneled in through the blades. A lot of excellent info there.
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